Since Donald Trump began his campaign for the US presidency, we’ve heard about the proposed border wall. Some have protested it. Some have cheered it on. Now that Homeland Security is issuing notices to local landowners and requesting proposals for prototypes, it looks as if this thing is really happening. Whether we took it seriously or not, we did have advance notice. But there are populations that haven’t been warned in advance whose numbers will be profoundly affected, in ways that haven’t been completely studied or entirely determined. The only thing that we do know is that the effects of border walls on these populations are often unintended, wide-ranging, and significant. What we do know, according to peer-reviewed studies, is that for these populations, border walls “represent a major threat.” We’re referring, of course, to wildlife. From Australia’s rabbit-proof fence, to razor-wire fencing between Slovenia and Croatia, to the current U.S.-Mexican border fence, history is rife with examples of barriers that have caused serious problems for animals. Borders — whether made from concrete, barbed wire, mesh, chain link, or razor-fencing — pose obstacles and dangers to the survival of animals at both an individual and species-wide level. If the government’s ideal wall design is met (and even if it’s bumped down to a more “modest” proposal), we are looking at serious ramifications for the wildlife that exist on either side of our southwest border. What might that ideal wall look like? According to US Customs and Border Protection, features shall include: 1) The wall design shall be reinforced concrete. 2) The wall design shall be physically imposing in height. The Government’s nominal concept is for a 30-foot high wall. Offerors should consider this height, but designs with heights of at least 18 feet may be acceptable. Designs with heights of less than 18 feet are not acceptable. 3) It shall not be possible for a human to climb to the top of the wall or access the top of the wall from either side unassisted (e.g. via the use of a ladder, etc.) 4) The wall design shall include anti-climb topping features that prevent scaling using common and more sophisticated climbing aids (e.g. grappling hooks, handholds, etc.) 5) The wall shall prevent digging or tunneling below it for a minimum of 6 feet below the lowest adjacent grade. 6) The wall shall prevent/deter for a minimum of 1 hour the creation a physical breach of the wall… 7) The north side of wall (i.e. U.S. facing side) shall be aesthetically pleasing in color, anti-climb texture, etc., to be consistent with general surrounding environment. The manufacturing/construction process should facilitate changes in color and texture pursuant to site specific requirements. 8) The wall design shall be able to accommodate surface drainage. Now try to imagine an existing animal that wouldn’t have problems going over, under, or around that. If you thought ‘birds,’ put a pin in it; we’ll get there, but for now, suffice it to say that the gift of flight isn’t a free pass across borders. What are the dangers, exactly, that these animals face, and what animals, exactly, are in danger?

HABITAT FRAGMENTATION

Animals do not recognize political boundaries. When we break up habitats — even when it’s not intentional — we cut off groups of animals from each other, limiting genetic diversity. We change and limit access to resources. We change the the habitat itself. We cause ecosystem decay, a process author David Quammen describes in his book, Wild Thoughts from Wild Places, “whereby a patch of habitat — if it’s too small and too thoroughly insularized — loses species as though spontaneously.” He comes by this understanding by looking at island biogeography. Islands, he notes in his 1996 book, Song of the Dodo, “are where species most commonly go extinct,” and it makes sense to pay attention to them, “because we live in an age when all of Earth’s landscapes are being chopped into island-like” pieces. How then, does a patch — or fragment — ensure that it maintains its “full compliment of species?” Only by “continu[ing] to receive immigrants (wandering individuals) from other patches.” The US-Mexican political boundary stretches for 2000 miles. Of those miles, President Trump has proposed covering half (the other half of which will be protected by natural barriers). Even halved, the manufactured border presents an obstacle (and fragmentation) that cannot be effectively negotiated. Imagine being a reptile or an amphibian.

LOSS OF RESOURCES Seasons are meaningful to animals. So are precipitation patterns. Access to resources, which change with those seasons and patterns, matter to animals. Animals will travel to access the resources they need — food, water, shelter, mates, territory — and some of those things will exist on either side of a border that humans have made without thought to the waxing and waning of resources, the seasonal (or otherwise) changes in availability. What animals will walk hundreds to thousands of miles to access resources that were previously a matter of mere miles or only simple feet?

