Tuesday, March 22

Evapotranspiration

Another great UNESCO teaching guide, "The Water Cycle," indicates:

Water evaporates from bare soil just like it does from puddles, lakes and seas. Plants take in water through their roots and lose it through their leaves. This is called transpiration. The two processes together, e.g., from a forest or a field of crops, are called evapotranspiration.

A forest can put between 20 and 50 tons of water vapour into the air per hectare per day. Each year 150,000 km2 of rainforest are cut down (more than the area of Bangladesh).

Therefore, deforestation isn't just bad in terms of soil erosion. It's also dangerous in terms of the water table, and has potentially devastating "downstream" consequences, as well. (In other words, clear-cutting a forest doesn't just hurt me; it huts my neighbors, too.)

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