Spatially differentiated impacts of climate change on the carbon sequestration potential of afforestation and reforestation

Removal of CO2 from the atmosphere (CDR) will most likely be required to reach the goal of the Paris Agreement to limit global warming to well-below 2°C above pre-industrial temperature, in addition to rapid reduction of greenhouse gas emissions. Re-/afforestation (A/R) is among the most prominently discussed CDR methods, as it can be realized at low cost and is already implemented in many places today. However, forests are vulnerable to various disturbances caused by climate change, such as wildfires, droughts, and heat stress, which can lead to a decreased CO2 uptake or even a release of previously stored carbon back to the atmosphere. There is still a high uncertainty on the effects of climate change on the CDR potential of A/R. Here, we show spatially explicit how climate change affects the potential of A/R to sequester and store carbon under severe climate change (SSP3-7.0) and moderate climate change (SSP1-2.6), as simulated by the dynamic global vegetation model LPJmL5. Utilizing a highly stylized global afforestation scenario, we explore changes in net primary productivity, soil respiration and CO2 emissions from fires and identify the region-specific underlying causes (such as soil moisture changes or heat stress). We also demonstrate to what extent CO2 fertilization could counteract detrimental effects of climate change and highlight the possibility to underestimate climate impacts by overestimating the CO2 fertilization effect. By revealing and explaining spatial patterns of simulated future climate impacts on the CDR potential of A/R, our study contributes to a more profound understanding of the role A/R might be able to play in removing CO2 from the atmosphere.