Ways of minimizing environmental damage from the fences could include the creation of cross-border bridge areas so that ecosystems remain connected and "green corridors" of wilderness without roads that would be less attractive to smugglers, according to a report released Monday and prepared for the Mexican government by experts and activists from both nations.
The report also suggested "live" fences of cactuses, removable fencing, and more permeable barriers to allow water, insects and pollen to cross the border. Ecologists say among the species affected would be Mexican jaguars and black bears, and the endangered, antelope-like Sonora Pronghorn.
On Monday, Mexico's Environment Department said the proposed fences would seriously hurt species that cross the 1,952-mile border and that the United States needs to alter or mitigate the barriers where necessary.
"The eventual construction of this barrier would place at risk the various ecosystems that we share," said Environment Secretary Juan Rafael Elvira, noting that the border is not just desert, but includes mountains, rivers and wetlands.
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Mexico also wants Washington to expand its environmental impact study on the fences and will file a complaint with the United Nations' International Court of Justice in the Hague, Netherlands if necessary.
The proposed fencing includes at least 370 miles of vehicle barriers and metal walls supplemented by "virtual" barriers of sensors, mobile towers packed with sophisticated cameras, strong lights, radars and sensors and other technology.
The environmental report said the fences could isolate border animals into smaller population groups, affecting their genetic diversity. The strong lights and radar could interfere with nocturnal species, and the construction and traffic along the walls could affect a wider strip of border land than just the fences themselves, activists say.
Environmentalists say construction of the fencing could wipe out endangered species like the Sonoran Pronghorn — of which only about 100 still exist — in the coming years.
Exequiel Ezcurra, director of research at the San Diego Natural History Museum, said the pronghorns are used to moving across the border in search of scarce grassland.
The pronghorn "is without doubt the species in the most desperate situation, the number one victim of all the tension and movement on the border," Ezcurra said.