The urban dimension of climate change
The effects of urbanization and climate change are converging in dangerous ways. The global population, today more than 50% urban, faces unprecedented negative impacts in terms of quality of life and social stability.
Indeed, in the coming decades climate change may make hundreds of millions of urban residents – especially the poorest and most marginalized – increasingly vulnerable to floods, landslides, extreme weather and other natural disasters. City dwellers may also face reduced access to freshwater as a result of drought or the encroachment of saltwater on drinking water supplies. Furthermore, thermal expansion of oceans and melting ice will lead to a rise in sea levels threatening many coastal settlements. These are the forecasts, based on the best available science.
While all coastal cities face such threats, the impact on those with populations of over 10 million inhabitants will be substantial. Without extensive adaptation efforts, a one-metre sea level rise in New York, US, could not only inundate coastal areas, but have a devastating impact on the subway system, sanitation facilities, power plants and factories. Lagos, Nigeria, like other cities in the region, is built on low-lying marshy ground. Already subsidence, coastal erosion, flooding, salty groundwater and soil, are problems which a rise in sea levels would render potentially disastrous. In 2010, many people died in Rio de Janeiro, Brazil, when unusually heavy downpours washed away some shanty settlements or favelas nestled precariously on steep slopes above the city centre.
Urbanisation and climate change
While some cities are shrinking, many urban centres are seeing rapid and largely uncontrolled population growth, creating a pattern of rapid urbanization. The fastest rates of urbanization are currently taking place in the least developed countries, followed by the rest of the developing countries – comprising three-quarters of the world’s urban population.
Human activity in cities such as the combustion of fossil fuels, large-scale industrial pollution, deforestation and land use changes, among others, have also led to increasing greenhouse gas (GHG) pollution of our atmosphere together with a reduction of the capacity of oceans and vegetation to absorb them.
Developing countries generate only 25% of the per capita emissions of developed countries. A select number of developed countries and major emerging economy nations are the main polluters. These uneven contributions are at the core of both international environmental justice issues and the global community’s struggle for effective and equitable solutions.
The dynamics of urban centres are intimately linked to geography, including climate and location in relation to natural resources. But urbanization is not only a source of risks – certain patterns of urban development can increase resilience. Climate-friendly urban planning and design is therefore essential in achieving long term urban climate change mitigation and adaptation results.
Linkages between urban areas and climate change
How urban centres contribute to climate change requires an understanding of how transport, heating and cooling systems, industries and other urban activities and buildings act as emitters.
The climate, natural endowments, spatial form and economic base of a city significantly shape energy-use patterns and GHG emissions. Moreover, affluence has been repeatedly acknowledged as a significant driver of such emissions, along with the size, growth, structure and density of the urban population.
Urban development can bring increased vulnerability to climate hazards, but a focus on the exposure of urban settlements to climate change hazards alone is insufficient to understand climate change impacts. Attention to urban resilience, development, socioeconomic and gender equity, and governance structures as key determinants of adaptive capacity and actual adaptation actions is also necessary.
Many slum residents around the world are often environmental refugees who have fled from floods, droughts or other calamities in outlying areas. And in the slums themselves, residents often live in places highly vulnerable to the impacts of disasters such as floods, and are also least able to cope with the effects.
But we have the know-how
We have the science and the know-how to tackle many of the problems cited above. Cities and towns contribute significantly to climate change – from the fossil fuels used for electricity generation, transport and industrial production, to waste disposal and changes in land use.
It is here where cities can make a difference. Cities after all represent the greatest achievements of human civilisation, and although urban areas, with their high concentrations of people, industries and infrastructure, are likely to face the most severe impacts of climate change, urbanisation will also offer many opportunities to develop cohesive mitigation and adaptation strategies to deal with climate change. To be effective, such strategies must be integrated in urban planning frameworks and include actions on energy infrastructure, urban mobility, building design, water management and solid waste management.
Several hundreds of cities are already taking action. Promising examples include the cities of Austin, Chicago, Durban, Hamburg, Maputo, Mexico City, Nantes, Sao Paulo and several cities in China, Korea and the Philippines. The Cities and Climate Change Initiative of UN-HABITAT is currently supporting cities in 20 countries in Africa, Asia and Latin America to develop and implement such climate action plans.
The populations, enterprises and authorities of urban centres will be fundamental players in further developing and implementing these strategies. The policy development and implementation capacity of cities must therefore be harnessed in the emerging international climate change funds and frameworks.