Ecoclimatic sensitivity of tropical ecosystems to climate change at the Last Glacial Maximum

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Anna George and John W. Williams, Geography, University of Wisconsin-Madison, Madison, WI, Suzette G. A. Flantua, Biological Sciences, University of Bergen, Bergen, Norway

Background/Question/Methods
Tropical regions are key to studying global climate change, because of their high biodiversity, tropical rainforests’ high carbon storage, and positive feedbacks in carbon and water cycling. By studying these ecosystems’ changes due to past climatic forcings, we can identify common climate-related ecosystem responses across continents and time periods with more regional trends, enabling better ecosystem response predictions to anthropogenic climate change. Pollen data of the Neotoma Paleoecology Database, a community-curated paleoecology resource, historically were weighted towards temperate and high-latitude ecosystems in North America and Europe. However, recent data mobilization campaigns across the tropics now enable macro-scale analysis of tropical ecosystems’ climate sensitivity since the Last Glacial Maximum (LGM).
Using Neotoma APIs, we downloaded all Neotoma pollen records from 23 kya BP to present located between 30˚N and 30˚S latitudes. We selected data and temporal quality criteria and recalibrated outdated age-depth models using the bchron R package. We obtained the latest maps of global surface air temperature (SAT) data at 5°×5° resolution (Tierney et al, 2020) and bilinearly interpolated all SAT temperatures to site locations. We estimated climate sensitivity via various metrics of community turnover. We analyzed the spatiotemporal patterns through mixed effects models with elevation and temperature predictor variables.
Results/Conclusions
The initial data retrieval from Neotoma yielded 3600 global pollen datasets and over 300 tropical datasets. There were c. 280 tropical sequences with two or more chronology control points, for which we recalibrated age models for over 90. For the tropics, there are currently 44 sequences between 23 and 19 kya BP, 62 sequences between 19 and 15kya BP, 140 sequences between 11 and 8kya BP, and 279 sequences between 3kya BP and present. The average difference in tropical SAT between the LGM and present is -3.9˚C. Initial results suggest a high community sensitivity of tropical ecosystems, particularly in montane regions. Variations among tropical regions in apparent climate sensitivity can be attributed to site factors such as elevational position and continentality. These results suggest that 21st-century climate scenarios with global temperature changes on the order of 4˚C will have substantial effects upon tropical plant distributions and community composition.