How repeated droughts impact the stability of the Amazon forest

The Amazon forest has traditionally served as an important carbon sink, but mounting evidence suggests that it is transitioning into a carbon source. This shift is driven by both local and regional disturbances, including extreme drought events. To anticipate how the Amazon may respond to climate change, we analysed its response to recurrent extreme drought events using satellite data.

Our study explored the concept of stability through multiple lenses. We first examined how the Amazon forest responded to individual droughts, considering the legacy effects of preceding droughts and wet periods. Then, we also quantified the stability of the Amazon in response to cumulative drought impacts, assessing its potential transition to a degraded ecosystem when a critical precipitation threshold is crossed.

We found that more severe droughts caused a more pronounced decrease in canopy vitality within a year following the event. Moreover, the response of the Amazon was influenced by legacy effects: recent dry periods reduced the forest’s stability, while preceding wet events mitigated the drought impact. Increased drought frequency also led to signs of critical slowing down in the Amazon forest vegetation. Regions experiencing more intense and prolonged droughts were more vulnerable to this phenomenon, although the severity of impacts varied regionally.

In summary, while the Amazon forest has shown resilience to past extreme drought events, the predicted increase in drought intensity and duration is likely to amplify critical slowing down across the forest, particularly in the more seasonal southern regions. The intricate connection between the Amazon forest vegetation and its water sources could trigger cascading effects, leading to further stability loss with global repercussions.