Turning Off the Pump

Interesting piece in yesterday's New York Times about the link between deforestation and drought. Especially tropical deforestation. A mature tree in Amazonian rainforest transpires about 1,000 liters of water a day; the entire Amazonian Basin sends up about 20 billion tons of water a day into the atmostphere. The atmosphere over Amazonia carries more water than the Amazon River – which itself contains about one fifth of all the freshwater on the planet.

According to the article:

"One way forests may move water is known as biotic pumping. As water transpires into the atmosphere above the forest, the theory holds, it creates a low-pressure system that sucks in air surrounding it, eventually and continually pumping moisture inland from the ocean.Cutting down forests degrades these low-pressure systems, essentially turning off the pump. Large-scale deforestation is thus believed to be a major contributor to the extreme drought in Brazil".

and

"Forest represent a kind of ecological infrastructure that helps maintain comfortable living conditions on the plante, whether by taking up and holding carbon dioxide, cleaning water through their roots, preventing floods by stabilizing soil – or, in this case, regulating climate". 

Lots of reasons to stop cutting down tropical forests. And, really, how many soybeans and hamburger patties do we need?  

Uxpanapa

The Uxpanapa region of southwestern Veracruz originally contained one of the largest expanses of tropical forest in Mexico. Between the years of 1974 and 1976, over 85,000 hectares of forest were cleared as part of a plan to resettle Chinanteco communities that had been displaced by the construction of the Cerro de Oro dam in Oaxaca.  Unfortunately, the deforested areas proved unsuitable for mechanized agriculture and the land was subsequently abandoned. A lot of lessons here. [NOTE: I was visiting a student's research site in Uxpanapa when I happened on these guys. They had just stopped cutting to have their lunch].

Erosion

This is what it looks like when you deforest an entire watershed, cause massive amounts of erosion, and silt up a river. Nice colors, but a large price to pay for the next generation that tries to live here. [Photo is from Central Luzon, Philippines; scanned from a slide].