【気候科学】森林管理によって温暖化を摂氏1.5度以下に抑えることができる

Forest-based mitigation could be a more efficient climate mitigation option than bioenergy carbon capture and storage (BECCS) in efforts to limit warming to 1.5°C above preindustrial levels, reports a study published in Nature Communications this week. The modelling study shows that the replacement of ecosystems with crops for BECCS to achieve a 1.5°C target over 2°C results in net losses of carbon from the land.

Land-based climate mitigation, either through BECCS or through forest afforestation-reforestation and conservation, will have a key role in limiting warming to 2°C. However, the carbon cycle response to the extensive land-based mitigation required to achieve the more ambitious 1.5°C target is uncertain, raising doubts about the effectiveness of this mitigation strategy.

Anna Harper and colleagues use a model that includes BECCS and forest management options to show that the simulated total land carbon storage is reduced with the land-use changes required to go from a 2°C scenario to a 1.5°C using BECCS. Replacing high carbon ecosystems with high-yield bioenergy crops, results in loss of vegetation and soil carbon, which offsets any gains from BECCS. In such cases forest management would be a more effective method to balance the carbon budget needed to stabilize warming to 1.5°C.

The authors note that the effectiveness of BECCS depends on how it is implemented in terms of choice of biomass, the fate of initial above ground biomass and the offset of fossil fuel emissions in the energy system. Nonetheless, the results indicate the need to account for the impact on carbon cycles of replacing ecosystems with bioenergy crops.