The World in 2050_ Four Forces Shaping Civilization's Northern Future - Laurence C. Smith [46]
The third point—and frankly one that is all too often neglected by policy makers and scientists alike—is that these numbers alone do not tell the whole story when it comes to human water supply. Recall that water, unlike oil, is a circulating resource. It recycles constantly through the hydrologic cycle, in infinite loops of rain, runoff, evaporation, and various storage compartments, like ice. From a practical standpoint the throughput of freshwater (or “flux”) is just as important as the absolute size of its various containers. The total volume of water held in rivers at any given instant is tiny, but it is replaced quickly, unlike, say, an ancient glacier or slowly oozing aquifer. A water droplet moves down a natural river in a few days, whereas the same droplet moving through glaciers, groundwater, and deep ocean currents could be stuck there for centuries to hundreds of thousands of years. This explains the seeming paradox that despite the world’s rivers’ instantaneous storage capacity of just two thousand cubic kilometers of water, we pull almost twice that amount from them every year.198
This is why rainfall and surface water, despite their diminutive holdings, are so critically important to land-based ecosystems and people. Their fast throughput is what makes them so valuable. But because their storage capacities are so tiny, we are vulnerable to the smallest of variations in that throughput. Unlike an ocean or glacier, the atmosphere and rivers have no meaningful storage capacity from which to draw water in dry times or hoard it in wet times. Therefore, terrestrial life is highly sensitive to floods and droughts, whereas marine life is generally not. Tuna have plenty of worries, but droughts are not one of them. Battling this vulnerability is a prime reason why we have built millions of dams, reservoirs, lakes, and ponds throughout the world. Yet even after all this massive engineering, we still have only enough of these artificial impoundments to store slightly less than two years’ water supply.199
The other big problem for humans, of course, is that this small bucket of fast-recycling river water is spread very unfairly around the planet. Canada, Alaska, Scandinavia, and Russia are veined with so many permanent streams, rivers, and lakes that most have never been named, whereas Saudi Arabia has no natural ones at all. Water-rich Norway has 82,000 cubic meters of renewable freshwater per person while Kenya has just 830.200 And to a very large degree, this unfair distribution of surface water is created by the pattern of the global atmospheric circulation itself.
Rainmaker, Land Baker
Just a hundred steps into the rain forest my head was thudding, my shirt drenched, and I couldn’t breathe. It wasn’t claustrophobia—although I couldn’t see well through the green gloom of filtered canopy light—but the wet, steaming heat. It was like inhaling vapors over a teakettle. Something went soft under my foot—I had unwittingly crushed an exotic caterpillar the length of my hand. I excused myself from the group and walked gasping back toward the boat, but was intercepted by an aboriginal man. He was selling tiny clay couples with enormous genitalia, eternally frozen in joyous copulation. Back on the boat, a hot breeze blew down the Amazon River but my skin dripped even faster. The air was totally saturated. I couldn’t wait to get back to my air-conditioned hotel room in Manaus.
I must have caught the Amazon on a bad day. Most living things love tropical rain forests. Their wide green sash—plain on any world map, roughly encircling the equator—is bursting with life and contains the vast majority of species, known and as yet undiscovered, on Earth. Rain forests grow there thanks to the condensate downpours dumped by the moist, rising air masses of the Intertropical