A time series of global irrigation and groundwater depletion maps reveals geographical patterns in the use of fresh water for agriculture. The amount of water involved is enormous. Worldwide, the irrigation of farmland accounts for about 70 of the fresh water diverted by human activity. We might each drink only a few liters (quarts) of water per day, but the food we eat can require a thousand times as much water to produce. Some of the underground aquifers tapped for irrigation replenish so slowly that they are considered a non-renewable resource. The overuse of this groundwater could have long-term consequences for food security and the stability of global markets in food, cotton, and other agricultural products. A new study by researchers at University College London and NASA's Goddard Institute of Space Studies in New York City combines trade data and a global water usage model to determine which crops are grown with non-renewable groundwater and where those crops are consumed. The study appears in the March 30, 2017 issue of Nature.
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