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Er wordt verslag gedaan van 3 jaar milieubeleidsanalyse voor de milieubalans, met nadruk op de onderbouwing van de in MB95, MB96 en MB97 getrokken conclusies. Samen met de RUU en CSTM zijn kwantitatieve en kwalitatieve methoden ontwikkeld. Aan de hand van een instrumententheorie van Glasbergen is een inventarisatie en karakterisering van beleidsinstrumenten uitgevoerd. De beleidsmixen zijn geanalyseerd per doelgroep en per thema. In de vergelijkende beleidsanalyse zijn voor een groot aantal kwantitatieve en meer kwalitatieve factoren tijdseries opgesteld voor 44 cases (doelgroep-stof-combinaties) over de periode tussen 1970 en 1995. Met behulp van het zo opgebouwde gegevensbestand was het mogelijk kwantitatieve relaties te leggen tussen de beleidsimpuls, maatschappelijke aandacht, kosten van maatregelen enerzijds en de emissiefactor anderzijds. Inzicht is verkregen in het verloop en de duur van beleidsprocessen en het effect van het aandeel juridische, financiele en communicatieve instrumenten in de beleidsmix. Een aparte analyse is gewijd aan de milieu-convenanten en meerjarenafspraken over energie met de industrie.

A catchment-scale mass-balance model of linked carbon and nitrogen cycling in ecosystems has been developed for simulating leaching losses of inorganic nitrogen. The model (MERLIN) considers linked biotic and abiotic processes affecting the cycling and storage of nitrogen. The model is aggregated in space and time and contains compartments intended to be observable and/or interpretable at the plot or catchment scale. The structure of the model includes the inorganic soil, a plant compartment and two soil organic compartments. Fluxes in and out of the ecosystem and between compartments are regulated by atmospheric deposition, hydrological discharge, plant uptake, litter production, wood production, microbial immobilization, mineralization, nitrification, and denitrification. Nitrogen fluxes are controlled by carbon productivity, the C:N ratios of organic compartments and inorganic nitrogen in soil solution. Inputs required are: 1) temporal sequences of carbon fluxes and pools- 2) time series of hydrological discharge through the soils, 3) historical and current external sources of inorganic nitrogen; 4) current amounts of nitrogen in the plant and soil organic compartments; 5) constants specifying the nitrogen uptake and immobilization characteristics of the plant and soil organic compartments; and 6) soil characteristics such as depth, porosity, bulk density, and anion/cation exchange constants. Outputs include: 1) concentrations and fluxes of NO3 and NH4 in soil solution and runoff; 2) total nitrogen contents of the organic and inorganic compartments; 3) C:N ratios of the aggregated plant and soil organic compartments; and 4) rates of nitrogen uptake and immobilization and nitrogen mineralization. The behaviour of the model is assessed for a combination of land-use change and nitrogen deposition scenarios in a series of speculative simulations. The results of the simulations are in broad agreement with observed and hypothesized behaviour of nitrogen dynamics in growing forests receiving nitrogen deposition.

The future of transport, whatever it will be, cannot be consideredseparately from that of cities. But what, where and whenis the city today? The ability to provide opportunities for humaninteraction is the essential reason for cities to exist. In thepre-industrial past this required high-density, compact urbanforms. Modem transport and communication techniques havehowever increasingly offered human beings ways of interactingat a distance. Physical proximity is no longer needed by manytypes of urban activities. As a result, cities have decentralised,as industry first, then residences and services have fled the diseconomiesof high-density agglomerations. For the future,some even predict the advent of an entirely diffuse, 'virtual' city.Actual evidence is at best mixed. Next to ongoing decentralisation,there are also signals that point in the opposite direction,as there are activities that show a tendency to physicallyconcentrate, underscoring a persistent need for physical humaninteraction. These activities include business and financial services,the emerging sectors of culture, entertainment and themedia, but also certain types of residences and of production.As a result, rather than decentralisation or concentration, contemporarycities show a complex combination of decentralisationand concentration.How will these contrasting movements shape the cities ofthe future? Are telecommunication technologies going to radicallyalter current trends? Or will the quest for sustainability dothis? And what will the role of transp01tation- as cause and effect-be? The diffuse urban-regional accessibility warranted bythe car and the inter-metropolitan connections provided by theaeroplane have been essential conditions for the urbanisationpatterns of the recent past. But will the car and the aeroplanealso be the transportation means of the cities of the future?

Suburbanisation by families with children can be considered as a dominant factor in determining the structure of a city's population. However, due to urban restructuring programmes, a modest counter process can be observed. Some families who could afford to buy a house in the suburbs decide instead to stay in the central areas of the city. In so doing, they form a relatively new category of gentrifiers: middle-class families with children. In this paper, they are identified as 'yupps': young urban professional parents. They combine the next step in their life cycle—having children—with continuing their career and their preference for an urban lifestyle. The Amsterdam study, reported here, gives some insight in the personal characteristics of yupps, their motivations to live centrally, their activity patterns and constraints. An analysis of their daily lives reveals the significance of the neighbourhood as a crucial factor in the daily integration of such contrasting demands as building a career, caring for children and keeping up with cultural pursuits and social contacts. It is further argued that—in a class-specific context-changing gender relations lie at the root of family gentrification, resulting in the construction of new male and female identities.

