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Abstract: The effluent from a Chinese paper mill (pH 7.1) was concentrated, and the solid residue was dried and ground. Crude lignosulfonate was obtained as a brown powder, and a novel sand-fixation agent was synthesized by means of graft copolymerization of the lignosulfonate with acrylic acid and formaldehyde. The newly synthesized product had good water solubility, potentially good biodegradation, and produced no additional pollution. The crusts formed on shifting sands using this agent had higher crushing strength and better resistance to wind erosion than those produced with two other recently patented fixatives. [Copyright &y& Elsevier]

Cultivated for millennia, the grapevine held a special status as one of the most important fruits in the historical Levant and the Mediterranean world. However, since past farmers typically did not leave written accounts of their activities, viticulture history is often shrouded in ambiguity, especially concerning the classification of grapevine landrace varieties. Hence, the study of archaic viticulture relies heavily on methodological fusion to unravel its more readily discernible biological and oral traditions. We therefore merged archaeological fieldwork, historical archival analysis, field geography and ethnographic interviews to collect multifarious data on the Dabouki grapevine. Our analytical synthesis enabled us to depict how, over the course of history, diverse communities variously grew this cultivar in dryland vineyards. The cultural history of the Dabouki stretches from at least the Ottoman era, when it was widely planted throughout the region under various names, to its current revival by enterprising Israeli and Palestinian winemakers. The majority of our research was conducted within a unique environmental corridor in the western Negev of Israel where dense concentrations of relic Dabouki grapevine survive. Our paper surveys the cultural history of the Dabouki grape as a flagship cultivar in the intergenerational horticultural regimes of arid land farmers in the western Negev of the southern Levant. Remarkably, archaic Negev viticulturalists used the same cultivars across successive historical periods and varying socioeconomic contexts. As such, the paper illustrates that arid regions with longstanding winegrowing traditions are ideal for locating endemic grapevines that apparently can withstand challenging growing conditions. Focusing on the enduring legacy of the Dabouki, we suggest how historical knowledge of ancient dryland farming systems and landrace cultivars can bolster the sustainability of contemporary viticulture. • Arid regions in the southern Levant with longstanding winegrowing traditions are ideal for locating landrace grapevines. • Historical knowledge of archaic dryland farming systems and cultivars can bolster the sustainability of modern viticulture. • Dabouki grapes were integral in the intergenerational horticultural regimes of dryland farmers in the western Negev. • In the western Negev, grapevines were traditionally cultivated on sycamore or fig trees to protect them from ground heat. • Multidisciplinary data and genetic analytics were used to mine the biological and cultural heritage of an archaic cultivar. [ABSTRACT FROM AUTHOR]

The semi-arid central Karoo of South Africa is an important livestock farming region, oftentimes characterized by water scarcity and limited grazing resources. This paper builds on previous research that has predominantly focused on post 19th century Karoo rainfall characteristics. The paper aims to: 1) establish the long-term frequency and longevity of droughts or dry periods; 2) explore spatial hydroclimatic variability across the Karoo during given dry/drought periods; 3) compare the timing and duration of 19th century Karoo droughts with those of neighboring regions to the east (Lesotho) and north (southern Kalahari); 4) establish the possible role of the El Niño Southern Oscillation (ENSO) in drought occurrence across the Karoo-Kalahari-Lesotho region; 5) determine whether the so called 'global drought' of 1877-78 is evident in the central Karoo; and 6) place 19th century droughts in a 20th– 21st century context (or visa versa) for the Karoo. Documentary sources were accessed, photographed and digitized from a variety of repositories (Libraries, Museums, and online sites such as READEX). Multi-station instrumental rainfall records (1861–2022) were made available by the Rubidge family at Wellwood farm. Historical droughts (1861–2022) in the Karoo were spatially highly variable in severity. However, severe droughts in the Karoo have decreased in frequency and amplitude (rainfall deficit) between 1861 and the present. • Historical droughts in the Karoo were at times highly variable in space and time. • Long and severe droughts have decreased in frequency and amplitude. • The 1877-78 drought was the most hydrologically severe 2-year drought. [ABSTRACT FROM AUTHOR]

Abstract Archaeological studies typically describe arid areas as extremely unpleasant areas for human occupation and use. Without suggesting that arid areas are pleasant places, however, this paper provides a reassessment of the meaning of aridity for an area showing a vast amount of evidence of (past) human activities. Several climatic proxy data suggest that at the transition between the late Bronze Age and the Early Iron Age (around c. 1300-1100 BC) the southern Levant witnessed more arid conditions, while after 1100 BC relatively moist conditions would have prevailed. In drylands, small changes in temperature and water availability can have large effects on subsistence options. Building on cooperation between an archaeologist and a water scholar, this paper offers an approach to study how people in the past were able to craft a livelihood in the arid environments in the southern Levant and elsewhere. Focusing on the Zerqa area, the paper explores the potential of this cooperation by studying effects of climatic changes at the transition from the Late Bronze Age to the Iron Age through a modelling approach. Changes in temperature and moisture availability were simulated, showing that increased aridity could have been met by either naturally available water (especially groundwater) or artificially added water (although the timing appears to be crucial). While the model approach under discussion offers an approximation of the past, it shows the potential impact of climatic changes on the subsistence of past communities. It shows that details can mean the difference between survival or collapse. Highlights • Modelling provides boundaries for thinking about ancient resilience. • Rainfed crop yields could be sustained with irrigation, even in the frequent dry years. • Increasing aridity might have been a trigger for expanding the irrigation system. • The Zerqa Triangle was affected by the LBA crisis, yet continuity is visible as well. • Aridity did not necessarily bring crisis, even in arid areas like the Zerqa Triangle. [ABSTRACT FROM AUTHOR]

In this longitudinal and qualitative study of rural life in western Turkey, I argue that ecological conditions, state policies, and villagers’ agency play a significant role in the suburbanization of villages. This paper traces the history of how villagers in the Yuntdağ north of Manisa, an arid and rocky region, used nomadic heritage and Islamic culture as economic resources. I argue that villagers have gone from being cultural heritage entrepreneurs to wage laborers, incorporating and identifying with the ethno-national identity of the nation while adjusting their lives to the state. In so doing and with the bureaucratic redefinition of the villages in the region as urban neighborhoods, the meaning and definition of rural life gradually is erased. Based on over fifteen years of ethnographic fieldwork, 2000–2015, this paper considers the suburbanization of rural life and the highly gendered economic decisions villagers make. [ABSTRACT FROM AUTHOR]

With increasing global population, the production of more food and fiber has led to an expansion of the areas under cultivation, of which low-lying flat areas (including marginal graben bottoms) are of particular interest. Marginal grabens have been the center of agricultural development around the world. This paper examines the opportunities and challenges related to natural resources in rural development and highlights the knowledge gaps and priorities for the research and development of marginal grabens with specific reference to Ethiopia's Rift Valley marginal grabens, which have sufficient land banks to accommodate irrigated agriculture. Repeated transect walks, focus group discussions and interviews carried out in Northern Ethiopia, have been employed to address these research questions, while content analyses and descriptive statistics have been used to analyze the data. This paper shows that marginal grabens are rich in blue and green waters due to their topographical and geological characteristics, and are fertile plains suitable for irrigated agriculture. However, marginal grabens can reach closing and closed basin status in arid and semi-arid environments. Salinization, waterlogging, incisions and sedimentation also threaten the livelihoods of smallholder farmers in the grabens. Thus, appropriate river basin governance, integrated land management, and wise water allocation is needed to optimize land and water resources during rural development in the (semi)closed marginal grabens of northern Ethiopia and elsewhere in the world with similar geographical settings. [ABSTRACT FROM AUTHOR]

