Border Fences Pose Threats to Wildlife on U.S.-Mexico Border, Study Shows

July 12, 2011

AUSTIN, Texas — Current and proposed border fences pose significant threats to wildlife populations, with those animals living in border regions along the Texas Gulf and California coasts showing some of the greatest vulnerability, a new study from The University of Texas at Austin shows.

Border fence in the Otay Mountain wilderness
Border fences like this one in the Otay Mountain wilderness in California can prevent animal populations from interbreeding and dispersing. Photo: Scott Nicol

"Our study is the first comprehensive analysis of threats to species across the entire U.S.-Mexico border," says Jesse Lasky, a graduate student in the laboratory of Tim Keitt, associate professor of integrative biology. "The scale at which these fences stretch across the landscape is large, so it's important for us to also have a large-scale view of their effects across the continent."

Among the species at risk include four species listed as threatened globally or by both the U.S. and Mexico, and another 23 with small range sizes. The animals include the Arroyo toad, the California red-legged frog and the jaguarundi.

"We were able to identify a list of animal species that are most at risk and should be prioritized and monitored for change," says Lasky. "We're hoping this helps point decision-makers toward the animals to look at first when making priorities for conservation."

Most at risk of extinction are smaller populations of wildlife that occur in more specialized habitats, the study shows. Even animals that may appear to have large ranges may live in isolated habitats within those ranges that can be heavily disturbed by border fences. Human population growth along the border also poses threats to the wildlife.

Lasky says when the ranges of these animals are separated by barriers, including border fences and roads, the animals' ability to move is limited. The isolated populations are then more vulnerable to unforeseen disturbances, such as a hurricane or fire, which can wipe out an entire population. The isolation also increases inbreeding depression, which means the animals have limited opportunities to mix their genes with others and accumulate harmful mutations.

Coues' Rice Rat and Reticulated Collared Lizard are both Texas threatened species. Coue's Rice Rat occurs in Texas at the edge of its range and has most of its border range occupied by areas of high human impact and pedestrian fences. Reticulated Collared Lizards were identified as a species that would be at risk if extensive barriers were built across its range in the future. Image: Jesse Lasky

The study analyzed the ranges of 313 non-flying mammals, reptiles and amphibians and identified three major regions where wildlife is most vulnerable: the high human population areas of coastal California and coastal Texas and the unique "sky island" Madrean archipelago habitat in southeastern Arizona.

These regions have high numbers of vulnerable species. Some species in California have barriers that block as much as 75 percent of their ranges.

"The U.S.-Mexico border spans regions of extraordinary biological diversity as well as intense human impacts," says Keitt. "Loss of biological diversity can have negative impacts on the ecosystem services that are the basis of our life-support system."

The U.S. Department of Homeland Security is waived from environmental regulations when building security infrastructure. There are about 750 miles of border fences and human migration barriers along the border.

The study, by Lasky, Keitt and coauthor Walter Jetz, an associate professor in the Department of Ecology and Evolutionary Biology at Yale University, appeared May 3 online in the journal Diversity and Distributions.

For more information, contact: Lee Clippard, Lady Bird Johnson Wildflower Center, 512-232-0104; Dr. Tim Keitt, associate professor of integrative biology; Jesse Lasky, graduate student researcher.