(2003). Neighbourhood effects on social opportunities: the European and American research and policy context. Housing Studies: Vol. 18, No. 6, pp. 797-806.

National as well as international observers have praised the Dutch national urbanization policy as being exceptionally successful in the recent past. Looking at the urbanization process of recent decades, however, one could wonder if this praise was well deserved. It is acknowledged that national or regional plans are generally only the start of a long-term planning process in which many other actors are involved. Therefore, there is generally no direct connection between these plans and the eventual outcomes. However, if the eventual local outcomes are in conflict with the initial goals of the national or regional plans, the effectiveness of the process between plan acceptance and application in practice becomes very doubtful. The empirical analysis presented in this article suggests that the actual Dutch urbanization process since the 1960s was far from what the national planners wanted it to be. Some successes were surely reached, most of all with the policy of growth centres, but the general tendency of unplanned suburbanization remained unbroken despite all planning efforts. Explanations for this lack of success are probably partly due to administrative or political problems, but much more to the generally limited possibilities for influencing or counteracting the effects of economic, technological and socio-demographic processes through physical planning policy.

The European Parliament (EP), like the US Congress, is often depicted as a parliament with strong committees and weak parties. This article compares the powers of the EP's committees with their counterparts in national legislatures and examines the role of party groups in the committees. Analysing the principles guiding the appointments to committees, the selection of committee chairs, and the distribution of reports within the committees, we show that national party delegations inside the transnational groups are often key gatekeepers in the division of spoils within the groups, with group leaders restricted in their ability to direct the actions of their committee members. The distribution of reports between party groups and national delegations produces interesting variation, with the two largest groups (PES and EPP) largely in control of key reports, while the size of national parties inside the main groups is the primary factor in explaining the output of national delegations

In a recent issue of this journal Priemus discusses the implications of the shift in the Dutch housing market from suction to pressure. He rightly asserts that the impact made by surpluses on a market differs from that made by shortages, and that this difference will lead to a new generation of housing policies. However, he largely ignores regional differences. Priemus’s suggestions for housing policy in regional housing markets with pressure are worth considering and refreshing, but should be taken with much caution in regional housing markets with suction. This paper elaborates on the findings of Priemus and theorizes housing market pressure/suction on a regional level as well as in different segments within the housing market. It also deals with the negative external effects of a more liberalized housing policy for other social, urban and spatial policies. It is argued that Priemus’s set of instruments for a new housing policy should be supplemented with pressure/suction-based policies on urban renewal...

Since the 1980s, subsequent Dutch governments have promoted self-employment of immigrants to reduce their unemployment rates. These policies have been focused on the (potential) actors themselves, i.e. the immigrants who have started or who may want to start a business. Taking mixed embeddedness as a point of departure, entrepreneurship and self-employment cannot be solely understood by focusing on the micro-level but has to include the larger macro and meso structures that impact on these actors' choices. In this paper, therefore, the focus is on the opportunity structure and on the policies that affect this set of options for starting a (small) business. A typology of policies that may alter this opportunity structure is offered.

This article considers the gendered character of the contemporary playground. Based on observational studies in eight Amsterdam playgrounds and interviews with users, it is shown how playground participation, activities and micro-geographies are structured by gender. Furthermore, not only does the playground function as a gendered space, its physical and symbolic landscapes also reinforce this binary divide. In addition, the contested character of this divide is illustrated with examples of girls and boys challenging traditional gender behaviour. In its gendered access, the playground is comparable with other public spaces: in contrast, however, it has not yet been the focus of feminist critique. This article points out the wider significance of creating emancipatory public play environments.

Many assume that high levels of social and/or ethnic segregation, which often go hand-in-hand with high levels of ethnic concentration, will obstruct integration and participation in society. Concentration is also felt to hamper the social mobility of those with a weak social position and/or low skills, particularly immigrants of non- Western origin. Although these ideas may have some validity in contexts where extremely high levels of social and ethnic segregation exist, they are hardly tested in contexts with more moderate levels of segregation and stronger welfare states. This paper addresses this deficiency by providing some evidence on the relationship between segregation and integration in Dutch cities, Amsterdam in particular. The findings show that, where a relationship between segregation and integration does exist, it is not a very strong one. In Amsterdam some similarly segregated population categories appear to perform differently in terms of integration. In addition, the social mixture of the residential environment hardly has any effect on the social mobility of those living there. On the other hand, I find that the level of social inequality in society is important for understanding the level of segregation. Educational programmes and variations in labour market access are crucial for understanding variations in integration. Conse quently, programmes that are aimed at de-segregation, mainly by mixing neighbour hoods socially and ethnically, will probably contribute little to enhancing integration in society.