This paper documents the various dipinti in a cave dwelling on the southern slope of the Byzantine town of 'Avdat, located in the central Negev highlands of Israel. The dipinti are viewed in their architectural and spatial contexts and discussed in light of previous dipinti finds in another cave dwelling at the site. This helps to build an evidentiary base for associating the cave with monks present in the town. Thus, the paper expands our currently limited knowledge of Byzantine monastic communities and activities in the Negev Desert region. [ABSTRACT FROM AUTHOR]

Desert tourism has grown steadily in several regions of the world, due to a post-modern fascination with remoteness, barrenness, silence and solitude. This paper evaluates the trend towards tourism development in South Africa's arid Karoo region. It utilises several methodologies – analysis of discourse, demand and supply – to track the changing profile of tourism in the Great Karoo. The paper concludes that the reputation of the Karoo has shifted profoundly from being hostile, dangerous and boring to being attractive, enticing and spiritual. At the same time, tourists are increasingly expressing favourable opinions of the Karoo as a destination, while accommodation facilities are growing apace. The overview also finds that tourism services in some Karoo towns are developing at a much faster rate than others, so the tourism performance is uneven. A survey of tourists in the Karoo found that the arid environment and small-town ambience offer significant attractions, and Karoo guest houses have a positive outlook for the future. These findings suggest that the Great Karoo is indeed in the process of becoming a tourism destination. [ABSTRACT FROM AUTHOR]

Scarcity of in situ vegetation data inhibits research and natural resource management in the Sudano-Sahelian zone (SSZ). Satellite and aerial remote sensing (RS) constitute key technologies for improving the availability of vegetation data, and consequently the preconditions for scientific analysis and monitoring. The aim of this paper was to investigate how the hands-on application of RS for vegetation analysis has developed in the SSZ by reviewing the scientific literature published between 1975 and 2014. The paper assesses the usages and the users of RS by focusing on four aspects of the material (268 peer-reviewed articles), including publication details (time of publication, scientific discipline of journals and author nationality), geographic information (location of study areas and spatial scale of research), data usage (application of RS systems and procedures for accuracy assessments), and research topic (scientific objective of the research). Three key results were obtained: i) the application of RS to analyze vegetation in the SSZ has increased consistently since 1977 and it seems to become adopted by a growing number of scientific disciplines; ii) the contribution of African authors is low, potentially signalling a need for an increased transfer of knowledge and technology from developed countries; iii) RS has primarily been used to analyze changes in vegetation productivity and broad vegetation types, whereas its use for studying interactions between vegetation and environmental factors has been relatively low. This calls for stronger collaborative RS research that enables the mapping of additional vegetation variables of high relevance for the environmental problems facing the SSZ. Remotely sensed vegetation data are needed at spatial scales that suits the requirements of both research and natural resource management in order to further enhance the usefulness of this technology. [ABSTRACT FROM AUTHOR]

The aspirational goal of a land degradation neutral world, to be realized by reducing the rate of land degradation and increasing the rate of restoration of degraded land, was agreed at the Rio+20 Conference in 2012. This paper evaluates the feasibility of introducing a Land Degradation Neutral (LDN) scheme as an activity of the United Nations Convention to Combat Desertification (UNCCD). It concludes that national and international implementation would involve political, organizational and technological challenges. Monitoring restoration of desertified land by revegetation would be feasible immediately, but monitoring cuts in national rates of desertification would not, because no baseline rates are currently available; national and international scientific capacities to measure desertification are limited; and further scientific knowledge is required to supplement existing knowledge of desertification processes and of land use and land cover change processes generally. This paper therefore suggests introducing an LDN scheme in phases. Phase 1 would focus on restoring degraded lands, improving national land use planning systems, and establishing international and national monitoring capacities. Phase 2 would reduce desertification rates with the help of fully integrated land use planning and monitoring systems. Phase 3 would set a target year for realizing an LDN goal, based on experiences in Phases 1 and 2. All three phases would be informed by accessing existing scientific knowledge, and gaining new knowledge by launching a scientific LDN process that can evolve in parallel with the political process. [ABSTRACT FROM AUTHOR]

Water is a scarce resource in arid regions, and hence water harvesting is critically important in these regions for which many different means are adopted including groundwater and rainwater harvesting. This paper examines the feasibility of rainwater harvesting from roof catchments in arid regions of Australia. For this, ten representative locations in the arid regions of Australia are selected. Also, ten different sizes of rainwater tanks ranging from 5 kL to 50 kL and three different combinations of water uses are considered. A model is developed to simulate the performance of a rainwater harvesting (RWH) system. It is found that the reliability of a RWH system is highly dependent on mean annual rainfall at the location of interest. It is found that a 20 kL tank can provide a reliability of 61%–97% for toilet and laundry use depending on the location within the Australian arid regions. At the current water price, RWH system is not financially viable in the Australian arid regions. The methodology adopted in this paper can be adapted to other similar arid regions of the world. [ABSTRACT FROM AUTHOR]

The qualitative component of the effectiveness of seed dispersal by endozoochory encompasses seed deposition. Neltuma flexuosa , a keystone tree of the Monte biome, is dispersed by several animals and in this paper we aimed to study the qualitative aspect of its dispersal. We studied the effect of the dung of Bos taurus (cow), Equus ferus caballus (horse) and Dolichotis patagonum (mara) on seed germination and growth of N. flexuosa seedlings. We conducted greenhouse experiments using dung or field soil as substrate, under two water regimes: pot capacity and pulsed irrigation; testing manually scarified seeds collected from trees. We observed that the effect of dung on the two key processes of plant regeneration was different and depended on the animal species: it either reduced or did not affect maximum germination, and promoted or did not affect seedling growth, compared to the soil. Horse and mara manure reduced germination, while manure from both domestic animals promoted seedling growth. The water storage capacity, drying rate and nutrient level of the substrates did not directly explain the results obtained. Overall, cow dung appeared as the best microsite for early regeneration of N. flexuosa , while mara manure was the most restrictive for this process. • Dung impacts the quality component of Prosopis flexuosa seed dispersal. • Manure from distinct animals differentially affects early seedling establishment. • Cow dung provides the most favourable microenvironment for plant regeneration. • Mara faeces provides the least favourable microenvironment for germination and growth. [ABSTRACT FROM AUTHOR]

Dust storms are a major cause of central Sonoran Desert weather fatalities. Through back-trajectory analysis of North American Monsoon dust storms in central Sonoran Desert of the United States. This study is specific to central Arizona (USA) from 2009 to 2022 using the HYSPLIT model. Our findings have shown that dust storms originate from southerly or near-southerly regions. The dust storms displaying the highest concentrations of particulates show a preference to originate from the southwest. This coincides with the development of a 500 hPa ridge to the east of the study area. The highest concentration storms' back-trajectories display the lowest heights above the ground. Given their southwestern origin, these storms travel upslope along the seasonally dry river beds of the Gila River and its tributaries. Weaker dust storms originate over a wider area with a shift to a southerly direction. Such origination indicates that weaker dust storms are traveling downslope through the washes and channels of the dry Santa Cruz River. As dust concentrations drop, storm direction drifts east and dust height is suspended higher. This paper highlights the spatial variations in central Arizona dust storms, showing the likeliest paths of the strongest events and assists in identifying aeolian dust origins. • Identification of source regions of dust storms impacting the central Sonoran Desert located in the Arizona region of the Southwestern United States. • Use of the HYSPLIT back trajectory model. • Most large dust storms impacting central Arizona have a southwestern origin, having traveled upslope along the normally-dry Gila River and its tributaries. [ABSTRACT FROM AUTHOR]

