Can trees offset carbon footprint?

• Position: Global Warming

How effective are new trees in off-setting the carbon footprint? A study by Lawrence Livermore (Calif.) National Laboratory suggests that the location of the new growth is an important factor when considering such carbon offset projects. For instance, planting and preserving forests in the tropics is more likely to slow down global warming. However, the study also concludes that planting new trees in certain parts of the planet actually may warm the Earth.

New forests in mid- to high-latitude locations could create a net warming effect. Specifically, more trees in mid*latitude locations like the U.S. and most of Europe only would create marginal benefits from a climate perspective, but those extra trees in the boreal forests of Canada, Scandinavia, and Siberia could be counterproductive, maintains atmospheric scientist Govindasamy Bala.

Forests affect climate in three different ways: absorbing the greenhouse gas carbon dioxide from the atmosphere to help keep the planet cool; evaporating water to the atmosphere and increasing cloudiness, which also helps keep the planet cool; and absorbing sunlight (the albedo effect), thus warming the Earth. Previous climate change mitigation strategies that promote planting trees only have taken the first effect into account.

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