Biodiversity-Ecosystem

. 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 upon so called ecosystem services - benefits that nature provides us for free of charge . 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 a crucial role for the standard of life during a city: ecosystem services regulate a city's climate, filter emissions and may protect a city against flooding. Despite the importance of a healthy ecosystem, little is completed to mitigate the negative impact that by factors including over-exploitation, global climate change , land use change, conurbation , traffic, air pollution and invasive species have on it.