There is growing global consensus that assessments of land degradation be conducted at regional or smaller scales. Working at this scale allows for locally relevant environmental and land use conditions to be incorporated into the assessment methodology. In this paper, a recently developed regional approach to assessing land degradation in the Hardeveld bioregion of the Succulent Karoo is applied to the Little Karoo region of this biome. The methodology uses fuzzy classification statistical techniques to combine field data with multiple Sentinel-2A and Landsat vegetation indices, as well as regionally modelled soil variables. The resultant habitat condition archetype map values show strong correlation with field observations of perennial plant and bare soil cover in 96 ground-truthed plots. The archetype map indicates that heavily degraded hotspots of high bare ground cover occur throughout the project region, although there is an overall lower average habitat condition in the western half of the Little Karoo. The mean habitat condition archetype value for the entire project area is 0.54 (standard deviation = 0.13), on a continuous scale where 0 and 1 represent the most degraded and pristine extremes, respectively. Random forest regression analysis of various environmental covariates of degradation indicates a strong relationship between habitat condition and topographic as well as rainfall variables, although the limited accuracy of modelled livestock data may obscure the negative impacts of overgrazing. The 30 m resolution habitat condition archetype map builds upon previous degradation research in the Little Karoo and has the potential to inform future conservation, restoration, and rangeland management decisions. The methodology was successfully transferred to a new region and provides an opportunity to improve reporting on the extent of land degradation across South Africa. • Effective transfer of methodology for regional scale assessment of degradation. • Western Little Karoo has lower habitat condition score than the eastern part. • Topography, rainfall, and land use history influence habitat condition score. • 30 × 30 m habitat condition map can inform sustainable land management decisions. [ABSTRACT FROM AUTHOR]

Abstract: Salinization caused by irrigation mismanagement is a major cause of desertification. Monitoring of land degradation caused by salinization and other processes has been subject to international scientific debates leading to the commitment by global decision-makers to address these threats collectively through the UNCCD. This paper discusses the experience of monitoring land and water degradation in the salinity-prone irrigated arid environments of the Northern Sahara in light of current international scientific developments affecting both conceptual and methodological approaches. The paper integrates a range of simple and accessible methods to achieve a multidisciplinary analysis including remote sensing, use of national research archives, interviews with decision-makers and direct surveys of cultivators. Revised assessments of the extent and ecological processes of salinization emerge from the analysis. As irrigated areas expand globally, the new conceptual and methodological techniques in dryland development science have the potential to enable scientists in affected areas to contribute to global efforts to monitor degradation effects caused by desiccation, salinity and human responses. [Copyright &y& Elsevier]

Abstract: Biofuels are considered as a climate-friendly energy alternative. However, their environmental sustainability is increasingly debated because of land competition with food production, negative carbon balances and impacts on biodiversity. Arid and semi-arid lands have been proposed as a more sustainable alternative without such impacts. In that context this paper evaluates the carbon balance of potential land conversion to Jatropha cultivation, biofuel production and use in arid and semi-arid areas. This evaluation includes the calculation of carbon debt created by these land conversions and calculation of the minimum Jatropha yield necessary to repay the respective carbon debts within 15 or 30 years. The carbon debts caused by conversion of arid and semi-arid lands to Jatropha vary largely as a function of the biomass carbon stocks of the land use types in these regions. Based on global ecosystem carbon mapping, cultivated lands and marginal areas (sparse shrubs, herbaceous and bare areas) show to have similar biomass carbon stocks (on average 4–8 t C ha−1) and together cover a total of 1.79 billion ha. Conversion of these lands might not cause a carbon debt, but still might have a negative impact on other sustainability dimensions (e.g. biodiversity or socio-economics). Jatropha establishment in shrubland (0.75 billion ha) would cause a carbon debt of 24–28 t C ha−1 on average (repayable within 30 year with yield of 3.5–3.9 t seed ha−1 yr−1). Land use change in the 1.15 billion ha of forested area under arid and semi-arid climates could cause a carbon debt between 70 and 118 t C ha−1. This debt requires 8.6–13.9 t seed production ha−1 yr−1 for repayment within 30 years. If repayment is required within 15 years, the necessary minimum yields almost double. Considering that 5 t seed ha−1 yr−1 is the current maximum Jatropha yield, conversion of forests cannot be repaid within one human generation. Repayment of carbon debt from shrubland conversions in 30 years is challenging, but feasible. Repayment in 15 year is currently not attainable. Based on this analysis the paper discusses the carbon mitigation potential of biofuels in arid and semi-arid environments. [Copyright &y& Elsevier]

Abstract: The Namib is a relatively well-studied hyperarid desert. Much of the research effort was coordinated through the institutional framework of the Gobabeb Research and Training Centre, which was established in the middle of this desert fifty years ago. The initial discoveries focused on the Namib''s remarkably high biodiversity and adaptations to desert conditions, analysed against the foundations of research into this desert''s particular climate, geomorphology and geology. The antiquity of this desert, its extreme hyperaridity, and strong climatic gradients provided unusual windows into ecosystem drivers in arid lands, past and present. The Gobabeb Centre itself evolved to translate much of its knowledge into application and is today geared to increase this trend even further, driven by the urgent need for knowledge-based environmental management, such as ecological restoration of mining areas. The current volume collates nine papers which review a cross-section of Namib research, with special focus on projects conducted through Gobabeb. These papers concern different facets of geomorphology where Namib research has led global understanding, reviewed in three papers, and one climatological review of the moisture regime. A review of reptile research illustrates the relationship between biodiversity processes and environmental factors, which is further sharpened in a comparison of dune lizard ecology between continents. The review of botanical research in the Central Namib fittingly binds much of the accumulated knowledge of desert plants into a detailed vegetation map. A review of research on the highly variable ephemeral river systems of the Namib illustrates how academic knowledge accumulated at Gobabeb connects to applied research, which is also the topic of the final paper concerning the knowledge gaps and research needs to provide the information required for ecological restoration. [Copyright &y& Elsevier]

Abstract: This paper argues that soil salinity needs to be more broadly acknowledged as a driving factor in plant ecology—not only in the ecology of halophytes—in order to understand and make more accurate predictions for the impact of environmental change on biodiversity and vegetation patterns throughout the semi-arid world. It summarizes recent research on soil salinity and plant distributions in semi-arid environments throughout the world: there is empirical as well as experimental evidence that soil salinity, even at low levels, is an abiotic stress factor that influences vegetation patterns and diversification. Lines of evidence demonstrating salinity''s potential influence as a selective agent in East Africa and North America are presented. The paper then synthesizes recent results from spatial ecology, plant and insect systematics and behavioral ecology, focusing on Australia, that support a role for salinity in evolutionary ecology of Acacia. On a shorter time scale, soil salinity may play a role in weed invasion and woody vegetation encroachment in Australia. [Copyright &y& Elsevier]

