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

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.