Stretching from the arctic of Alaska to the Florida Keys, and the coast of Maine to Hawai'i's volcanic islands, the United States supports an extraordinary diversity of life. Encompassing more than 3.5 million square miles of land and with 12,000 miles of coastline, the nation spans 120 degrees of longitude – nearly a third of the globe. This expanse includes an exceptional variety of terrains, from Death Valley at 282 feet below sea level to Mt. McKinley at 20,320 feet above. The resulting range of climates has given rise to a wide array of ecosystems, from tundra and subarctic taiga to deserts, prairie, boreal forest, deciduous forests, temperate rain forests, and even tropical rain forests. Military installations are widely represented among these ecosystems.

This tapestry sustains a remarkable array of species. Although the total number of species inhabiting our lands and waters is far from fully known, a recent tally puts the number of U.S. species that have been formally described and named by science at approximately two hundred thousand (Stein et al. 2000). Additional species continue to come to light as new areas are explored, and new and increasingly powerful techniques for documenting diversity are developed. While many of these discoveries are among poorly known groups of organisms, such as insects and fungi, even among such relatively well known groups such as the flowering plants up to thirty new North American species are described every year. The U.S. military has played an important role in helping to discover and understand the nation's biological wealth. When Captain Meriwether Lewis of the First Infantry and Lieutenant William Clark set out in 1803 to cross the continent with their Corps of Discovery, they were under orders from President Jefferson to record everything they could about the countryside, including "the soils and face of the country, its growth and vegetation productions . . . the animals of the country . . . the remains and any which may be deemed rare or extinct." Many of western North America's most characteristic, and charismatic, wildlife species were first scientifically documented by the Corps of Discovery, including grizzly bear, pronghorn antelope, and mule deer.

Intrepid explorer and plant collectorMajor General John Charles Fremont (top) was one of many 19th-century Army officers who contributed to the early understanding of the natural history of the western United States. The beautiful California flannelbush (Fremontodendron californicum) is one of many plants named in his honor. (Top photo: University of Utah. Bottom photo: Douglas Ripley)

Lewis and Clark's journey was followed by many other military expeditions exploring different routes across the continent, many of which included accomplished naturalists. The expeditions fueled the dramatic expansion in scientific knowledge about our flora and fauna that took place in the mid-1800s. A multitude of western plants and animals enshrine in their names the contributions of military men, such as Captain John C. Frémont (Fremontodendron californicum, the California flannelbush), Captain Howard Stansbury (Uta stansburiana, the western side-blotch lizard), and Captain John W. Gunnison (Cynomys gunnisoni, Gunnison prairie dog).

As exploration of the American continent brought the nation into better focus, it became clear that the lands and waters harbored a spectacular assemblage of plants and animals. And while most people think of tropical rainforests as the region on Earth teeming with the greatest diversity of life, for certain groups of organisms the United States turns out to be a global leader. For example, more salamander species are found in the United States than any other country on Earth, with the greatest concentrations of diversity in the Southeast. A number of other freshwater groups exhibit similar patterns, including freshwater mussels and crayfishes. For gymnosperms, a plant group that includes conifers like pines and spruces, the United States is second only to China in its variety of species.

Hawai‘i's inclusion in the United States, first as a territory in 1898 and later as a state in 1959, added tremendously to the richness of the nation's biological fabric. This set of mid-oceanic volcanic islands has never been connected to the mainland, and all life forms naturally occurring in the archipelago either arrived from elsewhere or evolved in place from earlier arrivals. The combination of isolation from other land masses, multiple islands within the archipelago, and the island's dramatic contrasts in terrain and climate – from tropical beaches to icy volcanic peaks – has led to perhaps the most distinctive and unique flora and fauna in the world. A species that is restricted to a specific area is referred to as endemic to that area, and Hawai‘i has some of the highest levels of endemism in the world. More than two-fifths (43%) of Hawai‘i's vertebrate animals are endemic, as are 87% of its vascular plants, and 97% of its insects (Stein et al. 2000). Not only are these species found only in Hawai‘i, but many are extremely localized, a factor greatly contributing to the high levels of endangerment found in the Hawaiian flora and fauna that will be discussed in a later section.

How is Our Biodiversity Faring?