This paper documents the consequences of the first living arrangements of young adults after leaving the parental home (without a partner, cohabiting, or married) for their housing situation, whether they rent independently, share accommodation, or own their own homes, both immediately after leaving home and in the first eight years after leaving. Data are analysed from two retrospective life-course surveys conducted in the Netherlands in the 1990s, using multinomial logistic regression models. The paper finds a strong influence of the timing and pathway of leaving on the housing situation immediately after leaving: those nest-leavers who make stronger commitments in their household careers (by cohabiting, or by marrying) are more likely to own a home and less likely to share. Although through the years after leaving home this influence decreases, it remains discernible and significant even eight years after leaving. This is remarkable, given the fluidity of the housing careers of nest-leavers.

During the 1990s, pension funds seemed to dominate the world's capital markets, reaping unprecedented rates of return. This stands in glaring contrast to the budgetary difficulties of most nonfunded European pension arrangements, which are a result of the changing demographic composition of the population. As a result, a growing number of European states is trying to transform the existing pay-as-you-go systems into funded pension arrangements. After a critical examination of these demographic projections, the claim that funded pension systems are not subject to ‘demographic stress’ is critically assessed. Finally, given the logic to which funded pension arrangements are subject, it is argued that the introduction of such institutions could result in a growing financialisation of the economy. It is claimed here that this is not without dangers for the long-term wealth-generating capacity of firms. So, not only are the reasons for pension restructuring less compelling than is generally thought, restructuring could also result in unwanted side-effects.

Local planning in mountain areas requires spatial information on site factors such as vegetation that is commonly lacking in rugged terrain. This study demonstrates a procedure for the efficient acquisition of a vegetation map using topographic attributes and nominal vegetation data sampled in the field. Topographic attributes were derived from a digital elevation model (DEM) and nominal vegetation data were reduced to normalised scores by detrended correspondence analysis (DCA). The procedure for mapping vegetation types addressed the relations between DCA scores and topographic attributes, spatial correlation of DCA scores and classification of predicted DCA scores based on a cluster analysis of DCA scores at observation locations. The modelled vegetation classes corresponded with the impression obtained in the field. We also showed that the final result is rather sensitive to which samples are included in the analysis.

In the eyes of many, the events of 11 September have validated Huntington's prediction of a 'clash of civilizations' between the Islam and the West. Accordingly, the Muslims communities in the West are seen as vanguards of a hostile civilization. The essay aims at exploring the significance of such a geopolitical script in popular geopolitics. It deals with the position of Muslim communities in Western Europe. The analysis focuses on Moroccans in the Netherlands, a Muslim community resulting from recent immigration and on the new media. The empirical section examines how the events and their aftermath were presented and represented on websites run for and by young Dutch Moroccans (websites that have became key public places for this first generation of Muslims born in the Netherlands), and aims at assessing to what extent the 'clash of civilizations' script inform their understanding of the events.

The Dutch physical planning system is at a turning point. Recently the government proposed a new institutional framework for spatial planning. At first sight, the intended changes look like an example of improvements resulting from a learning process. However, the main lines of the proposal blatantly deviate from the insights into planning, balanced decisionmaking, and ‘governance’ that have emerged during the past decade. This is illustrated and explained from three perspectives. First, the growing need for change was put forward several times by the Scientific Council for Government Policy, a think tank whose task is to advise the government from a certain intellectual distance. The development of ideas by this agency is an example of cognitive learning. Second, the example of infrastructure planning that is crucial in this cognitive development is used to illustrate this by confronting the ideas with the experiences in two major national projects. As a third line, the deviations between the empirical evidence, the analysis, and the advice to the government on the one hand, and the governmental proposal on the other, are explained in relation to the ‘advocacy coalition framework’ theory on policy-oriented learning.

This paper addresses the question of the extent to which job access at labour market entry influences socio-economic status later in life. Multivariate models of workers' socio-economic status at the ages of 30, 40 and 50 were estimated using longitudinal data. The results show that job access at labour market entry is indeed instrumental in career advancement over the life course. The importance of job access at labour market entry increases significantly with age. Good job access at the beginning of the labour career evidently gives workers an advantage over others who start in less favourable labour markets.

The author offers a conceptual investigation of the tension between openness and protection in well-developed welfare states. Because of a combination of demographic tendencies and labor market shortages, a growing number of European welfare states is currently exploring market-led immigration policies. However, the level of protection these welfare states offer seems hard to reconcile with the low threshold markets that are needed to incorporate newcomers. The author argues that the “solution”lies not so much in a clear political choice for either but rather in the coordinated institutionalization of differentiated citizenship rights. The author illustrates this case with examples taken from the Dutch context, claiming further that the particular combination of corporatist welfare arrangements and the tradition of lenient enforcement in the Netherlands provides a “natural”habitat for the kind of regime pluralism that differentiated citizenship requires.

