In the 124 years since the first national park, Yellowstone, was created, the national park system has grown to include 369 park units. In all, these units cover more than 80 million acres of land, an area larger than the state of Colorado. The mix of park units is highly diverse and includes more than 20 types; these range from natural resource preserves encompassing vast tracts of wilderness to historic sites and buildings in large urban areas. The Park Service’s mission is twofold: to provide for the public’s enjoyment of these parks and to protect the resources so that they will remain unimpaired for the enjoyment of future generations. The Park Service’s 1980 survey of threats found not only that the parks’ resources were being harmed but also that improvements were needed in determining what cultural and natural resources existed in each park, what their condition was, and how and to what extent they were being threatened. In response, the Park Service called for the development of resource management plans to identify the condition of each park’s resources and the problems with managing them, including significant threats. Three times since 1987, we have reported that the Park Service has made limited progress in meeting the information and monitoring needs it had identified in 1980. Our findings included incomplete, out-of-date, or missing resource management plans and an incomplete inventory of threats, their sources, or mitigating actions. In 1994, after examining the external threats to the parks, we recommended that the Park Service revise its resource management planning system to identify, inventory, categorize, and assign priorities to these threats; describe the actions that could be taken to mitigate them; and monitor the status of the actions that had been taken. Such an inventory has not been implemented, according to Park Service headquarters officials, because of funding and hiring freezes that have prevented the completion of needed changes to the planning system’s guidelines and software. In commenting on a draft of this report, the Park Service said that implementing this recommendation is no longer appropriate. The Park Service’s comments and our evaluation are presented in the agency comments section of this report. For internal, as for external threats, the Park Service has limited systemwide information. It does not have a national inventory of internal threats that integrates information it already has, and many of its individual units do not have a readily available database on the extent and severity of the threats arising within their borders. However, in commenting on this report, Park Service officials told us that headquarters has the systemwide information it needs to make decisions and that many decisions are made at the park level, where the superintendents decide what information is needed. They added that rather than developing a database of threats to resources, they need better data on the condition of resources to allow park managers to identify those that are the most threatened. According to headquarters officials, the Park Service has developed systems focused on particular categories of resources. Park managers and headquarters staff use these systems to identify, track, or assess problems, resource conditions, or threats. An overview of these systems follows: The Museum Collections Preservation and Protection Program requires parks to complete a checklist every 4 years on the deficiencies in the preservation, protection, and documentation of their cultural and natural resource collections. An automated system is being developed to collect these data. The data are used to make funding decisions. Another system for monitoring the condition of a cultural resource is the List of Classified Structures, which inventories and gives general information on historic structures in the parks. Headquarters officials said that the list is not complete because of insufficient funding. Headquarters rangers report that automated systems are in place to track illegal activities in parks, such as looting, poaching, and vandalism, that affect cultural and natural resources. Headquarters officials report that the inventory and information on the condition of archeological resources, enthnographic resources, and cultural landscapes are poor at present but that there are plans to develop improved systems, if staffing and funding allow. Although the Park Service’s guidance requires the parks to develop resource management plans, it does not require the plans to include specific information on the internal and external threats facing the parks. Such information would assist managers of the national park system in identifying the major threats facing parks on a systemwide basis, and it would give the managers of individual parks an objective basis for management decisions. At the eight parks studied, the managers identified 127 internal threats that directly affected natural and cultural resources. Most of these threats fell into one of five broad categories: the impact of private inholdings or commercial development within the parks, the results of encroachment by nonnative wildlife or plants, the damage caused by illegal activities, the adverse effects of normal visits to the parks, and the unintended adverse effects of the agency’s or park managers’ actions (see fig. 1). The majority of the threats affected natural resources, such as plants and wildlife, while the remainder threatened cultural