Planting trees to mitigate climate change could actually cause warming rather than cooling globally due to the non-carbon effects of land use change, according to new research from the University of Bristol.
The research team investigated the full effects of carbon and non-carbon impacts of land use change in the four future climate change scenarios developed by the Intergovernmental Panel on Climate Change (IPCC). It is the first study to assess the effect of land use in both afforestation (planting trees) and deforestation in the IPCC scenarios, called representative concentration pathways (RCPs).
The researchers found that in RCP 4.5, a mid-range future climate projection that includes afforestation to help mitigate climate change, the land use change actually resulted in a small net positive warming. This was primarily due to the addition of new forest in mid-latitudes, which decreased the reflectivity of the earth’s surface and increased local and global temperature.
This small net gain in global temperature could mean that RCP 4.5’s universal carbon tax, a proposed mitigation policy that incentivises growing and preserving forest, may be counter-productive with respect to climate change.
Despite their findings, the researchers nonetheless recognise that afforestation and the avoidance of deforestation still have wider environmental benefits, such as preserving biodiversity and protecting unique and irreplaceable forests.