A geographic model to assess and limit cumulative ecological degradation from Marcellus Shale exploitation in NY State

Background/Question/Methods

When natural resources are exploited, environmental costs and economic benefits are often asymmetric. A current example is the disparity between financial rewards and environmental impacts from fossil fuel extraction by hydraulic fracturing. In New York State, most scrutiny has been focused on water quality in affected aquifers, with less attention paid to broader ecological impacts beyond individual drilling operations. We developed a GIS-based model, built on a hexagonal grid underlay nested within the US EPA EMAP system, to examine potential cumulative statewide ecological impacts. In a two-step process, we characterized  >19,000 hexagons, each sized to approximate the footprint of one drilling site (2.57 km²), using ecological attributes, then developed a method for apportioning resource access that includes assessments of cumulative ecological costs. Over one-fourth of the hexagons were excluded as off-limits on the basis of six criteria: slope suitability, regulated wetland cover, length of high-quality streams, mapped road density, and open water cover. Three additional criteria were applied to assess estimated ecological vulnerability of the remaining sites: densities of grassland birds (North American Breeding Bird Survey), percent core forest (Coastal Change Analysis Program), and total density of all state-mapped streams were determined and used in combination, to rank the 14,000 potentially accessible sites. In a second step, an iterative process was used to distribute potential site access among all towns (sub-county governments) within the Marcellus Shale Formation. At each iteration, one site is selected per town, whether randomly, or in rank order of increasing vulnerability. Results were computed as percent cumulative ecological impact versus number of sites committed, and compared with a most-conservative selection process (ranked by statewide vulnerability).

Results/Conclusions

Random selection with proportional distribution by town resulted in larger cumulative ecological impacts, but rank-ordered selection by town was in many ways comparable to selection by statewide vulnerability ranking. For example, if half of all potential well sites are exploited using apportioned, non-random selection, the models estimate reductions of 6% in core forest degradation, 17% in stream degradation, and 7.5% in grassland bird habitat degradation. These outcomes allow for a political solution for managing resource access fairly, based on a balanced geographic distribution of economic benefits, coupled with an underlying scientific basis for assessing the ecological costs that are publicly shared.  Potential applications include permit fees (or comparable instruments) set on a sliding scale to match cumulative ecological impacts.