An Observation-Based Estimate of Precipitation Changes from Forestation in Europe

Abstract:

Land cover changes affect the climate through the release or uptake of greenhouse gases and by altering the water and energy balance of the land surface. Numerous modeling studies have highlighted that alterations at the land surface can result in considerable changes in precipitation. Yet, land cover-induced precipitation changes remain largely unconstrained from observations. Here we assess precipitation changes induced by forestation of rainfed agricultural land in Europe by modeling the MSWEPv2.2 precipitation climatology with generalized additive models. Locally, we find an increase in precipitation following forestation, in particular in winter, which is confirmed by a paired rain gauge analysis. In addition, forestation entails downwind alterations of precipitation, which are often larger in magnitude than the local effect. During summer, forests increase downwind precipitation in most regions, especially further away from the coasts. In contrast, the downwind effect in winter is positive in coastal areas but near-neutral and negative in Continental and Northern Europe, respectively. The combined local and non-local effects of a realistic reforestation scenario, constrained by sustainability safeguards, increase summertime precipitation by 15 % on average (0.24 mm/day), potentially offsetting a substantial part of the projected precipitation decrease from climate change under RCP8.5. We therefore conclude that land cover-induced alterations of precipitation should be considered when developing long-term land management strategies.