IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

7.6.5 Human settlement

Adaptation strategies for human settlements, large and small, include assuring effective governance, increasing the resilience of physical and linkage infrastructures, changing settlement locations over a period of time, changing settlement form, reducing heat-island effects, reducing emissions and industry effluents as well as improving waste handling, providing financial mechanisms for increasing resiliency, targeting assistance programmes for especially impacted segments of the population, and adopting sustainable community development practices (Wilbanks et al., 2005). The choice of strategies from among the options depends in part on their relationships with other social and ecological processes (O’Brien and Leichenko, 2000) and the general level of economic development, but recent research indicates that adaptation can make a significant difference; for instance, the New York climate impact assessment projects significant increases in heat-related deaths (Rosenzweig and Solecki, 2001a), based on historical relationships, while the Boston CLIMB assessment (Kirshen et al., 2007) projects that heat-related deaths will decline because of adaptation over the coming century.

The recent case study of London demonstrates that climate change could bring opportunities as well as challenges, depending on socio-economic conditions, institutional settings, and cultural and consumer values (London Climate Change Partnership, 2004). One of the opportunities, especially in growing settlements, is to work towards a more sustainable city and to improve the quality of life for residents (Box 7.5). This can be achieved by making sure that urban planning takes into account the construction density, the distribution and impact of heat emissions, transportation patterns, and green spaces that can reduce not only heat-island effects.

Box 7.5. Climate-change adaptation and local government

Threats and opportunities presented by climate change are typically focused at a local scale; and it makes sense for local authorities, including mayors, to consider adaptive responses. Climate change can threaten lives, property, environmental quality and future prosperity by increasing the risk of storms, flooding, landslides, heatwaves and drought and by overloading water, drainage and energy supply systems.

Local governments around the world already play a part in climate-change mitigation, but they can also play a role in adaptation (see Chapter 14, Section 14.5.1; Chapter 18, Section 18.7.2), as guarantors of public services and as facilitators, mobilising stakeholders – such as local businesses, developers, utilities, insurers, educational institutions and community organisations – to contribute their technical and even financial resources to a joint initiative, such as the one formed for London (London Climate Change Partnership, 2004).

In many cases, in fact, good governance is a key to climate-change risk management strategies. For example, effective zoning can prevent the encroachment of housing on slopes prone to erosion and landslides; and adequate investment in and maintenance of infrastructure will make the settlement less vulnerable to weather extremes.

Models have been established to predict the impact of urban thermal property manipulation strategies resulting from albedo and vegetation changes (Akbari et al., 1997) and urban form manipulation (Emmanuel, 2005). The diurnal air temperature inside urban wooded sites and the cooling effect of trees on urban streets and courtyards, and of groves and lawns, has been extensively quantified in Tel-Aviv, Israel (Shashua-Bar and Hoffman, 2002, 2004). For the Los Angeles region, several studies (Taha, 1996; Taha et al., 1997) projected the effects of increasing citywide albedo levels on mitigating the regional heat island (California’s South Coast Air Basin, or SoCAB). A doubling of the surface albedo or a doubling of vegetative cover were each projected to reduce air temperature by approximately 2°C. Moreover, the study area was projected to experience a decrease in ozone concentration.

Other adaptive responses by settlements to concerns about climate change tend to focus on institutional development, often including improved structures for co-ordination between individual settlements and other parties, such as enhanced regional water supply planning and infrastructure development (Rosenzweig and Solecki, 2001a; Bulkeley and Betsill, 2003). Often, settlements exist in a splintered political landscape that makes coherent collaborative adaptation strategies difficult to contemplate. Policy responses and planning decisions are also hampered by the reactive nature of much policymaking and by the failure to co-ordinate across relevant professional disciplines, related mainly to current obvious problems, when climate change is viewed as a long-term issue with considerable uncertainty.

One approach for improving the understanding of how settlements may respond to climate-change impacts is to consider ‘analogues’ - circumstances in recent history when those settlements have confronted other environmental management challenges. In Vietnam for example villagers have been forced over the centuries to clean, repair and strengthen their irrigation channels and sea dykes before the start of every annual tropical storm season (UNISDR, 2004). In many cases, settlements have acted under the pressure of immediate crises to seek solutions by going beyond their own borders. Cities such as Mexico City have both drawn upon water from and sent sewage water to hinterlands outside their boundaries to deal with weather-related water scarcity and floods. These actions have imposed externalities on those hinterlands (Romero Lankao, 2006).