A continuous wall along the border between the United States and Mexico, as proposed repeatedly amid much controversy by US President Donald Trump, would have a major deleterious effect on biodiversity. This is the conclusion drawn by William Ripple, professor of ecology at Oregon State University, US, and lead author of a paper published in the journal BioScience.

Ripple is joined by 15 co-authors on the paper, including Rob Peters and Jennie Miller of the conservation organisation Defenders of Wildlife. The article has thus far been endorsed by 2,500 scientists from 43 countries and six continents.

The paper outlines three ways the border wall and associated security measures would threaten biodiversity: by ignoring environmental legislation, eliminating and fragmenting animal and plant populations and habitats, and diminishing bi-national research and conservation projects.

“Some of the affected animals are charismatic as well as threatened,” Ripple says, noting the plight of the jaguar (Panthera onca), which is included on the International Union for Conservation of Nature’s Red List as Near Threatened due to loss of habitat.

The likes of the Mexican wolf (Canis lupus baileyi), Sonoran pronghorn (Antilocapra americana sonoriensis) and Peninsular bighorn sheep (Ovis canadensis nelsoni) would also be imperilled further by a hard border. All three, like the jaguar, are recognised as endangered by the United States Fish and Wildlife Service and consequently subject to the protections outlined in the Endangered Species Act (ESA).

“A continuous wall would disconnect any jaguars and ocelots in the US from their major range in Mexico,” Ripple adds. “And it’s not just solid walls that are the issue; certain types of fencing can be a complete barrier to individual wildlife species. All of that should be considered.”

Increasing security in the border region would see the US government waive their own federal environmental laws, such as the ESA and the National Environmental Policy Act, in the name of homeland security.

The ESA was passed into law in 1973 with overwhelming bipartisan support and, like the species it was put in place to protect, now finds itself threatened following a proposal to limit its powers by the US Interior Department.

Ripple and the other authors and signatories urge the US government not to take this course. The paper includes the following four-point call to action:

Congress should ensure the Department of Homeland Security (DHS) follows environmental laws, and the DHS should:

*Conduct surveys of at-risk species, habitats and ecological resources prior to new construction;
*Mitigate environmental harm as completely as possible;
*Work to facilitate scientific research in the border region.

As of 2017, the DHS had constructed 1,050 kilometres of pedestrian and vehicle barriers, the paper notes.

“The border extends about 3,200 kilometres and bisects many important habitat types from desert to forest to scrublands to mountain ranges,” Ripple explains. “These are important wildlife habitats, high in biological diversity, that span both sides of the border. I hope national leaders will listen to our conservation message.”

1,506 native terrestrial and freshwater animal and plant species call the border region home, the paper states. 62 of these are listed as critically endangered, endangered or vulnerable by the International Union of Conversation of Nature.