Last week, U.S. Geological Survey released a new report raising concerns about Marcellus shale drilling on the Allegheny Plateau. Researchers used geospatial data and high resolution aerial imagery from 2004-2010 to study landscape changes in two key Pennsylvania counties – Susquehanna County in the northeast and Allegheny County in the southwest.
They documented substantial forest and wildlife ecosystem changes due to Marcellus well drill pads, new roads and pipelines for natural gas plus coalbed methane exploration. Keep in mind that much more natural gas development of Marcellus has occurred since 2010.
"Large-scale landscape disturbance can have a significant impact on ecological resources," says Terry Slonecker, lead author of the USGS research. It's leading to "forest fragmentation", a situation where forested areas get "carved up" with roadways and drill pads that also lead to limiting geographic habitat area for some animal species.
Data from the report will be used to assess effects of disturbance and land-cover change on wildlife, water quality, invasive species and socioeconomic impacts. In Allegheny County, 647 natural gas sites resulted in more than 1,312 acres of disturbance, including 140 miles of new roads and 8 miles of new pipelines. In Susquehanna County, 294 natural gas extraction sites resulted in more than 1,742 acres of disturbance, including 34 miles of new roads and 53 miles of new pipelines.
The study, "Landscape Consequences of Natural Gas Extraction in Allegheny and Susquehanna, Counties, Pennsylvania, 2004 to 2010," is the third of a series planned relating to natural gas landscape disturbance.
Though Marcellus shale gas developers may be among the largest contributors, they're not the only ones responsible for this fragmentation, points out Slonecker. Other industries like coal, wind and coalbed methane can just as easily subdivide ecosystems.
Forest fragmentation and edge effects can negatively affect water quality and runoff. It can also affect the long-term survival of the forest itself.
When forests become patches...
Allegheny County's wooded areas have been subdivided, creating 35 new "forest patches" out of larger tracts of woodland, according to the study. Some species of wildlife cannot or will not live within these smaller patches of "edge forest," preferring instead the wider ranges of so-called "interior forest."
"For example, certain birds require interior forest area," adds Slonecker. "So when you start to slice and dice the landscape with roads and pipelines, much less interior forest is available for them to exist."
The "edge effects" on natural ecosystems can be substantial for some distance. Forest edge is partially sealed by proliferating vines and second growth underbrush. As human activities increase, natural habitats are divided into smaller and smaller patches with decreased ability to support viable populations of individual species
Habitat loss and forest fragmentation can be important threats to biodiversity of flora and fauna dependent on that habitat. And that impacts wildlife diversity as well. But Slonecker adds that research on this topic hasn't been conclusive.