In 1900, about 160 million people lived in cities, the equivalent of about 10% of the world's population of 1.6 billion at that time. By 2000, around half of the world's 6 billion people lived in urban areas, and the percentage has continued to grow (Chapter 1). If conservation is to be a universal phenomenon, new ways must be found to enable people who live in cities to be active participants in conservation.
The conservation of nature in cities can be approached from many directions. Benton-Short and Short (2007) provided a social perspective, while Shiro (2004) took a planning approach based on considering cities rather like gigantic organisms, and Isenberg (2006) provided a more historical perspective, with examples from the United States, Europe, and Africa.
While the conversion of forests or farmlands into cities inevitably causes a loss of biodiversity, urban-dwellers actually use less of some resources per person than do those living in the countryside. Apartments in tall buildings are more energy-efficient than individual houses, and cities tend to have more efficient means of providing water, energy and transport than do rural areas. In London, per capita carbon dioxide emissions are only a little more than half of the average for the entire country, while New York City's inhabitants produced less than a third of the average per capita emissions for the United States as a whole. São Paulo and Rio de Janeiro also have substantially lower per capita emissions of carbon dioxide, but cities like Beijing and Shanghai, which contain many factories that produce high emissions, score well above the national average. But at a global level, cities emit 50–60% of greenhouse gases (GHG), rising to around 80% if indirect emissions are included, according to figures by UN-Habitat.
Of course, cities pose problems for ecosystems as well. Cities occupy 2% of the land surface, yet consume 75% of its natural resources. With more people packed into smaller areas of land, infectious diseases may be more easily transmitted. Biodiversity in cities, especially at ecosystem and species levels, is particularly threatened by invasive alien species. This is to be expected, because cities tend to be the focus of international trade which carries invasive species with it (Schwarz et al., 2006). This effect extends also to birds, and the avifauna of urban areas tends to become increasingly homogenized, with rare species tending to drop out and cosmopolitan species such as pigeons and sparrows dominating (Clergeau et al., 2006). And people living in cities need to draw on the surrounding countryside for many of their essential resources, especially food, water and energy.
They also need protected areas, which provide significant benefits to cities, including water supplies, recreation, and various economic and other values. Many people living in cities seek protected areas to provide significant psychological well-being, finding a week in the wilderness of a national park to be an invigorating and life-sustaining respite from the pressures of living in crowded and impersonal cities. Protected areas also depend on cities, for political support, as a source of visitors, and for ensuring a cultural link between urban people and their environment.
Many conservation organizations have recognized the importance of incorporating natural spaces as part of the urban infrastructure. This extends far beyond simple neighbourhood parks, though of course these play an important role. Some cities have been quite ambitious in integrating biodiversity into urban planning. London, for example, has adopted a formal Biodiversity Strategy, with five main elements: enable those who live or work in London to have greater contact with nature in their own locality; protect London's important wildlife habitats and identify over 1,500 such sites; enhance the habitats of public parks and open spaces or create new wildlife habitats for public enjoyment and environmental education; encourage provision of facilities for environmental education and opportunities for all sectors of society to be actively involved in environment projects; and engage a wide range of organizations and individuals in a supporting partnership for the Biodiversity Strategy (Goode, 2005). Many cities have national parks within their borders, or immediately adjacent to them, including large metropolises such as Los Angeles, Rio de Janeiro and Sydney. Protected areas within cities can help protect water resources, provide recreational opportunities, help promote environmental education, and create local jobs.
IUCN has sought to coordinate conservation action within cities, led by the World Commission on Protected Areas (WCPA) Task Force on Cities and Protected Areas, which in turn has contributed to the Global Partnership on Cities and Biodiversity, which began in 2006. And more than 300 local governments have joined in a network to support IUCN's Countdown 2010, which seeks to reverse the rate of loss of biodiversity by that date.
Urban areas can be expected to provide more support to protected areas when people living in cities recognize the benefits such areas provide. For example, Dudley and Stolton (2005) found that around a third (33 of 105) of the world's largest cities obtain a significant proportion of their drinking water directly from protected areas, including Barcelona, Bogota, Brasilia, Caracas, Jakarta, Johannesburg, Karachi, Los Angeles, Madrid, Melbourne, Mumbai, Nairobi, New York, Perth, Rio de Janeiro, São Paulo, Singapore, Sydney, Tokyo and Vienna.
Many other cities manage forests specifically for watershed protection, including Seoul, Tokyo, Beijing, Rangoon, Santiago, New York, Stockholm, Munich and Minsk. Some 90% of the Melbourne (Australia) water supply comes from the uninhabited forested mountainous catchments to the north and east of the city. The majority of these catchments are outside protected areas, but are managed to protect these forested catchments by the government-owned company Melbourne Water. Linking a very practical contribution of protected areas or other biodiversity-rich areas to cities helps to build stronger support for them.
