The role of sustainable urban development in biosphere conservation E 3.8 193 Grime (1979) assumes that urban biotic communities are subject to great disturbances and that this generally favours the penetration of alien species. By contrast, Newsome and Noble (1986) note that most invaders are highly specialized and could not cope with disturbances. • There is also uncertainty about whether, as a general principle, high species diversity increases (Brown, 1989) or decreases (Simberloff, 1989; Trepl, 1993) resistance to invasion. • The ratio of species-increase to species-extinction varies from region to region. Although the increase in the number of species resulting from invasions in Central Europe clearly exceeds the fall resulting from extinction, this ratio cannot necessarily be transferred to other regions. Studies on the number of ferns and flowering plants in Central European cities are at least one point of reference. They reveal that the number of extant species correlates to the population figures and density. Whereas 530–560 species are found in small to medium-sized towns, the figure rises to over 1,300 species in cities with over 1 million inhabitants (Sukopp, 1998). Relationship to the syndromes of global change The susceptibility of urban ecosystems to the invasion of species can be illustrated by various syndromes of global change (Chapter G; WBGU, 1997, 1998a). Two ofthe 16 syndromes identified by the Council refer to environmental degradation as a result of different forms of urbanization (Table E 3.8- 2). 1. The Favela Syndrome, which the Council has already described in detail (WBGU, 1998a), describes the process of unplanned, informal and consequently environmentally harmful urbanization. It is characterized by poverty, such as slums. 2. The Urban Sprawl Syndrome (WBGU, 1997) describes the process of urban expansion with far reaching environmental consequences. New spatial structures arise from the formation of urban conglomerations, andthere is a corresponding need for adaptation. In particular, the spread of settlements to the peripheries of towns in both syndromes leads to a reduction ofthe ecological potential in the area surrounding the town. However, the reasons for this vary greatly. Whereas there is economic pressure for use in the Urban Sprawl Syndrome, the Favela Syndrome is a matter of ensuring the survival of poverty-stricken people. In the inner cities this pressure for use can still be kept at bay, to a certain extent, in respect of open space by measures under administrative law. Because ofthe frequently low degree of organization in the planning, monitoring and enforcement bodies it is very difficult to prevent the occupation of open space on the outskirts of towns. The ecological concerns are relegated to the background when faced with securing livelihoods. The development radiating from towns in industrialized countries often leads to damage to the landscape as a result ofthe expansion of urban structures and infrastructure. With regard to the biosphere, the key issues are the conversion of natural habitat into farmlandand an increase in soil pollution resulting from traffic emissions.As the disadvantages of urban conglomeration increase, eg high land prices or heavy traffic pollution, the wish for semi-natural living leads to urban sprawl in the environs ofthe towns.The associated expansion ofthe infrastructure divides recreation areas and natural habitats. As a consequence ofthe conversion ofthe natural habitat (in Germany alone around 90 ha day -1 ) there is a severe loss of biological diversity. For example, it can be assumed that the conversion of agricultural land in the United Kingdom has led to the permanent loss of around 30 per cent of animal and plant species (WGBU, 1994). Whereas spatial expansion is crucial in the Urban Sprawl Syndrome, in the Favela Syndrome the extent and speed of poverty-induced influxes of people into existing settlement structures leads to damage to the biosphere. Losses of biological diversity and varying conditions for the invasion of alien species can be seen with both development patterns. Table E 3.8-2 Development trends ofthe Favela Syndrome andthe Suburbia Syndrome. Sources: WBGU, 1995a, 1997, 1998a Favela Syndrome Population growth, rural exodus, waste accumulation, contamination, sealing, collapse of traditional agriculture, reduction of cultural diversity, social and economic marginalisation, troposphere pollution, freshwater depletion, eutrophication, reduction ofthe groundwater level Suburbia Syndrome Higher aspirations, individualisation, sectoral structural change, economic growth, urban sprawl, fragmentation of ecosystems, conversion of semi-natural ecosystems, sealing, emergence of new economic areas, deregulation, increasing traffic volumes, expansion of traffic routes
