Ineffectiveness of local zoning to reduce regional loss and fragmentation of wintering habitat for white-tailed deer

Abstract

Land-use zoning and regulations are frequently used to protect habitat for species threatened by habitat loss and fragmentation. Habitat protection, however, is rarely followed by habitat monitoring; consequently, knowledge about the efficacy of zoning as a species conservation tool is limited. We used a time series of Landsat satellite imagery (1975–2007) to quantify habitat changes in and adjacent to 187 areas zoned on private, commercial forestlands to protect habitat for wintering white-tailed deer (Odocoileus virginianus) in Maine. Near the northern edge of their geographic range where snow can restrict mobility and access to forage, white-tailed deer depend on mature conifer forests as wintering habitat. Our primary objective was to evaluate effectiveness of land-use zoning to conserve and prevent fragmentation of mature conifer forest. Between 1975 and 2007, the incidence rate of timber harvesting in zoned areas was high (97%). Cumulative area harvested (25%) and the associated reduction of mature conifer forest (13%) that resulted from stand-replacing harvests were considerably lower in zoned areas, indicating that regulations were successful at limiting timber harvests within zones. Reduction of mature conifer forest within unzoned 2-km buffers surrounding protected areas was considerably higher (45%). Remaining patches of mature conifer forest became increasingly fragmented, with a greater than 3-fold increase in number of patches and greater than 80% reduction in mean patch area. Regenerating forest increased from 5% to 36% in the landscapes surrounding zones, and although it can offer important browse, travel across young forest is costly for deer during periods of deep snow. Circa 2007, approximately 55% of the mature conifer forest present across our study area in 1975 remained, and our results suggest that less than 50% of the regenerating areas harvested in mature conifer forest will return to conifer dominance. Forest type conversion will, thus, extend effects of habitat fragmentation into the future. Areas protected for wintering deer collectively represent only 2% of the forested land base in our study area, and we conclude that habitat protection focused solely on those narrowly-defined zones has been ineffective at achieving regional conservation of winter habitat for deer. This study demonstrates how remote sensing can be used to overcome the difficulty of monitoring protected forest areas, and exemplifies the need for monitoring to understand the long-term benefits of zoning as a means of wildlife habitat conservation.