by Shannon Julius
Shale gas development physically and chemically alters the surrounding landscape, and native plants and animals can be particularly susceptible to these changes. In the Marcellus and Utica shale region—a largely forested area that encompasses the states of Pennsylvania, Ohio, and West Virginia—shale gas wells are being drilled with increasing density. A shale gas installation, including the well pad, compressor station, and storage areas, requires 3.56 ha on average. If an edge effect is considered, installations can affect approximately 15 ha of forest per site. Kiviat (2013) reviewed the potential ways that shale gas development can impact biodiversity. The most serious threats are physical alteration of terrestrial landscapes, chemical contamination of water and soil, and alteration of regional hydrology. Terrestrial alterations include construction of well installations, which cause deforestation and habitat loss, and construction of roads and pipelines, which create forest fragmentation. Chemical contaminants come from fracturing fluid and recovered wastewater. Hydrologic alterations are caused by water withdrawals and an increase in impermeable surfaces. Minor impacts on plant and animal health can come from noise, light, and air quality. Certain species are particularly at risk from shale gas development activities and some are able to thrive in the altered conditions.
Kiviat conducted a literature review to analyze the consequences of various shale gas development activities on nearby plants and animals, and identified species that might be impacted positively or negatively from shale gas development. The first major consequence of shale gas drilling is physical alteration of the land from the construction of well pads, roads, and pipelines. The construction of a well pad destroys any organisms that had occupied the space prior to construction and contributes to habitat loss and deforestation. Edge effects from well pads range from 10 meters for trees to as much as 500 meters for birds. These installations, along with their associated roads and pipelines, fragment the surrounding forested area. Fragmentation affects seed dispersal, pollination, predator-prey relationships, and herbivore-plant relationships. These factors are crucial to the functioning of local ecosystems, and if disturbed will particularly harm orchids, herbs, lichens, amphibians, birds, and a certain species of butterfly. Roads and vehicular traffic additionally create the possibility of road mortality, especially with frogs. Certain species of nonnative plants, on the other hand, can thrive in these fragmented and industrial conditions. Many weeds disperse along roads; others will grow in the disturbed soils at the edges of roads, pipelines, or well pads and will spread from there into the nearby forests. Other effects from well pad construction are the warming and drying of remaining forest, which create favorable conditions for certain nonnative plants and songbird nest predators. The new conditions may also make a landscape that is favorable for deer, which threaten herb populations. It will be difficult for these forest ecosystems to recover even after wells come to the end of their useful life (usually around 20-40 years) and the surrounding area is remediated, as it can take 75–100 years or more for forests to regenerate and mature.
The hydraulic fracturing process can negatively impact biodiversity by adding toxic chemicals to regional water and soil, which happens when accidental spills or leaks of fracturing fluid or wastewater occur. Such spills release VOCs, diesel, metals, sodium chloride, and many other substances to nearby surface water. Sodium chloride is especially a problem for biodiversity as many streams are already high in salt content and many amphibians, lichens, mosses, conifers, and aquatic plants are sensitive to salt. When hydraulic fracturing fluid resurfaces as toxic and radioactive wastewater, it is stored in open-air ponds that are potential ecological traps for water birds, muskrat, turtles, frogs, and aquatic insects. Water quality can also decline due to sediment pollution from heavy equipment on rural roads or by inadequate erosion control at drill sites. In one study in Arkansas, stream turbidity increased with shale well density.
Hydrologic alteration is another side effect of shale gas development. Significant water withdrawals for hydraulic fracturing fluid may harm stream fishes and aquatic invertebrates that require a minimum level of water throughout the year. Replacing forest with impermeable well pads increases total storm water runoff, which can decrease water quality and species diversity in streams. Freshwater mussels and aquatic salamanders are two species that are known to be particularly sensitive to hydrological conditions and could be negatively impacted by these changes. Groundwater tables and their flow into streams and wetlands might also be affected by this changing hydrology.
Minor impacts come from noise, light, and air emissions. Diesel compressors on shale gas well sites create noise 24 hours a day. Loud noises are known to interfere with acoustic communication of frogs, birds, and mammals. They can also cause hearing loss, stress, and hypertension in many animals, and bats tend to avoid loud noises altogether. These effects can lead to an overall change in population composition if mating success is disturbed. Well pads are lit throughout the night and sometimes have continuous artificial lighting. These lights can attract and kill moths and aquatic insects. Other animals can have their mortality, reproduction, and foraging affected positively or negatively by artificial light. Diesel exhaust, VOCs in fracturing fluids, ground level ozone, and road dust can negatively affect air quality. This will likely harm nearby moss and lichen population, but not much research has been done to see how it can affect animals.
Range-restricted species are particularly vulnerable to shale gas development. One study showed that 15 plants and animals’ geographic ranges overlap the Marellus and Utica shale region by at least 36%. The study notes that some species whose ranges have not been mapped may be quasi-endemic or have seasonal habitats in this region. Alternatively, some native organisms may thrive in the new habitats created by shale gas development. Bare and disturbed soils can be nest sites for bees, wasps, reptiles, and birds. Snakes are attracted to warm pavement in cold weather; they and other animal species will likely thrive in the warmer microclimate around well pads. Metal-tolerant plants and mosses could also be very successful in these new industrial climates.
Shale gas development is not the only risk to biodiversity in the Marcellus and Utica shale region; there can be similar impacts from coal mining, logging, urban sprawl, agriculture, and climate change. These factors will probably act synergistically with shale gas development and cause a more serious problem than current research indicates. Shale gas development is a unique problem in its use of toxic chemicals, rapid development, and geographic extent. The authors recommend careful management of chemicals, wastewater, soil, and other pollutants in order to protect regional biodiversity. One technique that can be utilized in order to minimize risks to biodiversity is reusing wastewater, which reduces total withdrawals from local water resources and reduces vehicle traffic necessary to transport water in and out of a site. Another technique is drilling further horizontally underground to reduce the total number of well pads and limit fragmentation. Placing well pads closer to highways or on land already lacking in biodiversity would also be beneficial. Finally, the researchers note that in order to remediate efficiently, post-well activities should be considered on a landscape level, not site by site.
Kiviat, E., 2013. Risks to biodiversity from hydraulic fracturing for natural gas in the Marcellus and Utica shales. Annals of the New York Academy of Sciences 1286, 1–14. http://www.fraw.org.uk/files/extreme/kiviat_2013.pdf