Careful carbon offsets
Computer models of tree planting to offset carbon dioxide show that care must be taken not to plant too many trees in mid-latitude or high altitude locations. [BBC article]
Computer modelling indicates that trees only really work to cool the planet if they are planted in the tropics. The research has been discussed at an American Geophysical Union meeting.
Planting more trees in high latitudes could be counterproductive from a climate perspective Dr Govindasamy Bala “What we have found is 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,” said ecologist Govindasamy Bala of Lawrence Livermore National Laboratory.
“[In] the seasonally snow-covered regions [at even higher latitudes], planting new trees could be actually counter-productive,” he told BBC News.
The basic idea is that trees absorb CO2 during photosynthesis. They can also evaporate water into the atmosphere causing clouds to form, reflecting incoming solar radiation. This works well in the tropics but not so well here in the U.S. More forest cover means more darker, heat absorbing, regions. And in areas that are covered by snow during part of the year, planting trees could actually be counterproductive, due to decreased reflection of solar radiation.
This new study highlights the importance of getting our facts right before we plunge ahead with solutions. On one hand we have an immense problem (climate change global warming) and increasing personal and political will to do something about it. On the other hand, even though the severity of problem is generally agreed upon, we aren’t yet sure which solutions will actually work.
