Search

This contribution tests the added value of including landslide path dependency in statistically-based landslide susceptibility modelling. A conventional pixel-based landslide susceptibility model was compared with a model that includes landslide path dependency, and with a purely path dependent landslide susceptibility model. To quantify path dependency among landslides, we used a Space-Time Clustering (STC) measure derived from Ripley's space-time K function implemented on a point-based multi-temporal landslide inventory from the Collazzone study area in central Italy. We found that the values of STC obey an exponential decay curve with characteristic time scale of 17 years, and characteristic space scale of 60 meters. This exponential space-time decay of the effect of a previous landslide on landslide susceptibility was used as the landslide path dependency component of susceptibility models. We found that the performance of the conventional landslide susceptibility model improved considerably when adding the effect of landslide path dependency. In fact, even the purely path dependent landslide susceptibility model turned out to perform better than the conventional landslide susceptibility model. The conventional plus path dependent and path dependent landslide susceptibility model and their resulted maps are dynamic and change over time unlike conventional landslide susceptibility maps.

Landslides are a major category of natural disasters, causing loss of lives, livelihoods and property. The critical roles played by triggering (such as extreme rainfall and earthquakes), and intrinsic factors (such as slope steepness, soil properties and lithology) have previously successfully been recognized and quantified using a variety of qualitative, quantitative and hybrid methods in a wide range of study sites. However, available data typically do not allow to investigate the effect that earlier landslides have on intrinsic factors and hence on follow-up landslides. Therefore, existing methods cannot account for the potentially complex susceptibility changes caused by landslide events. In this study, we used a substantially different alternative approach to shed light on the potential effect of earlier landslides using a multi-temporal dataset of landslide occurrence containing 17 time slices. Spatial overlap and the time interval between landslides play key roles in our work. We quantified the degree to which landslides preferentially occur in locations where landslides occurred previously, how long such an effect is noticeable, and how landslides are spatially associated over time. We also investigated whether overlap with previous landslides causes differences in landslide geometric properties. We found that overlap among landslides demonstrates a clear legacy effect (path dependency) that has influence on the landslide affected area. Landslides appear to cause greater susceptibility for follow-up landslides over a period of about 10 years. Follow-up landslides are on average larger and rounder than landslides that do not follow earlier slides. The effect of earlier landslides on follow-up landslides has implications for understanding of the landslides evolution and the assessment of landslide susceptibility.

This paper presents and discusses a procedure for measuring landscape openness, which is an important characteristic of the visual landscape. The procedure aims to ensure the quality of descriptions of landscape openness while being flexible enough to produce descriptions suitable for various purposes. Geo-data and a Geographic Information System (GIS) are used to develop the procedure, which consists of five steps: 1) select road network and apply sampling strategy; 2) merge terrain and topographic datasets and create contour lines; 3) identify visual limitations; 4) compute visible space; and 5) select and calculate variables. The procedure is applied to a case study to illustrate the possibilities. The paper includes a discussion of the realism, generality, precision and sensitivity of the procedure. The balance between a high degree of realism and a high degree of generality ensures a procedure which can be used by policy-makers and planners for a wide range of purposes at various levels.

Geographic Information Systems automatically calculate the area of a polygon from the coordinate values of the vertices that describe its boundary. Uncertainty in these coordinate values results in uncertainty in area estimates. Earlier articles showed how area uncertainty of individual polygons could be calculated. In this article we propose a covariance equation to quantify the impact of uncertainty in the position of a vertex on uncertainty in the area of all polygons sharing this vertex. The approach is based on the assumption of absence of spatial correlation in positional errors, but includes variation in the positional accuracy. The equations were implemented and applied to a case study area, described by a set of 97 adjacent polygons with different per unit area utility values (/ha). We were then able to calculate how uncertainty in the coordinate values propagated into uncertainty in the utility value of the complete set of polygons

Can social media become the new data source for certain social indicators? What does social media offer in comparison with classical sources for official statistics? This research analyzes the potential of Twitter data to obtain indicators of active citizenship. We use a methodology developed for a case study in Spain and test its replicability by applying it to England and the Netherlands. Twitter data offers an advantage to assess change in active citizenship over time and at high spatial resolution, while survey data — traditional sources for official statistics — are more authoritative and robust. Collecting and analyzing Twitter data is also faster than traditional survey processes. However, we found that Twitter usage specificities in each country ease or hinder the process, affecting the time to secure an indicator. Whilst future research will focus on other social indicators and sources of data, this research is an important step in developing an evidence-based understanding of the strengths and weakness of social media to inform policies.

Anthropogenic and climate-related stressors challenge the health of nearly every part of the global oceans. They affect the capacity of oceans to regulate global weather and climate, as well as ocean productivity and food services, and result in the loss or degradation of marine habitats and biodiversity. Moreover, they have a negative impact on maritime economic sectors and on the social welfare of dependent coastal populations. In order to overcome the deficiencies of traditional single-sector management, in the recent decades several scientific approaches emerged, based on the view of marine systems as Complex Adaptive Systems (CAS), i.e. systems where components interact in non-linear, path dependent ways, with lock-in and feedback loop mechanisms, and unpredictable effects also across scales. These approaches have been introduced into the texts of several international agreements related to marine CAS, and related management practices, with contrasting results in relation to effectiveness and integration of governance. This thesis evaluates for the first time the current international and European legal frameworks from the perspective of marine CAS. To accomplish this objective, four research objectives are formulated: (1) Develop a framework for marine CAS assessment and management; (2) Evaluate the entire European Union (EU) legal framework against the framework developed; (3) Evaluate the international legal framework for the assessment and management of the global oceans against the framework developed; and (4) Evaluate the implementation of the EU and global legal frameworks into practice. Chapter 2 develops a framework for marine CAS, based on the combination of two promising theoretical approaches: Adaptive Management (AM) and Transition Management (TM). The framework is based on the idea that AM and TM have the potential to overcome each other’s limitations, which are related to the insufficient attention to micro-level socio-economic components, and to the limited incorporation of environmental aspects into socio-technical assessments, respectively. More into detail, the proposed framework is articulated into three components. First, the two sets of marine social-ecological systems and connected socio-technical systems (e.g. fisheries, maritime transportation, coastal tourism and energy) must be clearly identified, and the complex interactions and influences between socio-economic patterns of production and consumption, and ecological components must be assessed. Second, the achievement of ecological resilience of a marine social-ecological system should be performed in coordination with transitions of unsustainable connected socio-technical systems. This implies that sustainability should be evaluated in relation to the pressures socio-technical systems generate on the ecological resilience of connected social-ecological systems, and related impacts. Third, the implementation of the two approaches should be articulated into iterative, learning- and science-based policy cycles, with mechanisms to foster coordination between the policy cycles of social-ecological and socio-technical systems. The benefits of this framework are threefold. First, the assessment of the two sets of social-ecological and socio-technical systems, taken together, allows to overcome current AM limitations and include micro-level socio-economic components into the assessment of ecological resilience. Second, by linking AM managers with established transition arenas, it is possible to overcome TM limitations and streamline the consideration of ecological aspects into the TM process. Third, by linking AM and TM policy cycles, it is possible to reduce the current legal and policy fragmentation. Chapters 3 and 4 apply the framework proposed in Chapter 2 to evaluate the EU and global legal frameworks for the assessment and management of marine CAS. Chapter 3 presents the first comprehensive review ever realised of the entire EU legal framework, composed of more than 12,000 EU legal acts, from the perspective of marine CAS assessment and management. It concludes that the EU legislation does not provide a fully coherent framework for the assessment and management of EU marine CAS. Although the Marine Strategy Framework Directive (MSFD; 2008/56/EC) is a major step towards this purpose, the present research highlights three major limitations: (1) the limited capacity of the MSFD to support the coordination between Member States sharing the same marine region or sub-region; (2) the insufficient characterisation of marine ecological resilience, in particular in relation to socio-economic elements, ecosystem services, human benefits and cross-scale interactions; and (3) the limited capacity of the MSFD to tackle the fragmentation of the EU legal framework and integrate ecological resilience into the objectives of sector-based laws and policies. Chapter 4 reviews 500 multilateral agreements, evaluated for the first time from the perspective of marine CAS. It shows that there is no international agreement aiming at the ecological resilience of the global oceans social-ecological system. Instead, the international legal framework is fragmented along two dimensions. On the one side, global agreements focus on specific objectives for determined socio-economic activities, ecological features or anthropogenic pressures. On the other side, regional agreements are in place for 18 ocean regions of the world, with a varying level of inclusion of elements of marine CAS assessment and management. The need is highlighted for a reformed global ocean governance framework, which should be based on a bio-geographical approach to the ecological resilience of the global oceans, and build on iteration, learning, and science-based advice to policy and management. Chapter 5 evaluates the implementation of the EU and global legal frameworks into the practice of assessment and management of a case-study area, the Adriatic Sea. It shows the importance of the MSFD as the first policy trying to deliver a CAS approach to marine assessment and management. However, the case-study investigation confirms the three limitations of the MSFD, laying in: 1) an insufficient geographical approach, where implementation is driven at national level and the requirement of cross-border cooperation is weak; 2) the vagueness of legal requirements, and the limited capacity to include socio-economic aspects into the required assessment; and 3) an insufficient capacity to coordinate with other laws, policies and programmes at various levels of governance. Based on the identified limitations, suggestions are advanced on how to strengthen the implementation of the MSFD, both at Adriatic and EU level. These suggestions are further advanced in Chapter 6, which includes detailed proposals on how to foster integrated large-scale marine monitoring in the EU, in order to contribute to the implementation of the MSFD in an efficient and effective way, also in relation to costs. Chapter 7 synthesizes the major findings of this thesis and evaluates the capacity of the framework to deliver a CAS approach to marine systems. It concludes that AM and TM, although holding different visions on sustainability and referring to different principles, have the potential to be put in synergy at the practical level. Further scientific research and management practices should focus on the need for AM and TM to overcome the relative isolation and foster synergies across sector-based management, in order to integrate environmental considerations into economic sectors. Suggestions are advanced to improve legal frameworks and policy practices at the global and EU level. They focus on the need: (i) to fill the gaps in the geographical scope of legal texts and to foster international cooperation at the right social-ecological scale; (ii) to increase guidance in translating complex scientific requirements into clear management objectives, and improve related data collection and sharing; and (iii) to reduce current legal and policy fragmentation through targeted, ecological resilience-based marine environmental impact assessments and maritime spatial planning. Lines for further scientific research are suggested, focusing on: (i) improving the evidence-base through additional case-studies; (ii) analysing legal frameworks and governance regimes in place for other marine social-ecological systems, like e.g. the United States of America, Canada, Australia and China; (iii) improving existing tools, or creating new ones for marine ecological resilience assessment; and (iv) developing innovative instruments and mechanisms to strengthen global oceans governance.

