Large variations in afforestation-related climate cooling and warming effects across short distances

Abstract

Climate-related benefits of afforestation depend on the balance of the often-contrasting effects of biogeochemical (carbon sequestration) and biogeophysical (energy balance) effects. These effects are known to vary at the continental scale (e.g., from boreal to tropical regions). Here, we show based on a four-year study that the biogeochemical vs. biogeophysical balance in paired forested and non-forested ecosystems across short distances and steep aridity gradient (∼200Km, aridity index 0.64 to 0.18) can change dramatically. The required time for the forestation cooling effects via carbon sequestration, to surpass its warming effects, associated with the forests reduced albedo and suppressed longwave radiation, decreased from >200 years in the driest sites to ∼70 years in the intermediate and ∼40 years in the wettest sites. Climate-related benefits of forestation, previously considered at large-spatial scales, should be considered at high-spatial resolutions in climate-change mitigation programs aimed at taking advantage of the vast non-forested dry regions.