Broad concern about the decline of wildlife species began in the late 19th century, instigated in part by massive commercial slaughter of such species as the passenger pigeon, and the decimation of many waterbird colonies for plumes to adorn women's hats. These early concerns led to such things as the passage of the Lacey Act⁷ in 1900 and establishment of the National Wildlife Refuge System in 1903. By mid-century it was apparent that many species were in decline from a variety of causes. This included the bald eagle, the nation's symbol, whose reproduction was plummeting due to pesticide-related thinning of its eggshells. As awareness of environmental problems increased, a host of seminal federal legislation was passed in the late 1960s and early 1970s, including the Clean Water Act, Clean Air Act, and National Environmental Policy Act (NEPA). The first endangered species protection act was adopted by Congress in 1966, and replaced by the more expansive Endangered Species Act of 1973.⁸

Wiregrass and other plants in the understory of a longleaf pine forest recover quickly after a prescribed burn conducted at Fort Bragg, North Carolina. (Photo courtesy of Fort Bragg)

Ensuring the continued survival of the nation's species requires that we have a sound understanding of how they are faring. That is, which species are widespread, abundant, and secure, and which are rare or declining, and at increased risk of extinction? Assessing a plant or animal's conservation status – or extinction risk – requires accurate information about the species' distribution, its population numbers, trends in those numbers, and any threats placing stress on those populations. The U.S. Fish and Wildlife Service, which with the National Oceanic and Atmospheric Administration has primary responsibility for administration of the ESA, is charged with assessing the condition of plants and animals for the purpose of determining which warrant protection under that Act. For this purpose, the service seeks to identify those species considered endangered, defined as "an animal or plant species in danger of extinction throughout all or a significant portion of its range," and those considered threatened, defined as "an animal or plant species likely to become endangered within the foreseeable future throughout all or a significant portion of its range."⁹

Overall, 1,312 U.S. species were listed under the Endangered Species Act as of June 2007, of which 1,009 were endangered, and another 303 threatened. The number of listed species is dynamic, as additional species are considered for possible listing, and other species considered for delisting due either to recovery, extinction, or reassessment of condition. For example, thanks to the elimination of the pesticide ddt and other conservation practices, bald eagle numbers in the lower 48 states have climbed from a low in 1963 of 417 nesting pairs to nearly 10,000 pairs at present. Based on this strong recovery, the species has now been removed ("delisted") from the federal endangered species list.¹⁰ The federal endangered species list, however, is not a sufficient gauge of the overall condition of the U.S. biota. As Figure 1.1 shows, the rate of listings under the ESA varies dramatically, reflecting not only the biological condition of plants and animals, but also the availability of funds and shifts in policy. As described in more detail later, these federally listed species occur on both public and private lands, and are particularly well represented on military properties.

A better overview of the broad condition of U.S. species is contained in the conservation status assessments carried out by NatureServe and its network of state natural heritage programs. This public-private partnership serves as a clearinghouse for scientific information about the condition and location of the nation's species and ecosystems, with a particular focus on those that are rare or otherwise of conservation concern. Based on about a dozen factors that relate to increases in risk of extinction, these assessments are designed to categorize species into one of five "conservation status ranks," ranging from critically imperiled (G1) to secure (G5) (Table 1.1).¹¹ Because the status of species may vary from place to place, assessments are carried out at a rangewide scale (where "G" indicates global), as well as at the state level (where "S" indicates state or subnational). As an example, the red-cockaded woodpecker is categorized as vulnerable (G3) across its entire range, which stretches from Texas to Maryland. Its status in any particular state, however, may differ from that rangewide status. In North Carolina, for instance, the woodpecker is considered to be imperiled (S2), while in Virginia it is regarded as critically imperiled (S1), and in Maryland as possibly extirpated (SH). Combining rangewide and state-level conservation status ranks offers a powerful tool for placing local conservation priorities into a broader context.

By assessing the conservation status of each and every species in the best known groups of plants and animals, NatureServe and its state natural heritage program partners have been able to create a comprehensive view of the overall condition of the U.S. flora and fauna. Summarizing status information across 23 plant and animal groups, representing 22,500 individual species, indicates that approximately one-third (33.6%) of U.S. species display some level of increased risk of extinction (Figure 1.2). Of particular concern are the approximately 8% regarded as critically imperiled (G1) and 9% categorized as imperiled (G2). Looking at risk patterns across the various groups of plants and animals reveals some striking patterns (Figure 1.3). While considerable conservation attention is focused on the plight of rare birds and mammals, these groups actually have relatively modest levels of imperilment when compared with several of the groups dependent on freshwater habitats. Freshwater mussels, for which the United States is the global leader in number of species, emerge as the group of organisms with the highest levels of imperilment, with 69% of mussel species categorized as vulnerable, imperiled, or already extinct. Flowering plants, however, contain by far the largest number of at-risk species, due both to the large number of species in this group overall (more than 15,500), and the many rare and highly localized plants that occur in different regions.