Global challenges posed by an increasing food demand and climate change call for innovative mechanisms that consider both agriculture and forests. Agriculture and forests are deeply interconnected in mosaic landscapes, just as multiple pieces of the same puzzle. These pieces are handled by numerous stakeholders with different and often contrasting goals. Hence landscape management is steered by power, access to scarce resources, but also vulnerability and hazards. In this thesis I analyze the roles each stakeholder plays on these dynamics, including policy makers, agribusiness actors and subsistence farmers. I explore landscapes as interconnected tiles of a game, in which players are real stakeholders and their goals determine land use dynamics on the game board just as in reality. Sometimes agreements made in the game translate to real-life actions influencing policy and management decisions. Other times the game is just fun and eventually contributes to social learning and trust.

Balancing options for shrimp farming A landscape approach to investigate the future of shrimp farming in the Mekong Delta Olivier Joffre While providing an option for development in coastal areas, shrimp farming is usually associated with high environmental cost due to the loss of mangrove forest and high social cost as farmers suffer heavy financial losses due to disease outbreaks. Planning shrimp farming requires to integrate risk as well as social and environmental cost. This thesis, using the Mekong Delta as a case, presents an approach to investigate, with local stakeholders, options to plan a resilient and sustainable shrimp farming sector. First, Olivier Joffre analyzed the different shrimp production systems from economic point of view before analyzing farmer’s strategies and providing insights on drivers that will push or, at the opposite, constraint farmers to choose integrated mangrove shrimp systems. This knowledge was integrated in an Agent Based Model (ABM) that was calibrated using Role Playing Games (RPG). The effect of future scenarios and different policies on the farmers’ decisions was tested using a combination of RPG and ABM. For one coastal district of the Mekong Delta, the results showed that promotion of intensification of shrimp production has a high social cost and decreases the total production in the study area after 10 years. Policies for supporting the spread of integrated mangrove-shrimp systems, such as Payment for Ecosystem Services, or access to an organic value chain, are not strong enough to influence farmers’ decision toward adopting these systems. Without any adaptation to climate change a sharp decrease of the production is expected. The approach brought local farmers’ knowledge to the attention of decision makers.

Thesis Summary Spatial information in public consultation within Environmental Impact Assessments Angela N. Mwenda Established in the United States of America in 1970, Environmental Impact Assessment (EIA) is an interdisciplinary approach that considers the anticipated impacts of development on the environment, and proposes timely mitigation of these impacts to the extent possible. Since then, EIA has continued to be established in countries worldwide, with modifications being made to suit regional and local requirements. Essential to EIA is an attempt to balance environmental concerns with social, economic and other human needs, which has led to partnership with society, to the extent that public participation is deeply incorporated into EIA. Also central to the EIA process is information related to the natural and human environment. Sources of this information, particularly those that contain spatial elements, are valuable due to their ability to provide information on location. Sources of spatial information are numerous, and may include photographs, maps, satellite images, orthophotographs, verbal descriptions, animations, and virtual reality, among others. Despite its innovative presentation of project-relevant information and communication function during public participation, debate exists on the value of spatial information to EIA. For example, high levels of visual realism may hinder the interpretation of spatial information, while high costs, and technical demands may cause certain types of spatial information to be inaccessible to a large number of stakeholders. These challenges are not unique to any one country, and have also been observed in developing countries, where, in addition to a deficiency of information, less developed and poorly enforced legislative, administrative, institutional and procedural frameworks for EIA intensify the challenges. For example, despite an official recommendation for the use of spatial information during public participation within EIA in Kenya, whether this happens, and the extent, was largely undocumented. In view of this observation, an investigation into the use and status of spatial information during public participation within EIA in Kenya was considered. The main objective of this research was to establish whether spatial information is used in public participation within EIA, and if so, the extent of its use. Three specific sub-objectives were developed, namely: to confirm the presence and extent of public participation within EIA in Kenya; to establish the extent to which spatial information is used in EIA in Kenya; and to evaluate, using case studies, the use of spatial information during public participation within EIA in Kenya. Combined methods of surveys and case studies were used to address the sub-objectives earlier developed. In response to the first sub-objective, namely, to confirm the presence and extent of public participation within EIA in Kenya, five dimensions for the evaluation of public participation within EIA were identified from legal and best practice requirements. These five dimensions were: notification, participation methods, venue, language used, and type of participants, which were then constituted into a Consultation and Public Participation Index (CPPI), developed within this research to analyze a sample of 223 EIA Study Reports submitted to the Environment Authority between 2002 and 2010. EIA Study Reports record activities during the EIA Study Stage, where public participation activities are most intensive, hence their choice as a source of data for the survey. Following analysis of the five dimensions presented in the CPPI, public participation was found to be relatively low, with the highest score of 1.65 out of a possible score of 5. The dimensions of ‘participation methods’ and ‘type of participants’ scored the highest, followed by ‘venue’, ‘notification’, and ‘language used’, in that order. Variations within the dimensions was also evident during the study period. Despite a 95% mention of public participation in the EIA Study Reports, the low CPPI scores were attributed to gaps in reporting and limited choices per dimension. In response to the second sub-objective, namely, to establish the extent to which spatial information is used in EIA in Kenya, survey methods similar to those used to address the first sub-objective were employed, where a sample of 434 EIA Study Reports submitted to the Environment Authority between 2002 and 2013 were analyzed for the presence/absence of spatial presentations, levels of visual realism exhibited, and content presented in the spatial presentations. Almost all (95%) of the EIA Study Reports sampled displayed a variety of spatial presentation types, with preference for the combined use of spatial presentations with low and high levels of visual realism. On the content, information depicting a combination of project location and project activities/details was most popular. In response to the third sub-objective, namely, to evaluate, using case studies, the use of spatial information during public participation within EIA in Kenya, two case studies were conducted, the first in Katani, in the Eastern Province of Kenya, and the second in Kericho, in the Rift Valley Province of Kenya. Both case studies were based on a conceptual framework developed in this research to assess the interplay between EIA, public participation, spatial information and type of participants. In both studies, EIA stages was limited to the EIA Study stage, levels of public participation was limited to ‘inform’, and categories of participants was limited to ‘affected persons’. Seven aspects of spatial information were deemed relevant to public participation, namely: availability, accessibility, content, appropriateness, language, translation, and technical support. In the first case study, all the seven aspects were evaluated, using a cadastral map, where it was established that the requirements for accessibility, language, translation and technical support were met, but those for availability were unsatisfactory, and unconfirmed for content and appropriateness. Out of the 7 aspects of spatial information that were deemed relevant to public participation, the second case study was limited to the aspect of ‘content’, and specifically distance perception. It was argued that distance perception is critical when determining potential benefits or threats from a proposed project. Three types of spatial presentations with different levels of visual realism were used, namely a topographic map, overlay map and aerial map. From this case study, preference was noted for topographic maps, indicating that higher levels of visual realism in spatial presentations were not always preferred. On whether maps improve distance perception, the results indicated that they encourage Euclidian distance perception. The unique point of the case studies was that they were conducted in ‘real-life’ settings, similar to those in which actual EIAs are carried out, as opposed to highly controlled and laboratory-like set ups. Two main innovations are evident: the consultation and public participation index (CPPI) and the conceptual framework developed in this research. The CPPI brought together, for the first time dimensions that are specifically relevant to public participation within EIA, that is, notification, participation methods, venue, language used, and type of participants. These dimensions offer the opportunity for deeper and more structured analysis of public participation within EIA, and the opportunity to improve practice. The second innovation, the conceptual framework, brought together the elements of EIA, public participation, spatial information and types of participants. The novelty of this conceptual framework was the combination of these elements and their placement within the framework of EIA, which will encourage in-depth investigation on their quality and effectiveness to EIA. Still related to the conceptual framework was the emphasis on ‘affected persons’, who often face direct impacts from development projects, yet are often not included in EIA public participation activities due to their low socio-economic status and challenges in accessing them, e.g. poor infrastructure and insecurity. It is due to their increased stake in any decision made that we specifically sought their opinions in this research.

Land use is constantly changing. For example, urban areas expand as a result of population growth, cropping patterns change to fulfil the demand for bioenergy and natural vegetation recovers in locations where farmers cease to farm. Understanding these changes is pivotal to explore future land-use scenarios and to design spatial policies. Land-use models are increasingly being used for these purposes. They function as virtual laboratories in which scientists or policy analysts can conduct experiments. In order to reliably apply models for these purposes, they need to be calibrated, where calibration is the adjustment of parameters to improve the model’s performance. Consequently, the value of modelled land-use scenarios and policy assessments depends on the quality of the calibration. Assessment of the quality of the calibration is termed validation, and is ideally performed independently in the sense that the data that is used for validation has not been used for calibration. The development of a land-use model can be described by four sequential phases: analysis and conceptual modelling, computer programming of the conceptual model, calibration of the computerized model, and experimentation with the calibrated model. The first three phases all have their own evaluation procedures: conceptual validation, code verification and operational validation, respectively. Operational validation provides insights into the strengths and weaknesses of a particular model application, and sometimes it can suggest directions for improvement. However, available assessment methods have limitations for their application in land-use modelling. Therefore, there is a demand to develop and apply more appropriate methods. The work presented in this thesis first considers the properties of land-use models that are important for their assessment, and subsequently presents and applies several methods that can be used for this assessment. Many land-use changes are directly or indirectly the result of human decisions. However, human decisions are inherently uncertain, and therefore land-use models cannot be expected to simulate these land-use changes exactly. This is acknowledged by many land-use models as they use a stochastic component to simulate land-use changes. Therefore, land-use models should not only be validated on their predictive accuracy, their capacity to accurately allocate land-use changes on the map, but also on their process accuracy, their capacity to realistically simulate land-use change processes. Moreover, many models start from an initial land-use map and simulate changes relative to this map. The amount of change for a simulation is typically small relative to the entire map, which means that a large part of the result is caused by persistence. For this reason, a benchmark, such as a naive predictor, is required to properly asses the accuracy of simulation results. This benchmark can be implicit to the assessment method itself, or explicit, i.e. another land-use model which serves as a reference model. Outperforming the benchmark can be considered a minimum threshold to pass; however, it cannot directly inform whether a model is acceptable as this depends on the purpose of the model, the requirements of the study and the application domain. The predictive accuracy of a land-use model is typically assessed by comparing a simulation result with the actual land-use map at the end of a simulation. A common method for this is the Kappa statistic, which expresses the agreement between two land-use maps corrected for the expected agreement from a random allocation given the distribution of class sizes. However, this is not an appropriate reference level to assess the predictive accuracy of land-use models, because it does not account for the amount of change. This thesis presents Kappa Simulation, a new map-comparison method that is identical in form to Kappa, but which instead applies a more appropriate reference model based on random allocation of class transitions relative to the initial map. This implicitly accounts for the amount of change, which truly allows gauging the predictive accuracy of changes in land-use models. However, Kappa Simulation cannot differentiate between near-hits and complete misses, while this distinction is often very relevant for land-use modellers. This thesis therefore presents Fuzzy Kappa Simulation. This statistic is an improvement of Kappa Simulation, as it applies a fuzzy interpretation of class transitions and their locations. This means that it can account for near-hits, which makes it arguably the most suitable map comparison method to assess the predictive accuracy of land-use models. Because of the intrinsic uncertainty underlying land-use change processes, a realistic land-use model does not necessarily generate a high predictive accuracy, which justifies a separate assessment of its process accuracy. Ideally, process accuracy is assessed directly from the values of model parameters. However, it is often impossible to observe real-world values for these parameters because drivers for land-use changes are correlated or they cannot be measured. Therefore, the process accuracy is typically assessed indirectly from the land-use patterns generated by the model. Two groups of methods exist to characterize land-use patterns: landscape metrics and fractal metrics. Landscape metrics are a collection of algorithms that have been applied in landscape ecology to characterize land-use patterns. In this thesis, landscape metrics have been used to compare the simulated land-use map with the observed land-use map instead. Fractal metrics, which have their origin in complexity science, are another type of measures to characterize regularities in (urban) land-use patterns. Examples are power-law distributions for urban clusters and fractal dimensions of patches of urban land. Moreover, fractal metrics can be interpreted in absolute terms since they represent general regularities in urban systems for which values are known from literature. Therefore, fractal metrics also allow evaluation of the process accuracy of a synthetic application for which no observed land-use pattern is available for comparison. Neighbourhood rules represent the influence of the existing land-use distribution on the location of land-use changes. This includes the persistence, conversion and attraction/repulsion of land uses in the neighbourhood of a location. Because neighbourhood rules cannot be estimated directly from data, they need to be set in a calibration procedure. The work in this thesis indicates that agents consider their neighbourhood at different spatial scales: the direct vicinity of a location has a strong influence on the allocation of new urban land, but neighbourhood rules over larger distance – typically the size of urban regions – also improve the model performance. This thesis also discusses a special type of neighbourhood rules: rules describing the influence of the existing activity distribution on the allocation of activity changes, where activities denote a quantity or density related to a land use, such as inhabitants for residential land use. This study shows that relatively simple rules can grow a realistic urban settlement structure, which confirms that neighbourhood rules improve the process accuracy of a land-use model. It should be noted that while the methods presented and applied in this thesis are objective, the selection of assessment methods remains subjective. Moreover, because no method is yet capable of describing land-use patterns satisfactorily, more subjective methods such as visual assessment of simulation results or interpretation of parameter values remain of added value in the calibration and validation of land-use models.