Abstract: Despite the present hyper-aridity, archaeological investigations in South-east Arabia have demonstrated that the region supported extensive human communities throughout the Neolithic and Bronze Age. These early populations utilised the region’s natural environment in a variety of ways, ranging from the exploitation of coastal resources to practicing pastoral and agrarian lifestyles in the interior. Palaeoclimate data suggests the corresponding period was characterised by considerable climatic variability yet, to date, few studies have attempted to investigate the relationship between climate, the environment and early human populations in the region. This paper combines new high-resolution palaeoclimate data from Awafi palaeolake, United Arab Emirates (UAE), with the region’s archaeological record from the Neolithic through to the onset of the Bronze Age. The evidence presented in this paper suggests that the environment of South-east Arabia offered different constraints and opportunities for early human occupation and subsistence. In particular, abrupt phases of aridity are demonstrated to have had a profound impact. Most notable is the change which occurred following the onset of climatic aridity at 5900 cal yr BP, when the region’s semi-nomadic, herder-gatherer populations abandoned much of the landscape and concentrated in selected environmental refugia, such as along the northern Omani coast. Human repopulation during the Bronze Age coincided with a return to more pluvial conditions under which a network of oasis agricultural settlements appeared along the piedmont zone of the northern Hajar Mountains. [Copyright &y& Elsevier]

Abstract: The paper discusses the changing relationship between pastoral nomads and farmers, one of the recurring themes in the history of the arid Near East. In many parts of this region that history has often been characterized in terms of changing cycles of sedentary farming and pastoralism, linked respectively to notions of cultural florescence and collapse. The paper reviews the complex history of cultivation, herding, and industrial activity (copper mining and processing) that has been established for the Wadi Faynan in southern Jordan, a desertic region used today largely by Bedouin herding groups, from the Early Bronze Age to the present day. As recent studies indicate for the Negev region as a whole, it concludes that notions of simplistic cycles in nomad–sedentary relations are unhelpful: historical contingency played a far more important role than the physical landscape and the changes effected to it by climatic shifts over the past 6000 years. [Copyright &y& Elsevier]

More than 50 years after the first comprehensively designed projects, the significance of research on past societies and their interactions with landscapes has even increased: Studying arid landscapes opens many areas of general interest about adapted lifestyles and livelihoods, since aridity touches upon problems of desertification and climate change, decentral water and food security. This synoptical paper sheds light onto the premises, functionalities and questions of water harvesting systems in antiquity and asks about the implications of runoff-based economies and societies in the Old World Dry Belt. By comparing results and considerations of the individual contributions to this special issue on ancient water management in general, and water and soil harvesting in particular and other relevant studies, it aims at extracting commonalities and differences between the interlinkages of environmental conditions and human intervention. Moreover, it embeds the various approaches, methods and results of the special issue's authors into overarching considerations oriented towards achieved results, application-oriented aspects and towards focal open questions. Differential analysis of the studied cases, i.e. systematic evaluation of the differences and similarities increases the understanding of the complex issues of runoff agriculture under various environmental and socio-economic conditions. The relevance of the models of ancient water-harvesting based systems evolved during the last decades for modern challenges is given special regard. • Interdisciplinary research in drylands models ancient resource management and livelihoods on a local and regional scale. • Potentials and dynamics of agro-ecosystems are outlined on basis of ancient water harvesting systems. • Studies of ancient resource management are relevant for actual development, sustainability and resilience objectives. • Comparative and complementary analysis of different studies and regions enhances understanding of issues at question. [ABSTRACT FROM AUTHOR]

In the hyperarid Atacama Desert (Northern Chile), the economic and social development is supported using fossil groundwater. The groundwater extraction (GWE) has significantly increased over the last 30 years, reaching ∼4.2 m3.s−1 in 2018 (+1890%) at the Pampa del Tamarugal Aquifer (PTA). But opposite assumptions lead to uncertainties concerning the role of the increasing anthropogenic pressures and the ephemeral recharge events in the water table (WT) variations. This paper analyzes: (i) the long-term groundwater levels changes between the late 1950s (post Saltpeter Work) and the early 2010s, and (ii) the short-term response of groundwater levels, based on the analysis of the 1998–2018 WT time series at 10 observation boreholes. Results indicate that the WT variations in space and time are strongly related to the anthropogenic pressure changes. Since the late 1950s, the WT is declining in the major part of the PTA. Nevertheless, local reduction of GWE together with ephemeral recharge events in alluvial fans allowed local WT rises. But after a large GWE increase (+114%) between 2004 and 2006, all observation boreholes highlight a general WT decline (−9.8 ± 5.8 cm.yr−1). Over the years, anthropogenic pressures became the dominant factor of the WT variations and led to overuse the aquifer. • Groundwater use has increased 1890% over the last 30 years. • Water table variation in space and time depends on anthropogenic pressure changes. • Water table decline averages ∼10 cm.yr-1 over the 2008–2018 decade. • Recharge events from floods do not outweigh groundwater use increase. • Pampa del Tamarugal Aquifer is overexploited. [ABSTRACT FROM AUTHOR]

This paper presents empirical evidence of historical vegetation and climate change in the arid Pro-Namib and hyper-arid Namib Desert spanning the late 19th century to the present based on one hundred archival landscape photographs that have been re-photographed or 'matched'. Each photo site was evaluated for changes in woody cover and taken together serve as a proxy for how climate has changed in the region. Vegetation change was related to values for precipitation and temperature derived from the Global Land Data Assimilation System for the period 1948–2017 as well as the number of fog days expected at a site. The resulting analysis reveals a trend of increased vegetation cover associated with increased precipitation (fog and rain) in the coastal Fogbelt and the inland Savanna transition with a shrinking of the hyper-arid Minimum zone between the two. These findings accord with projected effects of global warming on the Benguela upwelling system but are at variance with regional climate model forecasts that project widespread aridification. In the absence of long-term climate data, the results of this research are an important contribution of evidence-based knowledge of past climate trends and their relationship to future climate change scenarios for the region. • Global change models predict Namibia becoming hotter leading to aridification. • We used historical photos of the Pro-Namib and Namib Desert to test this forecast. • Correlations between historical climate values and vegetation change were analysed. • Contrary to expectations, woody plant cover has increased at most locations. • Past trends of increased rainfall and fog predict environmental futures. [ABSTRACT FROM AUTHOR]

Abstract Over the last 30 years, geoarchaeological surveys undertaken in the Near East have offered a powerful way of studying, inter alia, water supply systems at a microregional to regional scale. However, efforts to synthesize the results of surveys at a sub-continental scale in order to understand local differences and similarities, and compare local strategies through time, require specific tools. In this paper, we develop a methodology designed to characterize and facilitate comparison of strategies employed across the arid areas of Western Syria. This requires microregional field studies undertaken at the level of specific landscapes to be integrated within a wider GIS framework, based upon thematic layers (soils, rainfalls, hydrology) at a uniform spatial scale of assessment (in this case the pixel of a Landsat image), and a common description of the agronomic potential in those areas in which specific hydraulic installations were employed. In contrast to the usual practice of modelling, which depends upon the downscaling of environmental data (land cover, rainfall maps) generated at a continental scale, we stress here the need to generalize upwards, from observations made at the microregional level, by using common descriptors and qualitative indicators. The GIS analysis of these data provides a weighted average model derived from field evidence for the different technical choices made (i.e. the decision to utilize specific water management devices) in relation to the various agronomic landscapes. Highlights • Long term history of Syrian arid steppic landscapes enlighted by water mastering techniques • Modelling spatial location of past water management devices in arid areas • Modelling the regional agronomic potential in Near East arid areas [ABSTRACT FROM AUTHOR]

