Amazonian cultures and environments

Amazonia under mid-Holocene drought

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Most climate models simulate increased drought for Amazonia over the 21st century, which is predicted by Earth System models to lead to increased forest die-back, especially in climatically-sensitive ecotonal areas such as lowland Bolivia at the southern margin of Amazonia.  However, huge uncertainty exists over the geographic scale of this die-back, with model predictions ranging from negligible to basin-wide.  Reducing this uncertainty is vital for understanding the consequences of climate change for Amazonian biodiversity, ecosystem services and functioning.

In this project (2015-2019) we sought to improve understanding of the long-term impact of drought upon Amazonian forests by comparing the geographic distribution of southern Amazonian transitional forests under today’s humid climate versus the significantly drier climate of the mid Holocene (ca. 6,000 years ago, 6 ka BP).  
The project combined palaeoecology, remote-sensing/GIS, and modelling.  Palaeovegetation data (fossil pollen) were collected from a transect of radiocarbon-dated lake-sediment cores to compile a map of the tropical forest-savanna ecotone of SW Amazonia 6 ka BP.  Using GIS and satellite remote sensing, the magnitude of the ‘6 ka BP versus present-day’ ecotonal shift.  The suite of PMIP3/CMIP5 6 ka BP climate model simulations were used to drive vegetation models to examine the range of model simulated mid-Holocene drying and impacts on rainforest extent. The aim of the modelling was to constrain the forest's natural/baseline sensitivity to rainfall and potentially inform future projections.

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