The main objective of this thesis is to develop an approach for exploring, analysing and interpreting movement patterns of pedestrians interacting with the environment. This objective is broken down in sub-objectives related to four research questions. A case study of the movement of visitors in a natural area is used to develop and demonstrate the approach. To achieve the objectives, four research questions were formulated: • How can movement patterns evidencing the stopping behaviour of pedestrians be detected? • What is the validity of the detected movement patterns for describing stopping behaviour of pedestrians? • How can movement patterns be applied to study the movement behaviour of visitors in natural areas? • How can movement patterns be formalized to represent the interactions between pedestrians and between pedestrians and their environment?

Vulnerability to natural disasters and the human pressure on natural resources have increased the need for environmental monitoring. Proper decisions, based on real-time information gathered from the environment, are critical to protecting human lives and natural resources. To this end, mobile sensor networks, such as wireless sensor networks, are promising sensing systems for flexible and autonomous gathering of such information. Mobile sensor networks consist of geographically deployed sensors very close to a phenomenon of interest. The sensors are autonomous, self-configured, small, lightweight and low powered, and they become mobile when they are attached to mobile objects such as robots, people or bikes. Research on mobile sensor networks has focused primarily on using sensor mobility to reduce the main sensor network limitations in terms of network topology, connectivity and energy conservation. However, how sensor mobility could improve environmental monitoring still remains largely unexplored. Addressing this requires the consideration of two main mobility aspects: sampling and mobility constraints. Sampling is about where mobile sensors should be moved, while mobility constraints are about how such movements should be handled, considering the context in which the monitoring is carried out. This thesis explores approaches for sensor mobility within a wireless sensor network for use in environmental monitoring. To achieve this goal, four sub-objectives were defined: Explore the use of metadata to describe the dynamic status of sensor networks. Develop a mobility constraint model to infer mobile sensor behaviour. Develop a method to adapt spatial sampling using mobile, constrained sensors. Extend the developed adaptive sampling method to monitoring highly dynamic environmental phenomena. Chapter 2 explores the use of metadata to describe the dynamic status of sensor networks. A context model was proposed to describe the general situation in which a sensor network is monitoring. The model consists of four types of contexts: sensor, network, sensing and organisation, where each of the contexts describes the sensor network from a different perspective. Metadata, which are descriptors of observed data, sensor configurations and functionalities, are used as parameters to describe what is happening in the different contexts. The results reveal that metadata are suitable for describing sensor network status within different contexts and reporting the status back to other components, systems or users. Chapter 3 develops a model which describes mobility constraints for inferring mobile sensor behaviour. The proposed mobility constraint model consists of three components: first, the context typology proposed in Chapter 2 to describe mobility constraints within the different contexts; second, a context graph, modelled as a Bayesian network, to encode dependencies of mobility constraints within the same or different contexts, as well as among mobility constraints and sensor behaviour; and third, contextual rules to encode how dependent mobility constraints are expected to constrain sensor behaviour. Metadata values for the monitored phenomenon and sensor properties are used to feed the context graph. They are propagated through the graph structure, and the contextual rules are used to infer the most suitable behaviour. The model was used to simulate the behaviour of a mobile sensor network to obtain a suitable spatial coverage in low and high fire risk scenarios. It was shown that the mobility constraint model successfully inferred behaviour, such as sleeping sensors, moving sensors and deploying more sensors to enhance spatial coverage. Chapter 4 develops a spatial sampling strategy for use with mobile, constrained sensors according to the expected value of information (EVoI) and mobility constraints. EVoI allows decisions to be made about the location to observe. It minimises the expected costs of wrong predictions about a phenomenon using a spatially aggregated EVoI criterion. Mobility constraints allow decisions to be made about which sensor to move. A cost-distance criterion is used to minimise unwanted effects of sensor mobility on the sensor network itself, such as energy depletion. The method was assessed by comparing it with a random selection of sample locations combined with sensor selection based on a minimum Euclidian distance criterion. The results demonstrate that EVoI enables selection of the most informative locations, while mobility constraints provide the needed context for sensor selection. Chapter 5 extends the method developed in Chapter 4 for the case of highly dynamic phenomena. It develops a method for deciding when and where to sample a dynamic phenomenon using mobile sensors. The optimisation criterion is to maximise the EVoI from a new sensor deployment at each time step. The method was demonstrated in a scenario in which a simulated fire in a chemical factory released polluted smoke into the open air. The plume varied in space and time because of variations in atmospheric conditions and could be only partially predicted by a deterministic dispersion model. In-situ observations acquired by mobile sensors were considered to improve predictions. A comparison with random sensor movements and the previous sensor deployment without performing sensor movements shows that the optimised sensor mobility successfully reduced risk caused by poor model predictions. Chapter 6 synthesises the main findings and presents my reflections on the implications of such findings. Mobile sensors for environmental monitoring are relevant to improving monitoring by selecting sampling locations that deliver the information that most improves the quality of decisions for protecting human lives and natural resources. Mobility constraints are relevant to managing sensor mobility within sampling strategies. The traditional consideration of mobility constraints within the field of computer sciences mainly leads to sensor self-protection rather than to the protection of human beings and natural resources. By contrast, when used for environmental monitoring, mobile sensors should above all improve monitoring performance, even thought this might produce negative effects on coverage, connectivity or energy consumption. Thus, mobility constraints are useful for reducing such negative effects without constraining the sampling strategy. Although sensor networks are now a mature technology, they are not yet widely used by surveyors and environmental scientists. The operational use of sensor networks in geo-information and environmental sciences therefore needs to be further stimulated. Although this thesis focuses on wireless sensor network, other types of informal sensor networks could be also relevant for environmental monitoring, such as smart phones, volunteer citizens and sensor web. Finally, the following recommendations are given for further research: extend the sampling strategy for dynamic phenomena to take account of mobility constraints; develop sampling strategies that take a decentralised approach; focus on mobility constraints related to connectivity and data transmission; elicit expert knowledge to reveal preferences for sensor mobility under mobility constraints within different types of environmental applications; and validate the proposed strategies in operational implementations.

