Schumaker, N., T. Ernst, D. White, J. Baker, and P. Haggerty. 2004. Projecting wildlife responses to alternative future landscapes in Oregonís Willamette Basin. Ecological Applications 14(2):381-401. WED-01-167
Increasingly, environmental quality is becoming recognized as a critical factor that should constrain land use planning. One important measure of a landscape's quality is its capacity to support viable populations of wildlife species. But the ability of land managers to balance conservation with other competing objectives is limited by a shortage of methodologies for assessing landscape quality. In response to this shortage, the research community has begun developing a variety of multi-species, landscape-level, assessment models. Useful models must strike a balance between parsimony and biological realism and must be designed to make the most of limited life history data. This paper applies two such assessments to an examination of wildlife responses to scenarios of landscape change within Oregon's Willamette River Basin. The study uses GIS maps of pre-European settlement and circa 1990 habitat conditions, and three possible realizations of how the Basin might appear in the year 2050. Our simpler assessment generated statistics of landscape change from the GIS imagery and species-habitat relationships for all 279 amphibian, reptile, bird, and mammal species in the basin. Our more complex assessment used an individual-based life history simulator to estimate population sizes for a small subset of this fauna. These two assessments offer complementary kinds of information about wildlife responses to landscape change: estimates of habitat changes for a large number of species representing a region's biodiversity, and estimates of changes in the persistence of populations of key species. We found both good and poor correlations between our two assessments, depending upon the species and landscape. Both assessments agreed in their overall ranking of the landscapes' quality for wildlife. In most cases, the percentage change in habitat quality underestimated the percentage change in population size. In a few cases, small gains in habitat quality were accompanied by very large increases in wildlife populations. We attribute discrepancies in our two assessments to the influence habitat fragmentation had on our individual-based model. As such, our study provides a methodology for separating the influences of habitat quality and quantity from those of habitat pattern.