What impact do neighbourhoods have on social mobility? For years, this question has received widespread international attention in scholarly debates and within society at large. This paper seeks to contribute to this discussion by presenting the results of an investigation into the relationship between household social mobility and the composition of the residential environment. The analyses are based on an extensive empirical longitudinal study conducted in the Netherlands. The most remarkable conclusion is that, in the Dutch context, the environment has only a modest influence on the social mobility of households with a weak economic position. It was found that the chance of a household living purely on welfare benefits at the beginning of the study period to escape the ‘welfare trap’ was barely dependent on the number of similarly challenged households in the immediate vicinity. Interestingly, the environment proved to have a more powerful effect on the social mobility of households with a stronger economic position. The probability that households with at least one paid job at the beginning of the research would still have a job at the end clearly decreases as the share of benefit-dependent households in the neighbourhood rises. A possible explanation for this is that for the first category (weak starting position) the negative effect of their own welfare situation is far more determinative for their future prospects than the compo sition of their environment. Because these negative individualistic conditions are absent for the second category (stronger starting position), environmental factors may play a relatively larger role. Another interpretation is that area-based policies are not just targeting the areas with bigger problems more intensively, but especially the long-term unemployed in these areas, and not so much the short-term unemployed (those who had a job at the start of the research period and lost the job afterwards).

The research in this paper focuses on the housing career during a household's life-course. The housing career is the sequence of housing states defined in terms of tenure and the quality/price of the dwellings that households occupy while they make parallel careers in family status and the job market. The research brings out, more than the literature on separate residential moves, that many households are in a stable housing state over long stretches of their life-course. Housing careers are notable for having a relatively simple structure and, in general, an upward trend in quality, price and tenure of the sequence of dwellings occupied. As expected, there is a close relationship between the type of housing career and a household's income and income growth. Regional variation in tenure composition and the price of the stock have a strong influence on the development of the housing careers in different regions.

Geografen die zich over grensregio's buigen hebben vaak meer aandacht voor de grens dan voor de regio. Zij zijn vooral geïnteresseerd in de functie van de grens en haar betekenis. Daardoor blijft de grensregio vaag gedefinieerd als de regio aan de grens. Sinds in het proces van Europese integratie grensoverschrijdende samenwerkingsverbanden gemeengoed zijn geworden, duidt men met grensregio's juist op regio's die zich over de grens uitstrekken. Onderzoek in grensregio's laat vaak zien dat het verdwijnen van scherpe staatscontroles aan de binnengrenzen van de Europese Unie niet tot de verdwijning van de grens leidt. De grens blijft een belangrijk en betekenisvolle scheidingslijn in het sociale en economische gedrag van bewoners van grensregio's. Ook hebben grensbewoners vaak weinig kennis en belangstelling voor de grensoverschrijdende politieke samenwerkingsverbanden.

This article explores the interrelationship between planning and law from an institutional point of view. Interest in institutions and general norms in the social and behavioral sciences has led to interdisciplinary cross-pollination. Theories of planning and law occupy a special position because they are rooted in practice. In practice, the main concerns are how institutions are validated in daily policies and how the meaning of institutional norms may change in the course of action. This article addresses how institutions evolve in the practice of planning and law. General norms are evoked, and may be given new meanings, when problems and social conflicts arise. The author investigates how this process plays out in various systems of planning and law. He contrasts the induction of norms in Anglo-Saxon systems to the deductive reasoning behind the German system and discusses the pattern of political “self-limitation” in the Dutch system.

Aggressive internationalisation activities by global retailers frequently encounter, in addition to responses from indigenous rivals, the regulatory mechanisms of the governments of host or target nations. However, these public regulatory mechanisms are themselves in a state of flux, often as a function of internal conflict between government policy sectors. Internationalisation itself is also an agent of change and we illustrate this using the example of retail regulatory systems in Britain and the Netherlands at the time of Wal-Mart's entry into the EU. In both countries, an ambivalent stance by the central government was evidenced by the publication of reports by planning authorities and investigations by competition authorities.

This paper examines the spatial transformation of the city from children’s point of view. Three important daily living domains – children’s outdoor play spaces, leisure centres and caring institutions – are examined. Empirical findings are made from studies in Amsterdam, where new urban developments affecting children are most apparent in the Netherlands. Conclusions show that developments are both diverse and paradoxical. On the one hand, we see processes that progressively contribute towards the exclusion of children from urban public space. Safety considerations underpin these processes heavily. Children’s marginal position in the public domain is further reinforced in the planning and design of new residential areas. Children do not seem to be a factor that merits consideration. On the other hand, never before has so much attention been paid to children. Adults’ efforts to give due consideration to children’s position lead to the creation of many new domains especially created for children. These give children a ‘face’ in the city, but these spaces are characterised by privatisation, institutionalisation and segregation. In the context of the Netherlands it is not altogether clear what shape the future will take, but it seems to be most likely that indicated developments will continue.

