Forest Fragmentation In Natural Gas Drilling
From Wikimarcellus
Forest fragmentation is a key ecological concept thought to be closely related to the maintenance and promotion of biodiversity of plant and animal species requiring a forest habitat. Fragmentation essentially occurs once an undivided forest somehow becomes separated into a series of often disconnected patches thus disturbing natural habitats of occasionally very rare species whose ecological niche can primarily be found in deep forest. Natural gas drilling requires the withdrawal of some agricultural and forested acreage for at least a year or more, and it has been argued that this can be a contributing factor to fragmentation and have an ensuing impact on woodland biodiversity. Of course, many other factors can also affect forest fragmentation, and historically these have included a variety of natural and anthropomorphic sources.
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Definition of Forest Fragmentation
Fragmentation can have quite varied definitions. It is discussed in the fields of wildlife habitat, biodiversity and land-use planning. It occurs naturally, as in the case of forest fires or disease, or from forest management practices such as clearcut logging which took place in the 19th and early 20th century in Pennsyvania's forests. It is a complicated process that results from interaction between the forest landscape and human demands on the land to divide it into ever smaller pieces. Simply passing land from one generation to the next serves to subdivide forested land as different heirs find diverse uses for their inheritance. Regardless of whether fragmentation occurs as the result of suburban development, clearcutting, agricultural use or natural gas well drilling the result is to take a contiguous native forest and divide it into smaller pieces that create a patchwork of different pieces with other vegetation and land uses.
Old growth forests
Once, before it was settled by Europeans, the northeast was covered by a dense "old growth" forest. Original timber stands that had never before been logged or disturbed differed in many ways from later stands of regenerated forests that may already have been harvested a number of times. For example, the litter made up of decaying leaves, dead trees and branches covering the forest floor representing eons of composing was much more lush, wet and deep.
In recently regrown forests, the floor is nowhere near so deep. The soil is much drier and more subject to errosion. Original forests were inhabited by a variety of native plant and animal species. Later forests don't even consist of the same trees as once were there. For example, the original forests covering most of Pennsylvania were primarily made up of beech and hemlock. Later regrown forests are extensively of mixed stands of hardwood. Invasive species such as the Norway maple, Japanese knotwood, autumn olive and other plants imported from abroad have overrun whole sections of Pennsylvania. Many original native plants and animal species are extinct, or else limited to only a few isolated stands of original forest, that somehow escaped being clearcut in the late 1800s - early 1900s.
While the concept of forest fragmentation is relevant to restoring native forests over a period of two hundred years or more, it is of far less concern than we would have for orignial "old growth" forests were they still in existence. In other words, the biodiversity "horse is already out of the barn" when it comes to more recent stands of trees and foliage. Fragmentation should be discouraged, but only as it relates to plans for long term restoral of at least some portions of the long-ago-distroyed, original native forest.
Exurbanization
In the Northeastern U.S., urban sprawl has been the single biggest cause of fragmentation. It has become increasingly popular for city residents to move into the areas between city and country--or, as it is sometimes called exurbanization--that is, when urban dwellers move to rural areas.
Parcelization
Landowners, as a group, are an agining population. Of 12.5 million acres of Pennsylvania forest in private hands, 25% is owned by those 65 or older. The disposition of the acreage after the landowner's demise is of concern. The forest land is often divided upon the death of landowner into parcels and left to children or other heirs. This creates parcilization. The biggest concern is inheritance taxis. Sale of timber may not be enough to cover federal and state taxes. That creates an automatic incentive to convert the land to other more profitable uses that at least provide sufficient renumeration to pay taxes.
Mitigation
Agricutural and urban development are the most damaging causes of fragmentation, because they may permanantly withdraw land from being habitat for woodland plantlife, birds and other creatures. Forests that are harvested for wood are less damaging. because they represent only a temporary withdrawal of habitat. However, conservation efforts need to focus on maintaining sufficient amounts of mature forest in order to meet the requirements of forest-interior specias. Natural gas drilling, because it represents only temporary withdrawal of habitat for construction of well pads, should also be viewed as far less damaging than urbanization or agricultural uses of the forest. Once drilling and hydro-fracturing are complete, well pads that cover several acres during the drilling phase, can often be reduced down to the size of a two-car garage All that is needed is room for a well head or "Christmas tree" and a tank or two to capture any residual flowback water still coming up the well.
History of Forests In Pennsylvania
Pennsylvania's vast expanse of forest was cut in the late 19th and early 20th centuries. This led to tracts of immature, regenerating forests that provided an ideal habitat for white-tailed deer, bobcats and ruffed grouse. At the time, the deer population was quite depressed, because of unregulated hunting. The deer population at the present date has more than completely recovered.
An important distiction must be drawn between a forest fragmented through urban development and agricultural uses compared to a forested landscape composed of a patchwork of mature and regenerating stands caused by timber harvesting. The former condition usually damages forest bird populations more as it represents more or less loss of destruction of habitat for an indefinite period. Timber harvesting only represents a temporary reduction in habitat for those species that live in the interior of mature stands of trees. Mature forests require much more time to regenerate. The construction of well pads, pipelines and roads to support natural gas drilling have elements of both types of disturbance. Accomodation of pipelines and roads leads to permanant withdrawal of land, but well pads once no longer needed for drilling operations are usually reclaimed in a year or two. Saplings and ground cover are seeded. So this kind of activity should be viewed as no more threatening to biodiversity than tree harvesting. Roads no longer needed are allowed to regenerate naturally, and only pipelines and their rightaway remain as permanant factors of deforestation. Effective conservation requires foresters to develop and maintain necessary habitiat for species that need a mature forest. Almost all of Pennsylvania's forest represents at the least second growth and often third, forth or fifth growth if the timber has been repeatedly harvested.
Remediation
Restoration after drilling can help reduce or eliminate forest fragmentation and result in larger patches of connected or interior forest.
One big source of interruption of natural landscape by drilling is the intallation of flowback impoundments--essentially large (several acre) plastic lined ponds for the retention and evaporation of flowback water from hydro-fracturing operations. These are generally fenced so deer and other animals will be kept away from them.
Actually there are fewer impoundments now as the trend is for moving to "closed loop" systems wherein large metal containers are used to hold the water that comes back up the well after hydro-fracturing.
Best Management Practices
For example, in West Virginia, site plans expect E & P companies to follow Best Management Practices guidelines in order to restore the well site. These include replacing topsoil, and restoration of vegetation by planting crops, grass, or trees. Discharge of surface water from the well pad should be strictly limited and the quality of streams and ground water supplies protected.
Typically some of the procedures followed in well site reclamation efforts include:
- building and installing ditches and ponds to collect any runoff that will carry sediment from the excavation and cuts made at the well site.
- The sediment settles in the pond before runoff water is released into neighboring streams or rivers.
- Ponds that hold drill cuttings or other flow-back water are lined with very thick plastic liners, and are not used for runoff water from the drilling site.
- Flow-back water and drill cuttings, sometimes referred to as brine are removed by tanker truck and transported to a water treatment facility and never released into streams.
- In order to control errosion, the soil on outslopes of ponds are fertilized and limed. Then they are seeded with herbaceous species, and the area is mulched to prevent soil erosion.
- Once water control is established, then a local tree cutter is hired to clearcut the well pad area.
- Once drilling operations have concluded and most of the flow-back water has alredy surfaced, a well head or "Christmas tree" that connects to gathering lines. Barrels are left behind to collect any additional condensate or water.
- Reclamation efforts undertaken include:
- removing all ponds and ditches
- regrading the well pad site to its previous contour
- the area is reseeded according to the landowner's wishes.
