[15 October 2012] -- Global urbanisation will have significant implications for biodiversity and ecosystems if current trends continue, with knock-on effects for human health and development, according to a new assessment by the United Nations Convention on Biological Diversity (CBD).
The assessment, which draws on contributions from more than 123 scientists worldwide, states that over 60 percent of the land projected to become urban by 2030 has yet to be built. This presents a major opportunity to greatly improve global sustainability by promoting low-carbon, resource-efficient urban development that can reduce adverse effects on biodiversity and improve quality of life, it says.
The Cities and Biodiversity Outlook is the world’s first global analysis of how projected patterns of urban land expansion will impact biodiversity and crucial ecosystems.
The world’s total urban area is expected to triple between 2000 and 2030, with urban populations set to double to around 4.9 billion in the same period. This urban expansion will draw heavily on water and other natural resources and will consume prime agricultural land.
The report states that urban expansion is occurring fast in areas close to biodiversity ‘hotspots’ and coastal zones. In rapidly urbanising regions, such as large and mid-size settlements in sub-Saharan Africa, India and China, resources to implement sustainable urban planning are often lacking.
“More than half the global population already resides in cities. This number is projected to increase, with 60 percent of the population living in urban areas by 2030,” said Achim Steiner, UN Under-Secretary General and Executive Director of the United Nations Environment Programme.
“This report makes a strong argument for greater attention to be paid by urban planners and managers to the nature-based assets within city boundaries. Sustainable urban development that supports valuable ecosystems presents a major opportunity for improving lives and livelihoods, and accelerating the transition to an inclusive green economy,” he added.
Cities are also increasingly recognised for their role in supporting plant and animal species and diverse ecosystems. For example, over 50 percent of Belgium’s floral species can be found in Brussels, while 65 percent of Poland’s bird species occur in Warsaw.
Urban green spaces perform important ecosystem services, such as filtering dust, absorbing carbon dioxide from the air and improving air quality. Data from the United Kingdom shows that a 10 percent increase in tree canopy cover in cities may result in a 3-4°C decrease in ambient temperature, thus reducing energy used in air conditioning.
Urban biodiversity also delivers important health benefits. Studies have shown that proximity to trees can reduce the prevalence of childhood asthma and allergies. Sustainable urban planning, which addresses biodiversity issues along with other priorities such as poverty alleviation, employment, and housing, can bring positive effects for health and the environment.
The Cities and Biodiversity Outlook highlights a wide range of successful initiatives by cities, local authorities and sub-national governments in both developed and developing countries. In Bogotá, Colombia, measures such as closing roads on weekends, improving the bus transit system and creating bicycle paths resulted in increased physical activity among residents, and a reduction in greenhouse gases emissions.
The report also provides detailed analyses of regional urbanisation trends and their impact on biodiversity and ecosystems.
The region will be home to almost half the world’s increase in urban land over the next 20 years. The most extensive changes will occur in India and China.
India’s growing urban clusters (such as the Mumbai-Delhi industrial corridor) are likely to transform entire regions, with significant impacts on habitat and biodiversity.
Loss of agricultural land to urbanization, combined with insufficient planning for food supply lines, places a severe constraint on future food security for India’s growing population.
Lifestyle changes in India due to urbanisation may decrease pressures on forests due to less use of fuelwood and charcoal.
In China, urban areas are increasingly encroaching on protected areas.
Africa is urbanising faster than any other continent, and most population growth will occur in cities of less than 1 million people. These cities often have weak governance structures, high levels of poverty and low scientific capacity regarding biodiversity.
Low levels of formal employment in cities places high dependency on the provision of ecosystem services (e.g. water and food production) from areas either within or close to city limits.
Latin America and the Caribbean
The number of cities in the region has grown sixfold in the past 50 years.
Urban sprawl caused by housing for low-income residents often occurs in important areas for biodiversity and ecosystem services, such as wetland or floodplains. These are mistakenly considered to be of marginal value by planners.
Europe and North America
The Cities and Biodiversity Outlook was produced by the Secretariat of the CBD in partnership with the Stockholm Resilience Centre (SRC) and Local Governments for Sustainability (ICLEI). The Secretariat of the Convention on Biological Diversity operates under the United Nations Environment Programme (UNEP).