Military Disturbances and Associated Ecosystem Consequences
Ground disturbances at bombing ranges,
such as here at theWarren Grove Air National
Guard Range, New Jersey, are typical
of impacts caused by military training operations.
(Photo: Douglas Ripley)
Military lands are important ecological reserves because they often encompass
large tracts of land that are protected from intensive agriculture and urban development
(Boice 1997, Ripley and Leslie 1997a, 1997b, Lillie and Ripley 1998).
Furthermore, some of the finest examples of fire-maintained ecosystems within
the southeastern United States are found on military bases in and adjacent to artillery
ranges where frequent fires are assured and unexploded ordnance provides
protection from development (Peet and Allard 1993). But how do military training
activities compare to the natural disturbance regimes? And how might military
disturbances interact with land management activities on military bases?
Disturbances from military missions may enhance or exacerbate their effects
on ecosystem components. In general, military training in terrestrial environments
can be broadly categorized into two major types of disturbances ground maneuvering
(tracked and wheeled vehicles) and air-to-ground impacts. Military installations
subject to usage by the U.S. Army are often subject to additional impacts
from training exercises. Typically, maneuvers on Army installations involve
large vehicles that can cover large areas in a single training exercise. The available
land base for training has a strong influence on the intensity and frequency
of usage (Demarais et al. 1999) and thus on the disturbance effects.
Large-vehicle maneuvers are a widespread use of land and consistently are
shown to have negative effects across a variety of terrestrial ecosystems. These
repeated human-induced disturbances have no natural analog. The negative effects
of ground maneuvering training have been studied in California (Lathrop
1982, Prose 1985), Colorado (Milchunas et al. 1999), Georgia (Dilustro et al.
2002), Kansas (Quist et al. 2003), Washington (Severinghaus and Goran 1981),
Wisconsin (Smith et al. 2002), Texas (Severinghaus et al. 1981), Manitoba (Wilson
1988), and western Europe (Vertegaal 1989). Although studies have been conducted across a variety of ecosystems (e.g. deserts, prairies, pine-oak forests, etc.)
several generalizations have emerged. In particular, it is the cumulative effect of
repeated military disturbances that ultimately results in reduced abundance of
perennial species, overall losses of native species, increased numbers of introduced
species, and an increase in the amount of bare and compacted soil.
The careful cleanup of inert ordnance at the
Barry M. Goldwater Range, Arizona, is an important
part of the range restoration programs
by the U.S. Air Force and U. S. Marine
Corps. (Photo: Douglas Ripley)
While most studies have focused on effects of large vehicles, the observed results
probably also include the effects of other vehicular disturbances as well (i.e.
off-road vehicles) that oftentimes occur in conjunction with tracked vehicle maneuvering
activities. Road-like features, including active and remnant trails and
vehicle tracks, are the most prevalent disturbance features at installations with
high-usage maneuvering areas (Dilustro et al. 2002, Quist et al. 2003). These disturbance
features act to increase fragmentation of the landscape, which can in
turn affect ecosystem-level processes (i.e. spread of fire, flooding, drainage, etc.).
In native grasslands where maneuvering has been examined, at least one study,
(in Central Plains grasslands at Fort Riley Military Reservation in northeast
Kansas), has shown increased bare soil, reduced total plant cover, and compositional
shifts in plant communities (Quist et al. 2003). Reduced cover of the perennial,
matrix-forming grasses and native species, and increased cover of annual
and introduced species were also associated with high-usage maneuvering training
activity. Quist et al. (2003) also reported high-usage maneuvering associated
with increased sediment and reduced abundance of benthic insectivores, herbivore-
detritivores, and silt-intolerant aquatic species. Watersheds with high military
maneuver usage also were characterized by an abundance of trophic generalists
and disturbance-tolerant species. Overall, the Quist study suggests that
high-usage maneuvering areas had significant ecological effects on the properties
of both terrestrial and aquatic ecosystems, with respect to recovery from past disturbances
and ecological resilience to future disturbances. In an effort to prevent
significant degradation of training areas and to provide a coordinated assessment
and monitoring of these impacts, the U.S. Army has implemented an Integrated
Training Area Management (ITAM) program.1 This program emphasizes monitoring
of military impacts (erosion, siltation, soil compaction, loss of native plant
cover, hydrologic alterations, etc.) on training lands.
Seven students from the Young Women's
Leadership School in New York City's Harlem
assist in various aspects of the Mill Creek
stream restoration project at Eglin Air Force
Base, Florida. This program is part of an ongoing
effort to restore streams on the Eglin
Reservation that are home to the endangered
Okaloosa Darter. (Photo: Jerron Barnett, U.S.
In contrast to ground maneuvering activities, air-to-ground missions are capable
of mimicking natural disturbance regimes in some ecosystems. This is particularly
true when active bombing and gunnery ranges exist within fire-evolved
ecosystems like prairies, savannas, and some wetland types. Aerial bombing and
gunnery ranges used by fighter and bomber aircraft, and artillery and mortar gunnery
from ground-based weapon systems can provide the ignition sources in fireevolved
ecosystems. Some of air-to-ground ranges that date back to pre-World
War II contain remnant fire-maintained plant communities no longer found in the
surrounding fire suppressed landscape.
An impact area on Avon Park Air Force Range in central Florida known to receive
over a thousand high explosive rounds and several thousand non-explosive
rounds strikes annually (Delany et al. 1999) has created a long history of frequent
mission-caused wildfires that in turn have provided some of the variation inherent
under a natural fire regime. Ordnance-ignited wildfires on this impact area
are frequent (>1/yr), may occur year-round, and have occurred since the 1940s.
As a result, the vegetation within the impact area has never been fire suppressed.
Despite bomb craters created by high-explosive munitions, portions of the impact
area with native vegetation support endangered birds, numerous rare plant
populations, and some of the highest natural-quality examples of fire-maintained
plant communities found in central Florida (Orzell 1997). Similar native speciesrich
plant communities, often containing enclaves of rare plants, have been
recorded elsewhere in or near active air-to-ground impact areas in the southeastern
United States (Peet and Allard 1993, Sorrie et al. 1997).
Restoration of long-leaf pine forests and
red-cockaded habitat at Fort Stewart, Georgia.
These scenes show various stages of
the prescribed burning process and the final
result of a mature long-leaf pine forest
providing excellent habitat for the endangered
red-cockaded woodpecker. (Photo:
The influence of anthropogenic disturbance, in particular that associated with
land management activities (forestry, grazing, etc.) and the military mission on
ecosystem-level processes, is also pertinent when discussing disturbance effects.
The interactive effects of ecological disturbance regimes and human disturbances
(resulting from land management and military activities) also need to be considered,
but few studies have examined these interactions. A study conducted by
Dilustro et al. (2002) at Fort Benning, Georgia, in the Fall Line Sandhills ecoregion
found significant interactions with other activities. In particular, forestry
management practices with heavy mechanized training sites were found to favor
pine dominance, and open-site, successional or fire tolerant ground cover plant
species (Dilustro et al. 2002).2
Proceed to Next Section: Management Implications