Plant a tree and warm the planet

Stan Beer
Wednesday, 11 April 2007 04:55

Science - Climate

There are many in the scientific community who believe that the solution to our planet's global warming problem is to plant more trees. However, according to a new study, wholesale unplanned reafforestation could in fact worsen rather than improve the climatic conditions of Earth.

According to researchers, including Ken Caldeira of Carnegie’s Department of Global Ecology and Govindasamy Bala at Lawrence Livermore National Laboratory, the problem is that if trees are planted in the wrong regions of the world the resultant effect could be heightened rather than lessened global warming.

Trees are generally thought to lessen the effects of global warming because they act as carbon sinks and emit water vapour to produce clouds.

However, the researchers say that simulation shows that trees planted in temperate and snowy regions could in fact increase global warming because their dark color absorbs sunlight in greater quantities than snow which reflects sunlight and they produce less clouds than trees in warmer regions. In contrast, researchers the found that because tropical forests store large amounts of carbon and produce large quantities of reflective clouds, they are especially good at cooling the planet.

“Tropical forests are like Earth’s air conditioner,” Caldeira said. “When it comes to rehabilitating forests to fight global warming, carbon dioxide might be only half of the story; we also have to account for whether they help to reflect sunlight by producing clouds, or help to absorb it by shading snowy tundra.”

Therefore the key to reducing global warming, according to the researchers, is reafforestation of forests in tropical regions while leaving forests in other regions alone.

As a side note, since 1970 more 600,000 square kilometers of Amazon tropical rainforest in Brazil has been destroyed, with more than 20% of the destruction occurring since 2000. Al Gore's recent film, An Inconvenient Truth, largely ignored the deforrestation component of global warming while focussing almost exclusively on man-made carbon dioxide emmissions.