Afforestation (planting forests) is one of many suggestions as a way to deliberately change the earth’s climate to attempt to reverse the effects of climate change (known as ‘geoengineering’). Planting more trees seems like a an obvious, natural solution. Carbon offsetting, RED+ and lots of other schemes around the issue of climate change have been based on the preservation or increase of forests. But does it work?
We've known for some time that boreal forests contribute to climate change rather than help prevent it, because of changes in the surface reflectance (the albedo). But thus far, forests in other places have been thought to be beneficial, storing up carbon and not affecting the albedo so much.
But our recent study suggests that globally, preserving and expanding forests actually causes a net global warming. We used the Met Office's latest climate model and did simulations of future climate change, with and without afforestion/forest preservation, and we found that though the deforestation has no discernable effect on the climate, the afforestation does.
Does this mean that we are advocating chopping down forests? No. As National Tree Week says, forests are about more than climate change. However much climate change is a key challenge for the future, we can't forget that other things are important too. The climate effect of the forest preservation and expansion is small - only about 0.1 °C. How do you value that against the mass loss of biodiversity, irrelplaceable ecosystems and ecosystem services that would be lost?
Saving or planting forests is not a panacea for climate change, but neither is it the enemy. Conserving forest is worthwhile for lots of other reasons, but we shouldn't kid ourselves that there wont be difficult decisions to make about protecting the unique forest habitats, especially tropical forests like the Amazon, and preventing climate change.
This blog was written by Cabot Institute member, T Davies-Barnard, University of Exeter.