Acrobat Reader 13. The world's marine ecosystems and the marine fisheries that they support are a vital part of the global food supply. An estimated 950 million people, mostly in developing countries, depend on fish as their primary source of protein. Yet there are continued signs that marine fisheries are in serious trouble.
Discussion then turns from the vast oceans to the far smaller freshwater resources.
Fresh water is unevenly distributed over the globe, with abundant supplies available in some localities and much smaller amounts available in others. This chapter looks at the expanded use of freshwater resources. It examines a proposed indicator of future pressures on these resources, the water stress index, and considers its limitations. It also reports on one analysis based on the index that concludes that by the middle of the next century, as much as 18 percent of the world's population could live in countries suffering from water scarcity. The chapter also reports on the potential for improving the efficiency of water use and managing water resources more effectively, measures that could markedly increase the availability of water to meet future needs.