Influence of Late Holocene Climate Change and Human Land Use on Terrestrial and Aquatic Ecosystems in Southwest Madagascar
Influence of Late Holocene Climate Change and Human Land Use on Terrestrial and Aquatic Ecosystems in Southwest Madagascar
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DOI：
10.3389/fevo.2021.688512
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发表时间：
2021-12-07
影响因子：
3
通讯作者：
Kennett, Douglas J.
中科院分区：
文献类型：
--
作者：
Domic, Alejandra I.;Hixon, Sean W.;Kennett, Douglas J.
马达加斯加的生物群经历了巨大的变化后，人类殖民的岛屿在晚全新世。人类到达的时间及其在巨型动物灭绝中的作用受到了相当大的关注。然而，人类活动对区域生态系统的影响研究仍然很少。在这里，我们专注于重建陆地和水生生态系统组成的变化，以评估人类土地利用和气候变化的影响。我们进行了一项古环境研究，使用沉积物记录，跨越过去类似的1,145年，从一个湖床在西南马达加斯加Namonte盆地收集。我们研究了物理（X射线荧光和地层学）和生物指标（花粉，硅藻和微型和大型木炭颗粒），以推断陆地和水生生态系统的变化。化石花粉数据表明，草原和干燥的落叶林在该地区的组成保持相对稳定，在干旱事件与向北移动的热带辐合带（ITCZ）之间类似的1,145和555校准日历年之前（cal yr BP）。木炭颗粒表明，该地区发生了广泛的火灾，这是由古记录所涵盖的整个跨度期间的气候驱动因素和人类行为共同造成的。随着牧民定居和类似于1,000 cal yr BP的地方性巨型动物消失，草原扩大，依靠大型动物传播种子的树木数量逐渐减少。干旱森林的花粉类群特征的丰度减少与木炭颗粒之间的突然增加类似230和35卡尔年BP，当农牧社区移民到该地区。森林砍伐和土壤侵蚀，表明相对较快的沉积速率和高K/Zr和Fe/Zr，加剧180和70卡年BP之间，并造成随之而来的增加湖泊浊度，导致更快的周转的水生硅藻群落。在过去近70年里，土地使用和持续的气候变化继续改变着当地的陆地和淡水生态系统。目前陆地和水生生态系统的组成反映了本地生物群灭绝、外来物种入侵和传统土地管理做法使用减少的遗留问题。
Madagascar's biota underwent substantial change following human colonization of the island in the Late Holocene. The timing of human arrival and its role in the extinction of megafauna have received considerable attention. However, the impacts of human activities on regional ecosystems remain poorly studied. Here, we focus on reconstructing changes in the composition of terrestrial and aquatic ecosystems to evaluate the impact of human land use and climate variability. We conducted a paleoenvironmental study, using a sediment record that spans the last similar to 1,145 years, collected from a lakebed in the Namonte Basin of southwest Madagascar. We examined physical (X-ray fluorescence and stratigraphy) and biotic indicators (pollen, diatoms and micro- and macro-charcoal particles) to infer terrestrial and aquatic ecosystem change. The fossil pollen data indicate that composition of grasslands and dry deciduous forest in the region remained relatively stable during an arid event associated with northward displacement of the Intertropical Convergence Zone (ITCZ) between similar to 1,145 and 555 calibrated calendar years before present (cal yr BP). Charcoal particles indicate that widespread fires occurred in the region, resulting from a combination of climate drivers and human agency during the entire span covered by the paleorecord. Following settlement by pastoral communities and the disappearance of endemic megafauna similar to 1,000 cal yr BP, grasslands expanded and the abundance of trees that rely on large animals for seed dispersal gradually declined. A reduction in the abundance of pollen taxa characteristic of dry forest coincided with an abrupt increase in charcoal particles between similar to 230 and 35 cal yr BP, when agro-pastoral communities immigrated into the region. Deforestation and soil erosion, indicated by a relatively rapid sedimentation rate and high K/Zr and Fe/Zr, intensified between 180 and 70 cal yr BP and caused a consequent increase in lake turbidity, resulting in more rapid turnover of the aquatic diatom community. Land use and ongoing climate change have continued to transform local terrestrial and freshwater ecosystems during the last similar to 70 years. The current composition of terrestrial and aquatic ecosystems reflects the legacy of extinction of native biota, invasion of exotic species, and diminished use of traditional land management practices.