Collaborative Research: Reconstructing Droughts in the Tropical Americas Using Tree-Ring Analysis

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This project uses the annual rings of tropical trees to reconstruct past rainfall in a drought- and famine-prone region, then applies this knowledge to understanding the role of natural and human-altered variability in the climate system in influencing regional patterns of drought in the past, present, and future. Prior research determined that high elevation tree species in Guatemala and Honduras do form annual growth rings that can be dated to their exact year of formation; this is unusual for tropical tree species. It is understood that variations in ring width in these trees reflect the amount of winter and spring rainfall. With this knowledge, the investigators will develop estimates of past precipitation along Guatemala's 'Dry Corridor,' a region that currently suffers from severe water and food security challenges. Tree-ring data will be collected from mountain sites across this region, and these will be used to develop estimates of past rainfall over the last five centuries or more. The benefit of these precipitation reconstructions using tree rings is that they can be used to understand whether current climate variability is exceptional compared to the last several centuries and the extent to which natural variability is entwined with a human-influenced changes. Specifically this research will evaluate the hypothesis that there are important modes of natural variability in Central American rainfall at time scales of decades and longer. This knowledge will help test and improve models that predict future rainfall trends both regionally and globally and can be applied to understanding their cause and consequences.This research expands the geographic extent of annual, climate-sensitive tree-ring data further into the American tropics. Knowledge gained from this project will be relevant in a region with populations that are particularly vulnerable to climate change, as it is likely that increases in drought and flooding will be the most direct and immediate consequences of global warming for human society. Changes in rainfall exacerbate existing and emerging threats to sustainable water supplies from growing populations, pollution, declining infrastructure, and boundary conflicts. A long-term perspective on the potential range of variability in precipitation, and in particularly decadal-scale fluctuations, is critical for predicting and planning for the consequences of changes in water availability. This research project provides a hands-on and international research experience for both graduate and undergraduate students from the United States and also facilitates the involvement of Central American students and scientists in geographic research with US collaborators. Coordination between US and Central American scientists will facilitate skills training and knowledge development so that local resources and information are available to address sustainability and vulnerability reduction efforts. This award is being co-funded by NSF's Office of International and Integrative Activities.