Watching the profound changes in the last decades in virtually any big city in Western Europe in the field of migration, minority and ethnicity, many national and urban governments in Europe fear for large spatial concentrations of immigrants who originate from non-industrialised countries. The basic assumption behind that attitude seems to be that large concentrations of (ethnic) immigrants would prevent their full integration and thus participation in society. Such a risk of insufficient integration would particularly be great when the immigrant population occupies the lower positions of the socio-economic ladder. However, two things should be investigated with care. First, what are the actual explanations for the social and spatial divisions that are encountered in cities? What does that imply for the (spatial) inequality in Dutch cities? Second, what can be said about the effects of recent changes that can be observed with respect to the explanatory dimensions in the Dutch context? How do these compar...

Leather, hide and fur were probably the preferred material for all kinds of equipment (tents, bags, pots and drinking vessels) and clothing in prehistory. It is therefore remarkable that our knowledge of this material is so restricted, and its survival even in suitable circumstances very limited. Palynological data and experimental methods attempt to explain this phenomenon.

Oxygen concentrations within forest floor litter were studied at various water contents and oxygen consumption rates. A micromanipulator moved micro-electrodes (dia 7.5 μm) downward at a velocity of 2 μm s−1. In oxygen profiles, particles and pores could be identified. The sizes of these particles agreed with particle sizes derived from a thin section of the same forest floor material. In oxygen profiles, no gradients in concentration occurred in litter macropores at water contents of 2–3.9 g g−1 dry weight, which represented the average range in field water contents. By contrast, steep oxygen gradients occurred inside organic particles. Larger organic particles in general had lower intraparticle oxygen concentrations, compared to smaller organic particles and in some particles oxygen was absent (>250 μm dia). These anoxic sites occurred at all water contents (2–3.9 g g−1 dry weight) and oxygen consumption rates (0.4–3.2 μmol g−1 h−1). The anoxic organic matter fraction of the forest floor did not significantly increase with water content nor with a stimulated oxygen consumption rate due to addition of glucose. The recognition that permanent anoxic sites exist in litter helps us understand how anaerobic processes, such as denitrification, may contribute to forest floor N2O production.

A conceptual model that accounts for the influence of pore geometry is needed to obtain soil water conductivity from bulk soil electrical conductivity measurements in unsaturated soils. Mualem and Friedman (1991) proposed such a model, based on the hypothesis that the tortuosity factor affecting bulk soil electrical conductivity is identical to that defined for prediction of soil hydraulic conductivity. Soil water retention curves (model input) and bulk soil electrical conductivity (model output) of two soils were measured simultaneously over a wide range of soil water conductivity using a multistep outflow (MSO) experiment in combination with time domain reflectometry. The model with only one free parameter can describe the measured data. Predictions indicate a large dependence of the model outcome on the value of the fitting parameter. The fitted tortuosity parameters were used for inverse modeling of the water flow during the MSO experiments, obtaining unique estimates of the hydraulic conductivity.

(1999). Spatial Development Patterns and Public Transport: The Application of an Analytical Model in the Netherlands. Planning Practice & Research: Vol. 14, No. 2, pp. 199-210.

This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and empirical relationships, describing the influence of meteorological conditions, topography, sediment characteristics and vegetation. A so-called adaptation length is incorporated to calculate the development of transport equilibrium along the profile. Changes in topography are derived from the predicted transport, using the continuity equation. Vegetation height is incorporated in the model as a dynamic variable. Vegetation can be buried during transport events, which results in important changes in the sediment transport rates. The sediment transport model is dynamically linked to a second-order closure air flow model, which predicts friction velocities over the profile, influenced by topography and surface roughness. Modelling results are shown for (a) the growth and migration of bare, initially sine-shaped dunes, and (b) dune building on a partly vegetated and initially flat surface. Results show that the bare symmetrical dunes change into asymmetric shapes with a slipface on the lee side. This result could only be achieved in combination with the secondorder closure model for the calculation of air flow. The simulations with the partly vegetated surfaces reveal that the resulting dune morphology strongly depends on the value of the adaptation length parameter and on the vegetation height. The latter result implies that the dynamical interaction between aeolian activity and vegetation (reaction to burial, growth rates) is highly relevant in dune geomorphology and deserves much attention in future studies. Copyright © 1999 John Wiley & Sons, Ltd.

