Assessing Legacies of Past Human Activities in Amazonia

ended

Amazon forests contribute vital ecosystem services, including maintaining biodiversity (>10,000 tree species) and storing large amounts of carbon. Amazonia also features prominently in global climate, carbon, and vegetation models, which assume tropical forests are effectively pristine and that past human disturbance mimicked natural processes. It is now evident that recurrent human disturbance of Amazonia, like fire and deforestation, were significant in some areas. Since those disturbances likely modify subsequent vegetation dynamics - including temporarily increasing forest capacity to absorb carbon - the emerging paradigm of human disturbance is a challenge to global ecological understanding. The focus of my project is thus to reliably determine whether human disturbances occurred in locations that form the basis of global models. A key expected outcome is to either legitimize or force revision to these models of carbon sequestration potential in Amazonia. I will innovatively integrate ecological, paleoecological, archaeological, chemical and biogeographic analyses to assess the degree to which past human disturbance drives the diversity patterns and carbon dynamics observed in modern Amazonian forests. For key long-term sites across Amazonia, I will quantify the: i) time since the last fire, ii) past fire frequency, extent and intensity, iii) past vegetation change in the presence and absence of human activity, and iv) continuity of past human activity over the last 1000 years. My results will provide the first quantification of local-scale recovery processes exceeding 100 years in tropical forests, and will determine if observed forest dynamics are driven by disturbances that occurred before modern ecological surveys began. I will then quantify the extent to which past disturbances create an overestimation of carbon storage potential, driving a profound reexamination of carbon sequestration and biodiversity patterns in Amazonia.