Over the years, we and others have examined the effects on the refuge system of secondary activities, such as recreation, military activities, and oil and gas activities—which include oil and gas exploration, drilling and production, and transport. Exploring for oil and gas involves seismic mapping of the subsurface topography. Seismic mapping requires surface disturbance, often involving small dynamite charges placed in a series of holes, typically in patterned grids. Oil and gas drilling and production often requires constructing, operating, and maintaining industrial infrastructure, including a network of access roads and canals, local pipelines to connect well sites to production facilities and to dispose of drilling wastes, and gravel pads to house the drilling and other equipment. In addition, production may require storage tanks, separating facilities, and gas compressors. Finally, transporting oil and gas to production facilities or to users generally requires transit pipelines. Department of the Interior regulations generally prohibit the leasing of federal minerals underlying refuges. In addition, under the National Wildlife Refuge System Administration Act of 1966, as amended, the Fish and Wildlife Service (FWS) is responsible for regulating all activities on refuges. The act requires FWS to determine the compatibility of activities with the purposes of the particular refuge and the mission of the refuge system and not allow those activities deemed incompatible. FWS does not apply the compatibility requirement to the exercise of private mineral rights on refuges. However, the activities of private mineral owners on refuges are subject to a variety of other legal restrictions under federal law. For example, the Endangered Species Act of 1973 prohibits the “take” of any endangered or threatened species and provides for penalties for violations of the act; the Migratory Bird Treaty Act prohibits killing, hunting, possessing, or selling migratory birds, except in accordance with a permit; and the Clean Water Act prohibits discharging oil and other harmful substances into waters of the United States and imposes liability for removal costs and damages resulting from a discharge. Also, FWS regulations require that oil and gas activities be performed in a way that minimizes the risk of damage to the land and wildlife and disturbance to the operation of the refuge. The regulations also require that land affected be reclaimed after operations have ceased. At least one-quarter, or 155, of the 575 refuges (538 refuges and 37 wetland management districts) that constitute the National Wildlife Refuge System have past or present oil and gas activities—exploration, drilling and production, transit pipelines, or some combination of these (see table 1).Since 1994, FWS records show that 44 refuges have had some type of oil and gas exploration activities—geologic study, survey, or seismic mapping. We also identified at least 107 refuges with transit pipelines. These pipelines are almost exclusively buried, vary in size, and carry a variety of products, including crude oil, refined petroleum products, and high-pressure natural gas. Transit pipelines may also have associated storage facilities and pumping stations, but data are not available to identify how many of these are on refuges. Over 4,400 oil and gas wells are located within 105 refuges. Although refuges with oil and gas wells are present in every FWS region, they are more heavily concentrated near the Gulf Coast of the United States. About 4 out of 10 wells (41 percent) located on refuges were known to be actively producing oil or gas or disposing of produced water during the most recent 12-month reporting period, as of January 2003. Of the 105 refuges with oil and gas wells, 36 refuges have actively producing wells. The remaining 2,600 wells did not produce oil, gas, or water during the last 12 months; many of these were plugged and abandoned or were dry holes. During the most recent 12-month reporting period, the 1,806 active wells produced 23.7 million barrels of oil and 88,171 million cubic feet of natural gas, about 1.1 and 0.4 percent of total domestic oil and gas production, respectively. Based on 2001 average prices, refuge-based production had an estimated total commercial value of $880 million. Substantial oil and gas activities also occur outside but near refuge boundaries. An additional 4,795 wells and 84 transit pipelines reside within one-half mile of refuge boundaries. The 4,795 wells bound 123 refuges, 33 of which do not have any resident oil and gas wells. The 84 pipelines border 42 different refuges. While FWS does not own the land outside refuge boundaries, lands surrounding refuges may be designated for future acquisition. The overall environmental effects of oil and gas activities on refuge resources are unknown because FWS has conducted few cumulative assessments and has no comprehensive data. Available studies, anecdotal information, and our observations show that some refuge resources have been diminished to varying degrees by spills of oil, gas, and brine and through the construction, operation, and maintenance of the infrastructure necessary to extract oil and gas. The damage varies widely in