Recurrent droughts increase risk of cascading tipping events by outpacing adaptive capacities in the Amazon rainforest

• Published in: Proceedings of the National Academy of Sciences - PNAS 2022-08, Vol.119 (32), p.e2120777119
• Main Authors: Wunderling, Nico, Staal, Arie, Sakschewski, Boris, Hirota, Marina, Tuinenburg, Obbe A, Donges, Jonathan F, Barbosa, Henrique M J, Winkelmann, Ricarda
• Format: Article
• Language: English
• Subjects: Adaptation; Amazon rainforest; Anthropogenic factors; Atmospheric moisture; canopy; Climate Change; Climate system; climate tipping elements; Climatic conditions; collapse; conceptual model; controlled study; Drought; Droughts; ecosystem; environmental change; Environmental changes; Environmental impact; environmental indicator; environmental risk; forest; Forests; Heterogeneity; human; Human influences; Humans; Moisture effects; network dynamics; nonhuman; Physical Sciences; rain; rain forest; Rainfall; Rainforest; Rainforests; Recycling; Subsystems; Thresholds; tipping cascades; tipping element; tree; Trees; trophic cascade
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2120777119

Tipping elements are nonlinear subsystems of the Earth system that have the potential to abruptly shift to another state if environmental change occurs close to a critical threshold with large consequences for human societies and ecosystems. Among these tipping elements may be the Amazon rainforest, which has been undergoing intensive anthropogenic activities and increasingly frequent droughts. Here, we assess how extreme deviations from climatological rainfall regimes may cause local forest collapse that cascades through the coupled forest-climate system. We develop a conceptual dynamic network model to isolate and uncover the role of atmospheric moisture recycling in such tipping cascades. We account for heterogeneity in critical thresholds of the forest caused by adaptation to local climatic conditions. Our results reveal that, despite this adaptation, a future climate characterized by permanent drought conditions could trigger a transition to an open canopy state particularly in the southern Amazon. The loss of atmospheric moisture recycling contributes to one-third of the tipping events. Thus, by exceeding local thresholds in forest adaptive capacity, local climate change impacts may propagate to other regions of the Amazon basin, causing a risk of forest shifts even in regions where critical thresholds have not been crossed locally.