It’s easy to loose sight of how our normal activities of daily living impact the environment on which we all depend for our livelihood. But they do –profoundly.

The environment is being over exploited, and it shows: climate change, pollution, fresh water depletion, declining food production, deforestation, and ocean over-fishing, among other things, threaten to plunge nuclear-armed humanity into a deadly struggle for control of vital resources.

Thousands of years ago someone realized that growing food was far easier and efficient than hunting and gathering, and sedentary civilizations began to appear near springs, rivers and other bodies of water. Today, our knowledge of agriculture has progressed to a science. But when it comes to water, not much has changed since the Bronze Age. While our technology is superior by several orders of magnitude –pumps and electricity- we still depend on natural precipitation, which we do not control, to replenish our rivers, lakes, aquifers and reservoirs.

That will not suffice. Over the next 40 years demand for fresh water will rise 50%, demand for energy will nearly double, and, according to the Food and Agriculture Organization of the United Nations, by 2050 humanity will need to grow 70% more food than today to feed itself. Already nearly 70% of the fresh water humanity uses goes to irrigation; where will the additional water come from?

We are draining rivers, lakes and aquifers at an unsustainable rate. The Ogallala Aquifer beneath the high plains, used to irrigate 27% of the farmland in the United States, is dropping three feet per year; at that rate it will run dry before the end of this century, perhaps sooner. In India, the Indus River Valley Aquifer is being drained at a rate of 20 cubic kilometers a year, and the North China Plain Aquifer, the main source of water for fields feeding millions, is dropping at a rate of 10 feet per year. Drought has taken its toll even on the mighty Amazon, and the great rainforest is dying at an alarming rate. The Colorado River and the Yellow River in China no longer reach the sea, and central Asian rivers, which once fed the Aral Sea, have been drained to the point that it is now a salty dry lake bed.