severity, duration, and visibility, ranging from infrequent small oil spills and industrial debris with no known effect on wildlife, to large and chronic spills causing wildlife deaths and long-term soil and water contamination. Some damage, such as habitat loss because of infrastructure development and soil and water contamination, may last indefinitely while other damage, such as wildlife disturbance during seismic mapping, is of shorter duration. Also, while certain types of damage are readily visible, others, such as groundwater contamination, changes in hydrology, and reduced habitat quality from infrastructure development are difficult to observe, quantify, and associate directly with oil and gas activities. Finally, oil and gas activities on refuges may hinder public access to parts of the refuge or FWS’s ability to manage or improve refuge habitat, such as by conducting prescribed burns or creating seasonal wetlands. The 16 refuges we visited reported oil, gas, or brine spills, although the frequency and effects of the spills varied widely. Oil and gas spills can injure or kill wildlife by destroying the insulating capacity of feathers and fur, depleting oxygen available in water, or exposing wildlife to toxic substances. Brine spills can be lethal to young waterfowl, damage birds’ feathers, kill vegetation, and decrease nutrients in water. Even small spills may contaminate soil and sediments if they occur frequently. For instance, a study of Atchafalaya and Delta National Wildlife Refuges in Louisiana found that oil contamination present near oil and gas facilities is lethal to most species of wildlife, even though refuge staff were not aware of any large spills. Constructing, operating, and maintaining the infrastructure necessary to produce oil and gas can harm wildlife by reducing the quantity and quality of habitat. Infrastructure development can reduce the quality of habitat through fragmentation, which occurs when a network of roads, canals, and other infrastructure is constructed in previously undeveloped areas of a refuge. Fragmentation increases disturbances from human activities, provides pathways for predators, and helps spread nonnative plant species. For example, officials at Anahuac and McFaddin National Wildlife Refuges in Texas said that disturbances from oil and gas activities are likely significant and expressed concern that bird nesting may be disrupted. However, no studies have been conducted at these refuges to determine the effect of these disturbances. Infrastructure networks can also damage refuge habitat by changing the hydrology of the refuge ecosystem, particularly in coastal areas. In addition, industrial activities associated with extracting oil and gas have been found to contaminate wildlife refuges with toxic substances such as mercury and polychlorinated biphenyls (PCBs). Mercury and PCBs were used in equipment such as compressors, transformers, and well production meters, although generally they are no longer used. New environmental laws and industry practice and technology have reduced, but not eliminated, some of the most detrimental effects of oil and gas activities. For example, Louisiana now generally prohibits using open pits to store production wastes and brine in coastal areas and discharging brine into drainages or state waters. Also, improvements in technology may allow operators to avoid placing wells in sensitive areas such as wetlands. However, oil and gas infrastructure continues to diminish the availability of refuge habitat for wildlife, and spills of oil, gas, and brine that damage fish and wildlife continue to occur. In addition, several refuge managers reported that operators do not always comply with legal requirements or follow best industry practices, such as constructing earthen barriers around tanks to contain spills, covering tanks to protect wildlife, and removing pits that temporarily store fluids used during well maintenance. Oil and gas operators have taken steps, in some cases voluntarily, to reverse damages resulting from oil and gas activities, but operators have not consistently taken such steps, and the adequacy of these steps is not known. For example, an operator at McFaddin National Wildlife Refuge removed a road and a well pad that had been constructed to access a new well site and restored the marsh damaged by construction after the well was no longer needed. In contrast, in some cases, officials do not know if remediation following spills is sufficient to protect refuge resources, particularly for smaller oil spills or spills into wetlands. FWS does not have a complete and accurate record of spills and other damage resulting from refuge-based oil and gas activities, has conducted few studies to quantify the extent of damage, and therefore does not know its full extent or the steps needed to reverse it. The lack of information on the effects of oil and gas activities on refuge wildlife hinders FWS’s ability to identify and obtain appropriate mitigation measures and to require responsible parties to address damages from past activities. Lack of sufficient information has also hindered FWS’s efforts to identify all locations with past oil and gas activities and to require responsible parties to address damages.