Drought Sensitivity of the Amazon Rainforest

TLDR

Amazon forests are a critical but poorly understood component of the global carbon cycle, and projected drying could accelerate climate change through carbon losses and altered surface energy balances. The study aimed to assess how Amazon forests respond to intense drought by analyzing records from multiple long‑term monitoring plots across Amazonia. Researchers used these long‑term plot records to evaluate forest responses to the 2005 drought, a potential analog for future events. The 2005 drought caused Amazon forests to lose biomass, reversing a long‑term carbon sink, with losses of 5.3 Mg C ha⁻¹ per 100 mm water deficit and a total impact of 1.2–1.6 Pg C, indicating vulnerability to future moisture stress and potential climate feedback.

Abstract

Amazon forests are a key but poorly understood component of the global carbon cycle. If, as anticipated, they dry this century, they might accelerate climate change through carbon losses and changed surface energy balances. We used records from multiple long-term monitoring plots across Amazonia to assess forest responses to the intense 2005 drought, a possible analog of future events. Affected forest lost biomass, reversing a large long-term carbon sink, with the greatest impacts observed where the dry season was unusually intense. Relative to pre-2005 conditions, forest subjected to a 100-millimeter increase in water deficit lost 5.3 megagrams of aboveground biomass of carbon per hectare. The drought had a total biomass carbon impact of 1.2 to 1.6 petagrams (1.2 × 10 15 to 1.6 × 10 15 grams). Amazon forests therefore appear vulnerable to increasing moisture stress, with the potential for large carbon losses to exert feedback on climate change.