Planning Alternative Future Landscapes in Oregon: Evaluating Effects on Water Quality and Biodiversity

Abstract

The development of spatially explicit landscape analyses is a principal activity in research on the relationships between human activities and changes occurring in natural systems. Using geographical information systems and related tools we produced digital and paper representations depicting the past, present, and potential future conditions of a 320 km2 watershed in western Oregon. These tools were used to identify trends over space and time in human occupancy and natural resources. Based on a set of values and desired future conditions developed by working with citizen groups, digital representations of the alternative future landscapes were evaluated for their effects on water quality and biodiversity using hydrological and ecological effects models. The water quality evaluative model, a non-point pollutant source geographic information system model, simulated storm events based on field data to calculate pollutant loads across the five alternative futures, the present, and the past. The biodiversity evaluative model measured the change in species richness and potential habitat area for breeding species in each alternative future and in the past and compared these data to the present.

Results from the water quality model show increases in the volume of surface water runoff and total suspended solids under the development-oriented futures in catchments undergoing significantly increased residential development or having a high percentage of area in erosive soils on steep slopes. Results from the biodiversity model show that all native species have at least some habitat in all alternative futures. If land use trends in the watershed continue unchanged or become more highly developed, there will be an increased risk to abundance of extant native species. The set of species at risk in the development-oriented futures differs significantly in composition and is placed at risk at a higher rate than in the past, suggesting that the kinds of habitat changes to date differ from those envisioned in the alternative futures.