Chapter 3: Safeguarding Freshwater Ecosystems

Sandra Postel

Like any valuable asset, the global water cycle delivers a steady stream of benefits to society. Rivers, lakes, and other freshwater ecosystems work in concert with forests, grasslands, and other landscapes to provide goods and services of great importance to humans. (See Box 3–1, p. 42.) The nature and value of these services can remain grossly underappreciated, however, until they are gone.

Today we are tempted to think that our globalized and technologically sophisticated world is immune to harm from deteriorating natural systems. But there is no side-stepping human dependence on the water cycle. More than 99 percent of the world’s irrigation, industrial, and household water supplies comes directly from rivers, lakes, and aquifers. Wetlands and river floodplains protect people from floods, provide spawning habitat for fish, recharge groundwater supplies, renew soil fertility, and purify water of contaminants.

Human impacts on freshwater systems have reached global proportions and have disrupted a wide range of valuable ecological services. (See Table 3–1, pp. 43-44.) Signs of overstressed and deteriorating ecosystems take many forms—disappearing species, decimated fish populations, falling water tables, altered river flows, shrinking lakes, diminishing wetlands, declining water quality, and pollution induced “dead zones.” Virtually all these indicators are worsening, and they collectively affect large areas of the globe.

Meeting today’s needs for water requires new approaches. Fortunately, forward-thinking cities, villages, and farming regions around the world are demonstrating that drinking water, food security, and flood control can be provided in ways that take advantage of ecosystem services instead of destroying them—and often for a fraction of the cost of conventional technological alternatives.

Special Focus, China & India

Box 3-2: India and Low-Cost Drip Irrigation, p. 53

Box 3-3: Investing in Natural Capital in China’s Yangtze Watershed, p. 56

Sandra Postel is director of the Global Water Policy Project in Amherst, Massachusetts, and a Senior Fellow at the Worldwatch Institute. An expanded version of this chapter appeared as Worldwatch Paper 170, Liquid Assets: The Critical Need to Safeguard Freshwater Ecosystems.