Nonlinear soil process models that are defined and calibrated at the point support cannot at the same time be valid at the block support. This means that in the situation where model input is available at point support and where model output is required at block support, spatial aggregation should take place after the model is run. Although block kriging does both in one pass, it is sensible to separate spatial aggregation from spatial interpolation. Contrary to aggregation, interpolation should better take place before the model is run because this enables a more efficient use of the spatial distribution characteristics of individual inputs. When a model is run with interpolated inputs, it is important not to ignore the interpolation error. Substituting conditional expectations in place of probability distributions into a nonlinear model leads to bias, essentially for the same reason that aggregating inputs prior to running a model is not the same as aggregating the output after the model is run. Running a model with inputs that are probability distributions will usually call for a Monte Carlo simulation approach. This causes a substantial increase in the numerical load, but apart from eliminating bias, an important advantage is that it shows how uncertainties in model inputs propagate to the model output. Many models used in soil science suffer not only from input error but also from model error, which is support- and case-dependent. Case dependency implies that model error can only be assessed realistically through validation. A major problem in validation is that the validation data are often collected at a much smaller support than the aggregated model predictions.

Buildings are products with special environmental characteristics. They are unique in having an indoor environment and uncommon because of the importance of siting and orientation and the usual long life-span of major components. There is a wide variety of instruments for environmental improvement of buildings. Requirement type instruments usually have only a limited scope, though there are some exceptions in Denmark, the United Kingdom and the Netherlands. Guidance type instruments tend to be more comprehensive. Scoring instruments are relatively comprehensive but also rather superficial and ad hoc. They require a more solid basis. Instruments based on life cycle analysis (LCA) are as yet deficient with respect to indoor environment, siting and user behaviour, leaving substantial scope for instrument improvement.

This paper discusses a two-dimensional second-order closure model simulating air flow and turbulence across transverse dunes. Input parameters are upwind wind speed, topography of the dune ridge and surface roughness distribution over the ridge. The most important output is the distribution of the friction velocity over the surface. This model is dynamically linked to a model that calculates sand transport rates and the resulting changes in elevation. The sand transport model is discussed in a separate paper. The simulated wind speeds resemble patterns observed during field experiments. Despite the increased wind speed over the crest, the friction velocity at the crest of a bare dune is reduced compared to the upstream value, because of the effect of stream line curvature on turbulence. These curvature effects explain why desert dunes can grow in height. In order to obtain realistic predictions of friction velocity it was essential to include equations for the turbulent variables in the model. In these equations streamline curvature is an important parameter. The main flaw of the model is that it cannot deal with flow separation and the resulting recirculation vortex. As a result, the increase of the wind speed and friction velocity after a steep dune or a slipface will be too close to the dune foot. In the sand transport model this was overcome by defining a separation zone. Copyright # 1999 John Wiley & Sons, Ltd.

The glacier Holmstrombreen, in Spitsbergen, surged into the ice contact scarp of a proglacial outwash sequence at some time during its Neoglacial maximum. The outwash sediments were pushed along a decollement to produce a moraine in which deformation extended for 1.5 km beyond the furthest extent of the glacier front. The style of folding and faulting and the nature of the pre-, syn- and post-tectonic sedimentary sequence across the whole push moraine is described from a continuously exposed section of the push moraine which extends from its proximal to distal extremities. The precise extent of incremental compressive shortening of the pushed sediments, of some 900 m, is established. The depth to the underlying decollement is inferred to be an average of about 30 m, indicating that stresses and movement were transmitted through a thin nappe with an aspect ratio of about 1 in 30. It is suggested that this nappe was frozen and that an artesian water pressure head of 60 m immediately beneath it reduced friction along its base to a very low value. It is calculated that a glacially generated force of about 1.5×10 7 kN was responsible for pushing the sediment nappe. The nature of the glacially controlled groundwater flow system rather than the magnitude of longitudinal forces generated by the glacier is the principle determinant of large-scale push moraine characteristics. The changing ice topography produced by the pushing event during the surge and in the post-surge decay had a major influence on the evolution of the meltwater drainage system and the style of fluvial sedimentation. The structure, sedimentary architecture and evolution of the whole glacitectonic/fluvial complex can best be understood by considering the impact of the surge on a complete outwash system. It is suggested that the setting and processes which produced the Holmstrombreen push moraine could account for many broad, multi-ridge and fold push moraines which formed proglacially, and that the thickness of original sediments above the decollement can be a guide to the thickness of contemporary permafrost.

A swarm of vertical gravel-filled dykes up to 6 m high and several decimetres wide, cut through an over-consolidated till at Killiney Bay. The dykes are rooted in a gravel layer and many display plumes of clastic debris ejected into the overlying sediments — `burst-out structures'. Such features have not previously been described. These clastic dykes are interpreted as the infillings of hydrofractures which formed when water pressures in the basal gravel layer exceeded the overburden pressure and tensile shear strength of the capping till. The burst-out structures extend up to 7 m from the tops of the dykes and provide strong evidence for forceful upward flow. Evidence suggests that the hydrofractures formed subglacially, probably during a minor re-advance. Their presence in Late Devensian (26–13 ka BP) tills with an Irish Sea provenance (`Irish Sea till') may have important implications for the subglacial hydrology of the last Irish Sea ice sheet. These hydrofractures cannot form in unconsolidated glacimarine sediment and their presence precludes a glacimarine origin for these deposits. They greatly affect the geotechnical properties of Irish Sea tills, in particular providing very permeable routes through otherwise impermeable layers, with important consequences in situations elsewhere in the Irish Sea basin, where they have been used as aquicludes in landfill and low-level nuclear waste disposal sites.

