Drought Resilience Debt Drives NPP Decline in the Amazon Forest

Climate change has substantially increased the frequency of extreme droughts in the Amazon basin, generating concern about impacts on the worlds largest tropical forest, which contributes about one-seventh of the global vegetation carbon sink. Most research to understand drought impacts has focused on the immediate influences of such events, neglecting post-drought effects on ecosystems recovery. Since ecological processes are influenced by antecedent conditions, we analyzed whether extreme droughts affect vegetation growth (i.e., net primary productivity, NPP) recovery. Here, we evaluated the NPP in the Amazon basin from 2003 to 2020, a period in which drought frequency was almost double the decadal incidence of the last century. We show that NPP does respond to the coupled impacts of individual droughts and the post-drought impacts during ecosystem recovery. In particular, our results reveal that the ecosystems undergoing recovery show NPP about 13% lower than reference values based on the pre-drought state or in areas undisturbed by drought. NPP deficits have consistently increased with the extreme droughts of 2005, 2010, and 2015 due to the combined effects of disturbances magnitude and the length of recovery. If the expected increase in drought frequency and intensity does occur, reduced recovery may lead the Amazon Forest to an alternative ecosystem state with lower carbon uptake, contributing to a warming global climate.Funding Agencies|CNPqConselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) [152325/2020-4, 05159/2018-6, 31015220178]; FAPERJFundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio De Janeiro (FAPERJ) [202.714/2019, 2033042017, E26/203.174/2016]; CAPESCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) [001]; Portuguese Foundation for Science and Technology (FCT)Portuguese Foundation for Science and Technology [UIDB/00239/2020, UIDB/50019/2020-IDL]; Serrapilheira Institute postdoctoral fellowship [Serra-1708-15159]