Afforestation and future climate

Afforestation and future climate; should we be re-evaluating its role in climate change mitigation policy?

Global land use change and its interaction with the climate system is recognised as an important component of the IPCC future climate scenarios. The full effects of carbon and non-carbon impacts of land use change in the representative concentration pathways show that the non-carbon impacts of land use change (changes in surface reflectance and evaporation) may cause a counter-intuitive net climate forcing. This challenges the assumption of the efficacy of afforestation in climate change mitigation policies.

In RCP 4.5, a mid-range future climate projection that includes afforestation to help mitigate climate change, the land use change results in a small net positive warming. This is primarily due to the addition of new forest in mid-latitudes, which decreases the albedo (reflectivity of the earth’s surface) and increases local and global temperature.

This small net gain in temperature could mean that RCP 4.5’s universal carbon tax, a proposed mitigation policy that incentivizes growing and preserving forest, may be counter-productive with respect to climate change. Without looking at the full effects of land use change, afforestation policies to reduce climate warming could actually do the opposite.

However, whilst this afforestation scenario may pose a perverse incentive with regards to climate alone, afforestation and avoided deforestation would undoubtedly have wider environmental benefits, such as preserving biodiversity and maintaining ecosystem services.

This research has identified a small but important contribution of non-carbon impacts of land use change which has been overlooked in the RCPs, compelling the need to include such effects in future scenarios. These findings imply that incorporating land use change in climate change mitigation policy also requires a consideration of broader environmental aims, with impacts not necessarily acting in synergism.

For more about this work, see the full open-access paper in Environmental Research Letters: Full effects of land use change in the representative concentration pathways