BE/CNH: Coupled Human/Ecosystems Over Long Periods: Mesa Verde Region Prehispanic Ecodynamics

该项目旨在了解公元600年至1300年美国科罗拉多州西南部人类、文化和环境的长期相互作用。该研究采用基于主体的模拟来检验农民如何在这片土地上定位和利用资源的各种模型。此外，模拟将检查家庭之间的农产品交换，以及交换是否导致家庭在特定时间和地点聚集到村庄，并在其他时间分散到较小的定居点。最后，模拟将研究为什么这个地区在公元1200年代晚期人口减少。该模型中的家庭在一个虚拟环境中活动，在这个虚拟环境中，海拔、土壤类型、温度、植被、潜在农业生产和降水在1800平方公里的研究区域内变化。模拟之所以成为可能，是因为研究区域在此期间有高分辨率的考古和环境记录，包括数千个考古遗址的清单、树木年轮记录以及可用地表水和地下水的估计。根据树木年轮记录重建的气候输入，农业产量估计每年都会发生变化，也可能对农业造成的景观退化作出反应。在较长时期内，同样的因素会影响地表水和地下水的可得性，而水的位置和可得性的变化也将纳入模拟。人口规模和住区在景观上的位置根据调查期间住户的经历而有所不同，而且人口从其他地区流出或流向其他地区。模拟将采用文化算法（遗传算法的变体），通过这些算法，家庭可以优化他们的景观和资源利用，与其他家庭交换玉米并竞争农业用地。这些算法还将用于模拟耕作策略的选择，包括那些使用地表水进行灌溉的策略。通过这种方式，模拟将用于确定农产品交换、土地竞争和农业战略变化如何影响家庭迁移和村庄形成。在模拟的所有变体中，家庭的行为将与研究区域考古遗址的数据库进行比较，该数据库指定了它们的位置、大小、功能和占用时间，从而可以评估每种变体与考古记录的匹配程度。这项工作有助于理解在经历重大气候变化和人口增长的小规模农业社会中不断变化的土地利用战略。它还有助于理解这些社会中经济制度和人口聚集的演变。特别是，这项研究将澄清在世界上最著名的考古地区之一梅萨维德地区导致村庄形成和人口减少的因素。此外，该研究还将开发工具，使未来对此类系统的检查更加有效。地下水模型将有助于预测未来气候变化时该地区地下水供应可能发生的变化。最后，通过澄清气候、文化和行为之间的关系，这项研究将有助于揭示其他领域人类和自然系统耦合的复杂性。该项目是2001财年环境生物复杂性特别竞赛颁发的奖项，重点关注自然和人类系统耦合的动力学。

This project seeks to understand the long-term interaction of humans, their culture(s) and their environment in southwestern Colorado, USA, from A.D. 600-1300. The research employs agent-based simulation to examine various models for how farmers locate themselves and use resources on this landscape. Further, the simulation will examine the exchange of agricultural goods among households, and whether exchange causes households to aggregate into villages in certain times and places, and disperse into smaller settlements during other times. Finally, the simulation will examine why this area is depopulated in the late A.D. 1200s. Households in this model act in a virtual environment where the elevation, soil type, temperature, vegetation, potential agricultural production, and precipitation vary over an 1800-sq-km study area. The simulation is possible because high-resolution archaeological and environmental records are available for the study area during this period, including an inventory of thousands of archaeological sites, tree-ring records, and estimates of available surface water and ground water. Estimates of agricultural production change annually according to climatic inputs reconstructed from tree-ring records, and possibly in response to landscape degradation due to farming as well. Over longer periods, the same factors affect the availability of surface water and ground water, and changes in the location and availability of water will also be incorporated into the simulation. Population size and the location of settlement on the landscape vary according to the experiences of the households during the period under investigation, and population flows from and to other areas. The simulation will employ cultural algorithms (variants of genetic algorithms) through which households may optimize their landscape and resource use with respect to other households with whom they exchange corn and compete for agricultural land. These algorithms will also be used to simulate selection of farming strategies, including those that use surface water for irrigation. In this way, the simulation will be used to determine how exchange of agricultural goods, competition for land, and changing farming strategies affected household movement and formation of villages. The behavior of households in all variants of the simulation will be compared against a database for archaeological sites in the study area that specifies their location, size, function, and period of occupation, allowing an assessment of how well each variant fits the archaeological record. This work contributes to understanding changing land-use strategies in small-scale farming societies experiencing significant climate change and population growth. It also contributes to understanding the evolution of economic systems and population aggregation in such societies. In particular, the study will clarify the factors that resulted in village formation and the depopulation in one of the most famous archaeological areas in the world: the Mesa Verde region. In addition, the research will develop tools to make the future examination of such systems more effective. The groundwater model will help to predict what might happen to groundwater supplies in this area as climate changes in the future. Finally, by clarifying the relationships between climate, culture, and behavior this research will be useful in unraveling the complexities of coupled human and natural systems in other areas. This project is an award emanating from the FY2001 special competition in Biocomplexity in the Environment focusing on the Dynamics of Coupled Natural and Human Systems.