Earthsky Interviews
Private: Amazon plants trigger seasonal change
07-15-2007 - Earth
That’s according Ranga Myneni of Boston University. He uses satellites to look down from above at trees that look green and lush all year round. Satellites measure radiant light reflected by green leaves. They reveal more or less dense leaf cover. Myneni told Earth & Sky that, contrary to what you might expect, there are 25% more leaves in the dry season.
He said that’s because there’s a lot of water deep underground, even in the dry season. The trees have evolved an extensive root system to tap into this water. Meanwhile, during the rainy season, there’s less sunlight and less leaf production.
Ranga Myneni: _In the rainy season the sky is cloudy and there is less light. And in the dry season the skies are generally less cloudy, and there is more light. And therefore, given that there is water, these trees are limited by light, so in the dry season they tend to put more leaves._
During this greener dry season, the leaves themselves pump more water into the atmosphere, which helps trigger the gradual change from a dry to a wet season.
Our thanks today to “NASA”:http://www.nasa.gov: explore, discover, understand.
Myneni said that measuring leaf coverage in the Amazon is important for several reasons. For example, he said, it’s likely that leaves store carbon emitted by industrial activity that otherwise would remain in the atmosphere and contribute to global warming. Knowing more about when rain forest trees are at their leafiest could help scientists understand the role of rain forests in helping to limit this greenhouse gas.
*Our thanks to:*
Ranga Myneni
It has been known for years that planting and mainaining trees will induce more rainfall in a normally arid area. Israel’s work in making a dessert habitable has had some pretty impressive results. I read, some years ago, a piece that advocated taking municipal solid waste and composting it, then spreading it on the Mojave Dessert and using irrigation to promote vegatative growth in an effort to wring a little rain out of the sky and make the dessert more useful. Of course, there was a huge outcry form the environmentalists that the “valuable” ecosystem would be destroyed.
Well, duh! Most folks recognize that desserts are not real productive and do little for humans or anything else but rattlenakes and cactus. Some believe the denizens of the dessert are more important than people. I do not.
Deserts have many amazing properties: among these, deserts can reflect much of the suns radiation (high albedo, around 40%). Deserts, also with no humidity, shed an impressive amount of heat at night. Trees, on the other hand have relatively low albedos ~15%. Our climate system has acheived a balance that we are barely begining to fathom. Before acting on opinions, it would be wise to gather as much information as possible.