Water = life on earth
Accessible water sets Planet Earth apart from every other planet we have discovered—in the universe. Water covers a majority of the planet's surface, and while only 3 percent of this is fresh water—and two-thirds of that is locked up as ice in the polar regions or in glaciers—there’s still plenty to sustain life.
But this life-giving liquid is in jeopardy from human activity
Over 700 million people in the world don't have ready access to clean water, and nearly twice this number have inadequate sanitation. As a result, 9000 children die every day from causes related to impure water. Meanwhile, the world spends over $65 billion annually on bottled water—the majority of this in the Rich World where it is unneeded.
As the climate warms and becomes less stable, it will affect rainfall patterns, drenching some areas with more rain than ever, while creating some 50,000 square miles of new desert every year. These weather-related "natural disasters" threaten the well-being of 135 million people in 100 countries—and are predicted to create tens of millions of environmental refugees in the coming decades. Low-lying areas, such as coastal regions of South Asia, are already being affected by rising sea levels, caused both by thermal expansion of sea water and by melting glaciers and polar ice caps.
Overuse and Pollution
In the US, we're over-pumping our aquifers (underground reservoirs of water) by 3.2 billion gallons a day. The Ogallala Aquifer, irrigating one-fifth of the US grain crop, is dropping by 12 billion cubic meters a year. A leading cause is meat consumption, as it can take nearly 2000 gallons of irrigated grain to produce 1 pound of beef. In other parts of the world, water sources are even more imperiled. In India, Coca-Cola bottling plants for soft drinks and water cause aquifers to drop dramatically. Water privatization is also an issue in many areas, as corporations try to capture the market on this precious resource.
Primarily due to agricultural run-off (farm waste and fertilizers) and burning fossil fuels, there are over 400 "dead zones" in the world's seas and oceans—including in the Chesapeake Bay and Gulf of Mexico—places so oxygen-depleted that sea life cannot live there. In addition, mercury levels in the oceans have risen precipitously during the industrial era, adding this toxin to the human food chain.
Another form of pollution is the over-acidification of the world’s oceans due to CO2 absorption. The resulting carbonic acid prevents shellfish from forming shells and threatens the survival of coral reefs.
Finally, there's simply trash. The oceans have become a repository for all manner of waste—especially plastics—to the point that there are now some 20,000 pieces of trash per square mile. Most of this originates on land, not from boats and ships.
Want to keep the water flowing? Here are some ideas:
Sources: The World's Water, Peter Gleick; Earth Under Fire , Gary Braasch; The Omnivore's Dilemma, Michael Pollan; UNDP; State of the World 2004, World Watch Institute; Earth Policy Institute; United Nations Environment Program