Shifted Baselines: Quantifying Past Human Influences on Andean Landscapes

了解生态系统中什么是自然的，而不是简单地接受看似自然的东西，这对所有自然过程的研究都很重要。在海洋生物学中，这一概念被概括为“不断变化的基线”，即每一代人都接受环境的退化，并认为这是“自然的”。碳储量、生长速率、植被演替和潜在的生物多样性都是人类活动改变的生态系统服务的重要组成部分。有时，社会变革以牺牲另一种进程为代价来促进一种进程。从历史上看，在像安第斯山脉这样的干燥环境中，水的保持可能是最重要的，但当面对全球气候变化时，碳的储存可能变得更加紧迫。决策者为应对气候变化和生物多样性丧失所做的努力，增加了对景观变化轨迹的更深入理解和对什么是自然的更清晰识别的需要。这个研究项目将调查秘鲁安第斯山脉一个生物多样性非常高的地区，在那里，人们正在努力保护安第斯山脉的栖息地，以促进生物多样性和碳封存，这片土地已经被人类操纵了几千年。目前的高海拔碳封存计划主要围绕着一种可以生长在比其他任何树都高的海拔上的树——枫树。这种树的林地是特有物种的重要栖息地。尽管人们相信波利皮斯曾经比现在丰富得多，从而推动了扩大森林的努力，但这一假设尚未得到验证。研究人员将为一系列海拔高度的生态系统定义“自然基线”，确定树木线的自然高度（对地上碳储存很重要），以及过去1.1万年中相对于气候变化的景观变化轨迹。研究人员将分析来自10个湖泊的沉积物岩心和200个土壤岩心，为建立这些自然基线提供历史数据，他们将调查气候变化如何与人类活动相互作用，从而产生改变的火灾制度、作物利用和森林覆盖。古生态学可以通过分析从土壤和湖泊沉积物中回收的化石花粉和木炭，提供有关系统如何变化的详细信息。全新世早期气候(大致从。（距今11000年至9000年前）与今天的情况非常相似，但安第斯山脉的人口数量非常少。因此，这一时期提供了对没有人类活动的安第斯生态系统的深入了解。制定关于当地土地利用甚至全球碳预算的区域保护政策，需要了解人类对生态系统影响的轨迹。该项目将提供有关安第斯山脉景观人为变化的时间、程度和性质的新数据，并为通过碳封存和保护生物多样性来限制气候变化影响的持续努力提供相关的基线数据。与互补学科（土壤科学、植物生理学、生态学和遥感）的科学家合作，将使项目结果能够整合到对安第斯山脉保护和减缓安第斯生态系统内碳释放的适当政策的更大预测中。

Knowing what is natural in terms of an ecosystem, rather than simply accepting what appears to be natural, is important for all investigation of natural processes. In marine biology this concept has been summarized as "shifting baselines" in which each generation accepts a degradation of the environment and perceives it to be "natural." Carbon storage, rates of growth, vegetation succession, and potential biodiversity all are important components of ecosystem services modified by human actions. Sometimes societal changes enhance one process at the cost of another. Historically, water retention may have been paramount in a dry setting like the high Andes, but when faced with global climate change, carbon storage may become more pressing. Efforts by policy makers to grapple with climate change and loss of biodiversity increases the need for deeper understand of the trajectory of landscape change and for clearer identification of what is natural. This research project will investigate an area of very high biodiversity in the Peruvian Andes, where efforts to conserve Andean habitats to promote both biodiversity and carbon sequestration are being undertaken in a landscape that has been manipulated for millennia by humans. Present plans for high elevation carbon sequestration center around Polylepis, a tree that can grow at higher altitudes than any other. Woodlands of this tree are important habitat for endemic species. While efforts to expand forests are fueled by the belief that Polylepis was once much more abundant than present, this hypothesis has not been tested. The investigators will define "natural baselines" for ecosystems across a range of elevations, determine the natural height of tree line (important for above-ground carbon storage), and the trajectory of landscape change relative to climate change for the last 11,000 years. The researchers will analyze sediment cores from ten lakes and 200 soil cores to provide the historical data to establish these natural baselines, and they will investigate how climate change interacted with human activity to produce altered fire regimes, crop use, and forest cover. Paleoecology can, through analysis of fossil pollen and charcoal recovered from soils and lake sediments, provide detailed information about how systems have changed. The early Holocene climate (from roughly. 11,000 years to 9,000 years before the present) was quite similar to that of today, but human populations in the Andes were very low. This period therefore offers insights into the Andean ecosystem without human activity.Forming regional conservation policy with regard to local land use or even global carbon budgets requires an understanding of the trajectory of human influence on ecosystems. This project will provide new data on the timing, extent, and nature of human-induced change in Andean landscapes and provide baseline data relevant to ongoing efforts to constrain the effects of climate change through carbon sequestration while conserving biodiversity. Collaborations with scientists in complimentary disciplines (soil science, plant physiology, ecology, and remote sensing) will permit project results to be integrated into a larger prediction of appropriate policy for Andean conservation and for attempts to mitigate carbon release within Andean ecosystems.