194 E Diversity of landscapes and ecosystems E 3.8.6 Models and concepts for sustainable urban development In order to reverse the urban development trends described above, new models have been developed and gained currency in the German-speaking world, known variously as ‘ecological urban redesign’, ‘the compact city’ or ‘the ecology of time’. AGENDA 21 expressly calls for sustainable development which respects economic and social development as well as incorporating the environment. Chapter 28 emphasizes the importance of towns to sustainable development. Associated with this is a call to local authorities to draft LOCAL AGENDA 21 processes together with all groups in society (UNCED, 1992). This procedure is different from the conventional planning methods because all relevant groups in society are involved. Another important principle of sustainability is formulated in the Aalborg Charter. According to this, town may not temporally or spatially export their ecological, economic or social problems. Instead, attempts should first of all be made to solve these at local level. Only when this has proved to be impossible should temporal or spatial balancing mechanisms be sought (ESCTC, 1994; Kuhn and Zimmermann, 1996). The Conference on Human Settlements HABI- TAT II was held in Istanbul in 1996 (WBGU, 2000a). The difficulty of establishing the term of ‘sustainable development’, anchored in AGENDA 21 in 1992, as a basic principle for the development of human settlements was overcome by the compromise wording: ‘Sustainable development equal to economic development, social compensation and ecological compatibility’ (BMBau, 1997). This is motivated by the concern of developing countries to exercise their right to ‘catch-up’ in development terms. At national and local authority level the HABITAT II process has taken some effect, especially as a result ofthe comprehensive involvement of local authorities, scientists, business and NGOs (Sibum, 1997). In Germany, a national report on the HABITAT II Conference has been compiled (BMBau, 1996) as well as a national plan of action based on the Global Action Plan of HABITAT II (ARL, 1996). Although the declaration of intent for sustainable urban development signed by the governments is not legally binding, it can be invoked politically. At the URBAN 21 international conference to be held in Berlin in 2000, the aim is to work towards concrete solutions tying in with the results of Rio de Janeiro and Istanbul. The focus will be on the problems ofthe growth of megacities in the developing countries and non-sustainable urban development in the industrialized countries.The URBAN 21 international commission will submit the ‘World Report on the Urban Future’ to the Conference. Finally, the Conference is to adopt a declaration that will outline the cornerstones of future worldwide urban policy and point out the way for urban development in the 21st century (BBR, 1999). Recommendations for action to promote sustainable urban development In terms of urban planning, ecological concerns are at the forefront with respect to biosphere conservation – however, without the integration of social and ecological concerns, the positive effects of purely ecological urban planning will remain marginal. An adequate foundation for evaluation is initially of central importance for the protection ofthe urban biosphere. In order to ensure a fair assessment ofthe conservation and use requirements ofthe biosphere, it is necessary to make a comprehensive inventory and valuation of existing biotopes. This requirement is accommodated in Germany by the nationwide mapping of biotopes, which now comprises over 200 maps, especially in small and medium-sized towns (Schulte et al, 1993). Since 1990 there has been international cooperation with Brazil to see whether the methods developed in Germany can be transferred to other countries and preliminary results have already been achieved (Schulte et al, 1994). For sustainable urban development geared towards the protection ofthe biosphere, the following points of departure for town planning also emerge: (Becker, 1992; Loske, 1996; Birzer at al., 1997): • Creation of structures for supply and disposal (energy and waste) that allow the efficient exploitation of resources used andthe introduction of biogeochemical cycles (Section E 3.2). • Prevention of urban sprawl in urban peripheral zones. However, subsequent population concentrations should not take place to the detriment of open spaces. Soil sealing should be reduced and ecological building should be promoted. • Drawing up concepts for inner city open spaces in order to increase the proportion of open spaces and to interlink them, for example, as habitat-type compounds (Fachdienst Natur und Umwelt der Stadt Neumünster, 1999). The aim should be to secure biological diversity and its functions in towns. Special significance is given to fallow land, gaps in building and green spaces.With fallow land in particular, there is usually special pressure for economic use, for which land use plans have frequently already made provision although this is in conflict with existing, often informal, uses.