Climate scientists Ken Caldeira and Govindasamy Bala showed that planting trees near the equator provides greater climate benefit than planting in northern countries, because the leaves of new trees planted in the north trap relatively more of the sun's heat.
"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 Dr Bala
On the other hand, says Bala, "...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 fact, planting more trees in high latitudes could be counterproductive from a climate perspective."
This has left me thinking about how important it is that this kind of study not confuse decisionmakers and the public about the important role that forests play in absorbing CO2, and that deforestation plays in increasing levels of CO2. For example, deforestation accounts for 20% of annual human-caused carbon emissions! Protecting forests is therefore a key component of any strategy to reduce carbon emissions (though issuance of carbon credits for protecting forests or planting trees should be carefully calculated based on such ecological factors as a local forest's CO2 uptake, and funds should be used to protect that forest for at least the amount of time required to insure that CO2 uptake).
We also need to remember that protecting forests in mid and northern latitudes provides many valuable ecosystem services in addition to carbon storage, for which people are working on ways to compensate landowners. Right now, owners of forested lands have few options for generating income from trees on their lands other than by cutting them down. Society needs to provide them with more ways to feed their families from income generated by their forests.
If a landowner's, municipality's, or even country's forests are providing valuable ecosystem services (in addition to timber, carbon storage, wildlife habitat, and shade) such as:
- mitigation of floods by trees, which uptake rain water that would otherwise flow into flooding streams and rivers
- filtration of drinking water
- soil stabilization that protects homes and roads from landslides and mudslides
- providing important habitat for pollinators of our crops (studies have shown the yields of some crops are greater when grown near intact forests, due to greater presence of pollinators)
- precipitation (forests help generate it - especially tropical forests, but also temperate ones)
- provision of natural medicines (key treatments for ailments from cancer to a common headache come from forests!)
- provision of fishing jobs by maintaining healthy fish and spawning habitat
Carbon offsets are one means of generating funds to pay landowners to keep their forests intact to protect and maintain ecosystem services. In my opionion, they remain an important, even if imperfect, tool, in spite of this new study (which should certainly be used to guide improvements to forest-based carbon offset schemes in temperate and northern latitudes).
However, carbon offsets should also be just the beginning of compensating landowners for the valuable ecosystem services that their forests provide to society.