Land-Cover Modeling Methodology - The FORE-SCE Model
FORE-SCE model methodology
Many factors determine how human beings modify the earth's landscape. Land-cover change is inherently a local event, yet broader scale socioeconomic and biophysical factors also affect how humans make decisions to use the landscape. Projecting future land cover requires modelers to account for driving forces of land-cover change operating at scales from local ("bottom-up") to global ("top-down"), and how those driving forces interact over space and time. As a result of the high level of uncertainty associated with predicting future developments in complex socio-environmental systems, a scenario framework is needed to represent a wide range of plausible future conditions.
Scientists at EROS have developed the FOREcasting SCEnarios of Land-use Change (FORE-SCE) modeling framework to provide spatially explicit projections of future land-use and land-cover change. FORE-SCE uses a modular approach to handle large-scale (national to global) and small-scale (local) drivers of change. A "demand" module provides overall proportions of future land-cover change at the regional level. A "spatial allocation" module ingests land-cover proportions from the demand module and produces spatially explicit maps.
Demand :: The "demand" component of FORE-SCE provides aggregate proportions of modeled land-cover classes for a future date, for the modeled region. Demand can take a variety of forms. The simplest method to determine future proportions of land cover is to simply extrapolate historical land-cover change. FORE-SCE can also ingest future, modeled land-cover proportions from economic models or other modeling frameworks, provided they provide future proportions of land use. Scenarios describe a unique set of socioeconomic and environmental conditions for future time periods, and can be used to construct future proportions of land-cover change, either through the use of formal modeling frameworks, or through more subjective, participatory scenario-construction workshops using land-use experts.
Spatial Allocation :: The "spatial allocation" component of FORE-SCE produces spatially explicit maps of land cover for each year of a simulation. FORE-SCE works by placing individual patches of land cover on the landscape, with patch characteristics based on historical patch characteristics for a given geographic region. FORE-SCE determines where to place these patches by using "suitability surfaces", images that depict the relative suitability of a pixel for supporting a given land-cover type. Suitability surfaces are constructed by examining statistical relationships between existing land-cover distributions, and variables such as topography, soil characteristics, climate, and distance to transportation networks. The number of land-cover patches for a given land-cover type is dictated by the "demand" component of FORE-SCE, with an adequate number of the correct land-cover class patches placed on the landscape until "demand" is met for a given yearly iteration. Modeling then proceeds with the next year and the process repeats until all years in a simulation are complete.