Carnegie Mellon University
March 20, 2015

Researchers Show Forest Fragmentation from Shale Development Could Be Reduced by Placing Natural Gas Lines Along Roadways

By Tara Moore / 412-268-9673 /

A team of researchers in Carnegie Mellon University’s College of Engineering found that forest fragmentation from natural gas development in Pennsylvania is caused by gathering lines, the smaller pipelines that carry extracted natural gas to the main distribution pipes.

In a paper in the journal Ecological Indicators, the scientists report that redirecting the lines so they follow the routes of existing roadways would greatly reduce fragmentation.

The research group includes Leslie Abrahams, a doctoral student in engineering and public policy (EPP) and civil and environmental engineering (CEE), and co-authors W. Michael Griffin, an EPP associate research professor, and CEE Professor H. Scott Matthews.

Shale Gas Well Pad

Forest fragmentation occurs when the key infrastructure related to Marcellus shale natural gas extraction — specifically the well pads themselves, as well as gathering lines and access roads — cuts through the forest, dividing it into smaller sections.

While it may seem at first glance that the well pads, which can require anywhere from three to nine acres of cleared forest land, would be the biggest culprit of fragmentation, the team discovered the main cause to be the gathering lines. While gathering lines are buried underground, the surfaces above them, called right of ways, are cleared of all trees, causing almost 19 acres of loss per well pad.

“If something cuts a cleared path through the forest, it could be dividing a species’ habitat in half,” Abrahams explained. “Flying squirrels, for example. The natural gas infrastructure can create openings in the forest that are too wide for them to glide across and suddenly their habitat is greatly decreased.”

The gathering line right of ways also create pathways that allow invasive species to access inner parts of the forest. Suddenly, indigenous animals are introduced to predators they’ve never learned how to avoid before, making survival much more difficult.

The research team used computer-modeling software to develop strategies to greatly reduce forest fragmentation.

The team’s major suggestion for future infrastructure development is to build future gathering lines, the major culprits of fragmentation, so they follow the same routes as existing roads. This way, no additional corridors are built, keeping future fragmentation to a minimum.

Additionally, requiring natural gas companies to collaborate on infrastructure development would help eliminate unnecessary fragmentation by forcing multiple companies to use the same pipelines.

“Eliminating the need for multiple pipelines that go to the same place would save developers money, while helping to protect core forest ecosystems,” Griffin said.

Another strategy is to reduce the number of necessary well pads by simply drilling more wells at each pad.

“One of the benefits of unconventional natural gas development is that you can develop multiple wells per pad because instead of drilling straight down, you go down and then out horizontally so you can have six or 12 different wells per pad,” Abrahams said.

“By simply drilling more wells per pad, and drilling those wells farther, you can still drill the same number of wells without clearing as much forested land. However, while it does reduce the level of fragmentation over the business as usual case, this strategy does not stop additional future fragmentation from occurring altogether because it does not address the placement of the gathering lines,” Abrahams said.

This work was funded in part by the National Science Foundation Graduate Research Fellowship Program, the Center for Climate and Energy Decision Making, and by the Department of Engineering and Public Policy.

Read the full paper, titled “Assessment of policies to reduce core forest fragmentation from Marcellus shale development in Pennsylvania,” at