Non-native invasive species are a leading threat to our nation's rich biodiversity, as well as to national security, the economy, and human health. Since colonial periods, thousands of non-native species have been introduced to the United States, some by accident and others quite deliberately. Based on the U.S. Department of Agriculture (USDA) Plants Database, currently 13 percent (5,303 of 40,140) of the vascular plant species in the nation are not native to North America. These would include most of Americans' favorite foods and many ornamental plants. The majority of non-native plants and animals existing in the U.S. are not harmful, but some non-native species cause tremendous damage when released outside of their native habitats. As defined by Executive Order 13112, invasive species are those non-native species that "cause economic or environmental harm or harm to human health." The Congressional Office of Technology Assessment reported in 1993 that 15 percent of invasive plants and animals cause severe economic and environmental harm.

Invasive species occur throughout the lands and waters of the United States, and military lands are no exception. These invaders are a major and growing problem on military lands, impacting the ability to train the nation's armed forces, degrading ecosystem health of these public lands, endangering native biodiversity, and potentially causing harm to human health. The military faces some unique challenges in combating invasive species on their lands, challenges related to their primary goal of maintaining the quality of military lands for realistic training exercises, while also meeting their responsibility to safeguard the quality of natural resources and biodiversity on their lands.

Numerous military installations across the country have employed successful and innovative methods to control invasive species, examples of which will be referred to throughout this chapter and in the case studies. Given the vast amount of land that the military owns and manages in the United States, the military has a unique responsibility in managing invasive species and in helping to prevent new introductions. The Department of Defense (DoD), however, can not stop the problem of invasive species on its own. Invasive species are a "beyond the fenceline" issue that must be addressed comprehensively, by Congress and other state and federal public land management agencies, as well as by private entities and individuals. Given the far-reaching nature of this problem, DoD has formed many diverse partnerships in battling invasive species, some of which are highlighted below.¹

Air Force c-130 aerial spray operations at Smoky Hill ang Range, Kansas. These operations are used periodically to control extreme outbreaks of the noxious weed musk thistle on the range. (Photo: Douglas Ripley)

Invasive species affect the nation's military installations and operations worldwide. The NationalWildlife Federation's recent report (Westbrook and Ramos 2005) on invasive species on military lands provides twelve cases outlining numerous threats and costs to military operations: from six-foot tall spiky yellow star-thistle shredding parachutes that average $4,000 apiece at Fort Hunter Liggett in California to Phragmites causing security concerns at Avon Park Air Force Range in Florida. Holloman AFB in New Mexico allocated over a half million dollars to remove invasive species from airstrips in order to protect the safety of Air Force pilots and prevent damage to aircraft worth tens of millions of dollars. And in Hawai‘i, dense non-native mangrove thickets can breach "line of sight" security for Marines assigned to protect base borders along the shoreline (Westbrook and Ramos 2005).

ECOLOGICAL IMPACTS

Beautiful invader? The mute swan (Cygnus olor) has been condemned by several policy makers and scientists as an invasive species. The bird was believed to have been imported to the U.S. to grace parks and estates, but now it is accused of eating an inordinate amount of submerged aquatic vegetation and displacing the native tundra swan. The darker-colored swans shown here are adolescents accompanying a parent. The control of this species is a particularly difficult problem for military bases in the Chesapeake Bay Region as it creates Bird Aircraft Strike Hazards (bash) and eradication programs have been met with protests from animal welfare organizations. (Photo: Fred Powledge)

Many reports have documented the ecological impacts of these non-native invaders, including citing invasive species as one of the greatest threats to biodiversity (e.g. Stein et al. 2000). Worldwide, an estimated 80 percent of endangered species could suffer losses due to competition with or predation by invasive species (Pimentel et al. 2005). In addition to direct competitive impacts to native species, some of the worst invasive species are able to alter native habitats and ecosystems. Invasions by non-native species have been shown to modify ecosystem processes, like nutrient cycling, fire frequency, hydrologic cycles, sediment deposition, and erosion (Kelly 2007). On the Marine Corps Base Hawai‘i, nonnative mangrove stands take over native marsh habitats, converting critical habitat for endangered Hawaiian waterbirds into mangrove thickets that are inhospitable to both native species and to realistic military training exercises on base. On Avon Park Air Force Range in Florida, invasive wild hogs compete with the endangered Florida scrub jay for food and destroy nesting habitat for many other endangered species (Westbrook and Ramos 2005). Such feral hogs are a growing menace at several other military installations. When invasive species cause habitat destruction and harm rare native species, the result can lead to reductions in available training lands on installations.

ECONOMIC IMPACTS

Invasive species impact the United States economy in many ways, negatively affecting economic sectors such as western ranching, Great Lakes shipping, southern forest plantations, and midwestern farming, just to name a few. Within the U.S., the estimated damage and management cost of invasive species is more than $138 billion annually, more than any other natural disaster (Pimentel et al. 2005). In addition to these costs, many economic losses from recreational and tourism revenues are difficult to calculate (Simberloff 2001); as a result, the $138 billion estimate may be low.

If monetary values could be assigned to the extinction of species, loss of biodiversity, and reduction of ecosystem services, costs from impacts of invasive species would drastically increase (Pimentel et al. 2005). For the military, the costs related to invasive species are significant and are increasing each year. To name one example, Camp Pendleton in southern California spent approximately $1.2 million over a five year period trying to control giant reed (Arundo donax) and tamarisk or salt cedar (Tamarix ramossima) (Westbrook and Ramos 2005). While it also can be expensive to prevent invasive species on military lands – for example through programs to wash tanks and other military vehicles before and after transport – prevention is a critical first-line defense against new invaders on military lands. Once established, managing invaders such as the giant reed and tamarisk, mentioned above, can often be a multi-year and multi-million dollar effort.

A seriously invasive species. Miconia (Miconia calvescens) was intentionally introduced in Hawai‘i in the 1960s as an ornamental, but it quickly became an aggressive invader. Its seeds can remain viable in the soil for as many as eight years. The leaves, which can grow to 2.5 feet in length, are dark green on top, often reddish-purple underneath. (Photo: Fred Powledge)

RECREATIONAL IMPACTS

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