Concerns surrounding the environmental credentials of carbon offset projects took centre stage again this week after a new scientific report suggested that far from tackling climate change tree planting projects could actually contribute to global warming.
The study, which was published yesterday in the Proceedings of the National Academy of Scientists, argued that while prevention of deforestation and promotion of afforestation can limit levels of CO2 in the atmosphere additional biophysical affects mean deforestation has a net cooling effect on the climate.
The report, which is based on the results of several large scale deforestation climate change models, argues that while most forests have little impact on global temperatures, those at the higher latitudes could increase temperatures because tree canopies absorb more heat than snow or scrubland. These increases in temperature are likely to be greater than any reduction in temperature brought about by the trees' ability to absorb atmospheric CO2.
Only afforestation projects in the tropics are likely to limit global warming, according to the reports' climate models, because these forests absorb higher levels of CO2 and also create clouds which reflect heat back out of the atmosphere.
However, with this positive effect only confined to tropical forests the report concludes that "global-scale deforestation has a net cooling influence on Earth's climate, because the warming carbon-cycle effects of deforestation are overwhelmed by the net cooling associated with changes in albedo and evapotranspiration".
The report's authors are quick to point out that their conclusion is not to be interpreted as a reason to promote deforestation as a means of tackling climate change, arguing that forests at high latitudes remain valuable resources for a myriad of environmental reasons.
However, the findings will increase calls for a moratorium on forestry-based carbon offset schemes in temperate regions such as Europe and North America.
Such projects have become popular in recent years with firms keen to offset their own CO2 emissions. Rock band Coldplay famously offset the launch of one of its albums by investing in a number of forestry schemes, while several IT companies including chip manufacturer Via and hardware giant Dell have offered customers the opportunity to offset the carbon emissions of new purchases through tree planting schemes.
However, these schemes have faced plenty of criticism with climate scientists arguing that there is no reliable means of calculating how much CO2 trees absorb over their lifetime, environmentalists such projects distract companies from the more important task of reducing carbon emissions, and jouranlists reporting that some of the projects have been poorly managed.
While many firms providing forestry-based offsets have responded to this criticism by shifting investment towards alternative offsetting projects based on renewable energy or improvements in energy efficiency, others have defended their continued spending on forestry initiatives by claiming they do have some net benefits.
But now those claims look more dubious than ever and while some offset firms may contest the new report's findings it does further highlight the lack of scientific certainty surrounding the environmental credentials of afforestation initiatives.
Once again the message for any firm interested in investing in carbon offset projects is to think very carefully about the environmental gains associated with such projects and audit them thoroughly to ensure your money is going towards initiatives that deliver indisputable climate change benefits.
After all, the last thing anyone investing in projects designed to tackle climate change wants is to have to face the horrible realisation that they could in fact be contributing to global warming.
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