Abstract This paper presents the estimates of nitrogen and phosphorus loads associated with different land uses in a semi-arid watershed in the Brazilian northeast (NE). To calculate the annual loads and calibrate de estimates, we used emission factors related to natural processes and human activities from land uses and monitored the nutrient concentrations in surficial waters. The concentrations of TN were above the 2.18 mg N L−1 limit for lotic environments while the TP exceeded the limit value of 0.15 mg P L−1 established in the Brazilian legislation. The total loads L e N , P corresponded to 16,621 t N yr−1 and 3,211 t P yr−1 or 1,292 t N km−2 yr−1 and 250 t P km−2 yr−1. The anthropogenic emissions accounted for 82.1% of the N and 91.3% of the P emitted. The results for the Salgado river basin are lower than those estimated globally, but exceed the values obtained for the South American continent in an order of magnitude. The use of nutrient loads instead of concentrations, particularly in areas where detailed studies on nutrient concentrations are unavailable, such as in the semi-arid NE Brazil, may become a satisfactory approach to evaluate the sensitivity of aquatic systems to a further introduction of anthropogenic effluents. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract This paper explores an original approach in which greenhouse gas (GHG) emissions and carbon (C) accumulation are assessed monthly and at landscape scale to account for the highly seasonal monsoon climate and the mobility of pastoral herds that characterize West African pastoral ecosystems. The study was conducted in northern Senegal, in the service area of the Widou Thiengoly borehole, a circular zone of 706 km2 centered on the borehole. The C balance was calculated using an ecosystem approach, i.e. taking all main sources of GHG emissions and C sinks of the ecosystem, not only anthropogenic sources, into account. The annual C balance of the pastoral ecosystem was −0.04 ± 0.01 tC-eq.ha−1.year−1, showing that total GHG emissions were mitigated by C accumulation in trees, soil and livestock. The C balance varied considerably with the seasons, with a positive monthly balance in the wet season, from July to October (+0.58 tC-eq.ha−1.month−1) and a negative monthly balance in the cold dry season from November to February and the hot dry season from March to June (−0.57 and −0.05 tC-eq.ha−1.month−1 respectively). Care should be taken when generalizing these results, which were obtained in a dry year, because of strong inter-annual variations in rainfall. Highlights • Sahelian rangeland ecosystems have a neutral carbon balance. • Accumulation of carbon and greenhouse gas emissions vary strongly between seasons. • The main source of greenhouse gas emissions is livestock. • The main carbon sinks are trees and soils. • Seasonality is explained by both rainfall patterns and pastoral practices. [ABSTRACT FROM AUTHOR]

Abstract MARAS (Monitoring of Arid and Semiarid Regions) consists of 379 ground monitors in Patagonia, a 624.500 km2 semiarid area of southern Argentina and Chile. The objective of this paper was to describe the system and analyze four variables of the initial data base. Floristic composition, diversity and cover were analyzed with intercept lines (500 points). Patches (resource-sinks areas) and Interpatches (areas that loose resources) were described using Gap intercept lines (50 m). Eleven Landscape Functional Analysis indicators were recorded in 10 interpatches: Soil stability, Infiltration and Nutrient cycling. Vegetation Cover was 43 ± 2%, Richness 15 ± 7 species/monitor, Interpatch Size 154 ± 134 cm and LFA Stability Index 46 ± 1%. Cover, Richness and Stability maps had bimodal distribution and maximum in S and NE areas, following rainfall gradients. Variability analysis shows that cover estimations are within 5% error at site and regional scales. Graphical analysis of single monitors shows observational biases in interpatch size and LFA Stability index. Richness estimations correlate significantly with α diversity (R2 = 0.80). Analysis of 5-year change in 115 monitors shows significant reductions in cover and interpatch length, especially N of the region. These base line evaluations enable analysis of future changes that were not possible with multiple techniques and isolated data bases. Highlights • 379 ground monitors of vegetation and soil were installed in Patagonia. • Six teams in two countries shared a single protocol and data base. • Errors of estimations at site and regional scales are acceptable. • Contour maps of main variables show gradients associated to aridity. • This baseline enables future change evaluation. [ABSTRACT FROM AUTHOR]

Abstract: Southern Spain’s semi-arid habitats are a Mediterranean ecosystem modelled mainly by historic factors which make them unique in comparison with North African deserts. Southern Spanish vertebrates have adapted to the recent emergence of semi-arid habitats in varying degrees of success. This paper reviews the current status of these terrestrial vertebrates (amphibians, reptiles, birds and mammals), their origins and their main features in relation to this biogeographic area. The vertebrate fauna of the semi-arid southeast of the Iberian peninsula differs widely from the one in the semi-arid Maghreb mainly because the former is composed by generalist vertebrates and much less so by species adapted to arid conditions. Moreover, a large fraction of the vertebrates in the semi-arid Iberia does not exploit the semi-arid areas but depends on riparian and human-managed habitats. The species diversity is rather low since only a small fraction of Palaearctic, European or Mediterranean species can adapt to the ecological limitations imposed by aridity and dwell in these semi-arid habitats. Such adaptations comprehend features like trophic plasticity, low morphological specialization, high dispersal ability, shortened life cycles and behavioural mechanisms to exploit the limited resources available. This paper identifies major conservation issues and proposes specific courses of action. [Copyright &y& Elsevier]

Abstract: To date, the interpretation of remote sensing images has not revealed wide-spread degradation of the vegetation in the Sahel. However, the interpretation of spectral information depends on a range of assumptions regarding the dynamics of the Sahelian vegetation as a function of rainfall variability and human management. Recent papers have presented diverging views on the vegetation dynamics of the Sahel and how these can be analysed with remote sensing images. We present a further analysis of the vegetation dynamics of semi-arid rangelands, in particular the Sahel, and the subsequent implications for the interpretation of remote sensing images. Specifically, the ecological processes driving the response of the Sahelian vegetation to rainfall variation are re-examined, and a regression analysis of NPP versus rainfall data is carried out. It is shown that the relation between the interannual variation in NPP and rainfall in the Sahel is non-linear and that this relation differs between sites with different average annual rainfall. It has been common practise in remote sensing studies for the Sahel to aggregate data from various Sahelian sites in order to obtain an average relation between rainfall, NPP and Rain Use Efficiency, and to assume these relations to be linear. This paper shows that this approach may lead to a bias in the interpretation of remote sensing images and that further work is required to clarify if wide-spread ecosystem degradation has occurred in the Sahel. [Copyright &y& Elsevier]

Abstract Past water resource developments in dryland regions rarely estimated the full suite of environmental and social impacts arising from damming and diverting water for food production. Nowadays there is a greater focus on sustainable resource development which considers the economic, social and environmental costs and benefits. A challenge is to apply tools and methods which can capture the often disparate knowledge and data describing many costs and benefits. This paper describes a proof of concept application of a large Bayesian Decision Net to estimate the total utility of water resource development according to criteria of social, economic and environmental sustainability. We focus on two water-scarce catchments in remote northern Australia which are under investigation for development. The study catchments contain a diverse set of ecosystem services and socio-cultural values, including important Indigenous values and high value freshwater ecosystems. The Bayesian Decision Net was shown to have many properties that made it useful for performing a social, economic and environmental sustainability assessment, in particular its ease of construction; its ability to handle quantitative and qualitative data types; its preservation of system knowledge and; its ease of use in aiding decision making. From the perspective of the sustainability assessment in our case study, the total utility of water resource development for new irrigation is negative in both the studied catchments. The overall utility of water resource development could be positive if irrigation development is highly sensitive to the environment and there are very low environmental impacts, and much higher net economic returns to irrigators eventuate, possibly through higher commodity prices, lower capital costs of irrigation development or some combination of both. Highlights • Development of water resources involves trade-offs between economy and environment. • Integrated social-environment-economy sustainability (SEES) assessments support trade-offs analyses. • Bayesian Decision Networks (BDNs) support SEES assessments with diverse data types. • BDN applied to irrigation development scenarios of two remote catchments in north Australia. • The economic and ecosystem service benefits of the case study irrigation developments are questionable. [ABSTRACT FROM AUTHOR]