IMPEDIMENT TO ALLIES In order to maintain accurate information about species-conservationists need to do field work. In situ studies are paramount to the work of conservationists, allowing them to collect and record data, observe behavior, and develop plans for the next steps in protecting endangered and threatened species. Theories on paper can be proved in the field. Studying wildlife isn’t convenient. It means long and unusual hours. It means uncomfortable quarters. It means extremes in weather. It means long stretches of little action, sometimes punctuated by mere moments, if ever, of action. Field work is necessarily done in places and at times that are not considered, by the average joe (or by border patrol), to be normal. Animals don’t care about your 9-to-5 or your sleep schedule. If you’re a field researcher, you’re up and active when and where the animals are up and active. When it comes to a border wall, this can be problematic. In an interview with BBC, conservation scientist Sergio Avila-Villegas elaborates: “With the heightened law enforcement and patrols spending time along the border, it is not easy for a researcher. For example, if you work with owls, that’s work you do at night, or if you’re hiking looking for evidence of wildlife it gets the attention of law enforcement…Every time I travel along the border I have to explain not only who I am and where I work but what kind of work I do, why I’m along the border and why I’m taking photographs.” Clinton Epps, a wildlife biologist at Oregon State University, agrees with this summation. In an interview with Nature he points out that “the border is not a friendly place any more. I would be hesitant to send a grad student there.” This is field research he initially wanted to do in 2009, while he was publishing a paper positing the effect of Bush’s border wall on native wildlife. At the time, the obstacle was lack of funds. Today, regardless of funds, Epps isn’t certain that the increased security and intensity would allow for a successful or safe study. Where does that leave wildlife, without their allies in the field?

A CLOSEUP: FIVE SPECIES IN PROFILE It would be impossible, within the scope of this article, to denote every animal potentially impacted by this wall. According to Eliza Barclay and Sarah Frostenson, a 2011 study “estimated that 134 mammal, 178 reptile, and 57 amphibian species live within about 30 miles of the [border] line. Of those, 50 species and three subspecies are globally or federally threatened in Mexico or the United States.” The animals listed below should give us all more than enough pause.

ENDANGERED/THREATENED ANIMALS The Jaguar The largest cat native to North America, the jaguar once ranged “from Argentina to Central America and Mexico and up into south-central states and even California and Louisiana.” However, “during the last 100 years the big cats almost completely vanished from the continental U.S. thanks to habitat loss and federal programs aimed at protecting livestock.” An estimated 15,000 jaguars live in the wild today, and of them, only one makes his home in the US. That cat is “El Jefe,” and he lives in the mountains near Tuscon, Arizona. Late last year a second cat — also a male — was spotted via camera trap in the southeastern portion of the state. According to the U.S. Fish & Wildlife Service, these males “are likely dispersing males from breeding populations in northern Mexico.” The jaguar requires a vast territory; the IUCN Red List notes that females generally cover a home range of 10 km². These territories are generally overlapped by male home ranges which vary from “28-40 km² and also [overlap] extensively. In other areas jaguar home ranges have been over 1,000 km².” Competition and/or ecological pressures may have caused these males to move into US territory. While optimism is warranted and encouraged, it’s also important to approach the sightings with a critical, scientific eye. In a 2005 article for Smithsonian.com, Dr. Alan Rabinowitz, one of the world’s leading big cat experts, pointed out that the emergence of the cats into [historic] US territory might be due to the dispersal of “a dwindling population in Sonora, Mexico, about 130 miles south of Douglas, Arizona. ‘I think that the [Sonora] population is in serious trouble, and we’re almost seeing it act like an organism reaching out and trying its hardest to survive in any way possible.'” Put another way, the reentry of these two jaguars into US land may signify more about the pressures they faced in Mexican territory than it does a positive sign for jaguar populations. What is absolutely a positive is that we have incontrovertible proof that the jaguar can move into the US, and that leaves room for female cats to join the party. With El Jefe carving out his own territory and the second cat potentially scoping out the possibilities, we have a sign that these animals can still make it here. The jaguar could very well become reestablished in the United States. But, Rabinowitz cautions, this can only happen if they “are not further threatened by an insurmountable barrier that disrupts their natural movement patterns.” A border wall such as the one the US government is pitching will almost certainly stop the jaguar’s American reemergence in its tracks. Once it goes up, our one established American jaguar will be cut off from any possibility of breeding; he’ll effectively be cut from the gene pool. The Gulf Coast Jaguarundi No, it’s not a typo. The jaguarundi is a wild cat only slightly larger than your domestic house pet. Slender, small, and unassuming, this little wild cat does not attract quite the same involvement and public fascination as the aforementioned, charismatic jaguar. Much remains to be learned about the species. In 2013, U.S. Fish and Wildlife Service listed habitat fragmentation and destruction as major threats to the species’ survival; a border wall, by definition, equals habitat fragmentation, which, the study affirms, “decrease[s] the probability of successful dispersal between patches of suitable habitat, thus increasing demographic and genetic isolation of populations.”

