Data for: A 2000-year sediment record reveals rapidly changing sedimentation and land use since the 1960s in the Upper Mara-Serengeti Ecosystem

The Mara River basin in East Africa is a trans-boundary river basin that highlights many of the development and conservation challenges in East Africa. The Mara River flows from its headwaters in the Mau Forest of Kenya through the northern portion of the Serengeti-Mara Ecosystem and into Lake Victoria in Tanzania, where it forms part of the headwaters of the Nile River basin. Changes in land use and landcover in the basin have raised concerns about the quality and quantity of water in the Mara River. We analyzed sediment cores from the Mara Wetland (near the river’s outlet into Lake Victoria) to evaluate how sedimentation rates and sources have changed historically, through a period marked by major changes in human and livestock population densities, land use, and disease epidemics (rinderpest). We collected sediment cores in August 2015 along a transect through the Mara Wetland from the upstream reaches to Lake Victoria. Slices of sediment cores collected from four distinct regions of the wetland were age-calibrated using radiocarbon and lead-210 dating methods. Core slices were then analyzed for sediment sources using a sediment fingerprinting approach, nitrogen and carbon stable isotope signatures, and mercury. Our results suggest that ecological conditions in the Mara River basin were fairly stable over paleoecological time scales (2000-1000 years before present), but there has been a period of rapid change in the basin over the last 250 years, particularly since the 1960s, likely due to anthropogenic factors. We also observed that downstream effects of landcover and land use change can be exacerbated by increasing occurrence of extreme rainfall events in the region. The Mara Wetland likely plays an important role in mitigating the impact of those factors on Lake Victoria. This work was the result of a partnership between Yale University, the Cary Institute of Ecosystem Studies, WWF-UK, WWF-Kenya and WWF-Tanzania.东非马拉河流域是一处跨境流域，集中展现了东非地区在发展与保护领域面临的诸多共性难题。马拉河发源于肯尼亚马乌森林的上游源地，流经塞伦盖蒂-马拉生态系统北部片区，最终注入坦桑尼亚境内的维多利亚湖，同时亦是尼罗河流域上游源头的组成部分。该流域内的土地利用与土地覆被变化，已引发学界与业界对马拉河水质与水量的高度关切。本研究针对马拉湿地（位于马拉河注入维多利亚湖的河口附近）的沉积物岩芯(sediment cores)展开分析，旨在厘清在人类与牲畜种群密度、土地利用及牛瘟(rinderpest)疫情发生显著变化的历史时段内，沉积物沉积速率与物质来源的演化规律。研究团队于2015年8月，沿贯穿马拉湿地的样带从上游河段至维多利亚湖布设采样点并采集沉积物岩芯。针对从湿地四个独立区域采集的岩芯切片，研究人员采用放射性碳测年(radiocarbon dating)与铅-210测年(lead-210 dating)方法完成年代校准。随后，通过沉积物指纹溯源法(sediment fingerprinting approach)、氮与碳稳定同位素特征分析以及汞(mercury)含量检测，对岩芯切片的沉积物物质来源进行解析。研究结果显示，马拉河流域的生态状况在古生态时间尺度（距今2000至1000年）内整体保持稳定，但在过去250年，尤其是20世纪60年代以来，该流域经历了快速的生态转型，这一变化大概率由人为活动导致。此外，研究团队还发现，该区域极端降雨事件频次的增加，会加剧土地覆被与土地利用变化所引发的下游生态效应。马拉湿地或在缓解上述环境变化因素对维多利亚湖的负面影响方面发挥关键作用。本研究由耶鲁大学(Yale University)、卡里生态系统研究所(Cary Institute of Ecosystem Studies)、世界自然基金会英国分会(WWF-UK)、世界自然基金会肯尼亚分会(WWF-Kenya)及世界自然基金会坦桑尼亚分会(WWF-Tanzania)联合完成。