Humans have altered global nitrogen cycling such that more atmospheric N2 is being converted (‘fixed’) into biologically reactive forms by anthropogenic activities than by all natural processes combined1. In particular, nitrogen oxides emitted during fuel combustion and ammonia volatilized as a result of intensive agriculture have increased atmospheric nitrogen inputs (mostly NO3 and NH4) to temperate forests in the Northern Hemisphere2,3,4. Because tree growth in northern temperate regions is typically nitrogen-limited5, increased nitrogen deposition could have the effect of attenuating rising atmospheric CO2 by stimulating the accumulation of forest biomass. Forest inventories indicate that the carbon contents of northern forests have increased concurrently with nitrogen deposition since the 1950s6,7,8. In addition, variations in atmospheric CO2 indicate a globally significant carbon sink in northern mid-latitude forest regions9,10,11,12. It is unclear, however, whether elevated nitrogen deposition or other factors are the primary cause of carbon sequestration in northern forests. Here we use evidence from 15N-tracer studies in nine forests to show that elevated nitrogen deposition is unlikely to be a major contributor to the putative CO2 sink in forested northern temperature regions.

Microbial C and N transformation rates in air-dried and subsequently rewetted coniferous forest floor material were examined in a laboratory incubation study. Gross N transformation rates were determined through parallel 15NH4+ and 15NO3- enrichment experiments. After drying of the litter for 12 d to a water content of 10% of dry weight, CO2 respiration, net N mineralization and nitrification rates were strongly restricted. Microbial biomass C was reduced to 67% of the amount in the continuously moist material. Remoistening of the dry litter to a water content of 340% resulted in a flush in C and net N mineralization within a few hours after rewetting. The increase in net N mineralization could be attributed to a larger increase in gross N mineralization relative to the increase in gross N immobilization. Gross N immobilization had increased to the same rate as gross N mineralization after 26 h, and a small secondary peak in respiration and microbial C was observed 48 h after rewetting. It was concluded that both biomass-derived substrate with a low C-to-N ratio and `nonbiomass'-derived substrate with a high C-to-N ratio have been released, and metabolized, as a result of the drying-rewetting treatment. Despite the very extreme drying treatment, the mineralization flush after rewetting could not compensate for the large reduction in CO2 and mineral N production during dry conditions due to its short duration. Since there was no increase in nitrification rate after drying and rewetting, the NO3- concentration at the end of the incubation was strongly reduced due to the extremely slow net nitrification rates during desiccation.

Grazing is often used in management of grass-encroached Scots pine (Pinus sylvestris) forests in The Netherlands, because it is thought to increase diversity of vegetation and humus profiles. To test this hypothesis, two 1 ha plots in a primary pine stand on drift sand were grazed for 7 years at high and moderate intensities. The humus profiles of these two sites and of a control site were sampled at various scales to assess changes in grass biomass, thickness of ectorganic horizons, organic matter stocks, root stocks, and pH. Whether grazed or not, site factors such as slope angle and aspect, distance to trees and parent material did not explain the spatial variability of the plots. Spatial variability could be linked to the tussock structure of the grass layer. With continued grazing, ectorganic horizons became more compact (particularly the F horizon), stocks of organic matter increased, grass biomass decreased, variances tended to decrease and ranges tended to increase. These results suggest that at the landscape scale, where much variation in grazing intensity can be expected, spatial variability of humus profile properties and thus site diversity will increase. However, grazing intensities in the experiment were far greater than those normally employed in management of grass-encroached forests. Therefore grazing will scarcely affect site diversity, unless grazing variability is enhanced by special treatments, such as temporary fencing to create locally high grazing intensities.

Animal coats and bird feathers from a variety of species have been analysed for their pollen content. The pollen data reflect the pollen production within the animal's habitat. The pollen in animal coats in general, but in birds' feathers particularly, thus represents another source for the presence of allochthonous pollen in sediments, apart from long-distance transport by wind or water or secondary deposition of, for example, marine sediments.

Over the past few years, parties on the extreme right of the political spectrum have drawn a surprisingly large number of votes in elections throughout Western Europe, and surprisingly often. What these parties have in common is their aversion to ‘foreigners’, by which they mean anyone who hails from another country. This paper considers whether the presence of foreigners in the immediate surroundings of people's homes is a factor in their decision to cast their vote for any of these parties. It is based on an analysis of data on two elections held in Amsterdam in 1994. The analysis reveals that the presence of Moroccans and Turks, two population groups that are associated with an Islamic lifestyle, in the immediate surroundings of the home actually does increase the support for parties on the extreme right. In contrast, the presence of people from Surinam or the Antilles does not have that effect, while the presence of foreigners from other countries does not have that effect at all.