This thesis argues that incorporating pastoral land rights into the formal system requires identifying and securing pastoralists’ rights on migration corridors and dry season pastures in a manner that, first, reflects their customary practices about ‘where’ and ‘when’ they require access to the land, and second, aligning both the ‘when’ and the ‘where’ within the legal framework for property rights and land administration. This approach may facilitate the legal recognition of pastoralists’ seasonal mobility and access to required resources in the formal system. Legal empowerment also gives pastoralists the ability to use the formal law to enforce their land rights, thereby securing their access to required seasonal resources. The main objective of this thesis is to assess how pastoralists’ seasonal land rights could be accommodated within the legal framework for property rights in land administration. Focusing on Northern Kenya, the main objective was divided into four sub-objectives: 1. Investigate whether pastoralism is still active in Northern Kenya and how formal rights can meet the requirements of the pastoralists’ seasonal land use. 2. Understand how non-pastoralist land use actors manage seasonal encounters with migrating pastoralists. 3. Describe how seasonal migrations and access rights could be aligned and secured as rights that overlap with private rights, within the legal framework for property rights and land administration. 4. Assess what tenure options are potentially suitable for securing seasonal migrations and access rights within the legal framework for land administration. Each of these sub-objectives are analysed in Chapters 2 to 5. The chapters are based on a series of papers published in, or submitted to international peer-reviewed journals. Chapter 2 assesses how the existing land laws supporting property rights are able to serve the requirements of pastoralists’ seasonal land use. This chapter forms the basis for the thesis. Data on the degree of livestock dependency among pastoralist communities, the spatial extent and patterns of their dry season migrations, the resulting encounters between pastoralists and non-pastoralist land use actors, and the perceptions of land rights held by actors were collected through a variety of methods and analysed. The results show that pastoralism is still active. The migration corridors reveal that herders maintain extensive dry season mobility, even though some of the corridors currently overlap with areas where land is privately owned by non-pastoralist land use actors. Moreover, the results show that most non-pastoralist land use actors have their land rights registered, but seasonal encounters with migrating pastoralists persist as pastoralists continue to exercise customary rights of communal use. This chapter concludes that existing land laws and property rights in land administration are suitable for sedentary land use, but do not address how to serve pastoralists land rights in time and space. Also, the map of the pastoralist’s migration routes obtained indicated that it is possible to predict where pastoralists will be at a given time/drought period. This information could be used by decision makers as a foundation for including pastoralists’ spatiotemporal land rights in land administration. Chapter 3 looks at the consequences for migrating pastoralists of the adjudication to non-pastoralist land users of exclusive real property rights during the process of setting up a cadastre in a land administration. It examines how non-pastoralist land use actors manage encounters with migrating pastoralists who need to enter their land to follow their traditional migration routes. The results of empirical research show that only a small percentage of non-pastoralist land users are willing to negotiate access contracts with the pastoralists; further, the majority are unwilling to have access arrangements formalized in the process of Land Administration. As land is continuously being adjudicated, surveyed and allocated for private purposes, the imposition of statutory rights on pastoralists’ areas, including migration corridors, permanently cuts out and extinguishes pastoralists’ rights to mobility and their access to required resources. The concluding argument in this chapter is that land adjudication should identify and confer all existing land rights to all users in order to avoid obstruction or renegotiation of pastoralists’ access rights. Chapter 4 explored how pastoral seasonal land rights could be secured through registration as overlapping rights. An opinion survey of experts on pastoral land rights revealed the view that seasonal migrations can be supported, but that access to grazing should be subject to negotiation with landowners. This chapter argues against making access subject to personal agreements, stressing the risk of negotiations failing, mainly because negotiated agreements are only binding on the parties involved. To avoid the risk of failure to acquire access through negotiation, registration is proposed as a legal tool to ensure security of access. The adjudication process for conferring private rights on land should view pastoral rights as being dynamic, because they apply across different areas at different times. The chapter discusses the attributes of pastoral rights within the framework of managing property rights, restrictions and responsibilities (RRRs), and describes how spatiotemporal rights could be aligned and included in the legal system through registration. Chapter 5 explores the tenure options potentially suitable for securing and protecting migration corridors within the legal framework for property rights. It focuses on the various tenure options that allow access to and use of land in Kenya: statutory (ownership and non-ownership rights), government land, customary rights, open access and negotiations. The opinion survey of land professionals led to the conclusion that spatiotemporal land rights can be secured within the legal framework for property rights and that government land reserved for pastoral purposes is a promising tenure option for securing spatiotemporal land rights. Where customary rights have not already been extinguished, migration corridors could be secured as public roads (government land) and dry season grazing areas could be secured as reserved land for the purpose of seasonal grazing. This would give pastoralists limited rights of use on the government lands. Through registration, the limited rights are enforceable within the statutory system of land administration. Where customary rights have already been extinguished, realignment of migration corridors or the establishment of new corridors and grazing areas might be necessary to avoid pastoralists’ seasonal land rights overlapping with private tenures or other land uses. The last chapter reflects on the main outcomes of the thesis. It argues that legal provisions need to be provided to cater for pastoralists’ seasonal land rights on migration corridors and dry season grazing areas. This chapter emphasizes that registration of the seasonal land rights gives pastoralists legal protection of their land rights and thus security of access to seasonal use of the land.

This dissertation has two objectives. The first objective is to link conceptually individual decisions and land-use/cover change (LUCC) patterns in rural regions. The second objective is to use these concepts to explore the influence of policy on LUCC as a response of farmers' decisions. To achieve these objectives, different approaches are used. Firstly, agent typologies are used to simplify and allocate the regional diversity of farmers' decisions. Secondly, an agent-based approach is used to link individual decisions and LUCC patterns in a regional model. Thirdly, this approach is applied to explore how farmers' response to national and global socio-economic and biophysical processes can affect the landscape of a Dutch rural region. Fourthly, this approach is applied to explore how farmers' participation in voluntary mechanisms to restore native vegetation can affect the landscape in rural Australia. Finally, the implication of these results for LUCC research and policy-making are discussed. In dit proefschrift wordt een actorgerichte benadering beschreven die landgebruiksveranderingen probeert te verklaren en simuleren als een reactie van boeren op socio-economische en biofysische veranderingsprocessen. Deze aanpak werd geïmplementeerd in een ‘agent-based’ raamwerk dat verschillende concepten en hulpmiddelen combineert: de bereidheid en capaciteit van boeren, besluitvormingscorridors, typologieën van ‘agents’ en beslissingsmechanismen gebaseerd op kansberekening. De beschrijving en implementatie van dit modelleerraamwerk heeft verschillende bijdragen gehad aan het onderzoek naar landgebruik

Over the last two decades many countries and regions throughout the world have taken steps to establish Spatial Data Infrastructures (SDIs). Developing SDIs requires a considerable amount of time, energy and financial resources. Therefore it is increasingly important to assess SDI outcomes in order to justify the resources spent on those infrastructures. The main objective of this thesis is to develop a framework for assessing Spatial Data Infrastructures. This thesis achieves this main objective in four sub objectives. First, for the reason that SDI complexity is seen as a serious obstacle for its comprehensive assessment, this thesis analyses SDI complexity by determining whether SDI can be viewed as Complex Adaptive System (CAS). Second, the principles of assessing CAS and the norms of general evaluation theory serve as the basis for developing a Multi-view SDI assessment framework. Third, the thesis evaluates the application process and applicability of the Multi-view SDI assessment framework to assess SDIs by applying it in 21 National SDIs. Fourth, the thesis expands the Multi-view SDI assessment framework by adding an assessment view for a goal-oriented SDI assessment. The thesis results show that SDI can be viewed as Complex Adaptive System (CAS). The principles of assessing CAS serve as a basis for developing a Multi-view SDI assessment framework which allows for a more comprehensive and less biased SDI assessment. The evaluation of the Multi-view SDI assessment framework in 21 National SDIs demonstrates it potential to assess SDIs. This thesis also expands the Multi-view SDI assessment framework by adding an assessment view for a goal-oriented SDI assessment. The developed assessment view is tested by applying it to measure the goals realization of the Dutch SDI.

The landscape is an important contributor to quality of life. People identify with landscapes and landscapes contribute to a sense of place and wellbeing. Changes in land use activities, such as agriculture, and in current spatial planning policies and practice accelerate the transformation of landscapes as many new elements are superimposed upon traditional landscapes, altering their visual appearance. These changes may have profound influences on people?s quality of life. The visual landscape should therefore be given explicit attention in landscape planning and policy making. An important landscape characteristic is landscape openness. It is defined as the amount of space perceivable to the viewer which illustrates the importance of the interaction of people with their environment. Landscape openness is an important characteristic and a measure of attractiveness. In the Netherlands landscape openness is one of the features of the visual landscape and is also one of the core qualities of the National Landscapes, which have to be protected or enhanced. Landscape openness is vulnerable for changes is the landscape and monitoring the effect of landscape changes on openness is therefore essential for policy makers and planners. Current methods to measure landscape characteristics such as landscape openness either are suitable for policy makers but not reflect essential characteristics of the phenomenon, or accurately reflect the phenomenon but are not suitable for policy making and planning. Current improvements in measurement techniques, enabled by GIS, and the availability of highly detailed topographic data covering large areas make it feasible to describe landscape openness with a higher degree of realism, while making few concessions to generality and objectivity. Procedures and methods used in previous studies to describe landscape characteristics like landscape openness for policy making and planning purposes do not take full advantage of these improvements. The objective of this thesis is to develop a procedure which takes advantage of these improvements, but also produces a sound description of landscape openness and meets the required standards for policy making and planning. We formulated three research questions: 1: How can landscape openness be measured? 2: How well does the measured openness correspond with perceived landscape openness? 3: Is the measured openness relevant for landscape policy makers? Nieuwe ontwikkelingen, zoals stedelijke en infrastructurele projecten en de uitbreiding van grootschalige landbouw introduceren veel nieuwe elementen in traditionele landschappen die de visuele kwaliteit veranderen. Deze veranderingen kunnen aanzienlijke invloed hebben op de kwaliteit van leven. Om het visuele landschap te beschermen of te verbeteren, moeten veranderingen van visuele landschappen expliciet aandacht krijgen in landschapsplanning en beleid. Openheid manifesteert zich anders in verschillende culturele landschappen en de ontwikkeling van prototypes voor openheid voor elk landschapstype kunnen worden gebruikt als richtlijn voor planning en beleid. Op Europees niveau worden landschappen doorgaans geclassificeerd door experts met behulp van een top-down benadering. Er is behoefte aan een koppeling tussen deze Europese top-down aanpak en de perceptiegebaseerde bottom-up benadering

Voor het ondersteunen van ruimtelijke vraagstukken wordt intensief gebruikt gemaakt van ruimtelijke gegevens. Het verzamelen en onderhouden van deze gegevens is een kostbare aangelegenheid. Bijvoorbeeld bij de aanleg van een nieuwe weg is informatie nodig over de bodemgesteldheid, de eigendomsituatie, ecologie, landgebruik, etc. Het beheer en onderhoud van deze gegevens is vaak bij verschillende organisaties belegd. Om ruimtelijke vraagstukken goed te kunnen ondersteunen is het delen (Spatial Data Sharing (SDS)) van ruimtelijke gegevens dan ook essentieel. In dit proefschrift staat het verkrijgen van gegevens centraal, vanuit sociaal-cultureel perspectief.

De alpiene boomgrens, gedefinieerd als de overgangszone tussen bergbos en alpiene vegetatie, kan een geleidelijke overgang zijn, een abrupte grens, of een mozaïek van plantengemeenschappen. De positie van de boomgrens in het landschap verschilt ook per regio. Deze verschillende ruimtelijke patronen worden veroorzaakt door processen die ook bepalend zijn voor de dynamische eigenschappen van de boomgrens, zoals de reactie op klimaat- of landgebruikveranderingen. Ruimtelijke patronen kunnen daarom een aanwijzing geven voor de te verwachten temporele dynamiek van een boomgrens, mits de onderliggende processen goed begrepen worden. Het doel van dit onderzoek is te begrijpen hoe ecologische processen de ruimtelijke patroonvorming en de vegetatiedynamiek van tropische alpiene boomgrenzen bepalen

