U.S. Border Fence with Mexico Threatens Endangered Wildlife
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By Melissa Gaskill of Nature magazine
The 1,000 kilometers of impenetrable barrier constructed along the Mexico-United States border, with the aim of stemming illegal human immigration, is also hampering the movements of animals, including several endangered species, a recent study finds.
The species most at risk are those with smaller populations and specialized habitats, says Jesse Lasky, a graduate student at the University of Texas, Austin, and an author on the study, published in Diversity and Distributions. Small range size is associated with a higher risk of extinction, and for some species, the barriers reduce range by as much as 75%. According to the study, species most at risk include four listed by the International Union for Conservation of Nature as endangered or threatened--the Arroyo toad (Anaxyrus californicus), the California red-legged frog (Rana draytonii), the black-spotted newt (_Notophthalmus meridionalis_) and the Pacific pond turtle (Clemmys marmorata)-together with the jaguarundi (Puma yagouaroundi), which is endangered in the United States and threatened in Mexico.
The study also identified three border regions where wildlife is most at risk from the barrier: coastal California, coastal Texas and southeastern Arizona's Madrean Sky Island Archipelago.
Fragmented communities
The Rio Grande Valley, in coastal Texas, contains one of two remaining stands of native Mexican sabal palms. The solid metal and concrete fence, around 5.5 meters high, with an 18-metre-wide strip of open land on either side, runs through a preserve created to protect the trees. Rare animals in the valley include the ocelot, of which fewer than 50 remain in the United States. The fence further fragments their habitat and separates the population in Texas from the larger and more genetically diverse population in northern Mexico.
The border barrier affects 60% to 70% of the habitat in the South Texas Wildlife Refuge Complex, which includes the Laguna Atascosa, Lower Rio Grande Valley and Santa Ana National Wildlife Refuges. At the request of the US Fish and Wildlife Service (FWS), about 100 openings for wildlife were incorporated into the fence in this area. But, says FWS wildlife biologist Mitch Sternberg, who was not involved in the study, these openings are too small for larger animals such as coyotes or bobcats, and bobcats follow regular trails and may not find the openings. "Bobcats don't go out looking for holes in fences as they travel back and forth through brushy habitats. Overall, wildlife connectivity does not exist in these sectors anymore," he says.
Sternberg, who monitors the area's bobcat population using cameras and radio collars on around 20 bobcats, says that the border barriers bisected the home ranges of the tracked bobcats. "I tracked some cats for a long time before the wall construction and did see significant shifts in territories," he says. A pair of collared bobcats that lived on the south side of the wall were trapped on the north side, where they were later killed on a highway while searching for new habitat. The presence of this fence-restricted pair may have caused another male bobcat to wander into an urban area--a rare occurrence--where it was killed by a vehicle. Another tracked pair abandoned their home range during construction of the barrier in their area.
Sternberg hopes to collar additional cats to study distribution and movement patterns after barrier construction, but says "I'm afraid most of the previous bobcats are dead due to forced dispersal during construction, so it will be a real challenge to replicate the study in those areas."
Environmental mitigation
The barrier was mandated under the Secure Fence Act, signed into law by George W. Bush in 2006, and Michael Chertoff, the then Secretary of Homeland Security, waived environmental laws for its construction. In January 2009, US Customs and Border Protection (CBP) committed US$50 million to fund mitigation of "unavoidable impacts to natural and cultural resources" from construction of the barriers, to be paid to the Department of the Interior over several years. In September 2010, CBP funded $6.8 million in mitigation projects, but approximately $30 million that was due to be allocated in 2011 was rescinded in the 2011 appropriations bill.
According to CBP spokeswoman Jenny Burke, the agency "remains committed to responsible environmental stewardship", and intends to resume the mitigation projects when funding permits.
The authors of the recent study recommend restoring historic connectivity through additional openings or removal of the barrier in key areas. Habitat restoration, particularly in areas where crossings are possible, could also mitigate some effects, Lasky says. "General land-use planning is important. We can plan new development and preserves with an eye to where we can promote connectivity and preserve areas where connectivity exists."
This article is reproduced with permission from the magazine Nature. The article was first published on August 2, 2011.
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19 Comments
Add CommentEverything endangers wildlife these days. I could sneeze in front of an "environmentalist" and get reprimanded for it.
Reply | Report Abuse | Link to thisEnough is Enough... We can not allow the destruction of our nation over some alleged endangered animals. For each species which disappears through natural evolution a new species appears. If the process is hurried for the betterment and/or survival of mankind so be it.
Reply | Report Abuse | Link to thisIt always amazes me how much the arguments of science is so exact to the arguments about God and religion... For every scientific discovery or theory there is an equal or opposite discussion, as with the subject of God and Religion.
Environmentalist will not be satisfied until they have moved society back to the middle ages then they will complain about the manure in the streets...
The fence may threaten animals, but I would bet allowing Mexico to overpopulate the US would send these same animals to extinction, along with destroying our country's infrastructure.
Reply | Report Abuse | Link to thisNice try, SciAm. Cramming your left wing political agenda down people's throats. I grew up with this magazine when it used to have some substance. What a shame...