More than one hundred U.S. species are already known to have been lost to extinction, and are categorized by NatureServe as "presumed extinct" (GX). This includes species that were once extremely abundant, such as the passenger pigeon and Carolina parakeet, along with more obscure organisms, like Whipple's monkeyflower (Mimulus whipplei) (yet another species named in honor of a military man, Lt. Amiel Whipple). Definitively establishing that a species has gone extinct is a difficult proposition since one must of necessity rely on the absence of evidence – which is not the same thing as evidence of absence. As a result, another 400 U.S. species are categorized by NatureServe as possibly extinct (GH); most of these species have not been seen in many years and are regarded as missing in action.¹²

A GEOGRAPHY OF IMPERILMENT

As any outdoors lover knows, wildlife is not distributed uniformly across the landscape, but individual species have very particular habitat preferences. Climate is the principle determinant of a region's flora and fauna: palm trees don't grow outdoors in Alaska, nor do caribou wander around Florida. Although the diver species generally increases as one moves south towards the equator, the natural diversity of species in any given region is dependent on a host of factors. These include the complexity of terrain, type of soils, interconnections with other regions, and even the lingering effects of Pleistocene glaciers. The states with the greatest number of species are for the most part clustered along the nation's southern edge (Figure 1.4). The top-ranking states for total number of species are California, Texas, Arizona, New Mexico, and Alabama (Stein 2002). Looking instead at the levels of risk (that is, the proportion of a state's species that are vulnerable, imperiled, or extinct), Hawai‘i and California dominate all others. Indeed, an extraordinary 63 percent of Hawai‘i's native species are at increased risk of extinction.

State natural heritage programs maintain databases of precise locational data for most rare and endangered species, representing a valuable resource for military planners and resources managers. Because these state-managed data are developed and maintained according to nationally consistent standards, they can be pulled together to provide a far more fine-grained view of the geography of imperilment across America. Figures 1.5 and 1.6 represent two perspectives on the distribution of imperiled species across the United States. Mapping the number of imperiled species (G1 and G2) against an equal-area grid (Figure 1.5) provides a striking depiction of where these very rare and often localized plants and animals are concentrated. Of particular note are the concentrations apparent throughout Hawai‘i, in many parts of California, in the central Appalachians, across the panhandle of Florida, and along the central ridge of Florida. Through use of an innovative "rarity-weighted richness" analysis (Figure 1.6), hot spots of rare and restricted range species stand out even more sharply, emphasizing the significance of the regions mentioned above. Even a casual perusal of these two maps suggests a considerable overlap between the geography of imperilment and the location of many of the military's landholdings, a topic that will be more fully explored in a later section.

Much of the coastal sage scrub habitat that once covered millions of acres of southern California coast is now fragmented or lost. Marine Corps Base Camp Pendleton serves as a refuge for this rich ecosystem. (Photo: Douglas Ripley)

CAUSES OF DECLINE

Although there are many causes for the declines of species, two in particular stand out. These are the loss or degradation of natural habitats and the introduction and spread of non-native species. Poised to eclipse even these is the prospect of significant climate change, which has the potential to fundamentally disrupt natural ecosystems and their component species.

The natural complexion of the American continent has changed dramatically in the time since European colonization. Although scholars now recognize that Native Americans extensively managed and manipulated their environment, the extent and condition of major habitats at the time of European settlement serves as a useful baseline for measuring change. The production of food, fuel, and fiber, and the construction of housing and other infrastructure has consumed vast areas of natural habitat. While much of this conversion is old news, the loss of natural habitat and other types of open space continue. Currently, about two million acres of open space are being lost to development a year, amounting to roughly six thousand acres each day (NRCS 2003).

Some natural ecosystems have been affected particularly dramatically. Taking advantage of the rich soils of the Midwest, agriculture has replaced more than 98 percent of the original tallgrass prairie, matching the level of loss to the longleaf pine forests of the Southeast. Wetlands play a particularly important role in providing fish and wildlife habitat and maintaining clean water, yet more than half (53 percent) of wetlands across the lower 48 states have been destroyed (Dahl 1990).

Loss of habitat, and its implication for military operations, is perhaps most vividly illustrated along the rugged coast of southern California. Coastal sage scrub is an aromatic habitat that covered many of the seaside hills stretching south from Los Angeles to San Diego. As one housing development after another has been built in the hills overlooking the Pacific Ocean, much of this unique habitat has been lost one piece at a time. Over the years, the cumulative effect of these piecemeal land use decisions resulted in the loss of much of the original coastal sage scrub, with the result that a variety of species dependent on this habitat type have declined significantly. Among these is the California gnatcatcher (Polioptila californica), a diminutive bird whose plight landed it on the federal list of endangered species. With metropolitan Los Angeles sprawling towards the south, and San Diego spreading north, a single large undeveloped tract of land stands in the way of these two major metropolitan areas' merging – Marine Corps Base Camp Pendleton. Home to the First Marine Expeditionary Force, Camp Pendleton is the only west coast amphibious assault training center. Stretching along 17 miles of coastline, the installation is something of an island of natural habitat in a sea of urbanization, and now harbors the largest contiguous stands of coastal sage scrub in the San Diego region.

Proceed to Next Section: The Role of Military Lands in Maintaining Biodiversity