Satellite data and images are provocative, even disturbing. They confront us with a global view that can be at once breathtaking, like a piece of art, and yet, in this era of rapidly changing climate, they paint a picture of the demise of the environment. How and if we will respond to what we see is uncertain. That uncertainty lies at the root of our perilous future.
Last month, my colleagues and I published a report, the centerpiece of which is a global map, derived from satellite data, that shows how the distribution of Earth’s fresh water has rapidly changed since 2002. We analyzed measurements from NASA’s Gravity Recovery and Climate Experiment satellites to determine trends in total water storage — groundwater, soil moisture, surface waters, snow and ice — over nearly a decade and half.
Although the map is strikingly simple — color coded from blue to red to show average increases and decreases per year in available fresh water — the story it reveals is complex and troubling.
There have always been geographically distinct classes of water “haves” and “have-nots.” Now, as the map shows, those regions are shifting radically.
Climate models predict that changing weather and temperature patterns will cause the world’s high-latitude and tropical regions — the areas that are already wet — to get wetter, while already dry, arid and semi-arid regions will get drier. But those models foresee major changes coming at the end of the 21st century. Our map clearly shows new patterns emerging today. This includes the U.S.: The northern half of the country has become much wetter, while the southern half has become much drier.
The water future the map portends is daunting.
In California’s Central Valley, parts of which are dark red on our map, mid-latitude drying, persistent drought and falling water tables are already driving the cost of drilling deeper wells far beyond what any average family can afford. And declining groundwater quality and subsiding land are signals that the aquifers are being pushed past their tipping point, losing more water than can be replenished in a year.
The farmlands of the Central Valley and America’s Great Plains, another hot spot on our map, feed the United States and the world. If global groundwater depletion continues there, and in similar regions , it will undoubtedly drive global food insecurity. Higher food prices, shifts in crop selection and changing food availability will be the logical outcome. Ultimately, difficult choices will have to be made, such as moving agriculture to where more water is available, or moving water to where the farms are.
Regions where groundwater and glaciers are disappearing also the health and livelihoods of the billions living in these areas. Several of these hot spots span political boundaries and coincide with volatile regions where the lack of water may act as a trigger for violent conflict. The role of drought in the Syrian war and the refugee crisis is well understood.
Governments and society are unprepared to cope with the water future that our research has literally mapped out. The rapid pace and global scope of change require a response across regions and national boundaries. Few institutions and networks with that kind of authority and reach exist, but they must be fostered, and fast. We need a new water diplomacy that will treat this crucial resource as a vehicle for cooperation rather than conflict.
The map points to the pressing need for national-level water policy discussions in the U.S. We must demand more accountability from elected officials, and from the food industry, the biggest user of water on the planet. Our leaders must know that, as voters and consumers, we expect their commitment to water security.
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