…GO PLANT A TREE?

Turns out you might have to go a long way to plant one. Maybe it would be better not to cut them down in the first place?

Care needed with carbon offsets
Jonathan Amos, December 15, 2006 (BBC News)
- Planting forests to combat global warming may be a waste of time, especially if those trees are at high latitudes, new research suggests.

- Scientists say the benefits that come from trees reducing atmospheric carbon dioxide can be outweighed by their capacity to trap heat near the ground.
- Computer modelling indicates that trees only really work to cool the planet if they are planted in the tropics…in the so-called mid-latitude region where the United States is located and majority of European countries are located, the climate benefits of planting will be nearly zero…[In] the seasonally snow-covered regions [at even higher latitudes], planting new trees could be actually counter-productive…
- three key factors are involved:
[1] forests can cool the planet by absorbing the greenhouse gas carbon dioxide during photosynthesis
[2] they can also cool the planet by evaporating water to the atmosphere and increasing cloudiness; a deck of white clouds reflects incoming solar radiation straight back out into space
[3] trees can also have a warming effect because they are dark and absorb a lot of sunlight, holding heat near ground level

"Our study shows that tropical forests are very beneficial to the climate because they take up carbon and increase cloudiness, which in turn helps cool the planet," explained [one of the research team’s leaders]…The further you move from the equator, though, these gains are eroded…planting more trees in mid- and high-latitude locations could lead to a net warming of a few degrees by the year 2100…"The darkening of the surface by new forest canopies in the high-latitude boreal regions allows absorption of more sunlight that helps to warm the surface…"
- The study finds little or no climate benefit when trees are planted in temperate regions.
The scientists warn that many schemes designed to offset emissions of carbon by planting trees may not be appropriate…