resources, such as artifacts, historic sites, or historic buildings. (See app. I for a summary of the threats in each category at each of the eight parks.) Overall, the park managers we visited said that the most serious threats facing the parks were shortages in staffing, funding, and resource knowledge. The managers identified 48 additional threats in these categories. We classified these as indirect threats to cultural and natural resources because, according to the managers, the shortages in these areas were responsible for many of the conditions that directly threaten park resources. (See app. II for a list of these threats at the eight parks.) In addition, the managers identified other threats in such categories as laws or regulations, agency policies, and park boundaries. After reviewing the information about these threats provided by park managers in documents and interviews, we decided that the threats were indirect and should not be listed among the direct threats. In gathering data for each park, we also identified threats to services for visitors. Our analysis showed that many of these threats also appeared as threats to cultural and natural resources. We did not compile a list of threats to services for visitors because this report focuses on cultural and natural resources. Private inholdings and commercial development within park boundaries accounted for the largest number of specific threats. The managers of seven of the eight parks we reviewed identified at least one threat in this category. For example, at Olympic National Park in Washington State, the managers said that the homes situated on inholdings along two of the park’s largest lakes threatened groundwater systems and the lake’s water quality. At Lake Meredith National Recreation Area in Texas, the managers were concerned about the impact of the frequent repair and production problems at about 170 active oil and gas sites (see fig. 2) and the development of additional sites. At the Minute Man National Historical Park, the long, linear park is bisected by roads serving approximately 20,000 cars per day. The traffic affects cultural resources, such as nearby historic structures; natural resources, such as populations of small terrestrial vertebrates (e.g., the spotted salamander and spotted turtle); and visitors’ enjoyment of the park (see fig. 3). Encroachment by nonnative wildlife and plants—such as mountain goats, trout introduced into parks’ lakes and streams, and nonnative grasses and other plants—accounted for the second largest number of reported threats. The managers at all of the parks we reviewed identified at least one threat in this category. At Arches National Park in Utah, for example, the managers cited the invasion by a plant called tamarisk in some riverbanks and natural spring areas. In its prime growing season, a mature tamarisk plant consumes about 200 gallons of water a day and chokes out native vegetation. At Olympic National Park, nonnative mountain goats introduced decades ago have caused significant damage to the park’s native vegetation. The goats’ activity eliminated or threatened the survival of many rare plant species, including some found nowhere else. Controlling the goat population reduced the damage over 5 years, as the contrast between figures 4a and 4b shows. Illegal activities, such as poaching, constituted the third main category of threats. The managers at the eight parks reported that such activities threatened resources. For example, at Crater Lake National Park in Oregon, the managers believe that poaching is a serious threat to the park’s wildlife. Species known to be taken include elk, deer, and black bear. At both Crater Lake and Olympic national parks, mushrooms are harvested illegally, according to the managers. The commercial sale of mushrooms has increased significantly, according to a park manger. He expressed concern that this multimillion-dollar, largely unregulated industry could damage forest ecosystems through extensive raking or other disruption of the natural ground cover to harvest mushrooms. Similar concern was expressed about the illegal harvesting of other plant species, such as moss and small berry shrubs called salal (see fig. 5). About 30 percent of the internal threats identified by park managers fell into two categories—the adverse effects of (1) people’s visits to the parks and (2) the Park Service’s own management actions. The number of recreational visits to the Park Service’s 369 units rose by about 5 percent over the past 5 years to about 270 million visits in 1995. Park managers cited the effects of visitation, such as traffic congestion, the deterioration of vegetation off established trails, and trail erosion. The threats created unintentionally by the Park Service’s own management decisions at the national or the park level included poor coordination among park operations, policies calling for the suppression of naturally caused fires that do not threaten human life or property, and changes in funding or funding priorities that do not allow certain internal threats to parks’ resources to be addressed. For example, at Gettysburg National Military Park, none of the park’s 105 historic buildings have internal fire suppression systems or access to external hydrants because of higher-priority funding needs. Park managers estimated that about 82 percent of the direct threats they identified in the eight parks we reviewed have caused more than minor damage to the parks’ resources.