Climate risks and adaptation in Asian coastal megacities: A synthesis

1IntroductionBackground and RationaleAs recent weather events have illustrated, coastalareas in both developing and more industrializedeconomies face a range of risks related to climatechange (IPCC 2007a). Anticipated risks include anaccelerated rise in sea level of up to 0.6 meters ormore by 2100, a further rise in sea surface temperaturesby up to 3° C, an intensification of tropicaland extra tropical cyclones, larger extreme wavesand storm surges, altered precipitation and runoff,and ocean acidification (Nicholls et al. 2007).The Intergovernmental Panel for Climate ChangeFourth Assessment Report (IPCC 2007a) points toa range of outcomes under different scenarios andidentifies a number of hotspots—including heavilyurbanized areas situated in the large low-lyingdeltas of Asia and Africa—as especially vulnerableto climate-related impacts. For instance, by 2080,the report points out, many millions more peoplemay experience floods annually due to sea levelrise (IPCC 2007a). More frequent flooding and inundationof coastal areas can also result in variousindirect effects, such as water resource constraintsdue to increased salinization of groundwater supplies.Human-induced pressures on coastal regionscan further compound these effects.The location of many of the world’s major cities—suchas Mumbai, Shanghai, Jakarta, Lagos,and Kolkata—around coastlines, rivers, and deltasprovides an indication of the population and assetsat risk. Thirteen of the world’s 20 largest citiesare located on the coast and more than a third ofthe world’s population lives within 100 miles ofa shoreline. Low-lying coastal areas—defined asareas along the coast that are less than 10 metersabove sea level—represent 2 percent of the world’sland area, but contain 13 percent of the urban population(McGranahan et al. 2007). A recent study of136 port cities showed that the population exposedto flooding linked with a 1-in-100-year event islikely to rise dramatically, from 40 million currentlyto 150 million by 2070 (Nicholls et al. 2008).Similarly, the value of assets exposed to floodingis estimated to rise to $35 trillion, up from $3 trilliontoday. The study also shows that significant,increasing exposure is expected for the populationsand economic assets in Asia’s coastal cities.In flood-prone cities such as Manila, potentialsea level rise and increased frequency and intensityof extreme weather events poses enormouschallenges on urban local bodies’ ability to adapt.Apart from their location, the scale of risk is alsoinfluenced by the quality of housing and infrastructure,institutional capacity with respect toemergency services, and the city’s preparednessto respond. The urban poor are most at risk fromexposure to hazards in coastal cities, as they tendto live in riskier urban environments (such asfloodplains, unstable slopes), tend to work in theinformal economy, have fewer assets, and receiverelatively less protection from government institutions(Satterthwaite et al. 2007).Despite its importance, few developing countrycities have initiated efforts to integrate climatechange issues as part of their decision-makingprocess. Given the risks faced by coastal cities andthe importance of cities more broadly as drivers of1