Joint Base Lewis-McChord
Size: 90,600 acres
Main activity: Training and mobilization
Ecological claims to fame: Includes some of the largest relics of native prairie left in South Puget Sound. Today, most of the 150,000 acres of prairie that once blanketed the area have been consumed by agriculture and development.

Beale Air Force Base
Size: 23,000 acres
Main activity: Reconnaissance
Ecological claims to fame: Contains a number of seasonal wetlands called vernal pools, habitat for endangered fairy shrimp. It's estimated that California's Central Valley has lost more than 90 percent of its vernal pools.

Naval Station Coronado -- San Clemente Island
Size: 37,000 acres
Main activity: Support for weapons research and development
Ecological claims to fame: Home to a number of endemic species, including the endangered San Clemente loggerhead shrike, one of the rarest birds in North America.

Camp Pendleton
Size: 125,000 acres
Main Activity: Amphibious Marine Corps training
Ecological claims to fame: The largest undeveloped expanse along the Southern California coast, Camp Pendleton supports 16 threatened or endangered species, and three of the four known populations of Pacific pocket mice. The installation is also home to Southern California's last free-flowing river, estuaries and rare coastal sage scrub habitat.

Nevada Test Site
Size: 880,000 acres
Main activity: Weapons testing
Ecological claims to fame: Includes portions of the Mojave and Great Basin deserts as well as a broad transitional zone between the two. The test site is one of only a few large, intact pieces of sagebrush habitat left in the Great Basin, and a population of threatened desert tortoises resides in its Mojave stretch. Nuclear testing fouled about 7 percent of the land; the remaining 93 percent exhibits little if any impact from grazing, mining and recreation. 

Idaho National Laboratory
Size: 569,135 acres
Main activity: Nuclear energy research
Ecological claims to fame: The lab is a federally designated national environmental research park, where scientists conduct ecological research to understand long-term change in natural systems and the impact of human activity. The lab showcases a relatively undisturbed sagebrush-steppe ecosystem, habitat for pronghorn antelope, sage grouse, pygmy rabbits and burrowing owls. More than 400 plant species and 269 vertebrates have been identified there.

Barry M. Goldwater Range
Size: 1.8 million acres
Main activity: Live-fire combat training
Ecological claims to fame:  Part of the largest contiguous chunk of Sonoran Desert habitat left in the U.S. The installation contains a significant portion of the endangered Sonoran pronghorn antelope's U.S. range.

Dugway Proving Ground
Size: 798,214 acres
Main activity: Biological and chemical weapons testing
Ecological claim to fame: Considered one of the “most important protected areas in the Great Basin,” Dugway Proving Ground is home to a relatively unscathed system of sand dunes, rare habitat that is easily disturbed by human activity.

Fort Carson and Pinon Canyon Maneuver Site
Size: 373,273 acres
Main activity: Combat training
Ecological claims to fame: Covers native shortgrass prairie habitat, more than half of which has been lost in Colorado. Fort Carson shelters declining species like mountain plovers, black-tailed prairie dogs and several rare prairie plants.

Los Alamos National Laboratory
Size: 28,000 acres
Main activity: Nuclear weapons and defense research
Ecological claims to fame: Boasts five vegetative zones and more than 900 plant species. Endangered southwestern willow flycatchers and threatened Mexican spotted owls are found at the lab.

Kirtland Air Force Base
Size: 52,000 acres
Main activity: Nuclear weapons management
Ecological claims to fame: Supports the second largest known breeding population of gray vireos in New Mexico. The birds are listed as threatened species in the state.