28 Comments to "Border Fences Pose Threats to Wildlife on U.S.-Mexico Border, Study Shows"

1.  John Christian said on July 19, 2011

Dear Friends, et al., One should praise, in many ways, this interesting and worthwhile biological and environmental essay -- yet, it seems that one can expand it much more to include wider, panoramic, and deeper views. The mere thought of any "fences along
the border or any border" is horrible. I was raised in Mexico since infancy and have lived and done ethnographic, photographic documentation there, especially in the Sierra Madre Occidental, the Chihuahuan Desert area, and other places. I have been aware of the biological and environmental damage and degradation of Mexico and of the Mexico - US border and other sites. In this case, the destruction and damage began long ago on both sides "of the river" way before any fences went up, not only of the animal and plant worlds, but also of National Parks, Precolumbian sites, ad infinitum. The basic problem is because of "homo sapiens" and of its increasing populations and ways. At this moment, the Huichol Indians, their friends, researchers, et al., are having to deal with one of those mining companies, in this case, one of those "Canadian" companies that use, principally, the method called "open pit" mining.
This will virtually create complete havoc in the Eastern ritual or sacred site of the Huichol Indians (which is on the eastern edge of the Chihuahuan Desert); of course, the degradation of the environment was already happening, to begin with, but the "open pit" turn out to be devastating. This is not the only place in Mexico or on this side. There are other "ecological horror stories" that are happening in other places and this is because of humans. The true
and real reasons are hardly even discussed in academia, nor in the political world, nor in the mainstream media or culture. There are certain topics that are seemingly "taboo" for anyone to mention at all or very little also because of many reasons, some of them which are highly charged. In the long run, it is the humans and their societies who must decide what kind of world and life they want. I knew the old Mexico and some of the border area long before these days.
Your essay, at least, is a beginning, but not a definitive one. Its not the poor, little creatures and the plants who are at fault. It is us, our growth, and ways. Thank you, for giving others the opportunity to send a comment, as in many places there is not that freedom to speak out, respectfully, John Christian

2.  Jimmy Ball said on July 21, 2011

I have been against the fence all along; if the US would patrol the Border with humans, gurad dogs, and technology would be better. Of course, we need to strickly enforce patroling. Ok to allow people to cross legally if they properly and legally come accross.

3.  Paul Beaver said on July 21, 2011

I think we are more interested in stopping numerous illegal aliens from lurking up from Mexico to the United States from the South.

That is the purpose of the fence.

4.  Rena Robinson said on July 21, 2011

And why are the border fences there?
To deter terrorists and illegal immigration.
Maybe we can make an appeal to potential terrorists and illegal immigrants to respect the wildlife along the border so we can remove the border fences.
Yeah, get real.
So what are we supposed to do?
If there's an answer to how to protect the United States border, please share it with the Obama administration.

5.  Ela Wach said on July 21, 2011

I think illegals pose threats to USA!!!!!!!!!
Who cares about frogs ettc.

6.  Joel Sprague said on July 21, 2011

Seems the Rio Grande River is just as big a barrier to movement of the species discussed in the article....a natural barrier thast has been in place longer than man has been conducting biological diversity studies. The refion in question is thousands of acres, seemingly large enough for species to thrive North and South of the river....just sayin.

7.  Wayne Roberts said on July 21, 2011

What a disgusting waste of University resources. How about the drugs, gangs, illegal immigrants etc. What is happening to my University ??

8.  Pam Irwin said on July 21, 2011

We need the border fence to protect humans! The creatures will adapt!!

9.  Oliver Watson said on July 21, 2011

I would gladly give up the frog in order to protect our sovereignty. Build the fence.

10.  doug robinson said on July 21, 2011

This is the kind of misguided thinking that comes from evolutionary biology. Man was made in God's image, animals were not. We need to do what is best to protect human life and liberty which may include building a fence. The animals will adapt (micro evolution).

11.  Bill Bellamy said on July 21, 2011

God forbid that we threaten the habitat of a rat. Of course I'm just a dumb rancher a few miles north of the border, but I figure that the fence will have about the same impact on the lizards and rats as it does on the homo sapiens who are determined to come across.

12.  David Christian said on July 21, 2011

This appears to be a political, not ecological study. The existence of the Rio Grande and weather events (flash floods, etc.) would have a 100 times greater impact on a specie than a fence would. This study was a waste of State resources. I would not be surprised if the results were pre-determined and the study was conducted to fit the results.

13.  Randy Bryant said on July 21, 2011

Does anyone think that the fences will stop illegal immigration or drug smuggling? It has already been shown that the electronic virtual fence has been a huge waste of money and doesn't even function. The real problem is with Mexico and it's economics and huge gap between the rich and poor.
"The animals will adapt", you have got to be kidding. If that were so, then other extinct species would have adapted!

14.  M. Oliva said on July 21, 2011

I had assumed that wildlife was endangered. Am glad to know that research now confirms the danger to wildlife that the wall poses. Hopefully that will insure we come up with solutions that don't decimate fragile wildlife (and don't reproduce Berlin wall-like environments across the region).

15.  gary davis said on July 21, 2011

To heck with the lizards and mice, we have an immigration mess on our hands.