Samples, a few millimetres in diameter, taken from bark of beech, birch, hophornbeam, oak, pine, sycamore and willow contained enough pollen grains for reliable counts (between 200 and 600 pollen grains per slide), not only from the said species, but also from the local vegetation. Pollen deposition at various levels in the vegetation and at different times of the year provide useful information on vegetation composition, and the possible effect of wind direction. No systematical study has been carried out so far concerning the potential and bias of this kind of pollen trap. This paper is merely meant to draw attention to the possibilities to use bark as an easily available pollen trap in the reconstruction of the vegetation. Analysis of archaeological bark samples forms another promising application besides pollen data from soil samples.

The contrast between, on the one hand, decreasing emissions of the metals cadmium, copper, lead and zinc and, on the other, their continuously increasing input into the economy is analysed for three case studies: The Netherlands as a whole, the Dutch housing sector and the Dutch agricultural sector. Flows of these metals through and their accumulation within the economy and the environment have been quantified for 1990 and for a constructed steady-state situation. To this end, the substance flow analysis method has been applied. The case studies show that there is a strong increase to be expected in the emissions from the 1990 to the steady-state situation. This increase is mainly due to the shift from landfill accumulation to emission to non-agricultural soil. At the same time, however, there is also an increase in the emissions to other media: air, water and agricultural soil. Emissions along these critical routes with respect to human and ecotoxicity show an approximately 30% increase for cadmium, lead and zinc and more than a doubling for copper. It is shown that this increase may lead to the surpassing of critical levels for human toxicity and terrestrial and aquatic ecotoxicity. Some possible measures are suggested to prevent critical levels being exceeded.

The structure of many clay soils in tropical Africa is composed of microaggregates that range in size from 0.03 to 1 mm. These structural units are often very stable and known as pseudo-sand or pseudo-silt; their presence is detected from the loamy feel of the soil. This paper tests the hypothesis that termites contribute to a stable microgranular, i.e., finely aggregated, soil structure. A termite mound was selected on pedologically unaffected, clayey weathering material derived from phonolite. The fate of microaggregates produced by termites has been followed through the various stages of mound building. Field evidence was supplemented with microscopic analysis. Development of the mound begins when lumps of soil are detached from the subsoil by termites and carried as microaggregates up to the surface. In the next stage the microaggregates are cemented to form the nest. Breakdown begins when the nest is abandoned and disintegrates by splash and runoff producing colluvium, or is demolished by ants. In the final stage this material is integrated in the soil of the mound. Soil aggregates produced by splash, ants and soil-forming processes have different size characteristics, but the original microaggregates produced by the termites are preserved in the matrix throughout. It is assumed that they owe their stability to impregnation with saliva or other body fluid excreted by the termites. Termites produce also microaggregates in the form of fecal pellets, but these appear to be unstable and are found only in the voids of the soil developed during the last stage.

Summary The quantification and achievement of eco-efficiency or dematerialization in the form of a factor X, with X varying between 4 and 50 is being espoused by a variety of analysts and advocates. Politically, these efforts are mainly confined to some European countries. They reflect a remarkable technological optimism. This article reviews some of the major issues pertinent to the factor X debate. The case is presented for quantifying dematerialization or eco-efficiency goals using a factor X. It is also found that the factor X lacks precision as yet, and that there is only limited interest in the possibilrty that achievable values for X may vary widely among economic activities given technological constraints. There is no agreement whether technological improvement alone will be sufficient to achieve a factor X in practice for economies as a whole. It seems likely, however; that government-driven technology forcing will be necessary to achieve a factor X in practical terms, especially when X is relatively large.

In The Myth of the Framework, Popper attacks the doctrine that truth is relative to one's intellectual background. The same collection refers to his "situational analysis." This article explores the implications of both for spatial planning. Spatial planners have to justify proposals. The article first summarizes earlier work on planning methodology evolving around the rationality principle and the implications for it of Popper's work for how to do this. It then discusses the notion of the definition of the decision situation, which flows from this principle. This, of course, implies taking a leaf out of Popper's book where he discusses situational analysis. The article then gives an account of the author's work on Dutch planning doctrine, relating it to the definition of decision situations in planning and confronting it with Popper's strictures against The Myth of the Framework. The conclusion is that, whereas in the sciences that are after explain ing reality in terms of universal laws, Popper's argument holds, in planning it does not. Planning is about the search for the right course of action. In it, Popper's concern with fighting relativism and what he calls "justification" is misplaced. The quality of decisions depends on the position and the concerns of the decision taker. Relativism is in-built and so is the need to justify decisions.