Threshold responses of songbirds to forest loss and fragmentation across the Marcellus-Utica shale gas region of central Appalachia, USA

Abstract

Since 2005, unconventional gas development has rapidly altered forests across the Marcellus-Utica shale basin in the central Appalachian region of the eastern United States, an area of high conservation value for biodiversity. Much is still unknown about ecological impacts of associated land cover change. Our goal was to identify threshold responses among bird species and habitat guilds to (1) overall forest loss and fragmentation in affected landscapes, and (2) distance from anthropogenic disturbance, both related and unrelated to shale gas. We conducted 2589 bird surveys at 190 sites across this region, and quantified community-level and species-specific thresholds relating to forest cover and distance to anthropogenic disturbance, using Threshold Indicator Taxa Analysis (TITAN). Forest interior species decreased abruptly in abundance and frequency of occurrence above a threshold of 17.0% overall forest loss, while early successional and synanthropic species increased abruptly above 30.5–36.5% forest loss, respectively. Broad quantile intervals around responses to distance from anthropogenic disturbance suggest these were not sharp threshold responses, but more gradual or linear responses. Among forest interior species evaluated, 48.1% increased in abundance farther from shale gas development, while 55.6% of early successional and synanthropic species decreased. We found evidence of avian threshold responses to overall forest loss and fragmentation in affected landscapes across the Marcellus-Utica shale region. Our results suggest that efforts to avoid shale gas development in regional core forests—particularly those still retaining ≥ 83% forest cover—can reduce negative effects on area-sensitive, forest interior dependent species.