Abrupt loss and uncertain recovery from fires of Amazon forests under low climate mitigation scenarios

Vegetation smolders in the aftermath of a tropical fire. Credit: NOAA

Tropical forests buffer climate change impacts by acting as a major sink for anthropogenic carbon emissions, which is essential to slowing down the buildup of atmospheric CO2. However, the response of tropical forests to more frequent weather extremes and long-recovery disturbances like fires remains uncertain. Analyses of field data and ecological theory raise concerns about the possibility of the Amazon crossing a tipping point, leading to catastrophic tropical forest loss. In contrast, climate models consistently project an enhanced tropical sink.

The authors bring these two bodies of work together by analyzing recent trends and future projections of tropical forest biomass and fire carbon emissions using GFDL-ESM4.1, a fully coupled global climate and carbon cycle model. Experiments with this model accounted for the simultaneous effect of fires, water stress, and plant competition.

The results showed a heterogeneous response of Amazonian carbon stocks. GFDL-ESM4.1 simulates a distinct response of forest carbon stocks across the tropical biome and among climate change scenarios. The model concurs with observations in predicting a larger forest biomass in the Paleotropics (tropical areas of Africa and Asia) than in the Neotropics (tropical Americas) under current climate conditions. Projection experiments suggest that climate change will exacerbate regional differences in tropical forest biomass.