Of urban ecosystems & the biosphere

World over cities are inter-linked through political, economic, social and technical systems and also through Earth’s biophysical life-support systems. Cities also have disproportionate environmental impacts at the local, regional and global level, well beyond their borders, yet they provide critical leadership in the global sustainability agenda.  Even though the urban areas cover only a small portion of the surface of the planet, they account for a major share of anthropogenic impacts on the biosphere. Yet, the impacts of urbanization on biological diversity and urban ecosystems as well as the potential benefits from ecosystem restoration in urban areas remain poorly understood. 

Cities acquire huge areas of significantly functioning ecosystems for their consumption and waste disposal and management. Most of the ecosystem services consumed by the cities are generated by ecosystems located outside of the cities themselves, and sometimes even half a world away. It has been estimated that most of the large cities of the world acquire ecosystem areas that are either equivalent to the size of the entire city itself or several hundred times the area of the cities themselves, even if we take in to account only the most basic ecosystem services such as food production, assimilation of nitrogen and carbon, water conservation and the like. As we know the present day analysis mostly focuses on what is referred to as the basic ecology in cities that often deals with aspects such as designing energy-efficient buildings, sustainable transport & providing communities with basic functioning urban environments.

This needs to change and we need to focus more on the ecology of cities that are characterized by various inter-disciplinary and multi-pronged studies with a socio-economic and ecological systems approach. This framework completely acknowledges the complete dependence of the cities on its internal and the surrounding landscape, and thereby portrays the links between urban and rural spaces. Here the city is expressed as an ecosystem by itself. However, we now need to be concerned with the generation capacity and potential of cities, not just to safeguard the well-being of its population, but also to effectively and efficiently manage the resources of urban areas as for development, transformation, sustainability and conservation as well.

We are aware that definitions of ‘urban areas’ and their ‘boundaries’ vary between countries and various geographical regions. The focus here is about the services and benefits provided by urban ecosystems, which are clearly defined as those spaces where the built environment covers a larger proportion of the actual land area. This is mainly because people in cities live at high densities. Most of the times, in the context of urban development and urban planning, the urban ecosystems are often portrayed as encompassing both the built infrastructure and the ecological / green infrastructure. This may certainly be new to ill-informed developers, but should never be the case of urban planners, as they are required to be aware of such significant concepts as part of their studies and experience. 

However, to explain in a simpler way, the ecological infrastructure captures the role that water, soil and vegetation play, either within or near the built environment, in delivering critical ecosystem services at different spatial scales. It includes building, streets, neighborhood, and the associated region). It includes all (natural) green and blue spaces that may be found in urban and peri-urban areas, including parks, gardens, yards, urban allotments, cemeteries, urban forests, single trees, green roofs, wetlands, streams, rivers, lakes, ponds, etc. But defining clear boundaries for urban ecosystems often proves very difficult because many of the relevant landscapes and interactions that are necessary to understand the overall functioning of urban ecosystems extend far beyond these urban boundaries defined by political or biophysical characters. 

Therefore, most of the times, the scope of urban ecosystem analysis and its services reaches beyond the urban space itself; it not only comprises the ecological infrastructure within cities, but also the hinterlands that are directly affected by the energy and material flows from the core urban areas and suburban lands. And these include the city catchment pockets and the more important peri-urban green spaces and even cultivated areas.  Though any ecosystem, however small or big they are, is important to meet urban ecosystem service demands, the focus needs to be on protecting, enriching and maintaining these ecosystem and their services that are critical to sustain the ever growing urban areas.