The growing availability of spatial data along with growing ease to use the spatial data (thanks to wide-scale adoption of GIS) have made it possible to use spatial data in applications inappropriate considering the quality of the data. As a result, concerns about spatial data quality have increased. To deal with these concerns, it is necessary to (1) formalise and standardise descriptions of spatial data quality and (2) to apply these descriptions in assessing the suitability (fitness for use) of spatial data, before using the data. The aim of this thesis was twofold: (1) to enhance the description of spatial data quality and (2) to improve our understanding of the implications of spatial data quality.Chapter 1 sets the scene with a discussion on uncertainty and an explanation of why concerns about spatial data quality exist. Knowledge gaps are identified and the chapter concludes with six research questions.Chapter 2 presents an overview of definitions of spatial data quality. Overall, I found a strong agreement on which elements together define spatial data quality. Definitions appear to differ in two aspects: (1) the location within the meta-data report: some elements occur not in the spatial data quality section but in another section of the meta-data report; and (2) the explicitness with which elements are recognised as individual elements. For example, the European pre-standard explicitly recognises theelement'homogeneity'. Other standards recognise the importance of documenting the variation in quality, without naming it explicitly as an individual element.In chapter 3 we quantified the spatial variability in classification accuracy for the agricultural crops in the Dutch national land cover database (LGN). Classification accuracy was significantly correlated with: (1) the crop present according to LGN, (2) the homogeneity of the 8-cell neighbourhood around each cell, (3) the size of the patch in which a cell is located, and (4) the heterogeneity of the landscape in which a cell is located.In chapter 4 I present methods that use error matrices and change detection error matrices as input to make more accurate land cover change estimates. It was shown that temporal correlation in classification errors has a significant impact and must be taken into account. Producers of time series land cover data are recommended not only to report error matrices, but also change detection error matrices.Chapter 5 focuses on positional accuracy and area estimates. From the positional accuracy of vertices delineating polygons, the variance and covariance in area can be derived. Earlier studies derived equations for thevariance,this chapter presents a covariance equation. The variance and covariance equation were implemented in a model and applied in a case-study. The case-study consisted of 97 polygons with a small subsidy value (in euros per hectare) assigned to each polygon. With the model we could calculate the uncertainty in the total subsidy value (in euros) of the complete set of polygons as a consequence of uncertainty in the position of vertices.Chapter 6 explores the relationship between completeness of spatial data and risk in digging activities around underground cables and pipelines. A model is presented for calculating the economic implications of over- and incompleteness. An important element of this model is therelationship between detection time and costs. The model can be used to calculate the optimal detection time, i.e. the time at which expected costs are at their minimum.Chapter 7 addresses the question why risk analysis (RA) is so rarely applied to assess the suitability of spatial data prior to using the data. In theory, the use of RA is beneficial because it allows the user to judge if the use of certain spatial data does not produce unacceptable risks. Frequently proposed hypotheses explaining the scarce adoption of RA are all technical and educational. In chapter 7 we propose a new group of hypotheses, based on decision theory. We found that the willingness to spend resources on RA depends (1) on the presence of feedback mechanisms in the decision-making process, (2) on how much is at stake and (3) to a minor extent on how well the decision-making process can be modelled.Chapter 8 presents conclusions on the six research questions (chapters 2-7) and lists recommendations for users, producers and researchers of spatial data. With regard to the description, four recommendations are given. Firstly, spend more effort on documenting the lineage of reference data. Secondly, quantify and report correlation of quality between related data sets. Thirdly, investigate the integration of different forms of uncertainty (error, vagueness, ambiguity). Fourthly, study the implementation and use of spatial data quality standards. With regard to the application of spatial data quality descriptions, I have two main recommendations. Firstly, to continue the line of research followed in this thesis: quantification of implications of spatial data quality, through development of theory along with tangible illustrations in case-studies. Secondly, there is a need for more empirical research into how users cope with spatial data quality.

Multi-Agent Systems (MAS) lijken een bijdrage te kunnen leveren aan het beter modelleren en begrijpen van de complexiteit van een interactief multiactor ruimtelijk planningsproces. De belangrijkste doelstelling van dit onderzoek was daarom het verkennen van MAS ten behoeve van toepassing in de simulatie van interactieve multi-actor ruimtelijke planning. Het model is gebaseerd op vier soorten kennis ten aanzien van de ruimtelijke omgeving: wensen, opvattingen, waarden en preferenties

InEurope, agroforestry systems have been used mainly in traditional agriculture toprovide a variety of agricultural and tree products. However, during the last three centuries, the agricultural landscape inEuropehas seen a steady reduction of agroforestry. The reduction has been greatest since 1950, as the introduction of land consolidation programmes and agricultural mechanisation encouraged the removal of hedges and isolated trees from agricultural land. However, as the environmental costs of intensive agriculture have become apparent, there has been an increasing interest in the promotion of ecologically sound practices. Novel silvoarable techniquescould potentially offer a range of environmental and economic benefits in comparison with conventional arable cropping.The EU project "Silvoarable Agroforestry forEurope" investigated the European context of modern silvoarable agroforestry. It aimed to reduce uncertainties concerning the productivity and profitability of silvoarable systems, and to suggest European policy guidelines for agroforestry implementation.Within this broad framework, an integrated assessment of the environmental and economic performance of SAF was undertaken with the objective of assisting decision-makers implement ecologically sound land management practices. This was done in four steps: (i) developing an environmental assessment platform, (ii) applying the platform to test sites across Europe, (iii) co-ordinating economic assessments to the same test sites, and(iv) joiningboth environmental and economic results into an integrated interpretation.Chapter 2 describes the environmental assessment methodology to evaluate SAF systems based on the adaptation of existing models and the development of specific algorithms to predict the environmental effects of SAF at a farm- and landscape-scale. Modeling is needed when experiments are costly or too time consuming as in the case of agroforestry, where we assumed an average rotation to last 60 years.The framework comprised the assessment of soil erosion, nitrogen leaching, carbon sequestration and landscape diversity and allowed the comparison of the environmental performance of SAF with arable monocropping using these four indicators.The method opted for a broad view of the four environmental indicators, is applicable over a large geographic range (fromMediterraneanto Temperate Europe) and is based on spatial data that are generally available.The method was tested in three landscape test sites inSpain, inFranceand in The Netherlands.A total of five tree species were modelled: wild cherry (Prunus aviumL.), black walnut (Juglanshybr.), poplar ( Populus spp), holm oak (Quercus ilexL. subsp. ilex) and stone pine (Pinus pineaL.).Chapter 3 systematically assesses the environmental effects of SAFfor a stratified random sample of 19 landscape test sites (LTS) in Mediterranean and Atlantic regions ofEurope.For each LTS, existing geographical and statistical data were compiled, harmonized and complemented by field surveys. LTS were subdivided into a maximum of four land units (LU) using cluster analysis. The LUs were considered to be homogenous with respect to soil properties and climatic conditions and were used to represent farm management units. The LUs were ranked according to their potential productivity from "best land" to "worst land".The impact of SAF was explored by introducing SAF over 10% or 50% of the farm/landscape to simulate "pessimistic" and "optimistic" adoption by the farmer. Two tree densities (50 and 113 trees ha -1 ) were compared and SAF could be implemented in the best or worst quality land of the LTS to simulate different management priorities.Across the 19 landscape test sites, SAF had a positive impact on the four environmental indicators with the strongest effects when introduced on the best quality land.The computer simulations showed that SAF could significantly reduce erosion by up to 65% when combined with contouring practices. Nitrogen leaching could be reduced by up to 28% in areas where leaching currently is high (>100 kg N ha -1 a -1 ), but this was dependent on tree density.With agroforestry, predicted mean carbon sequestration, over a 60-year period, ranged from 0.1 to 3.0 t C ha -1 a -1(5 to 179 t C ha -1 )depending on tree species and location.Landscape biodiversity was increased by introducing SAF by an average factor of 2.6.From the beginning of the research, Chapters 3 and 4 were co-ordinated and carried out in the same test sites. While Chapter 3 assessed the environmental effects of silvoarable agroforestry, Chapter 4 evaluated the profitability of the same scenarios as Chapter 3.Time-series of annual production data and economic data for crops and trees (grants, revenue and costs) for each LTS were combined in the farm-scale bio-economic spreadsheet model FarmSAFE.The economic performance of the arable and silvoarable systems was compared using the infinite net present value( iNPV ) for a time-frame of 60 years (discount rate = 4%).The Common Agricultural Policy (CAP) payments were modelled for arable and silvoarable systems assuming: 1) No CAP payments; 2) Pre-2005 CAP payments; and 3) Post-2005CAPpayments, assuming in the case of silvoarable systems that a Single Farm Payments would be made to the whole cropped area (whilst cropping occurred) and that 50% of tree costs would be covered for the initial 4 years of the tree rotation.The analysis inFrancesuggests that walnut and poplar silvoarable systems could provide a profitable alternative to arable and forestry systems, while inSpaina modest restructuring of the amount and delivery of agricultural payments would increase the attractiveness of silvoarable systems of holm oak and stone pine.In the Netherlands, low timber value and the opportunity cost of losing arable land for slurry manure application made both silvoarable and forestry systems uncompetitive with arable systems.Chapter 5 is the integration of results obtained in Chapters 3 and 4 into a multi-criteria decision analysis (MCDA). ThePROMETHEE outranking approach was used to evaluate the integrated performance of silvoarable agroforestry relative to a status quo, on hypothetical farms in the nineteen LTS inSpain,France, and theNetherlands. The criteria used in the evaluation were soil erosion, nitrogen leaching, carbon sequestration, landscape biodiversity, and infinite net presentvalue,the latter assessed under six levels of government support. The MCDA was not configured to reflect the position of a specific stakeholder (e.g. an NGO might rate environmental criteria higher than profitability, whereas farmers might rate profitability higher than environmental criteria) but a neutral weight distribution was adopted.InFrance, the analysis showed, assuming equal weighting between environmental and economic performance, that silvoarable agroforestry was preferable to conventional arable farming.The best results were observed when agroforestry was implemented on 50% of the highest quality land on the farm; the effect of tree density (50-113 trees ha -1 ) was small.By contrast, inSpainand theNetherlands, the consistently greater profitability of conventional arable agriculture relative to the agroforestry alternatives made overall performance of agroforestry systems dependent on the proportion of the farm planted, and the tree density and land quality used.The environmental and economic performance of SAF in Europe is highly variable since each country/region has its specific biophysical and economic conditions. However, inEurope, ecological integrity is increasingly seen as fundamental to economic and social well-being.This work provided an initial approach for an integrated environmental and economic analysis of SAF systems. The findings could be refined to support policy development for silvoarable agroforestry as a new land-use alternative for farmers. At the same time, the framework could be adapted to the investigation of environmental and economic consequences of other land-use alternatives (e.g. new crops, forestation) at the landscape / farm scale.

