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This is a difficult predicament if this is not enough already, and global climate change and greenhouse gases from the building, we are very complicated efforts to create a secure water future. Mountain glaciers and snowpacks are natural reservoirs feed many of the world's rivers and melting. As the temperature rose, more rain and snow than rain, they will melt faster. Alaska glaciers from behind by the Alps. But they are shrink-altitude regions of the fastest in Africa, Asia, Latin America and the world, including the majority of poor people live, and most of the world's population, growth will occur.           Water Like Earth Has     Few findings beamed back from outer space generate more intrigue than evidence of the possibility of water on other cosmic spheres. Earth's moon may have ice at the poles. Mars, our colder neighbor, appears to have frozen water in ice caps and possibly beneath its land surface. Europa, one of Jupiter's moons, may have water in a liquid state, thanks to volcanic heat emanating from its core.   No planet or moon comes close, however, to having water like earth has, with its vast oceans, fluid ribbons of fresh water, and voluminous lakes and aquifers—all connected in a solar-powered cycle of renewal. The beauty and variety of earth's landscapes and life-forms are made possible by water. And nature is not making any more of it: the water that is here is all there will be.   ... Human impacts on the hydrologic environment have increased on the order of nine-fold since 1950. This is an enormous change in a very short period of time. Only a portion of this impact stems directly from withdrawals of water for irrigation, industries, and cities, which have tripled over the last century. Most of it stems from human manipulation of natural flow patterns through the construction and operation of dams, reservoirs, dikes, and levees. Species that evolved over the millennia within earth's aquatic ecosystems are now reeling from these human-induced impacts. We have cast them into a race for survival for which they are not evolutionarily prepared. By virtue of our domination, we have become their stewards.   Ecologists now are warning us that stewardship of nature is not an altruistic act, but rather a rational one of self-preservation. The goods and services that aquatic ecosystems provide are too central to human well-being for us to get along for any great length of time without them. They perform functions we depend upon and cannot replicate. Technology has not freed us from this dependence, but has blinded us to it. Whether we realize it or not, our staying power as a species depends upon our ability to coexist with other species.   The deep conundrum we face is how to exercise stewardship of other species when the needs and aspirations of our fellow Homo sapiens are so large, and still growing. Within a generation, some 3 billion people will be living in countries that hydrologists classify as water-stressed based simply on the amount of water available per person. Is there hope for rivers and freshwater species in those places? Between 1950 and today, about 3.5 billion people were added to the planet; 3 billion more will likely be added over the next half century. All people must have access to sufficient water, food, and energy for a healthy and secure life. At the same time, a large global middle class aspires to the high-consumption lifestyles now enjoyed by the richest 1 billion people—including meat-rich diets, luxurious caches of clothes and cars, recreational golfing, and sizeable homes with lush green lawns. Even as world population is growing, per capita global water demand is rising, intensifying total human impacts on fresh water ecosystems.   As if this predicament was not difficult enough, global climactic change from the buildup of greenhouse gases will greatly complicate our efforts to create a water-secure future. Glaciers and mountain snowpacks, the natural reservoirs that feed many of the world's rivers, are melting. As temperatures rise, and as more precipitation falls as rain rather than snow, they will melt faster. Glaciers are already retreating, from Alps to Alaska. But they are retreating fastest in the high-altitude regions of Africa, Asia, and Latin America, where most of the world's poor people live and where most of the world's population growth will take place. For a period of time, accelerated glacial melting will produce an increase in river runoff; but then it will be gone. Officials in La Paz, Bolivia, for example, now openly worry about future water shortages because the glaciers that provide the city's water are retreating so quickly. As Robert Gallaire, a hydrologist with a French scientific institute studying the Bolivian glaciers told a reporter for the New York Times, "The problem is we are using reserves that are being reduced. So we have to ask, what will happen in fifty years? Fifty years, you know, is tomorrow."   Against this backdrop of demographic, consumptive, and climatic pressures, rivers and the panoply of life they sustain would seem doomed. However, disastrous loss of freshwater biodiversity is not yet a foregone conclusion. Homo sapiens is among the life-forms that rivers sustain. At some point, the compulsion to save ourselves, as a species, will trigger an impulse to save the aquatic ecosystems that life depends upon.         — Sandra Postel, Brian Richter, Rivers for Life: Managing Water For People And Nature Epilogue – Can We Save Earth’s Rivers                         Indexes/18