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

该项目利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，然后运用这些知识来理解气候系统中自然和人为变化对过去、现在和未来地区干旱模式的影响。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，可以追溯到它们确切的形成年份；这对热带树种来说是不寻常的。据了解，这些树木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”沿线过去的降水进行估计，该地区目前正面临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，这些数据将用于估算过去五个世纪或更长时间的降雨量。利用树木年轮重建降水的好处是，它们可以用来了解与过去几个世纪相比，当前的气候变率是否异常，以及自然变率与人类影响的变化交织在一起的程度。具体地说，这项研究将评估这样一个假设，即在几十年或更长时间尺度上，中美洲降雨存在重要的自然变率模式。这些知识将有助于测试和改进预测区域和全球未来降雨趋势的模型，并可用于了解其原因和后果。这项研究将年度、气候敏感的树木年轮数据的地理范围进一步扩展到美洲热带地区。从这个项目中获得的知识将与一个人口特别容易受到气候变化影响的地区相关，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。降雨的变化加剧了人口增长、污染、基础设施退化和边界冲突对可持续供水的现有和新威胁。对降水变异性的潜在范围，特别是对十年尺度波动的长期看法，对于预测和规划可得水量变化的后果至关重要。该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，也促进了中美洲学生和科学家与美国合作者参与地理研究。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，以便为解决可持续性和减少脆弱性的努力提供当地资源和信息。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.