16.  Mercie said on July 21, 2011

One of those "illegals" crossing the border back in 1926 was my grandfather as a baby. He was "illegal" until he took his oath of U. S. citizenship in a bomber plane over the Atlantic on his way to join Patton's army to fight the Nazis. Even the "borders" of our skin membranes are permeable, people. Pffft.

17.  Pat Dunavan said on July 21, 2011

I do not believe that the safety of this country and its citizens should play second fiddle to rats, lizzards, and toads, etc. I DO respect wildlife and I do believe we have a responsibility to be good stewards of our environment...but not at peril of jeopardizing the safety of this nation and its citizens. I fully respect research done by botanists and biologists, but that respect quickly wanes when their love of research surpasses common sense. Deal with it all you tree huggers, or the sound of a Texas morning brought into a new day by the songs of a mockinbirds and cardinals could be replaced bt the sound of pistols and AK-47 fully automatic rifles as drug cartels battle for supremacy in your city.

18.  C. Kershner said on July 21, 2011

This is a sad situation all around. The loss of wildlife should be mourned, not discarded as unimportant. R. Bryant pegged it, the real problem lies with the south-of-the-border leadership and its inability to provide a safe living environment and employment opportunities to its citizenry. Were there opportunities available for a comfortable life in those other countries, the people would not cross the U.S. border illegally and there would not be a fence - a fence that reflects the frustration of a nation.

19.  Mr Christian said on July 21, 2011

We really need to see wildlife corridors situated at frequent intervals along the border fence. For the reptiles and frogs, maybe small openings at the ground level will allow the reptiles and amphibians pass through the fence as needed.

20.  T. McCaslin said on July 21, 2011

Where do these people think their grandparents and great grandparents came from? Could be that they crossed a border or got on a boat. Just possible that English wasn't their first language. Perhaps they were uneducated. Does that make them terrorists any more than people seeking refuge now? Don't think so.
We have wildlife corridors here in Central New Mexico and they work. Right on, Mr. Christian.

21.  Angel Garza said on July 21, 2011

People who write that we should put the illegal crossing problem over animals are not seeing the picture. The wall stops non-flying animals from being able to reach their critical water source. It does not, however, stop illegals- just ask residents of any area that has a wall. If it worked the way it's supposed to, then we could have a discussion about putting animals before stopping illegals. But it doesn't- and never will.

22.  s.jennings said on July 21, 2011

The fence is a huge waste of money. People who want in this country find ways to do it and so does the Cartel. They have to be laughing. Fences are not the answer. They only matter to the guy who got the contract to build it.

23.  Angela Mendonca said on July 21, 2011

No matter how high or how long that fence is, people determined enough WILL get past it. All other animals, besides humans, seem to understand that there are no real borders other than those separating earth from sea. When is the human race going to get as intelligent?

24.  Steve Thompson said on July 21, 2011

Dear Humans,

I'm a frog, using a human friend's e-mail account.

Why all the mean comments about us frogs? And why all the dumb comments about terrorist Mexicans?

Kind regards,
Phillip Phrog

25.  T Millican said on July 22, 2011

Thank you, Pam Irwin.
Yes, we must protect humans first and wildlife second. We have a real security problem along the southern border.
I am disgusted that my tax dollars have paid for this study. Shame on you UT!

26.  J Vera said on July 22, 2011

I live in South Texas. The border wall/fence is one of the biggest wastes of taxpayers money I have ever seen. I wish I had been the contractor to build the fence, I could have retired. Currently there is a fence in Brownsville on the campus of UT that runs between the baseball field and golf course (about a mile from the river/border). The federal government had wanted to build the fence through the middle of campus (a couple of miles from the border but compromised on current location). What a waste! Have we not learned as a nation and history that border walls/fences DO NOT WORK!

27.  B. Morris said on July 30, 2011

I agree that the historical record shows that border fences and walls do not work. Only fostering equality and respect for human rights will solve our immigration "problem." Meanwhile, it's sad that the innocent animals have to be degraded to the status of collateral damage.

The point of the study seems to be to point out an issue and to begin a dialogue that will lead to solutions that can protect the security of the US while not disproportionately damaging wildlife. I think this is laudable. I am proud to be a UT graduate when I see this kind of quality work being done there.

28.  Lawrence said on Aug. 3, 2011

I am not unsympathetic to the issues raised in this study, and as a UT graduate I commend the fine research done; but the urgent national security need for the fences trumps the wildlife concerns discussed here.