Habitat loss due to widespread human alteration of land cover is a major threat to native wildlife communities and global biodiversity. In the United States, urban sprawl and exurban development are the fastest growing sources of land use change, and among the leading causes of species endangerment.
We know there are distinct changes in biological communities in urbanizing environments. However, the mechanisms underlying these patterns of change are less clear. As part of a long-term study of the effects of urban development on breeding songbird communities in the Puget Sound region, I examined the relationship between two species of closely related wrens, a forest dependent specialist and a habitat generalist, along an urban-to-wildland gradient.
I found evidence of increasing competition between these two species where they co-occur, leading to aggressive exclusion of the forest specialist by the habitat generalist in urbanizing landscapes. My findings include specific recommendations for land use planners to support forest dependent species, including retention of large forest patches (42-65 ha), maintenance of large, old woody debris, and removal/suppression of invasive vegetation.
Since 2005, unconventional shale gas development (“fracking”) has rapidly altered forests across the central Appalachian Mountains of the eastern United States, an area of high conservation value for biodiversity. Much is still unknown about ecological impacts of associated land use and land cover change.
To assess impacts of fracking development on forests and breeding songbirds, I conducted a region-wide assessment of 200 sites across the central Appalachians, comparing remotely sensed land cover data with field surveys of breeding birds.
I found evidence of biotic homogenization throughout affected areas, and surprisingly low thresholds of forest disturbance (< 17%) in landscapes impacted by shale gas development beyond which forest interior birds experience steep declines. My results suggest mitigation strategies requiring co-location of pipelines with existing infrastructure when possible, and implementing cut-back borders and integrated vegetation management along pipeline rights-of-way will reduce barrier effects and other negative impacts. These findings are being used by the U.S. Fish & Wildlife Service and policymakers to inform spatially explicit management objectives and regulatory decisions in the region.
Arctic and subarctic regions are warming at more than twice the rate of the global average, leading to a rapid expansion of shrubs and trees in tundra ecosystems. Global wildlife distributions are expected to shift towards range limits in response to climate-driven habitat changes. However, many species that breed in arctic and subarctic regions are already at the limits of their bioclimatic and geographic ranges, raising concerns about the implications of changing vegetation in these regions for biodiversity.
With start-up funding I received from the American Ornithological Society, I will conduct a pilot study in the summer of 2021 to investigate climate-driven changes in vegetation and bird communities in Denali National Park. I will re-survey historic bird and vegetation sampling plots originally surveyed by the National Park Service from 2002 to 2008. Results will shed light on bird community responses to shrub and tree expansion in one of Alaska’s most iconic wilderness areas.
The Earth’s ecosystems are undergoing rapid changes and unprecedented declines in biological diversity. There is a pressing need for accessible and reliable measures of key environmental determinants of biodiversity to help guide and monitor conservation strategies. Large-scale, open ecological datasets play an increasingly important role in biodiversity research and broad-scale conservation planning. At the same time, cloud-computing platforms like Google Earth Engine have increased the accessibility of remote sensing imagery and the speed of big data processing.
I work to leverage these advances by combining large biological datasets (e.g., North American Breeding Bird Survey, National Ecological Observatory Network) with remote sensing imagery (e.g., Landsat 8, Sentinel-2), using innovative quantitative and spatial modeling techniques. My goal is to advance our understanding of the effects of environmental change on animals to inform effective conservation strategies at local to global scales.
Habitat heterogeneity is an important determinant of species diversity, but is difficult to measure across large areas using field-based methods. Satellite remote sensing data offer spatio-temporally extensive and cost effective coverage of landscapes, and are increasingly used in conservation research to quantify and map habitat characteristics that are important for biodiversity.
In particular, satellite image texture analysis shows promise for characterizing vegetation heterogeneity across broad spatial extents. Image texture quantifies variations in the tonal values of pixels across an image, and thus provides information about the spectral and spatial heterogeneity of landscape features.
My research has demonstrated that satellite image texture effectively captures both structural and compositional elements of vegetation heterogeneity, in a variety of habitats and ecoregions. These findings highlight the exciting potential of satellite image texture for habitat mapping, biodiversity modeling, and conservation planning.
Dissimilarity texture measure (Farwell et al. 2020)
Data layers (columns a–e) corresponding to three sampled landscapes (rows 1–3), representing forest, grassland, and shrubland habitats (Farwell et al. 2021)
Maps of observed (first column) vs. predicted (second column) bird species richness, and difference from observed (third column) for all species and for specialists within forest, grassland, and shrubland habitats. (Farwell et al. 2020)
The former administration proposed changes to the Migratory Bird Treaty Act (MBTA), passed in 1918, which importantly prohibits incidental take, or the unintentional harm of migratory birds by industrial operations.
In a move that would largely benefit the oil and gas industry and electric utilities, the proposed roll-back would remove significant incidental take protections for migratory birds. The U.S. Fish and Wildlife Service would no longer have authority to enforce violations of the law— including environmental disasters like the Deepwater Horizon and Exxon Valdez oil spills.
As a consultant regarding the impacts of pipeline development on migratory birds, I worked with attorneys at the Southern Environmental Law Center (SELC) to draw attention to the likely harm this policy change would bring to species that are already experiencing steep declines.
I also served as an expert witness on the SELC’s case against the Federal Energy Regulatory Commission’s approval of the Atlantic Coast Pipeline (ACP), which would fragment some of the largest remaining expanses of mature, undisturbed forest remaining in the eastern United States. Learn more at StopTheACP.org.
