Accelerated sea-level rise and the effects on coastal areas represent one of the most important impacts of global climate warming as a large part of the world's population and food production is situated along low-lying coasts. Coastal nations of the world should now be planning for one-half to a meter rise in sea level during the next century. While the actual extent of sea rise realized may be larger or perhaps smaller, this amount establishes a reasonable baseline for coastal zone planning activities. With respect to actual measures, priority should be given to projects that are beneficial to presently existing problems in coastal areas.
The lowlands along the world's seas will be the areas most vulnerable to impact. They include the deltaic, barrier island, atoll, and marshy coastlines. Increased storm-induced flooding represents the major danger in developing countries because of loss of life. In western countries, beach erosion will be a primary concern, requiring substantial expenditure of public funds to maintain existing recreational beaches. Marshlands will probably be left to their own destiny, which signals a marked decline in most places.
The responses to accelerated sea-level rise must be based on more than a simple cost-benefit ratio; a host of important considerations cannot be expressed in simple dollar terms. Each area must be considered on a site-specific basis as there is considerable geographic variation in the environmental (e.g., hydrologic, geologic) and cultural (e.g., population, human development) factors. The problem is further compounded by the time lag of several decades that exists between public recognition of the problem and actual construction and full operation of major coastal protective devices. It may be necessary to retreat from the eroding shore in some areas, while fortifying and even reclaiming land in others. Clearly a global response is required in that international research and cooperative efforts represent the only reasonable approach.