Access to green spaces within cities provides many benefits to people, especially in regards to health, safety and well-being (Kuo et al., 1998). Fuller and Gaston (2009) have sought to assess the green space within 386 cities in 31 European countries, containing over 170 million people (over a third of Europe's population). They found wide variation in green space from 1.9% in Reggio di Calabria, Italy, to 46% in Ferrol, Spain, with cities in northern Europe tending to have greater proportions of green space compared to those in the south. Not surprisingly, they found that the proportion of green space per person generally diminishes as population density increases. Growing population density in cities certainly is a threat to the remaining green areas. For example, Mexico City is losing as much as 500 hectares of park and forest land annually to squatters and development, taking nearly half of the remaining protected open area in the capital over the past decade.
Some experts consider that fossil fuel is essential to the modern approach to urban life (Girardet, 1999). Until very recently, most cities had what might be considered a linear metabolism, with resources flowing into the system without consumers being concerned about either the origin of the resources or the disposal of their wastes. A more appropriate model for cities would be to mimic the circular metabolism of nature, where every output is also an input that helps to sustain and renew the whole system – the essence of ecosystem services. Recycling is already becoming standard behaviour in many cities, and the current financial crisis has demonstrated that it is quite possible to live a decent urban life without high levels of resource consumption. A sustainable city will be able to meet its own needs without threatening the natural world or the living conditions of its citizens.
Many metropolises are already relatively green, with Beijing, for example, producing almost all of its vegetables within its metropolitan region. Others are seeking to become greener.
Despite some significant efforts at greening cities, most of the world's cities are concentrated in neighbourhoods of impoverished biodiversity (Turner et al., 2004). Billions of people may lose the opportunity to develop an appreciation of nature, and lose the benefits that can be gained from such an appreciation. This suggests that a significant effort to provide opportunities for linking people to biodiversity within cities is both necessary and worthwhile.
Some cities have recognized this imperative. Jinan, capital of eastern China's Shandong Province, will plant up to 7,100 hectares of new forests in the next three years. The city is planning to have everyone over the age of 11 responsible for planting three to five trees a year, as part of the city's Blue Sky Project which is intended to create a clean and green environment in this rather polluted city within five years.
One innovative programme for linking urban youth to nature in the countryside is the programme known as “Kids for Tigers”, which was launched in India in 2001, with the objective of encouraging urban children from throughout South Asia to visit nature. While tigers were the draw card, many of the most important issues focused on water (Sahgal, 2005). Over one million children have participated in the programme, from 700 schools in 12 Indian cities.
In recent years, “urban ecology” has evolved as an initiative to integrate natural and social sciences to study the environments of cities and their regional and global effects, based on the principle that cities present both the problems and solutions to sustainability challenges of an increasingly urbanized world (Grimm et al., 2008). The Chicago Wilderness Area (Box 21.2) is one outstanding example.
While invasive species of plants often increase in urban areas, this may increase species richness in cities relative to rural areas, even protected areas. Cities are characterized by a highly heterogeneous patchwork of habitats, and people introduce non-native species of plants with relatively few individuals of each of these species in urban gardens.
Many cities have zoos and botanical gardens that serve as valuable repositories of wild native species, as well as providing an opportunity for urban people to have closer contact with species of plants and animals from all over the world.
Urban ecosystems often bear little resemblance to rural ecosystems, and bird communities often shift to grain-eating species at the expense of those feeding on insects; and many insect communities may lose their specialists while gaining more generalists. Many cities tend to have rather similar urban-adapted species, leading to homogenization as opposed to diversity (Grimm et al., 2008). And with cities being characterized by generally warmer temperatures and far more light at night, many nocturnal species are comparatively disadvantaged. Grimm and her colleagues advocate “reconciliation ecology”, where habitats that are greatly altered for human use are designed, spatially arranged and managed to maximize biodiversity while providing economic benefits and ecosystem services. They suggest that reconciliation ecology offers significant opportunities for ecologists to contribute to designing and managing new cities and helping to reconstruct older ones.
Since the biological communities in cities are the ones that half the human population normally experience, it is increasingly important to ensure that full advantage is taken of the last remnants of “nature” found in urban areas to build support for conservation more broadly.
City-dwellers should promote and vote for city-based strategies that are more resource-efficient, advocate education programmes about nature for urban centres and foster a culture of urban sustainability and conservation.
Urban decision-makers should be encouraged to engage more in biodiversity and protected area issues and to include these in relevant meetings, both national and international. One important opportunity could be the Mayors' Conference in 2010 in Nagoya, Japan, in parallel with the Conference of Parties of the Convention on Biological Diversity (COP CBD). They should also establish and recognize Municipal Conservation Areas as a significant contribution to the global network of protected areas and the international effort to conserve biodiversity and seek to incorporate biodiversity and protected area components in the planning of major urban-based sporting events, such as the Olympic Games (both summer and winter) and the World Cup. Finally, linking with the United Nations Centre for Human Settlement and other relevant parties could improve information flow among urban administrators and business leaders on environmental issues relevant to cities.
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