Wednesday, May 11, 2011

Excerpt from writing project

Virtually all scientists also agree that there is a fixed amount of water on Earth, and whatever water now exists on the planet simply moves around in its three main forms—liquid, solid, gas—according to a variety of mechanisms. The human body is about 70% water, so quite a bit of water is tied up in human bodies, in fact, about 600,000,000,000 pounds of it, which rounds out to about 72,517,985,612 gallons. Lake Superior is the largest body of fresh water in the United States; its volume is about 12,100 km3, envisioned as a cube 14.3 miles in all dimensions, which equals 31,794,757,632 cubic feet, or 165,332,739,686 gallons, or about two and a half times as much as is currently tied up in living human bodies. Lake Baikal, in southern Siberia, is the largest body of fresh water in the world, with about 23,000 km3, which equals 816,247,000,000,000 cubic feet, or 6,105,530,000,000,000 gallons, or 555,048,000,000,000 people, which scientists estimate is between 5,000 and 6,000 times the carrying capacity of Planet Earth. Obviously there is plenty of fresh water on Earth for the human population. Getting it from Lake Superior or Lake Baikal to where it is needed is quite a different matter.

We use water for many reasons, most or all of which are at least indirectly associated with the building of human tissues: agriculture, manufacturing, generation of electricity, medicine, etc. Agriculture, however, is the big user of water, which means that we are spending lots of water, indeed some estimates are up to 70% of available freshwater, to grow food. Thus we are consuming most of the planet’s available water simply to store water, in the form of cytoplasm, in ourselves. For example, it takes approximately 1000 tons of water (~240,000 gallons) to produce a ton of rice, about 450 tons of water (~107,900 gallons) to produce a ton of corn, and 1360 tons of water (~326,098 gallons) to produce a ton of soybeans. Water requirements for wheat are a little more difficult to calculate, mainly because wheat is grown quite differently than corn or rice, but a rough estimate is over 2000 tons of water (~526,000 gallons) per ton of wheat. Don’t bet the farm that these figures are anything other than approximations; I had to do quite a bit of conversion (gallons or bushels to pounds, etc.), but they are based on a wealth of readily available information. Some figures were given in metric tons (=1.1 US tons), so the weight estimates may be off a little bit if my sources did not indicate whether the unit was metric or US standard. For sources, see Internet sites listed in the References chapter, or simply do your own Google™ search, calculator and notepad in hand.

In 2009, world corn production was estimated at 817,110,509 million Mt (metric tons), rice at 678,688,289 Mt, wheat at 681,915,838 Mt, and soybeans at 210,900,000 Mt (again, see figures in agricultural information web sites in the References). Thus Homo sapiens used 1.96 x 1020 gallons of water, or about 32,000 times the volume of Lake Baikal, to produce the 2009 world corn crop. Given that Lake Baikal has enough water to make about 5,500 times the human carrying capacity for Planet Earth, these figures mean that in 2009, our species used water equivalent to 176,000,000 times the human carrying capacity for Earth, just to grow corn. Similar calculations for rice, wheat, and soybeans produce equally startling results. And, of course, we have not even considered all the other crop plants currently used by H. sapiens, including those with edible roots and leaves.

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