“Sustainability” has become the word of the day and the theme of our time. The word—which in essence means meeting the needs of the present generation without compromising the ability of future generations to meet their own (WCED 1987)—tends to conjure bucolic images of landscapes with green hills and empty spaces, but that may be a mistake. Our world certainly is replete with environmental problems: biodiversity loss, ecosystem degradation, landscape fragmentation, climate change, just to name a few. Urbanization—the spatial expansion of the built environment that is densely packed by people and their socioeconomic activities—has often been held responsible for all these problems. In the recent serge of interest in sustainability, some think that urbanization is key to regional and global sustainability, whereas others regard urban sustainability as an oxymoron. Is urbanization a problem or part of the solution for sustainability? Why is it relevant to landscape ecology?
The dualistic nature of urbanization
Year 2007 was a historic moment in human civilization: we have transformed ourselves from an agrarian species to a mostly urban species. Only 2% of the world population lived in urban areas in 1800, but this number jumped to 14% in 1900 and 30% in 1950. In 2007, we crossed the 50% mark—with no signs of slowing down. Clearly, urban areas have become the primary habitat for humans—cities, increasingly, are where people live and thus where we will have to make sustainability a reality.
The increasing urban nature of humanity has profound environmental, economic, and social implications for the world’s future. Urbanized areas account for about 80% of carbon emissions, 60% of residential water use, and close to 80% of the wood used for industrial purposes (Grimm et al. 2008; Wu 2008a, b). Cities suck resources from ecosystems near and far. The “ecological footprint” of a city—the land (and water) area that would be required to provide the urban population indefinitely with all the energy and material resources consumed as well as to absorb all the wastes discharged—can be tens to hundreds of times as large as its physical size (Rees and Wackernagel 1996; Luck et al. 2001). Urbanization influences local climate by creating urban heat islands on multiple scales (Buyantuyev and Wu 2010); it leads to excessive consumption and frequent contamination of water; it creates major producers of greenhouse gases and air pollutants; and it is the most drastic form of land transformation, devastating biodiversity and ecosystem services. In many parts of the world, urbanization is also linked to increased social inequity and poverty—the problem of “urbanization of poverty”.
Yet, cities epitomize the creativity, imagination, and mighty power of humanity. Cities are the centers of socio-cultural transformations, engines of economic growth, and cradles of innovation and knowledge production. Cities are magnificent for the splendid architectures that symbolize them, inspirational for the fascinating stories of human civilization that enrich them, and attractive for the opportunities and comforts that they offer. And, perhaps most importantly, urbanization offers a number of things that are critical to achieving sustainability.
The most remarkable thing about cities is that, even with urban sprawl, they take up merely 3% of the earth’s land surface, but accommodate more than half the world’s population. Cities have lower per capita costs of providing clean water, sanitation, electricity, waste collection, and telecommunications, and offer better access to education, jobs, health care, and social services. Try to imagine a world with nearly 7 billion but no cities. How much intact habitat would there be left for other biological species? What would happen to the economy and society, locally and globally? Could that be a more sustainable world?