Crop genetic resources are an important aspect of agricultural production. Agricultural innovation through plant breeding is generally seen as an efficient means to support food security and economic development in poor areas. Modern varieties of maize, a major cereal and the subject of this study, are at present used on roughly half of the tropical acreage of this crop. Several strategies are being developed to reach the other half, which involve farmers being more active in the innovation process. Field studies of farmers' seed and crop management aim to support the design of farmer-participatory plant breeding activities. In these approaches and studies there is a tendency to focus on seed selection as the core process of plant genetic innovation. The present study concentrates on the gene pool of maize in the western highlands ofGuatemala, as shaped by seed exchange and replacement by farmers. Maize is traditional in this area, and the main food crop.Chapter 1 gives a conceptual critique of existing models in participatory plant breeding. There is a tendency to focus on seed selection as the core process of plant genetic innovation. The present study argues that this model should be broadened and sees gene flow as a part of the creative process of crop evolution. This conceptual change implies that more attention should be paid to seed exchange, as seeds are a main vehicle for gene flow in cereals. Also, attention should not be paid only to individual decision making but alsoto the connections and structures which provide the conditions under whichexchange takes place. Over longer periods, individual seed exchange transactions add up to a collective gene pool structure, with 'emergent' propertiesbeyond the scope of individual farmers, but nevertheless important for the design of management strategies for crop genetic resources. The goal of this research is to gain insight into the shaping of the gene pool as a collective entity in the case of highlandGuatemala. To reach this goal, this study combines different research methods in an interdisciplinary way to reconstruct historical change and explain the current geographical structure in the maize gene pool.Chapter 2 explores the historiographic and ethnographic literature on highlandGuatemalato sketch five centuries of change in social connectivity and technological needs and identifying disasters with consequences for maize seed. It suggests that events likehuman disease epidemics of the colonial period, resulting in demographic decline, have had an important influence on the continuity and spatial distribution of maize genetic resources. Also it is pointed out thatthe twentieth centurybrought both regional social integration and local fragmentation, and that this, together with demographic recuperation, is importantin relation to the maize biodiversity and farmers' knowledge about it. Concerns about diversity conservation should not lead to attempts to resist economic integration; the formerly closed character of communities is largely a colonial product and historical connections between communities are perhaps deeper than often thought. The same may gofor maize genetic resources. Instead, maize agriculture should confront the challenges of modernity in ways that support collaboration between communities.Chapter 3 elaborates a more detailed study on historical change in farmer knowledge about maize diversity between 1927/1937 and 2004. In 1927 and 1937, two lists with local cultivars and their characteristics were drawn up by ethnographers for thetownshipofJacaltenango.Close inspection made clear that these two lists were rather consistent, and thata useful comparison with data on farmer knowledge in 2004 could thus be made. By using a sample of informants spread across several communities and ecologies in the township, an unequal spatial distribution of farmer knowledge was anticipated. A technique from cognitive anthropology, consensus analysis, was used to assess the likelihood of consensus about the presence of each cultivar. The current study found that absolute diversity losses were few, and involvedcultivars that are probably not genetically unique, sincethey were introduced before 1937 as a result of labour migration to coffee farms. Many newly introduced maize types were reported by farmers. Seed introductions corresponded to different forms of regional mobility, including forced migration and maize trade. This chapter further highlights the importance of taking into account spatial differences in knowledge between communities in the same township. A previous study in the same area, based on interviews in several township head towns, concluded, incorrectly, according to the present study, that substantial cultivar losses had occurred.Chapter 4 investigates contemporary farmer seed exchange and replacement based on 257 formal interviews in the highland townships of Chimaltenango. The study focuses on (1) the spatial distribution of cultivar names, (2) seed sources and flows, (3) reasons to discard seeds and (4) variables explaining choices between different seed sources. The fourth element was based on the application of classification trees to the interview data, supplemented with spatial data from another source. The distribution of cultivar names suggested that regional exchange of seeds of traditional and modern varieties occurs, but is constrained by altitudinal differences in the landscape. The data also indicate that most seed flows are local, and that regional seed flows are mostly taking place within the administrative department. Regional seed flows originate often in cities. When farmers discarded seed lots they were mainly motivated by their disadvantages (high plants and long growing cycles). This result was consistent with the finding that regional seed introductions were associated with seed lots with short plants and short growing seasons. This confirms that regional seed exchange is an important source of innovations. It is argued that farmers are dependent on regional sources to counteract the local tendency of cultivars to become taller and tardier. This tendency is probably the result of unintended selection for more competitive plants.Chapter 5 is a study of the spatial distribution of maize populations. By investigating a collection of 80 samples of maize seed from the department of Chimaltenango, and five modern varieties, it attempts to infer the seed exchange processes shaping the current spatial structure of the maize gene pool. Location, altitude, morphological, phenological, and molecular marker (SSR) data were analysed. The analysis identified altitudinal differences in the landscape as an important constraining factor in seed exchange, which is related to adaptation as measured by yield. Locally it found evidence for an isolation-by-distance effect, which points to a falling intensity of seed exchange over longer distances. However, over longer ranges (>8 km), this effect disappears. This was interpreted as evidence for the existence of different mechanisms for local and regional seed exchange. In this chapter,evidence for the influence of modern varieties is also presented. This influence was detected for the lower areas only.Chapter 6 argues on the basis of the findings in the preceding chapters that farmers in highland Guatemala maintain maize genetic resources in open systems. Although local seed exchange is common and is an important shaping force for the maize gene pool, occasional regional seed exchange is important in both past and present. The present spatial distribution of maize populations reflects dynamic processes and should not be conserved as such. To innovate, farmers take direct advantage of the differences between crop populations evolving in different places, in order to achieve phenotypic changes in their own fields. It is notartificial selection that is the main creative force in local innovation -the dominant view amongadvocates of participatory plant breeding- but the flow of seed lots in the landscape. Consequently, efforts to support seed-based innovation should not only focus on selection or local adaptation, but strengthen the capacities of innovation through seed exchange between locales. Innovation should seek to further exploitecological complementarities betweenareas (and not only the representation of broader zones of ecological adaptation). For this end, new regional infrastructures to handle seeds and information may need to becreated.

This thesis presents the application and comparison of three land-use planning (LUP) approaches in the coastal area of the Mekong Delta,Vietnam. The land use of the studied area is diverse, quickly shifting and strongly contrasting. The contrast is not only in terms of resources but also in economic profitability and environmental sustainability. The selected LUP approaches represent various levels of complexity and computation intensity, they range from empirical and qualitative to mechanistic and quantitative. A participatory LUP (PLUP) methodology, the guidelines for LUP by FAO enhanced with multi-criteria evaluation (FAO-MCE) and the land-use planning and analysis system (LUPAS) using interactive multiple-goal linear programming were selected. In order to compare them, they were applied with the same planning goal, in the same study area and for the same year (2004). The resulting land use plans were compared on their credibility and acceptability. The credibility is defined as the technical and scientific appropriateness of the approach, and the acceptability is defined as the perception of the stakeholders of its practical value. The LUPAS land use plan was most appreciated bystakeholders,it was also the most expensive method. The PLUP land use plan, which isdisagreedstrongest by the scientists, agrees best with the actual land use in 2004. In the dynamic and contrasting land-use systems of the coastal Mekong Delta, PLUP seems to be the most suitable approach for short-term advice, but for longer-term planning a combination of methods will probably work best.

Over the last few years many countries have spent considerable resources on developing their own National Spatial Data Infrastructure (NSDI) in order to manage and utilise spatial data assets more efficiently, reduce the cost of data production, and eliminate duplication of data acquisition. One of the key features of an NSDI is the national clearinghouse for spatial data, which can be regarded as the access network of an NSDI facilitating access to a nation's spatial data and related services. A clearinghouse can be defined as an electronic facility for searching, viewing, transferring, ordering, advertising and/or disseminating spatial data from numerous sources via the Internet. Such a facility usually consists of a number of servers, which contain information (metadata) about available digital data. A fully operational national clearinghouse enhances and innovates the NSDI of a countryThe main objective of this thesis is to analyse the development and impact of national spatial data clearinghouses worldwide as well as the impact of society on these facilities. The results obtained provide support for the development of strategies for establishing and maintaining clearinghouses. In order to achieve this main objective, the following five sub-objectives have been formulated:1) To assess the worldwide status of national spatial data clearinghouses.2) To assess the worldwide developments of national spatial data clearinghouses.3) To assess the impact of national spatial data clearinghouses on society, and inparticularthe GI-community.4) To explore the societal impact on the establishment of national spatial data clearinghouses.5) To explore the societal impact on the success of national spatial data clearinghouses.The results of these assessments and explorations provide a basis for identifying critical factors that affect national clearinghouses. This knowledge can be used to improve the use, content and management of (future) clearinghouses. Each of the chapters 2-6 focuses on a sub-objective as presented earlier.Chapter 2 systematically assesses and presents the worldwide status of national spatial data clearinghouses in December 2001. The examination of clearinghouse status was based on a web survey comprising an inventory of all established clearinghouses as well as measurements of twelve key characteristics: 1) year of first implementation; 2) number of data suppliers; 3) level of (meta)data accessibility; 4) metadata-standard applied; 5) number of datasets; 6) most recently produced dataset; 7) number of web references; 8) number of monthly visitors; 9) frequency of web updates; 10) language used; 11) use of maps for searching and 12) registration-only access. In December 2001, 59 countries had established their own national clearinghouse with significant differences in content, use and management.Chapter 3 systematically assesses and presents the development of all national clearinghouses throughout the world. Development assessment was primarily based on a longitudinal web survey, undertaken in April and December of 2000, 2001 and 2002 respectively. By December 2002, 67 countries had already established their own national clearinghouse. This quantity alone is significant. Of concern however, are the declining trends in use, management and content. One of the main reasons is likely be the dissatisfaction of the GI-community with the functional capability of national clearinghouses. Functional capabilities should perhaps be shifted from a data-oriented into a user and application-oriented focus; this is in line with the objectives of second-generation spatial data infrastructures (Rajabifardet al., 2003). Therefore, the main indications of critical (clearinghouse-internal) success factors are: the introduction of web services, the stability of funding, the provision of good communication channels, the formulation of a clear vision of the national clearinghouse function, the creation of user-friendly interfaces with less discipline-specific terminology, as well as trust in the clearinghouse.Chapter 4 systematically assesses and presents the worldwide impact of spatial data clearinghouses on society, and in particular the GI-community. The aim of this assessment is to assist policy makers in their task of evaluating whether or not investment in setting up and maintaining these facilities is justified. In order to achieve this objective a procedure was devised for the systematic evaluation of sustainable development within the worldwide clearinghouse population. The assessment procedure entailed a survey undertaken by clearinghouse coordinators (November 2003 - April 2004). A range of economic, social and environmental indicators was chosen to evaluate the relevance, efficiency and effectiveness of clearinghouses. This chapter also presents the results of complementary analyses, which were carried out to assess the significance of the impacts recorded. They were also used to assess the objectivity of the coordinators' responses. The results of these assessments reveal that clearinghouses (of the developed world) have mainly positive (economic) impacts. In addition, the results also indicate the significance of clearinghouses as relevant facilities for enhancing spatial data accessibility, for providing efficient means of accessing spatial data, and the effective promotion of data use and distribution. Finally, it is argued that results obtained can be used to justify present and support future investments in the clearinghouse system.Chapter 5 explores and presents the impact of society on the establishment of national clearinghouses. The aim of this exploration is to answer the following questions from a societal perspective: what are the critical factors influencing the establishment of national spatial data clearinghouses; why have some countries established a national clearinghouse, and why have other countries not done so? With these questions in mind, explorative and empirical analyses were carried out using the analysis of variances (ANOVA) and the decision tree method of data mining. The starting point was the worldwide status of established national clearinghouses in December 2002. The societal conditions of each country were characterised by attributes relating to nine societal aspects (economy, education, technology, environment, culture, demography, institution, health care, and jurisdiction). The main findings of this exploration indicate that all nine aspects can be considered as critical for such establishment, especially education, technology, institution, and health care aspects. Consequently, many societal attributes can be considered to play a critical role. Examples of critical attributes collected are: agricultural productivity, years of schooling, number of Internet secure servers, year of independence, and births attended by skilled health staff. These critical attributes give an approximate indication of the standard of living of a nation's society. It is plausible that the standard of living (rather than wealth) plays an important role in determining whether a country has an established national clearinghouse or not.Chapter 6 explores and presents the impact of society on the success of national clearinghouses for the situation of December 2002. It also identifies the societal factors behind the success of such a clearinghouse. A clearinghouse suitability index was developed in order to measure the success of clearinghouses. The society of each country was described by the same attributes relating to the nine societal aspects of Chapter 5. Several explorative analyses were performed based on statistics (e.g. partial least squares regression). Moreover, the success of potential clearinghouses was predicted for countries with no previously existing facility. These prediction results were tested against the results of the web survey of April 2005. The findings of the analyses highlight the importance of certain societal conditions for the success of national clearinghouses. However, society alone does not fully determine success, since clearinghouse-internal factors are also important. From a societal perspective, success is likely to be dependent on a combination of attributes from different societal aspects, in particular economy, education and technology. Critical factors for success could be those that raise the level of wealth in the country (e.g. taxes on income, gross domestic product, education expenditure and Internet accessibility). In April 2005, 83 countries had established their own national clearinghouse. In the near future newly established national clearinghouses, in countries where they have not previously been established, are likely to face serious obstacles or may even fail as a result of unfavourable societal conditions. This could, however, be reversed if critical clearinghouse-internal factors are implemented.Through the results obtained, it appears that no single best solution or recipe exists since each country has its own unique society. However, the results of this thesis will support clearinghouse coordinators and policy makers in the development of successful strategies for establishing and maintaining national clearinghouses. In this way, the results of this thesis can contribute to the enhancement of national clearinghouses andNSDIsin many countries.