The same plan delineates the strategy for recovering the species, which includes “assessing, protecting, reconnecting, and restoring sufficient habitat to support viable populations…in the borderlands of the U.S. and Mexico.” Key within that strategy is the partnership between Mexican and American organizations, which, it is probably not a stretch to assume, would be more than a little strained by the construction of a wall built to separate the two countries, and apparently meant to be paid for by the one that has no interest in its construction whatsoever. The Ocelot Notoriously shy, the beautifully spotted ocelot is unlikely to hang around where people are to be found — bad news for the species, in light of a proposed border which has sometimes been described, in perhaps an effort to soften the the blow of its impact, as more virtual than concrete. (The proposed plans suggest a different story, however). While they once ranged throughout Texas, Louisiana, Arkansas, and Arizona, currently, less than “fifty of the cats remain in Texas, which represents the northernmost reach of their range… Research shows that a ‘close genetic link’ exists between ocelots found in Texas and those found in Tamaulipas, suggesting they interbreed.” Mitch Sternberg, lead biologist for the South Texas Refuge Complex, affirms that “maintaining and restoring wildlife corridors between the U.S. and Mexico is critical to the long-term survival of ocelots in the U.S.” Recovery of the species “depends on finding enough room for the population to expand.” By carving up territory with walls and roads, we effectively limit the amount of population growth the land can support. The danger of the wall for ocelots, in other words, is that expansion of the species will be literally walled off. The Mexican Gray Wolf Like the incredible story of the red wolf, the Mexican Gray Wolf owes its current existence to the intervention of passionate humans and the currently embattled Endangered Species Act. Once common throughout areas of the southwestern states, the rarest of all gray wolf subspecies was effectively eliminated from the American wild by the 1970s. In 1998, cooperative recovery efforts allowed for the first Mexican gray wolves to be rereleased into Arizona, an incredible triumph.

Nevertheless, It has not been an easy run for this subspecies of gray wolf, which numbered 113 wolves (and only six breeding pairs) in the reintroduction site as of 2016. There remains a smaller number of wolves in Mexico — roughly 36 — but cutting off that population from the American population, just as it is regaining a foothold means limiting genetic diversity. Additionally, for reintroduction and reestablishment to be successful, more locations must be utilized. We cannot simply add the wolves to a single site and call it good. Authors Erikkson and Taylor note that “several sites along the U.S.‐Mexico border show promise, and scientists believe it is essential that protected wolf habitat areas include functional corridors for wolf populations in border regions. Border fencing is contradictory to maintaining these transboundary connections, and will have long term negative effects on Mexican wolves’ ability to move between suitable habitat in the U.S. and Mexico.” The Cactus Ferruginous Pygmy-Owl Remember that pin? We’re back to it. Meet the Ferruginous Pygmy-Owl. The bird is no longer on Arizona’s endangered species list, according to Audobon, but that doesn’t mean that the wall isn’t cause for concern. The greatest time to practice conservation? Probably before you’re deep within the mucky trenches. Most birds won’t be affected by the presence of a 30-foot wall, but University of Arizona researchers have found that “pygmy owls tend to fly really low. They are not great flyers: they are strong flyers, but they tend to fly low to avoid predation.” Specifically, the research showed that “of the [cactus ferruginous pygmy-owl] flights tracked, only 23 percent got up to four meters or higher…with some just inches off the ground.” Four meters is equal to 13 feet; the lowest height the government is accepting for proposals is 18 feet. Ostensibly, the owls are fine now, but the wall would cut off the Arizonan population from the Sonoran population. There’s nothing useful that can occur from cutting off populations of species off from each other, and in the case of the US population, that loss of genetic sharing might eventually lead to a weakening or winking out of local populations.

SO WHAT? At this point, maybe some folks are thinking, “Okay, but what’s a few species here or there, especially given security concerns?” To that, we’d offer this: There’s living, breathing proof, that the disappearance, (or reappearance) of species in a habitat effectively changes the landscape. Look at the reintroduction of an apex predator into Yellowstone National Park, an example now considered to be a classic illustration of the concept of the trophic cascade. Gray wolves, long absent from its historic territory, upon reintroduction changed the behavior and population size of its prey, the elk, a species that had gone largely unchecked in the region. With the population suppressed and moved by wolves, plants that had been cropped and eliminated by the herbivores sprang up anew, regained a foothold, and set to work transforming their environment.