Scientists Declare Border Wall a Disaster for Biodiversity

This week, scientists united to declare grave concern over the negative impacts of the U.S.-Mexico border wall on biodiversity. Consensus is rare in science, yet the irreparable harm of a 2,000-mile barrier on wildlife is so assured that more than 2,700 scientists from 43 countries joined together to ask U.S. political leaders to reconsider the Trump administration’s “big, beautiful wall.” Defenders helped unify scientists’ voices in this powerful message by outlining concerns in a scientific article, coauthored with esteemed biodiversity and borderlands scientists, that was published this week in the journal BioScience.

Thousands of scientists object to Trump’s border wall — The Washington Post
Thousands of scientists endorse study on border wall’s threat to wildlife — The Hill
Scientists Warn Trump’s Border Wall Would Be A Disaster For Wildlife — HuffPost

Our analysis reveals that the U.S.-Mexico border cuts through the ranges of more than 1,500 native terrestrial and freshwater animal and plant species. This includes 62 species listed as Critically Endangered, Endangered or Vulnerable by the IUCN Red List, the international ranking of imperiled species. Some of these 1,500+ species can fly over the wall, and a few have just a small part of their range on one side of the border. But for native U.S. species, a wall would cut off 34% of our 346 non-flying terrestrial and freshwater animal species from the majority of their range that lies south of the U.S.-Mexico border. That’s a life sentence for species like the jaguar and ocelot, and would elevate the likelihood that they are extirpated in the U.S. Even low-flying species like the ferruginous pygmy-owl, a candidate species for listing under the Endangered Species Act, could be harmed by the wall.

When it comes to barriers and biodiversity, the science is solid. Impassable barriers, whether border wall or fence, stop wildlife in their tracks. It means they can’t migrate across the border to find precious resources, such as food and water, which can make the difference between life or death in the resource-scarce desert. Peninsular bighorn sheep, for example, would no longer be able to move between California and Mexico to access water and birthing sites.

No movement across the border means that species can’t establish new populations to expand their species geographic range, hampering the conservation of imperiled species. A wall would make it impossible for endangered animals like the Mexican gray wolf and Sonoran pronghorn to disperse across the border to reestablish recently extirpated populations or bolster the small existing populations. It also means that wildlife can’t disperse to find new mates, which limits genetic diversity. Scientists discovered this for six plant species at the Great Wall of China, which prevented seed dispersal and caused genetically-distinct subpopulations on either side, thus radically altering the evolution of the plants.

Even when not “impassible,” border barriers harm wildlife because they require building new roads, which are used to patrol and maintain the barriers, and which disrupt animals’ normal behaviors and movement. Wildlife can also be killed trying to cross these roads.

Even if we set aside ecology and look at economics, the border wall would undermine millions of dollars and acres invested into conservation. The U.S. and Mexico have shared a long history of collaborative, coordinated efforts to protect natural resources in the borderlands. Within just 50 miles of the border lie 11 million acres of protected areas managed to conserve biodiversity, including four clusters of protected lands that sandwich 250 miles of border to create contiguous habitat corridors through five Borderlands Conservation Hotspots identified by Defenders. Whoever thinks of the border as a barren wasteland, think again: the borderlands are treasured, biologically diverse hotspots of North America that have been nurtured and invested in by both nations for generations. We identified five Borderlands Conservation Hotpots that are most vulnerable to the wall, and well-worth continued investment rather than division and degradation.

The five Borderlands Conservation Hotspots identified by Defenders of Wildlife, which highlight areas of high biological diversity and significant investment in conservation land and projects.

This week’s consensus of scientists asked the U.S. Congress and the Department of Homeland Security to follow the law, mitigate negative impacts to species, and allow scientific research in the borderlands. Nothing extreme, because even this would represent significant progress towards the protection of our natural heritage. Our science and technology are sophisticated enough that we need not compromise species for national security; our national sovereignty can be secured while protecting wildlife. Without doing so, we will not only divide nations but also nature itself.


Signatories are still welcome to endorse our scientific article. Please show your concern for the border wall and join as a signatory! Read more about the impacts of the border wall on wildlife in Defenders’ recent report and our three-part Medium series about the borderlands.