Ecology & the city


Ecology & the city

Many cities were founded in riparian areas, ecological transition zones or locations that are naturally species rich. To achieve meaningful, long-term success in urban biodiversity conservation, a large block of protected habitat, responsible development in adjacent areas and a balance between the needs of nature and the needs of human population are crucial, observes Antony P U

Over a half of the earth’s human population now lives in cities. Urban life has a huge impact on the mental and physical well-being of an individual. The human race has always closely bonded with nature. It is only recently that many of us have been confined to man-made environments. For us, contact with green spaces in urban concrete jungles is like going back home. Thus conservation of biodiversity in the urban scenario is very essential for healthy individuals and society. 

Many cities were originally established in riparian areas, ecological transition zones or other locations that are naturally species-rich. This creates both problems and opportunities for conservation biology. To achieve meaningful, long-term success in urban biodiversity conservation, a large block of protected habitat, ecologically responsible development in adjacent areas, and a careful balance of the needs of nature with the needs of human populations are required. Often, cities do not contain large enough habitat blocks to sustain viable natural populations of most plants and animals, but small blocks can link with the surrounding habitat on the city margins. Urban areas provide an opportunity to teach environmental processes and conservation to large numbers of people, including those who lack the means or motivation to travel to non urban areas, where exposure-based wildlife education has been located traditionally.

The need for wildlife-centred education is increasing. Children need first-hand experience with biodiversity to become passionate about its protection. Many conservation organisations realise that outreach and education must be a cornerstone of long-term conservation efforts, but there is still too little emphasis on the urban landscape, where most people live and work.

Ecosystem services

In an urban context, even small green spaces can provide high impact ecosystem services, if they are well planned. For example, small wetlands can improve urban hydrology by absorbing contaminants or buffering against flooding and vegetated rooftops can reduce the heating and cooling costs of buildings and slow runoff during rainstorms. Green rooftops can have the added benefit of enhancing local biodiversity, not only for the initially installed plants but also for beetles, spiders, birds, and additional plants that subsequently colonise the site.

Some of the insects and birds might be especially important as pollinators, given the growing interest in small-scale urban agriculture. Another important ecosystem service is the scope for improving some aspects of air quality in urban areas. Although the overall percentage reduction in pollution is small for most pollutants; urban trees can be a cost-effective component of pollution-reduction strategies in urban areas. Larger effects of urban vegetation are evident in carbon cycles. In the struggle to come to grips with global warming, the carbon budgets of cities will become much more important. Increased amounts of urban vegetation can sequester substantial amounts of carbon. Especially interesting is the possibility that urban trees can have a stronger effect on carbon budgets than trees outside cities. Exotic species may be equivalent to, or sometimes even better than native species in providing some services.

If trees and shrubs need to be purchased for greening of a developed urban space, the least expensive and most biologically effective option might actually be commercially available cultivars that are not native to the region. Non-native vegetation could be a reasonable solution for providing ecosystem services and perhaps also for providing human health benefits.

Human well-being

Physically, human health can be improved by urban ecosystem services such as reduction in air pollution. Exposure to natural environments can promote emotional well-being through mechanisms such as making problems feel more manageable. The psychological benefits of exposure to urban green space increase with greater biodiversity, as measured by species richness of plants, birds, and butterflies. Although there may be human health benefits from exposure to any urban green spaces, the ability of the public to benefit from species richness suggests that the protection or creation of biologically diverse urban environments is important.

Beyond the immediate benefits to human health, broader conservation goals can be served by creating high-quality interactions between people and the natural world. Improving human well-being might be seen as a by-product of successful conservation in urban areas, but this effect can catalyse people to be more supportive of other efforts at biodiversity conservation. The problems of urban conservation are not insurmountable, but success requires a careful start. The first step is to answer the fundamental questions of why urban biodiversity should be conserved and what species assemblages or ecosystem functions are desirable and achievable in an urban setting. Without such an explicit starting point, progress will not be effective and limited conservation resources may be wasted.

Enriching life

Many organic wastes generated by the urban life style are acted upon by bacteria and other soil organisms to provide useful by-products to nourish the soil. Other scavengers right from jackals to crows and kites play the active role of janitors while, many kinds of insects and birds are pollinators and seed-dispersal agents in the city landscape. Reptiles such as snakes and house geckos are vital biological pest control agents. These are just some of the visible merits of wildlife within an urban ecosystem. Urban biota could also be biological indicators of the health of the environment. Yet, an ever-growing population and the demands of human needs in a typical metropolitan city put pressure on the local flora and fauna. The impact of industrialisation, real estate, uncontrolled waste disposal and propagation of alien plant species, overexploitation of natural resources and habitat loss has already altered the composure of the urban ecosystem drastically.

Tackling biodiversity blindness

One other challenge to understanding the connection between urban biodiversity and human well-being is that much of this biodiversity goes undetected by the vast majority of people. Cities impact the biodiversity of their nearby surroundings. City activities generate sewage, solid waste and air pollution, which generally have an effect on the biodiversity in adjoining areas, such as rivers and marine or terrestrial hinterlands. The expansion of cities, both spatially and economically, also has tremendous impacts on these surrounding areas. Moreover, many resources needed in a city come from its surroundings (water, food, etc.) in the form of ecosystem services.

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