While cities only occupy two per cent of the Earth's land surface, they draw on their hinterlands for goods and services. Waste and emissions produced by urban dwellers, moreover have an impact on ecosystems elsewhere, even at the global level. For this reasons, cities depend on so called ecosystem services - benefits that nature provides us for free.
Those ecosystem services have provisioning (such as food and water), regulating (as flood control), cultural (such as for recreation) and supportive characters (like nutrient cycles). Healthy ecosystems and a rich biodiversity, i.e. the multiplicity of living organisms and ecosystems, are vital for cities to function properly. Not only do ecosystem services provide urban residents with food and clean water, they also play an important role for the quality of life in a city: ecosystem services regulate a city's climate, filter emissions and can protect a city against flooding. Despite the importance of a healthy ecosystem, little is done to mitigate the negative impact that by factors including over-exploitation, climate change, land use change, urban sprawl, traffic, air pollution and invasive species have on it.
Cities across the globe have started to implement approaches in city planning and to undertake initiatives to utilize and protect their urban and extra-urban ecosystems. UNEP has existing expertise in ecosystem services at a global level and is collaborating with partners like the World Bank to develop strategies to implement the same at the city level. Local involvement will ensure that smart investments are made to protect the services provided by the environment and enjoyed by cities.
Further the Convention on Biological Diversity (CBD) recognized local authorities as indispensable support for national governments in the implementation of the Convention. This decision, taken during the CBD COP 10 meeting in Nagoya in October 2010, is a real success as it underlined for the first time, the significant role of cities and local governments in the management and conservation of biological diversity. To recognize particularly the role of Ecosystems and Biodiversity in African cities, UNEP and UN-Habitat published Viumbe Hai – a brochure with six African case studies illustrating the sustainable use of ecosystems in the urban context.