The main objective of this thesis is to improve use and usefulness of information for rural land use decisions based on an operational demand-driven approach for land evaluation with case studies in Santa Catarina State, Brazil. To achieve this objective, the following research questions were formulated: (1) Are the existing land evaluation reports useful to rural decision makers?; (2) What interpreted information is necessary for rural decision-making?; (3) What are the implications of the planning environment for land evaluation?; (4) What primary information are necessary and feasible to collect or generate?; (5) What models and research methods can be used and which adaptations are necessary considering local conditions?; and (6) How do decision makers evaluate methods, tools and the new information? Is it worth to invest time and resources to further improve information?This thesis is a collection of papers, all dealing with case studies inSanta Catarina,Braziland related to demand-driven land evaluation, published or submitted to international peer-reviewed journals. The case studies presented in chapters 4, 5 and 6 were selected according to the main demands of users as identified in the previous chapters.Chapter 2describes and quantifies the use and usefulness of soil surveys and land evaluation reports to land use planners, observe the relation between latent demand and actual supply and suggest improvements on current methods. It is the basis for the thesis, indicating the main directions to be followed. The soil resource inventory and associated land evaluation had some utility, but were not in general used for their intended purpose, namely farm planning. This was mainly because they did not contain crucial information necessary to such planning in the actual context in which the farmer had to take decisions. The primary deficiencies were identified as: (1) no estimate of environmental degradation risk, (2) no financial analysis, (3) no social analysis of decision-makers' attitudes and preferences, (4) no risk assessment for weather, yields, profits and market, and (5) insufficiently-specific land use alternatives. These deficiencies could have been avoided with a demand-driven approach, evaluating and reporting according to the true needs and opportunities of the decision-makers.Chapter 3explains the farmers' decision environment in Santa Catarina state,Brazil, which is typical of many market-oriented but low-income economies, with respect to the actors, political, legal and social frameworks, interactions and dynamics, how these affect decision makers and implications for land evaluation. It shows that different groups of farmers have different needs for information and should be approached in different manner. Some farmers would welcome any information on improving their current farming systems, whilst others are also interested in innovative crops or agricultural processes. Yet another group might need motivation more than information. It suggests that if the land evaluation process is begun with a careful analysis of the decision environment of rural land users (farmers) and follows a demand-driven approach, the results will likely be more realistic and therefore more useful to both policy/planning institutions and direct land users. This should lead to more demand and a "virtuous cycle" where planning, land evaluation and clients' needs and possibilities are increasingly inter-linked.Chapter 4describes the applicability of a data-intensive watershed erosion and water quality model (AGNPS) in a relatively data-poor environment, reporting on the steps necessary to apply the model in a GIS setting, including data preparation, cell size selection, sensitivity analysis, model calibration and application to different management scenarios at small watershed scale in an area of intensive swine production. We calibrated the model by making a best guess for model parameters and performed a pragmatic sensitivity analysis using optimistic and pessimistic settings of these. It was not possible to calibrate over the entire rainfall range, which was thus divided into three (60 mm). Predicted sediment concentrations were consistently six to ten times higher than actual, probably because of sediment trapping by vegetated channel banks. Predicted N and P concentrations in stream water, adjusted by this empirical sediment concentration factor, ranged from just below to well above regulatory norms. The study shows that expert knowledge of the area, in addition to experience reported in literature, was able to compensate for poor calibration data. It was possible to apply the model for relative ranking of scenarios (actual, recommended, and excessive manure applications; point source pollution from pig farming) in comparative studies. Finally, we suggest that this methodology could also be useful as a starting point for calibration in a data rich environment.Chapter 5shows that visualization of scenarios with community participation was useful to increase participants' understanding of the water pollution problem, improve their perceptions, stimulate the search for solutions and generate new demands. This was the case even taking into account that rural decision makers are not well educated and not used to visualizing scenarios. In this, Santa Catarina is similar to many areas of the world. This study also addresses decision makers' opinions about the provided information.Chapter 6evaluates the potential of a participatory approach for integrating risk analysis into decision making for rural land use and decision makers' view of the supplied information. It particularly focuses on two of the main risk-oriented information demands in the region: (1) yield predictions for maize on different planting dates and (2) economic information for different land use options. It also investigates decision makers attitudes towards risk, and the degree to which these could be changed by objective information, in Santa Catarina State, Brazil, typical of transitional economies, where neither direct (farmers) nor indirect (extensionists) decision makers had been exposed to concepts of risk. Different groups had markedly different levels of knowledge, analytic capacity, economic conditions, perspectives and needs, and therefore should be approached differently and with group-specific information. Farmers were mostly moderately or extremely risk averse. However, at the end they declared themselves willing to take risks if they have adequate information. Despite their lack of previous exposure to these concepts, participants were able to understand the presented information. It finally suggests that a participatory approach, by gathering, presenting and periodically discussing demanded information with decision makers is certainly a practice to be further explored to effectively integrate risk assessment into rural decision making.Chapter 7:Demand driven land evaluation has been suggested by several authors as an attempt to make the information more relevant and useful to rural decision makers for land use planning. This research showed that this approach is possible in practice and should be further explored, but its effectiveness needs time to be definitely confirmed.

