populations. Currently, the amount of irrigated land worldwide is still growing, but because the population is growing even faster, per capita irrigated land area is decreasing. This has enormous implications for food production, because it places increasing pressure on available resources—particularly fertilizers and pesticides—to get greater yield out of every hectare in production.

Furthermore, we are seeing a swift and irreversible ecological change in aquatic ecosystems. Many fish species are threatened or endangered, and some aquatic ecosystems have been altered or destroyed completely. The issue of climate change is perhaps the quintessential global change issue, with enormous—and not completely understood—implications for water. It is clear, however, that as competition for fresh water grows, not only between regions but between different sectors within regions, political tensions and conflicts inevitably occur.

Approximately 1.1 billion of the world’s people do not have access to clean drinking water and 2.4 billion people—40 percent of the global population—lack adequate sanitation services.

Peter Gleick

All of the changes in the ecosystem are important, but the fact remains that we are already having problems meeting the water demands of our population. Approximately 1.1 billion people do not have access to clean drinking water and 2.4 billion people—40 percent of the global population—lack adequate sanitation services. These failures to meet basic human needs for water lead to hundreds of millions of cases of water-related diseases—cholera, dysentery, schistosomiasis, guinea worm—every year. The United States and Western Europe eliminated these diseases long ago, but they remain major problems in many parts of the world.

In the United States and Western Europe, our water quality challenges have shifted toward persistent chemicals, hormones, pharmaceuticals, and trace elements. Unsustainable groundwater overdraft is occurring in many parts of the world: groundwater is being pumped faster than it is naturally being recharged. This is a problem in California, India, and many other places around the world. In some cases, this is accelerating the deterioration of

Unsustainable groundwater overdraft is occurring in many parts of the world: groundwater is being pumped faster than it is naturally being recharged.

Peter Gleick



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