Written by Torin Miller,
Research Assistant
A few weeks ago, we took a look at
the impacts of shale gas drilling on wildlife populations, with a particular
focus on habitat fragmentation, water issues, and noise, light and air
pollution. This week, we’ll take a closer look at species-specific impacts
throughout the northeastern United States, with an emphasis on the Marcellus
Shale region. Specifically, this article will focus on forest songbirds and
bats, and the impacts that habitat fragmentation, greenhouse gas emissions,
water consumption and contamination, and noise pollution have on their
populations.
Forest songbirds and various bat species have been at the
center of the majority of the wildlife-related shale gas impact studies
conducted to date. The Marcellus shale region is covered by large swathes of
contiguous forest, which provides “habitat for a myriad of forest specialists
and interior wildlife, including numerous species of conservation concern and
many Neotropical songbirds,” a study in The Journal of Wildlife Management (JWM) states. According to the study, with less than 10
percent of the nation’s forests remaining in contiguous conditions, Pennsylvania’s
title as the second most-forested state in the northeast is incredibly
important for forest specialists such as songbirds and bats. “Bats may serve as
the proverbial ‘canary in the coalmine’ because many of their life history
traits make them sensitive to human-induced environmental changes,” a report by The
Delaware Riverkeeper Network (DRN) notes.
Specific, potential
impacts on both forest songbirds and bats, with a focus on habitat
fragmentation, greenhouse gas emissions, water consumption and contamination,
and noise pollution, will be outlined below.
Forest Songbirds
Shale gas development’s biggest impact on forest songbird
populations is habitat fragmentation. This is likely attributed to the fact
that songbird breeding success and abundance are highest in large blocks of
contiguous forest, according to a study in Environmental Science and Technology (EST). According to the JWM study, “Research
has shown that shifts in the bird community are occurring within the large
block of extensive forest in Northcentral Pennsylvania in association with
shale gas development.”
The JWM study found that
there has been an increase of human tolerant species near well pads and a
decline in forest specialists, and that the lack of forest specialists may have
been the result of edge avoidance or an influx of new species. As a result,
“[t]he increase in these novel community members within the forest may result
in increased levels of predation, parasitism, and resource competition,” the
study notes. The loss of forest specialists is important for a variety of
reasons. Notably, forest songbirds are important for insect control; “[t]hey
provide a valuable ecosystem service and their role in preventing and
suppressing insect outbreaks is well-documented,” the study states.
While habitat
fragmentation related to shale gas development casts the biggest shadow over
forest songbirds, resulting noise pollution also has its impacts. The EST study notes that
noise associated with shale gas development (both short-term drilling and
long-term compressors) may harm vocal species like songbirds. Additionally, a study in The
Wildlife Professional notes that loud
noises may affect the pairing success of songbirds, as their mating songs are
drowned out by external noises. The study also notes that unnatural noises may
create the possibility of “lower abundance, changes in reproductive behavior
and success, altered predator-prey interactions and altered avian communities.”
According to the JWM study, “it is
important to minimize disturbance to core forest habitat by minimizing
fragmentation and the number of new pads established.” The study notes that
methods to minimize disturbance include “clustering pad locations, maximizing
the number of wells per pad, and identifying and excluding from shale gas development
areas of high quality contiguous forest.”
Bats
Like forest songbirds, various bat species are impacted
by shale gas development. These impacts primarily originate from habitat
fragmentation, water consumption and contamination, and greenhouse gas
emissions.
Bat abundance and diversity is highest when natural
habitat is highest, and mature forests provide many places for bats to roost,
according to the DRN report.
Particularly, bats need large areas of undisturbed, mature habitat for roosting
and foraging, and shale gas development may disrupt large areas (and will
likely continue to do so), the study added.
Destruction or disruption of hibernacula is also a
concern, particularly for the endangered Indiana bat (Myotis sodalis),
which are known to hibernate at only 18 sites throughout Pennsylvania,
according to the Pennsylvania Game Commission. Bats require hibernacula with specific microclimate
conditions, including temperature, humidity and airflow. “Modifications to the
surface habitat surrounding hibernacula also can contribute to changes in
microclimate conditions, as well as influence the suitability of foraging
characteristics,” the DRN report notes.
The report also notes that disturbing hibernating bats can cause bats to lose
necessary fat reserves and abandon roost.
Bats rely on water for two primary purposes: personal
consumption and prey attraction. First, “[b]ats have relatively high rates of
evaporative water loss, and must obtain much of their intake from available
surface water resources,” the DRN report states.
Additionally, lactating females will select roost sites near water sources to
aid in milk production, the report notes. Second, riparian habitats attract
insects, which bats prey upon heavily. “Thus, the extensive withdrawal of water
resources from the environment, particularly in sensitive areas or areas under
drought conditions, will presumably affect roost-site selection and abundance
and availability of prey,” according to the report.
Wastewater contamination from shale gas development is a
concern for bat populations throughout the northeast. According to the DRN report, “[b]ats
have been observed congregating and drinking from holding ponds at industrial
sites,” and contaminants in ponds or other water sources can negatively impact
insect populations. Insects that ingest contaminated water and are then preyed
upon by bats may be harmful; “[b]ecause dietary accumulation and metabolic
capacity increase at higher trophic levels, and because insectivorous bats are
apex predators, bats are likely more susceptible to contaminants,” the report
states.
Lastly, greenhouse gas emissions resulting from shale gas
development may impact bat populations. Bats may be highly affected by climate
change because temperature changes affect hibernation, food availability and
young recruitment, according to the DRN report. Warmer
winter temperatures could affect energy requirements for hibernation, and
spring births may occur too early, which would increase juvenile mortality and
negatively impact recruitment, the report notes.
Overall, “[a]s with other industrial practices, shale gas
development contributes to water withdrawal and contamination, habitat loss and
degradation, and the emission of GHGs resulting in detrimental effects on bat
populations and their environment,” the DRN report
concludes.
Conclusion
While more observation
and analysis is necessary to truly understand the impacts of shale gas drilling
on forest songbird and bat populations, current studies do provide insight into
the potential impacts of habitat fragmentation, greenhouse gas emissions, water
consumption and contamination, and noise pollution have on these populations,
particularly throughout the northeastern United States. A subsequent Spotlight
article will take an in-depth look at legal implications of wildlife-related
impacts of shale gas drilling, with a focus on policy and legislation that
relates to, and resulted from, these impacts.
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