Evaluating the ability of human communities and environmental systems to adapt and recover to Late Holocene climate change in the Peruvian Andes.

在晚全新世（过去4250年），秘鲁档案（冰、海洋、洞穴和湖泊）的古气候重建提供了高分辨率的降水和温度变化记录，反映了ITCZ、SASM和ENSO的不同影响。在高原地区（安第斯山脉），记录表明三个不同的短期气候变化时期：公元800年之前降水增加，公元800-1350年降水减少和气温升高（中世纪气候异常），最后从公元1350年到现在，由于ENSO频率增强，变率增加。秘鲁安第斯山脉的人类历史记录表明，这些时期与人口变化（如人口增长、向外迁移、死亡率上升）、农业水管理基础设施（如灌溉渠）的发展/失败以及景观和环境的转变（如农业梯田建设、土壤侵蚀）相吻合。因此，这些气候和社会经济记录初步表明，高原社区及其粮食系统处于危险之中，过去可能非常脆弱，但由于环境、社会和经济因素的变化，脆弱性可能随着时间的推移而变化。我们的项目将试图描述这些因素在时间和空间上的重要性，从而评估这些社区和系统适应和恢复的能力。我们将解决以下研究问题：每次气候事件的规模、频率和特征是什么？哪些社会、经济和环境因素可能会增加每次事件的风险？社区和粮食系统如何预测、应对、抵抗和恢复，甚至失败？该方法将是秘鲁安第斯山脉独一无二的，它将基于介质的建模与高分辨率的古环境数据相结合。学生将使用前者来分析环境、社会和经济因素之间的关系，特别是人口、农业基础设施、土地利用和气候变化的变化。他们将利用土地利用、火灾历史、景观干扰和气候变化的经验数据，在精确的地质年代学框架内建立模型。他们将使用混合方法来实现这一目标。(1)整合具有区域社会经济发展和文化史重大变化的考古遗址的二手数据，使基于古agent的建模能够评估社区和系统（物理和生物）的适应和恢复能力。他们将在Netlogo编程环境中开发模型，以评估气候变化和资源战略相结合对人类在景观中的分布和结构的影响。学生将利用现有的古气候再分析，结合从古环境记录中获得的信息，提供气候边界条件，覆盖在高分辨率地形和土地覆盖上。(2)为了支持(1)，学生将从三个气候截然不同的地区——Cordillera Blanca（北部）、Cordillera Viuda（中部）和Cordillera Huanzo（南部）——的泥炭地收集连续的、未受干扰的沉积物岩心样本。已经收集了岩心样本，试点实验室分析表明，足够高的时间分辨率来检测千年至百年尺度的事件。利用ITRAX muXRF、x射线粒度分析和矿物磁学作为景观侵蚀指标，亚化石花粉粒和非花粉孢粉形态作为植被演替和土地利用指标，对地球化学和沉积特性进行实验室分析。基于高分辨率放射性碳年表的年龄建模，使用Oxcal/Bacon实现事件的时空相关性。这将是一项具有挑战性但具有开创性的研究。

During the Late Holocene (last 4250 years), palaeoclimatic reconstructions from Peruvian archives (ice, marine, speleothems and lakes) have provided high-resolution records of precipitation and temperature changes, which reflect the varying influences of the ITCZ, SASM and ENSO. In the highland zone (Andes), the records indicate three distinct periods of short-term climate change: rising precipitation until AD 800, lower precipitation and higher temperatures from AD 800-1350 (Medieval Climate Anomaly), and finally increased variability from AD 1350 to the present day due to enhanced ENSO frequency. The records of human history in the Peruvian Andes suggest that these periods coincided with demographic changes (e.g. population rise, out-migration, increased mortality), development/failure of agricultural water management infrastructure (e.g. irrigation canals), and transformation of the landscape and environment (e.g. agricultural terrace construction, soil erosion). These climate and socio-economic records therefore tentatively suggest that highland communities and their food systems were at risk and may have been highly vulnerable in the past, but that the level of vulnerability may have varied through time due to changing environmental, social and economic factors. Our project will seek to characterise the importance of each these factors across time and space, and therefore evaluate the ability of these communities and systems to adapt and recover. We will address the following research questions: What was the magnitude, frequency and characteristics of each climatic event? What was the social, economic and environmental exposure that may have increased the risk to each event? How did communities and food systems anticipate, cope, resist and recover, or even fail, with each event?The approach will be unique in the Peruvian Andes by coupling agent-based modelling with high-resolution palaeoenvironmental data. The student will use the former to analyse the relationships between environmental, social and economic factors, especially changes in demography, agricultural infrastructure, and land-use and climate variability. They will underpin the model with empirical data of land-use, fire history, landscape disturbance and climate change placed within a precise geochronological framework. They will achieve this using a mixed method approach. (1) Integration of secondary data from archaeological sites with major changes in regional socio-economic development and cultural history to enable palaeo-agent-based modelling to evaluate the ability of communities and systems (physical and biological) to adapt and recover. They will develop models in the Netlogo programming environment to assess the implications of the combination of climate changes and resource strategies for the distribution and structure of humans in the landscape. The student will use existing palaeoclimate reanalyses, in conjunction with information derived from the palaeoenvironmental records to provide climatic boundary conditions, overlain on high-resolution topography and land cover. (2) To underpin (1), the student will collect continuous, undisturbed sediment core samples from peatlands in three climatically distinct zones - Cordillera Blanca (northern), Cordillera Viuda (central), and Cordillera Huanzo (southern). Core samples have already been collected and pilot laboratory analysis demonstrates sufficiently high temporal resolution to detect millennial-centennial scale events. Laboratory analysis of the geochemical and sedimentary properties using ITRAX muXRF, X-ray particle size analysis and mineral magnetics as indicators of landscape erosion, and sub-fossil pollen grains and non-pollen palynomorphs as indicators of vegetation succession and land-use. Age modelling based on a high-resolution radiocarbon chronology using Oxcal/Bacon to enable spatial and temporal correlation of events. This will be challenging but groundbreaking research.