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

该项目使用热带树木的年轮来重建干旱和饥荒易发地区过去的降雨量，然后应用这一知识来理解气候系统中自然和人为变化在影响过去、现在和未来干旱区域模式中的作用。先前的研究确定，危地马拉和洪都拉斯的高海拔树种确实形成了年轮，可以追溯到它们形成的确切年份；这对热带树种来说是不寻常的。据了解，这些树的年轮宽度的变化反映了冬季和春季的降雨量。有了这些知识，调查人员将对危地马拉干旱走廊沿线过去的降雨量进行估计，该地区目前面临着严重的水和粮食安全挑战。树木年轮数据将从该地区的山区收集，并将用于估计过去五个世纪或更长时间的降雨量。这些利用树木年轮重建降水的好处是，它们可以用来了解当前的气候变化与过去几个世纪相比是否异常，以及自然变化与人类影响的变化交织在一起的程度。具体地说，这项研究将评估中美洲降雨量在几十年或更长时间尺度上存在重要自然变化模式的假设。这些知识将有助于测试和改进预测未来区域和全球降雨趋势的模型，并可用于了解其原因和后果。这项研究将年度气候敏感树轮数据的地理范围进一步扩展到美洲热带地区。从该项目获得的知识将与人口特别容易受到气候变化影响的区域有关，因为干旱和洪水的增加很可能是全球变暖对人类社会最直接和最直接的后果。降雨量的变化加剧了人口增长、污染、基础设施衰落和边界冲突对可持续供水的现有和新的威胁。对降水变化的潜在范围，特别是十年尺度波动的长期观点，对于预测和规划水资源供应变化的后果至关重要。这一研究项目为来自美国的研究生和本科生提供了实践和国际研究经验，并促进了中美洲学生和科学家与美国合作者一起参与地理研究。美国和中美洲科学家之间的协调将促进技能培训和知识发展，以便当地资源和信息可用于解决可持续性和减少脆弱性的努力。该奖项由美国国家科学基金会国际和综合活动办公室共同资助。

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.