"Humans are good at building big, deep tunnels with electricity, and are good at building big ladders, catapults - not a joke - and using drones and more. Animals are not," Jesse Lasky, a Penn State biologist, told Seeker.
Millis agrees. "Taller walls would only mean taller ladders," he said.
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Even many U.S. Border Patrol agents, who have been on the front lines of the problem for years, support better surveillance over more construction. Some have advocated using aerial drones, for example, over building more wall, according to a Reuters report.
"I have yet to hear from anyone directly involved in interdiction and border security endorse building a sold concrete wall," Ecologist Tim Keitt at the University of Texas told Seeker.
Region 'Under Siege'
Bryan Bird, director of the Southwest Program for Defenders of Wildlife, told Seeker that beginning in the early 1990s, the U.S. Border Patrol dramatically increased its immigration enforcement efforts in heavily populated border areas, essentially shifting undocumented immigration, drug trafficking and other illegal activities from urban areas to remote, sensitive borderlands. Enforcement-related road and wall construction, lighting projects and off-road vehicle and low-flying helicopter patrols proliferated.
"As a result, this pristine region - much of it on public lands set aside to protect rare and imperiled wildlife and sensitive habitat - is under siege," Bird said.
Environmental concerns, as outlined in the 2005 Border Ecological Symposium, include trampling of vegetation and other direct damage to wildlife and habitat, fragmentation of habitat and wildlife corridors, introduction of exotic species, air and water pollution, wildlife mortality and displacement, modifications of wildlife behavior in response to disturbances. The document also says the construction exerts added pressure on threatened and endangered species and presents obstacles to restoring these animals' habitats.
Impacts on Wildlife
Countless species, including many that are rare and endangered, have already been impacted by the existing wall and will be threatened further by its expansion and increased human patrols, Bird and several others told Seeker.
According to the IUCN Red List of Endangered Species, the jaguar - the largest cat of the Americas - disappeared from the southwestern U.S. portion of its range by the mid-1900s, due to deforestation, hunting, trapping and other human activities. Anti-fur campaigns and other conservation efforts led to a slow comeback, "but fencing and road projects proposed by the Border Patrol threaten to cut off the cross-border corridors they use," Bird said.
The Trump order could devastate the Mexican gray wolf population in the region, he and others said. In 1998, the U.S. Fish and Wildlife Service released captive-bred Mexican gray wolves into Southeast Arizona. In 2011 Mexican gray wolves were also released into the Mexican state of Sonora about 30 miles from the U.S. border. Currently there are about 100 wolves north of the border and 35 south of the border.
"The wolves are at risk of inbreeding resulting in a genetic 'bottleneck,'" Bird said. "They need to freely cross the international border to improve their genetic pool."
He added that the Sonoran pronghorn antelope faces a similar fate, with a "serious possibility of extinction in the wild" due to the expected genetic bottleneck.