Abstract: Concern about climate and its impact on human populations in the Sahel since the 1970s was an immediate response to the most recent of recurrent drought periods. Understanding the relative impact of this drought on rural life in the Sahel is, however, not straightforward. This is due to the fact that climate is only one of many factors influencing local adaptation strategies to environmental changes. Another explanation could be that climate in many rural communities in the Sahel is simply no longer the primary worry. The argument presented in this paper, supported by data from a small village in northern Burkina Faso, is that the villagers there are ‘beyond climate’ as their current livelihood strategies are increasingly climate independent. People have over the past decades engaged in livelihood diversification in order to negate the negative impact of climate variability on agriculture. In order to analyse the temporal perspective of climate–livelihood interaction, the paper employs human–environmental timelines. The results document the multiplicity of exposures shaping decisions in the village. While significant correlation exists between recent livelihood diversifications and major climatic events, it is equally obvious that recent political developments and the economic flow of project activities are crucial factors of change. [Copyright &y& Elsevier]

Abstract: During the United Nations General Assembly''s 58th Ordinary Session in 2003, a decision was adopted declaring 2006 the International Year of Deserts and Desertification (IYDD). This paper critically reviews this International Year. It draws on the key outputs from IYDD events from across the globe to highlight the challenges and ways forward in both combating desertification and implementing the United Nations Convention to Combat Desertification (UNCCD). The paper considers what the IYDD outputs mean for the current and historical controversies surrounding the desertification issue and presents an overall evaluation of the successes of IYDD for the different stakeholder groups within the desertification regime. It is concluded that while the International Year can be considered to have met the United Nations''s four objectives: to address the long-term oriented implementation of the UNCCD; raise awareness of the implications of desertification; facilitate networking with all stakeholders; and disseminate information relating to the UNCCD, the real challenge lies in moving the IYDD outcomes away from the conferences, meetings and networks that contributed to their generation, towards a more concrete, tangible effort to conserve deserts and effectively monitor and control desertification and land degradation on the ground. [Copyright &y& Elsevier]

Abstract: This is the first of two papers that describe the surface hydrology of the Lake Eyre Basin (LEB) (1,140,000km2) in central Australia and compares some key characteristics with those observed from arid regions globally. This paper concentrates on annual rainfall, whereas the second paper is devoted to streamflow. The first part describes the LEB''s climate (arid to semi-arid), which is dominated by a subtropical high pressure ridge stretching latitudinally across central Australia. Then follow major analyses that include the characteristics of rainfall, wet and dry spell lengths and cumulative surpluses and deficiencies, rainfall trends and intra- and inter-decadal fluctuations, and the relationship between rainfall and El Niño-Southern Oscillation (ENSO). The paper concludes with six conclusions, the key ones being: the variability of the annual rainfall (based on the coefficient of variation) in the LEB is approximately 60% greater than that found for stations located in arid regions in the rest of the world; there is a bias towards longer lengths of dry years than observed in the rest of Australia; and, there is a significant lag correlation between rainfall and ENSO, particularly in the east and in the latter part of a year. [Copyright &y& Elsevier]

Abstract: This is the second of two papers examining the surface hydrology of the Lake Eyre Basin (LEB) (1,140,000km2) in Australia. The streams are unregulated and are characterised by extreme discharge variation. The analyses reported cover only surface hydrology and include comparisons with arid zone catchments globally. The paper discusses spatial runoff and annual streamflow characteristics, flow duration and baseflow index (BFI) analyses, annual flood frequency analysis and flood transmission losses, a water balance study, wet and dry run length analysis and, finally, yield from hypothetical reservoirs located across the LEB. There are 12 conclusions listed at the end of the paper. We identify two highlights as follows: [•] The coefficient of variation of annual flows, Cv, varies from 0.98 to 2.62. Compared with 45 arid zone rivers world-wide excluding Australian rivers, the annual Cv of the LEB streams are approximately double the average variability found world-wide. [•] Large transmission losses occur as flood flows move down the middle reaches of the major river systems. The transmission losses vary non-linearly with flood size as a result of differing transmission efficiencies between primary channels and the floodplain, and varying floodplain utilisation. [Copyright &y& Elsevier]

Abstract: Riparian evapotranspiration (ET) is a major component of the surface and subsurface water balance for many semiarid watersheds. Measurement or model-based estimates of ET are often made on a local scale, but spatially distributed estimates are needed to determine ET over catchments. In this paper, we document the ET that was quantified over 3 years using eddy covariance for three riparian ecosystems along the Upper San Pedro River of southeastern Arizona, USA, and we use a water balance equation to determine annual groundwater use. Riparian evapotranspiration and groundwater use for the watershed were then determined by using a calibrated, empirical model that uses 16-day, 250–1000m remote-sensing products for the years of 2001–2005. The inputs for the model were derived entirely from the NASA MODIS sensor and consisted of the Enhanced Vegetation Index and land surface temperature. The scaling model was validated using subsets of the entire dataset (omitting different sites or years) and its capable performance for well-watered sites (MAD=0.32mmday−1, R 2=0.93) gave us confidence in using it to determine ET over the watershed. Three years of eddy covariance data for the riparian sites reveal that ET and groundwater use increased as woody plant density increased. Groundwater use was less variable at the woodland site, which had the greatest density of phreatophytes. Annual riparian groundwater use within the watershed was nearly constant over the study period despite an on-going drought. For the San Pedro alone, the amounts determined in this paper are within the range of most recently reported values that were derived using an entirely different approach. However, because of our larger estimates for groundwater use for the main tributary of the San Pedro, the watershed totals were higher. The approach presented here can provide riparian ET and groundwater use amounts that reflect real natural variability in phreatophyte withdrawals and improve the accuracy of a watershed''s water budget. [Copyright &y& Elsevier]

Abstract: Buffel grass (Cenchrus ciliaris) is one of the preferred species for revegetation of railway embankment steep slopes (batters) in Central Queensland, Australia. Its seed germination is inherently poor and becomes unpredictable, especially in semi-arid regions characterized by low rainfall, due to its extended period of dormancy. Thus its use for railway batters erosion control becomes a major concern where the development of good grass cover within a short time is required to minimize the risk of damage from storms. The effects of different germination media, and concentrations and soaking duration of sulphuric acid (H2SO4) on seed germination were evaluated. Final seed germination without treatment was only 18%, 15% and 12% in the potting mix, heavy clay soil and Petri dish, respectively. Final germination percentage and velocity of germination was significantly greater with potting mix, followed by clay and paper towelling. Similarly, days to first germination, final germination and mean time to germination (MTG) were significantly earlier for potting mix, followed by clay and paper towelling. Seed germination was highest (94%) on 4min of soaking with concentrated H2SO4, and declined with extended soaking reaching to a lethal duration after 10min. Seed germination was lower with lower concentration of the acid. Increasing acid concentration enhanced first germination, shorter duration for final germination and shorter MTG. At lower concentration also, increasing soaking duration beyond 20min reduced final seed germination. Concentrated H2SO4 treatment may be employed for improving buffel seed germination provided safety issues for bulk handling are addressed. [Copyright &y& Elsevier]