This article is even further misleading... coyotes, bobcats, ocelots and the jaguarundi aren't even remotely endangered. The California red-legged frog is (wait for it) endemic to California. The Pacific pond turtle is mainly found in the Northwest. The newt and toad are the only ones with a grain of truth, but I don't see how a fence is going to stop their migration(?)
Reply | Report Abuse | Link to thisWould not want facts to get in the way of your agenda.
All people need to do is use their brains and leave politics out of it to solve the 'problem'.
Reply | Report Abuse | Link to thisI still like the hard science SA gives me, but they really should stay out of the 'soft sciences' like politics. It's not their forte.
A wall is not the problem in the us. It is racist individuals who target the immigrants that take the pathetic jobs no American wants. More should be done to preserve these species, and individuals should focus on the economy, the current debt that's where the true us destruction is at.
Reply | Report Abuse | Link to thisWhat's your point exactly?
Reply | Report Abuse | Link to thisI say, Enough is Enough... We can not allow the destruction of Earth over some human defined region of land. For each species which disappears through man-made causes, we lose a link in the chain of life. If the process is hurried for the betterment and/or survival of mankind, so be we damned.
Reply | Report Abuse | Link to thisIt always amazes me how much the arguments of nationalists is also an argument for our species...
Hey mister, read something, anything, to educate yourself about the scientific process.
Environmentalists will not be satisfied until we have secured our Earth in a sustainable rhythm and we are not recklessly endangering others & our own existence.
Are you a scientist? Have you studied this? No? Then hush and let the professionals do their job.
Reply | Report Abuse | Link to thisThe endangering of even more irreplaceable species is yet another reason to eliminate physical borders. This is the same problem faced for the dwindling populations of bison in the Polish (Belovezhskaya Pushch) forest.
Reply | Report Abuse | Link to thisInteresting how politics trumps life and liberty. In this case the life and liberty of non-human animals.
Reply | Report Abuse | Link to thisI'm truly appalled that this politically motivated piece of crap is appearing in Scientific American. Where are the proven facts? Where is the scientific evidence? This article is nothing more that someone's personal opinion and supposition. The only specie endangered by this wall is the hoard of illegal aliens invading our border at an ever increasing rate. This invasion must be stopped at all costs or our nation will be fundamentally changed forever. Wildlife has dealt with environmental changes for millions of years and will certainly deal with this one as well. The only purpose of this article is to enflame the environmental wackos to protest this fence and delay its erection to the great advantage of the leftist movement.
Reply | Report Abuse | Link to thisYou bet over populating America with Mexicans would also endanger the species? That is quite a racist, ignorent claim. If you want to shoot your political guns I suggest you comment at another discussion board. The article is an intresting point of view, not a political slam.
Reply | Report Abuse | Link to thisIt's odd to see people reading "Scientific American" who don't seem to know that illegal immigration from Mexico is drastically curtailed by the simple fact that the US economy isn't the job generating machine it used to be. The geniuses that came up with the fence idea probably didn't know and didn't care about ecological impact.
Reply | Report Abuse | Link to thisRacist? Where in concernedcitizen’s comment is there any reference to race? This sort of name calling is a tired, old tactic of the left. If you can't argue with facts, then you argue with emotion and name calling. The point of his/her comments is that the purpose of the fence (i.e. stop the invasion of uninvited foreigners) far outweighs the supposed harm to the indigenous wildlife in the area. The other point, which you seemed to have missed, is that this article, consisting of nothing more than political motivation, supposition, personal opinion and absolutely no proven facts has no business being in a science based magazine.
Reply | Report Abuse | Link to thisThis article is a dinner bell for inbred Birchers to step up and tell everyone how bad the problem of illegals is, and how stupid it is to be an environmentalist.
Reply | Report Abuse | Link to thisFacts: the current administration has done more to protect the southern border than any admonistration. Illegal crossings are down, interceptions of people crossing is up, deportations are at at an all time high. By any measure, the problem, however you care to measure it, is getting smaller. But for some reason, a certain segment of the US population continues to see this as a threat to our very existence as a nation and makes this their number one concern. While expressing or holding no concern at all for the environment - except when their childrens water supplies are poluted, or their childrens air quality makes them sick.
When did conservative come to equal stupid, inhumane, selfish and shortsighted?
It happened when they elected the antichrist as vice president. I seriously doubt that this fence is all that devestating in over all terms of the environment but the general purpose of it is clearly an un-American nationalistic mimicry of a Musolini style despotism.
Reply | Report Abuse | Link to thisit seems to me that it should be intrinsicaly obvious to the most casual observer that errecting a barrier across any habitat or natural environment will have a deleterious effect on the indigineous populations, be they human, or other animal species. I suppose I could be wrong, but I'd guess the probability that I am is relatively low.
Reply | Report Abuse | Link to thisI must point out that the answer to your first question is "Mexican." Yes, the answer was in the reading that you were supposed to have done. Now I ask you to quote where exactly I used this "old tactic of the left," whatever that means. You are clearly a proponent of the This-Article-Is-Too-Political-For-Me group. I will admit that some of the data and especially the opinions in the article are very questionable. They used words such as "may be at risk" which does not conclude anything and I may understand that this article is quite political given its immediate lack of facts. Still... it's just a point of view. Love it or hate it I guess.
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