Though a lot has been done and achieved in erosion research and control in Kenya, most of the erosion research methods have in the past put emphasis more on quantifying soil loss or measuring soil erosion, rather than pinpointing to areas that are likely to suffer soil erosion. In most cases the erosion processes have been assumed to occur in a uniform manner at all levels of the landscape hierarchy, and hence the results of one level observation can be factored to cover other levels for which data was not collected. This has resulted in many people extrapolating site-specific point data to cover wider geographic regions, assuming uniformity of the erosion process over the region. Another interesting aspect of soil erosion is that though most attention is normally put on the negative effects of soil erosion, soil erosion has also some beneficial effects. For example, the deposition of eroded soil material to lower areas has sometimes improved the quality of the soil receiving the sediment, thereby improving agricultural productivity of the depositional areas. There have however been suggestions that the problem of soil erosion has been exaggerated and not proven to actually diminish crop yields against the background of improved crop productivity improvement techniques. All theses schisms makes it necessary to engage in soil erosion research, either to disprove the sceptics or to provide other means of assessing and viewing the problem of soil erosion.The general objective of the thesis was to develop and present a method, which can be used to assess the risk of water erosion for different levels of the landscape system hierarchy using spatial methods. The broad aim was to define relevant levels that form the basis for predicting and managing soil erosion and controlling its risk. The specific objectives were:To conceptualize and define from the landscape continuum hierarchically ordered landscape elements whose internal characteristics and parts influence the occurrence of soil erosion and whose spatial extent and geometry enable their capture and modelling by remote sensing and GIS.To prove that there are spatial features (erosion proxies) which are part-of, and internally contained in the hierarchically defined landscape elements that can aid in soil erosion risk assessment and modelling.To demonstrate that the selected erosion proxies can be related to actual occurrences of soil erosion by statistical methods and similarly be differentiated as either drivers or disrupters of erosion.To demonstrate that prediction models can be derived from field data collected on the erosion proxies and the developed models used for modelling of soil erosion risk spatially in a GIS for each of the defined levels.To test and validate the method in Kiambu.To address these objectives, concepts associated with hierarchy theory, landscape system construction, geographic information systems theories, and soil erosion theories were knitted together to develop a conceptual framework and a practical methodological approach to effect and realise the objectives.Kiambu district was selected for testing the developed methodology due to its intensive utilisation for agriculture and its location in a rugged terrain in the upper footridges and footslopes of the Aberdare Mountains where below-canopy soil erosion is obscured by vegetation vigour and intensive cropping. Soil loss studies through river sediment yields in the district, indicate that there are high amounts of soil lost annually by water erosion. These range from 20 t km -2yr -1in undisturbed forests, to 3000 t km -2yr -1in cultivated to grazing lands. Soil loss studies from runoff plots in Kiambu indicate that cultivated land loses between 20 and 30 t ha -1season -1and bare soil loses more that 70 t ha -1season -1. Other justifications were prompted by the fact that soil conservation in Kenya has been focussed to the 'Catchment Approach' without necessarily defining what the catchment means. Perception of soil erosion by farmers was also biased to visible features of erosion such as gullies and tended to ignore the finer features of erosion like rills, interill erosion and other visible forms or erosion.Recent developments in geographic information systems (GIS) technology have made it possible to model and represent geographical real world phenomena in computerised spatial databases through which they can be stored, analysed, and displayed. GIS can enable stepwise and ordered analysis of the landscape system components as deemed by the landscape researcher. Soil erosion is a product of the interaction of many geographical factors such as: soil surface cover, the erodibility of the soil mantle, the steepness and length of the eroding slope, the erosive energy of falling rain-drops and the specific management aspect of the eroding site. It can therefore be assessed and modelled in a GIS environment as is demonstrated in this thesis.ConceptsThe method integrates concepts, knowledge and implementation procedures. First there is a priori knowledge that is collated in order to facilitate the study of soil erosion in the context of a landscape system. Knowledge and practice are invoked to organise the landscape system into hierarchical levels through which equally ordered erosion processes can be studied, assessed and measured. The conceptual model revolves around the construction of hierarchical levels in a landscape system and how the landscape holons and their parts relate to soil erosion in terms of assessment, prediction and management.Hierarchical construction of the landscape system allows an ordered organisation of the landscape components into superordinate or subordinate parts which correspond to process time-scales and their corresponding spatial extents. Such an arrangement of the landscape system allows relevant observations and measurements to be made of the ordered processes. The concept deviates from viewing the landscape as an agglomeration of parts in which processes occur presumably in a uniform manner, and where only size changes allowing for smoothing of measured results in a linear generalisation transformation. The method identifies 'individual' landscape elements in each level of the landscape hierarchy in which processes occur within comparable time scales and for which data interchange and modelling can take place. They are termed 'holons' . The holons are used to represent the levels in the hierarchy.MethodologyThe overall methodology comprised several parts involving first the definition of landscape hierarchies, followed by field observations, and then spatial data capture for erosion risk prediction. Statistical analysis and spatial modelling of erosion risk in a GIS followed the first three steps. The first step mainly concentrated on defining the landscape hierarchies that could be used for assessing soil erosion risk spatially in a GIS. Landscape elements were identified to represent each level in the landscape hierarchy. These included the field-plot, the watershed and the landscape unit. The field observation part involved the collection of soil erosion data in a stratified and randomised strategy where 164 samples were collected for the field-plot holon types, 89 for the watershed holon types, and 104 samples for the landscape holon types. Maps were prepared for each of the levels before field data collection and data points plotted on them for field reference. Collecting soil erosion data involved measuring depths of erosion features formed by either water or gravity as agents of erosion. The erosion features included soil movement, translocated surface litter, visible flow channels, depth of stem washing, depth of root exposure, rills, gullies, and mass soil movement. Only the encountered erosion features on each proxy were observed and measured. Where there was no erosion, zero values were recorded. For prediction modelling, independent spatial data sets were prepared for the three spatial landscape holon types and their internally contained erosion proxies. Aerial photographs were used to capture the field-plot and watershed holon types while satellite images were used to capture the landscape level holon types. This was done in the spatial data capture part of the methodology. Statistical analysis involved confirming that the selected spatial erosion proxies influenced the occurrence of soil erosion, first by the occurrence of erosion features in the proxies and secondly by differentiating the contribution of each proxy to the overall erosion using the analysis of variance and the mean occurrence. The spatial modelling part of the methodology involved the production of logistic and logit regression prediction models from the initial random data, which were used to manipulate the newly created spatial data sets to produce erosion risk domains based on pre-defined erosion indicators, herein defined as erosion proxies for each of the levels. Properties of the proxies such as their slope-gradient, percentage ground cover and soil erodibility were used as the predictor variables after being tested for suitability as prediction variables by correlation analysis.ResultsIt was possible to use large-scale aerial photographs to capture field-plot and watershed level erosion proxies. Their real-world positions in the broader landscape were located using a global positioning system, commonly known as a GPS. The extracted holon types representing each level and their erosion proxies captured from the aerial photographs and satellite images were digitised and stored in a geographic information system. Field plots with their lands use kinds represented the lowest level of the hierarchy. Linear features in the watershed such as field-plot boundaries, footpaths, hedges, fences, tree lines, stonewalls, forest edges, wash-stops in tea and closed field boundaries represented the second level of the hierarchy. The highest level of the hierarchical construction, the landscape unit had river valleys, roads, and built-up centres representing the highest level erosion proxies. All the levels of the landscape hierarchy represented by different holon types, i.e. field-plots, watersheds, and the landscape units were stored as area objects while the erosion proxies inside them were stored as either area objects or as line objects. The field-plots were stored as area objects while the linear watershed proxies were stored as line objects. The landscape level erosion proxies that included built-up areas, river valleys, and road networks were stored as either linear objects or as area objects.From the descriptive statistics and analysis of variance it was possible to differentiate between the proxies that acted as the drivers of erosion as earlier postulated and those that acted as disrupters of erosion. The selected proxies for each of the levels and the frequency of their occurrences in each holon type supported the hierarchy theory of new and emergent erosion indicators for the different levels of the hierarchical organisation of the landscape system. Some proxies could be selected to act as the erosion indicators for each of the levels. Soil movement, rills, washed stems, exposed roots, flow channels and translocated surface litter occurred in all the field-plot level erosion proxies. Gullies emerged as new erosion features for the proxies of the watershed level while soil movement, rills, stem wash and root exposures occurred in one third of the watershed level erosion proxy types. Mass soil movement emerged as new erosion features for the landscape level proxies while rills dominated and occurred in all the proxies. Soil movement and gullies occurred in two-thirds of the landscape level erosion proxies.Important outputs from the prediction models were the odds ratios that provided quantitative values of how the erosion proxy properties influenced the risk of erosion. For the field-plot level holon types, a unit percent increase in slope created an increase in the risk of occurrence of soil erosion by 24% while a unit percentage increase in cover reduced the risk of occurrence by 8%. Slope added to the risk while cover reduced the risk. The risk contributed to by slope assumes constant cover and similarly the reduction in the occurrence of risk assumes constant slopes. For the watershed level holons, slope enhanced the risk of erosion by 36%. For the landscape level holons, a unit increase in percent slope enhanced the risk by 229%. A unit increase in cover percentage reduced the risk by 5% when the slope is constant. These figures obtained by the odds ratio show the erosion hazard conditioned by each of the proxy types. Slope and cover of the different multi-level erosion proxies proved to be important variables for predicting the hierarchical risk of erosion in the landscape system.The spatial data on predicted erosion risk provided useful information for erosion risk management. The spatial extent attribute made it possible to determine the amount of time and energy required for tackling the risk associated with any proxy. The object position helped in precisely targeting intervention measures, while the distribution showed the relative intensity of the risk in any given area and the proximity of the risk to known locations of the geographic feature space. The independently produced logistic and logit prediction models produced spatial patterns that corresponded very well with the predictor variables of slope and cover of the proxies. This obtained relationship gave credence to the predictive power of the models. The logistic regression models showed the probabilities of erosion risk in the proxies, while the logit models refined the risk zones due to the transformation of the probabilities to a longer linear stretch. The logit models therefore provided a broader spectrum of the predictions making it possible to distinguish areas with low risk from areas with very high risks of erosion that required immediate and prioritised attention.Strengths of the methodology and conceptual modelThe methodology seeks to establish a means by which soil erosion can be assessed and modelled at multiple levels in a landscape. It deviates from other single-level erosion assessment and risk prediction methods that are of common practice in Kenya and in many other parts of the world. It views the landscape as a medium in which water erosion processes are taking place in an intricate manner at different spatial hierarchies and which are also the entities for land use and erosion management. These spatial attributes offer the opportunity to predict and view the distribution of the risk of erosion on the broader landscape and at different attention levels. These create management opportunities are powerful tools for preventing or controlling soil erosion. The beneficiaries of the methodology outputs are seen as farmers, government departments, and other non-governmental organisations that are involved in soil and water management.Weaknesses of the conceptual modelThe following were the observed weaknesses during implementation:In intensive annual farming systems, the features of erosion are usually obscured by frequent tillage practices making their assessment only possible immediately after tillage and after the event of an eroding rainfall or during minimum tillage periods;The above reason means that temporal considerations must be embedded in the methodology where the observations in the field are timed to coincide with rainfall and field preparations; andAny organisations opting to use the method must be fully equipped with GIS facilities and technical capacity to manipulate the spatial databases and modelling their attributes. Technical capacity is also required in the fields of soil erosion assessment and statistical analysis. Remote sensing knowledge and data offer the best opportunities for capturing landscape objects for integration into a GIS. Acquisition of the data and capacity to manipulate the images both digitally and manually are unavoidable requirements of the methodology.Overarching discussions and conclusionsAfter collecting data on soil erosion and analysing it statistically, it has been shown that soil erosion in the field plot holon, watershed holon and landscape holon can be distinguished according to different erosion proxies for each of the holons. This finding can be used to refine the erosion prediction models such that the erosion processes are linked to the landscape holons with which they are closely associated. Scientific observations and measurements can also be ordered according to the holon type such that any extrapolations are directed to equal levels within the structure of the hierarchy. Different holons represent different levels of the landscape hierarchy.Due to the techniques of assessing soil erosion in the field as applied in this work, it was possible to show that soil erosion goes on even in tea plantations, coffee plantations and in forests. If erosion assessment is only based on farm fields, then the erosion in the in higher level holons such as watershed or the landscape unit will be masked somewhere during erosion impact evaluations. This thesis has also enhanced the recognition of soil erosion by using visible features to capture and measure incidences of past erosion. Soil movement, flow channels, translocated surface litter, are features of erosion, which are not usually discussed nor used for either assessing or quantifying soil erosion. Their use can now be integrated into further works. With the presented methodology of assessing soil erosion, more data will be generated and demonstrated to the farmers and other interested people on soil erosion and its hazard. The presented assessment and definitions in this work have also removed the problem of terminology especially in the definition of the landscape features for studying and managing soil erosion. The watershed has presented itself as the best management unit for many members of a community and can be adopted by any organisation concerned with collective management of soil erosion. The field plot remains the preserve of a single farmer while the landscape unit requires more of state interventions and deliberate management policy.Prediction modelling made it possible to assign a quantitative value to the risk of erosion. The landscape unit had the highest risk (229%), followed by the watershed (36%) and the field plot (24%). Resources and efforts must therefore be availed and directed towards addressing soil erosion risk occasioned by the landscape level erosion processes and proxies. Managing the landscape level alone will not have a net benefit if the two other levels are not also attended to since they equally suffer soil erosion risk. A holistic management approach will provide a more effective management approach to the soil erosion risk. Government priorities can be directed at the landscape level. Intermediate agencies such as Community Based Groups and organisations can tackle the watershed level risk while farmers and farming communities can tackle the field-plot and watershed levels.Researchable areas include in depth social studies that link biophysical spatial properties of the landscape to the socio-economic and policy instruments for each of the levels of the landscape hierarchy, i.e., field-plots, watershed units and the landscape units. Others are studies that link these landscape system holons with soil erosion proxies and soil erosion processes especially on their relationships with sediment yields, etc. to confirm further the notion of landscape hierarchies and erosion process resolutions. Finally, calibration and further testing of the prediction models in other parts of Kenya are recommended.

Publications on geodesy NCG KNAW, no. 55