Abstract: This paper introduces the Special Issue on Sustainable Land Use in Namaqualand which arose out of a conference held in the region in May 2005. It outlines the main themes and issues covered by 19 papers within an increasingly interdisciplinary debate on land use in this semi-arid region. The first theme describes the unique environmental, historical and social context for understanding current land-use practices in the region. The point is made that it is difficult to discuss the issue of land use outside of these contexts which are themselves strongly influenced by national and international events. The second theme addresses land use and its long-term impact on the biota, production systems and restoration potential of the region. A dual land tenure system of private and communal ownership, which is rooted in South Africa''s colonial and apartheid past, has profoundly influenced the way in which the land is used as well as the way in which benefits have been derived from agricultural production by different sectors of the population. The dynamic and complex nature of these practices and how strongly influenced they are by local circumstances is an important element in the contributions. The third main theme investigates the progress of South Africa''s post-apartheid land reform programme in the region. The slow pace of reform as well as the difficulty of finding a solution which benefits the most marginalised groups within Namaqualand society is highlighted. A final paper synthesises the debate and emphasises the rapid pace of change brought about by several important biophysical and socioeconomic events of the last century. An understanding of the pathways of change as well as their uncertainties forms an important part of this final synthesis. [Copyright &y& Elsevier]

Abstract: Southern South America (SSA) has today a high diversity of climates, environments, biomes, and biotas, as a result of the complex interaction through time of plants and animals with the geological forces (e.g. plate tectonics, sea-level changes, glaciations) that modulated the geography of the continent. Arid biomes are well represented in SSA today, but were arid biomes similarly important in the geologic past? How long in time can be found major arid biomes in SSA? With the aim of replaying these questions, in this paper we summarized the paleoenvironmental changes of SSA through Cenozoic, emphasizing the relationships between biomes and the geological forces that, through different climatic-environmental factors, have driven its evolution. We define SSA the south of the 15°S area. We prefer this geographical delimitation because with it we can see and follow the history of the biogeographic (historic and ecologic) relationships of Patagonian biota with the rest of the South American biota. Additionally, with this delimitation we possess the most complete Cenozoic South American land-mammal fossil record. We use biomes because biomes are taxon-free analytical units, and their pattern of change can be traced through time independently of the taxa present at different geological periods. Data on plate tectonics, volcanism, sea-level changes, marine paleotemperatures, and glaciations were taken from literature. To analyse the pattern of change of southern South American climates and environments through the Cenozoic, we used the fossil record of land-mammals as information source. When available, the record of vascular plants were used to contrast the inferences derived from land-mammals. Finally, we used standard geologic divisions (i.e. Epochs) as chronological units. The main conclusion of this paper is that from Early Paleocene to Late Pleistocene, southern South American climatic conditions changed from warm, wet, and non-seasonal, to colder, dryer, and seasonal. Concomitantly, biomes changed from tropical forest to steppes, across a sequence constituted by subtropical forests, woodland savanna, park-savanna, and grassland savanna. During the Quaternary, and as a consequence of glacial cycles, cold and dry conditions were interrupted by warmer and wet periods. Accordingly, several pulses of expansion and retraction of steppes (and, concomitantly, advances and retreats of the northern tropical forests) are recorded. This cyclic pattern of changes produced the provincialism that has characterized the South American biota from Early Pleistocene to the present. [Copyright &y& Elsevier]

Abstract: We discuss a new conceptual framework for arid and semi-arid systems that accounts for nonlinear dynamics and cross scale interactions in explaining landscape patterns and dynamics. Our framework includes a spatial and temporal hierarchy, and five key interacting components that connect scales of the hierarchy and generate threshold behaviors: (1) historical legacies that include climate, disturbance, and management regimes, (2) dynamic template of patterns in ecological variables and spatial context, (3) vertical and horizontal transport processes (fluvial, aeolian, animal), (4) rate, direction, and amount of resource redistribution between high and low resource areas, and (5) feedbacks among plants, animals, and soils. We illustrate how this framework can be used to understand, forecast, and manage ecological systems that exhibit nonlinear dynamics across a range of spatial and temporal scales. This paper provides the foundation for a series of papers from the Jornada Experimental Range ARS-LTER research site in southern New Mexico, USA that support this new conceptual framework. [Copyright &y& Elsevier]

Abstract: The impacts of grazing pressure and rainfall variability on rangeland dynamics have been the topic of much debate. Understanding the combined impact of these two factors is crucial for the development of efficient management strategies for rangelands. In this paper, the impacts of grazing and rainfall variability on the dynamics of a Sahelian rangeland in Northern Senegal are examined. Specifically, the paper assesses their combined impact on species composition, above-ground phytomass production and rain-use efficiency (RUE), on the basis of a 10-year (1981–1990) grazing experiment conducted in the Widou-Thiengoly catchment in the Ferlo, Northern Senegal. The experiment included both a high (0.15–0.20TLUha−1, corresponding to current grazing) and a medium (0.10TLUha−1) grazing pressure. It is shown that species composition, above-ground phytomass production and RUE markedly differ for these two grazing regimes—and that the differences are most pronounced in years with low rainfall. In dry years, both above-ground phytomass production and RUE are significantly reduced in the plots subject to a high grazing pressure. Consequently, the impacts of high grazing pressures on the productivity of the Ferlo are hardly noticed during years with normal or above normal rainfall, but the rangeland''s productivity is strongly affected during a drought. The findings have important implications for the management of rangelands; they indicate that high grazing pressures may increase the vulnerability of rangeland ecosystems and local people to droughts. [Copyright &y& Elsevier]

This paper presents the results of a multi-scale investigation of environmental change in the Old Peanut Basin of Senegal throughout the 20th century. Based on historical accounts, ethnographies, aerial photos, satellite images, field and household surveys as well as various participatory research activities with farmers in selected villages, the study attempts to make explicit layered scales of analysis, both temporally and spatially. It shows that, despite some general trends of resource degradation in the Old Peanut Basin, local farming systems have embarked on different pathways of change to adapt to their evolving environment. It also illustrates that high diversity with respect to soil fertility management exists at the farm and household level. Finally, the paper proposes a farmer-oriented approach to carbon sequestration in order to integrate recommended technical options more efficiently into the complex and dynamic livelihoods of smallholders in dryland environments. This approach includes pathway-specific land use and management options at the level of farming systems and, at the level of individual households, a basket of possible practices from which farmers can choose depending on their multiple needs, capacities, and adaptive strategies to cope with risk and uncertainty. [Copyright &y& Elsevier]

The Kalahari ecosystem is characterized by natural resource conflicts and land-use pressure resulting from intensification of human activities. This paper addresses three issues of concern associated with the Kalahari ecosystem resource management: (i) the major land-use/land cover shifts in the Kalahari ecosystem since 1970 and the resulting pattern in vegetation species composition, cover and density; (ii) the possible explanations for the observed shifts; and (iii) the possible resource conflicts likely to arise.Data collection involved the comparison of two sets of panchromatic photographs along two transects (Hukunsti–Ngwatle and Tshane–Tsabong) to study land-use/cover shifts that have occurred in the Kalahari ecosystem between 1971 and 1986. Secondly, the nature of possible conflicts resulting from population pressure and associated patterns of land-use was investigated by making observations on selected environmental variables along a 300km transect with diverse environments comprising different-sized settlements, vegetation communities and land-uses.Land-use/land cover shifts have occurred within the Kalahari ecosystem as evidenced by the two transects analysed in this paper. The main changes are the retreat of grass cover up to 18kms from settlements and the increase in thorny and non-thorny woody encroachers closer to the settlements. In the Matsheng area, land-use/land cover gradients reflect marked differences in human pressure. For instance, while settlements (kraals/households) and fields around Tshane (smaller and dwindling settlement) have declined to 5% at the 4km distance in 1986, these land-uses account for 22·3% of land cover at 4km around Hukuntsi (bigger and expanding village).Five major vegetation communities were identified using key plant species during the dry season. However, these communities do not have distinct land-use activities associated with them. Cattle densities were higher in communities found far away from settlements and water points where the grass cover was abundant. Cattle graze far from settlements to obtain quality fodder and trek to the water points around village pans or at cattle posts.There are no definite boundaries between vegetation communities and land-use activities, hence a lot of interaction between activities of these zones depends on the dispersion of resources. Shifts in land-use/cover changes can be accounted for by anthropogenic activities (arable agriculture, livestock grazing and human settlements) enhanced by natural factors like seasonal variations and prolonged droughts of the mid-1980s. It is argued in this paper that potential remedial measures include biosphere conservation areas, resource zoning and resource modeling plans to determine land suitability. [Copyright &y& Elsevier]

