Planting trees is always a good thing but if you want to offset global warming recent scientific evidence indicates that the benefits depend where you plant them.
The research, led by Lawrence Livermore National Laboratory atmospheric scientist Govindasamy Bala, appears in the April 9-13 online edition of the Proceedings of the National Academy of Sciences in an article entitled Combined climate and carbon-cycle effects of large-scale deforestation.
Planting and preserving forests in the tropics is more likely to slow down global warming. More trees in mid-latitude locations like the United States and most of Europe would only create marginal benefits from a climate perspective. Extra trees in the boreal forests of Canada, Scandinavia and Siberia could actually be counterproductive. The farther away from the equator forests are, the more likely they are to trap heat in their dense canopies, raising temperatures. This is known as the albedo effect.
Forests affect climate in three different ways. They:
- absorb carbon dioxide, a greenhouse gas, from the atmosphere and help keep the planet cool
- cool the air by evaporating water to the atmosphere and increasing cloudiness
- absorb sunlight (the albedo effect) that would otherwise warm the earth
Previous climate change mitigation strategies that promote planting trees have taken only the first effect into account.
“Our study shows that only tropical rainforests are strongly beneficial in helping slow down global warming,” Bala said. “It is a win-win situation in the tropics because trees in the tropics, in addition to absorbing carbon dioxide, promote convective clouds that help to cool the planet. In other locations, the warming from the albedo effect either cancels or exceeds the net cooling from the other two effects.”
The study concludes that by the year 2100, forests in mid- and high-latitudes will make some places up to 10 degrees Fahrenheit warmer than would have occurred if the forests did not exist.
The authors are quick to point out that the cooling from deforestation outside the tropics should not be viewed as a strategy for mitigating climate change. “Preservation of ecosystems is a primary goal of preventing global warming, and the destruction of ecosystems to prevent global warming would be a counterproductive and perverse strategy,” said Ken Caldeira, from the Carnegie Institution and a co-author of the report.
Resources:
- Lawrence Livermore National Laboratory: Trees to offset the carbon footprint?
- Treehugger: More Trees in the Arctic Could Mean… Worsening Climate Change
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Welcome to Verda Vivo. My name is Daryl Warner Laux.
[...] mythologies of going Green are frightfully deep and pervasive. If only it were so simple: Trade this evil for thus-and-such [...]