A simulation model of human-natural interactions in dynamic landscapes

Human population growth has had profound socioeconomic and ecological effects that cannot be fully understood without explicitly considering the interactions between environmental and socio-economic change at various spatial and temporal scales. In particular, the human-natural interface (HNI) is the area where urban sprawl, agricultural expansion, and other land use transition intermingles with natural ecosystems. A comprehensive and integrative coupled human and natural systems model is required for projecting future changes and studying their causes and consequences in the HNI. This model will need to effectively simulate multiple processes and their interactions, including human-driven land cover and land use changes, land management practices, succession of natural communities, and natural disturbances such as wildfires. To address this need, we developed the Coupled Human and Natural Geospatial Environments (CHANGE) model, which is capable of simulating human-natural dynamics and feedbacks over large heterogeneous areas. This raster-based, spatially explicit, stochastic computer model is programmed in C++ and combines a demand-allocation land use change module, a succession module for natural vegetation dynamics, and a spatially explicit fire initiation and spread module. To facilitate this integration, we developed a set of hierarchical rules and algorithms that allow the demand-allocation model to control transitions between natural and human-dominated land cover types while the vegetation dynamics and fire models drive more detailed vegetation dynamics within natural land cover types. We also implemented simulation of the HNI as an "overlay" class in which low-density human development was allowed to occur in naturally-vegetated land cover types.