This is a keynote paper focusing on regional perspectives on agriculture and biodiversity by exploring the situation in Northern Africa, the West African Sahel, East Africa and the Horn, and Southern Africa. The paper establishes that in all these regions agriculture accelerates loss of biodiversity because of attempts by farmers to increase crop and animal production to feed the increasing population and contribute to the growth of the national economies. Harmful agricultural practices, such as overcultivation, overgrazing, bush fires, cultivation of marginal and easily eroded land, mechanization and the widespread use of chemicals and pesticides, have intensified the degradation of the soil and vegetation and led to rapid decline of species types and their numbers. Agriculture and biodiversity can be complementary activities. If properly managed, agriculture should enhance and not be the enemy of biodiversity in the drylands of Africa. There is need to assess the agricultural potential of the semi-arid environments and develop specific agricultural policies or programmes to enhance their sustainable utilization and conservation of biodiversity. Information contained in this paper was gathered from the existing literature [Copyright &y& Elsevier]

With their modest rainfall, arid regions are characterized by relatively fewer species than the better-watered biomes. But this makes it all the more important that the biodiversity that is present in arid environments be given even higher priority; for each species lost from an arid region, the percentage of loss for the region''s biodiversity is much higher than in more species-rich regions. And some species, such as bees and ants, are particularly diverse in arid habitats. Realizing the importance of biodiversity in the arid regions where they live, local people have devised numerous ways of limiting their impact. Historically, such regions have been especially subject to changes in climate, which affect productivity; these changes have often been accompanied by conflicts. The paper will describe these from various parts of the arid world, as a basis for comparison. The paper will also examine economic issues relating to biodiversity in arid lands, focusing especially on the relationship between biodiversity and various kinds of development projects. The major challenges in implementing the Convention on Biological Diversity (CBD) in arid lands lie not so much in the biology of the species concerned, but rather in the social, economic, and political arenas within which people operate. We need to build a broader constituency for conserving biodiversity, extend the responsibility for conserving biodiversity far beyond government, bring local people into the conservation movement, ensure that sufficient information is available to those who need it, restore degraded ecosystems, and stimulate far greater public support for biodiversity. [Copyright &y& Elsevier]

With conservation of biological diversity depending as much on socioeconomic as on biological processes, this paper stresses the importance of clear policy objectives to guide strategies for preserving biological diversity. The first requirement is to define the essential elements and socioeconomic importance of biological diversity, so that these can be accommodated adequately in a national programme for sustainable rural development.Efficient application of this programme requires that its goals be clearly enunciated in national policy. There should also be maximum political support for its effective sociopolitically, economically and ecologically rationalised implementation by an accountable authority through a conducive institutional framework. Experience suggests that proprietorship and price are prime elements that need to be reconciled in such a framework of positive and negative incentives to individuals, to mitigate the opportunity costs and encourage the conservation of biodiversity. The present paper considers how these institutional requirements may be met, with particular reference to the special characteristics found in arid areas. [Copyright &y& Elsevier]

In the Sahel region, drought is of serious concern due to its consequences on the livelihoods of the populations. In this paper, opportunities for proactive drought policies are analyzed with qualitative techniques using a series of semi-structured qualitative interviews with key experts from the public, private, and other relevant societal sectors. The results show that adaptation options such as sustainable agricultural practices, migration, diversification of income sources, and social networks are most frequently used as a drought response by rural households in the region. To build resilience to drought in the Sahel, there is a need to disseminate climate-friendly agricultural practices accompanied by strong monitoring and evaluation system. It is also important to provide information on early drought warning and preparedness and mobilize more financial resources in implementing policies for building drought resilience. Finally, a drought policy should be participatory and results-based, and be based on long-term forecasting to ensure sustainability and resilience. • Proactive measures are advised in building resilience to drought. • The involvement of all stakeholders is necessary for building resilience to drought. • Failure of early warning and preparedness are constraints for any drought policy. • Lack of financial support negatively affects drought policy implementation. [ABSTRACT FROM AUTHOR]

Trees in agroforestry parklands influence crops both through competitive and facilitative mechanism, but the effects are challenging to disentangle due to the complexity of the system with high variability in tree cover structure and species diversity and crop combinations. Focusing on a landscape in central Burkina Faso dominated by Vitellaria paradoxa and Parkia biglobosa , this paper examines how tree cover influences crop yield at landscape scale using satellite data and spatial statistics. Our analysis is based on data from 2017 to 2018 with differences in rainfall to assess the stability in identified relationships. Our findings showed that tree canopy cover and tree density inside the fields tended to decrease crop yield because of competition, but also that these variables when considering the surrounding landscape exerted an opposite effect because of their buffering effects. The explanatory variables representing soil properties did have limited effects on crop yield in this study. These patterns were consistent during the two years of monitoring. Overall, our results suggest that farmers in this area might manage the tree cover in a way that optimizes sustainable yields as canopy cover and tree density in most parklands is below the limits identified here where competition outweight the facilitative effects. • We studied causes of crop yield variability in parklands at landscape scale. • Satellite remote sensing and field data was used in spatial statistics. • Trees in agricultural fields tend to reduce crop yield through resource competition. • Surrounding trees had positive influence on crop yield via buffering effects. • Fewer large trees have more positive influence on crop yield than many small ones. [ABSTRACT FROM AUTHOR]

The Nubian Flapshell Turtle, Cyclanorbis elegans , is classified as one of the most threatened chelonian species globally (Critically Endangered according to the IUCN Red List). The species is presumed extinct in most of its historical distribution range, but still survives along the White Nile between South Sudan and northern Uganda. In this paper, we utilised the maximum entropy model (MaxEnt) to evaluate the habitat suitability of the species to explore its distribution decline by comparing historical and current presence data, as well as correlate the predicted past and present distribution with human population density. Our assumption is that overexploitation of the turtle occurs (and has occurred in the past) in sites with high human density. We show that: (1) a large number of historical sites where the turtle was present had high human population densities, whereas (2) the current distribution model showed low overlap between areas with high probability of turtle presence and high human population density. We suggest that Nubian flapshells are likely to have become extinct because of high human density (and therefore high overexploitation) and remnant populations have only survived along waterbodies with low numbers of people. However, the presence sites of this species in northern Uganda are under pressure by rapidly growing refugees'settlements. We also hypothesize that the range of the Nubian Flapshell may be shifting to the south (where the general environment is wetter and cooler) due to climate change affecting the distribution of this freshwater species. The conservation implications of these evidence are also presented. • The Nubian flapshell turtle is one of the most threatened reptile species in the world. • A spatial modelling approach revealed intriguing extinction patterns across Africa. • There was an association between historical sites of presence and high density of humans (hence fishers). • There i san association between current remnant presence sites and low human density. • Refugees' settlements represent a serious torea for turtles in northern Uganda. [ABSTRACT FROM AUTHOR]