Coastal megacities and climate change

Abstract

Rapid urbanization is projected to produce 20 coastal megacities (population exceeding 8 million) by 2010. This is mainly a developing world phenomenon: in 1990, there were seven coastal megacities in Asia (excluding those in Japan) and two in South America, rising by 2010 to 12 in Asia (including Istanbul), three in South America and one in Africa. All coastal locations, including megacities, are at risk to the impacts of accelerated global sea-level rise and other coastal implications of climate change, such as changing storm frequency. Further, many of the coastal megacities are built on geologically young sedimentary strata that are prone to subsidence given excessive groundwater withdrawal. At least eight of the projected 20 coastal megacities have experienced a local or relative rise in sea level which often greatly exceeds any likely global sea-level rise scenario for the next century. The implications of climate change for each coastal megacity vary significantly, so each city requires independent assessment. In contrast to historical precedent, a proactive perspective towards coastal hazards and changing levels of risk with time is recommended. Low-cost measures to maintain or increase future flexibility of response to climate change need to be identified and implemented as part of an integrated approach to coastal management. © 1995 Kluwer Academic Publishers.