The federally Endangered Sonoran pronghorn would be hard hit by Donald Trumps border wall | Photo: Florin Chelaru, some rights reserved Californias border with Baja California is a complex region with unique environmental issues. Our Borderlands series takes a deeper look at this region unified by shared landscapes and friendship, and divided by international politics.
A female arroyo toad shelters under a streamside cottonwood in early March, twenty years from now. Its unseasonably warm, and theres something ancient stirring inside her. She listens. A male is singing. She finds his song beautiful. Everything in her wants to follow that sound, to find the male and mate with him. She would release her eggs for him to fertilize. Those eggs would grow in long submerged strings, until a new generation of arroyo tadpoles hatched from them a week later. Her drive to find that male is irresistable. But she cannot reach him.
A month and a half later, three hundred miles east, a small group of javelinas cools its collective heels in the shade of an ironwood tree. The engaging, pig-like beasts are hungry. A couple of them root in the soil of the wash, looking for tubers. Not far away, a mesquite hangs heavy with last years crop of pods. The javelinas can smell those pods, even after a season of drying on the branch. The one tree could feed the entire pack for two days, and the javelinas would disperse a few of the seeds elsewhere to make new mesquites. But thats not going to happen. Theres something in the way.
In July, wild eyes scan and a pair of slitted nostrils sift the desert breeze. The jaguar finds no good news in the air. He curls back his upper lip and tries again, head held high. Hes not looking for food. Here in the Patagonia Mountains of southern Arizona, game is plentiful enough to keep his ribs well hidden. Its plentiful enough, in fact, to support a few more jaguars, to provide a launch pad for North Americas largest wild cat to reinhabit the southern Rocky Mountains. But that would require the cooperation of one or more female jaguars. And thanks to a project propelled by destructive politics and fear, there wont be any lady jaguars in the Patagonia Mountains anytime soon.
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In previous articles in this series weve looked at a some of the likely unintended environmental consequences of the gigantic border wall proposed by Republican Presidential candidate Donald Trump, from the climate impacts of such a massive construction project to the walls inevitable disruption of stream courses resulting in massive floods.
But some of the longest-lasting environmental consequences of the proposed border wall would result from the wall doing precisely what its supposed to do: stop migration across the border. The wall will impede a lot more than just human beings from migrating. It will stop animals as well, and their genes, and even the plant species they disperse.
Javelinas in the creosote | Photo: Dave Hensley, some rights reserved
If youre wondering how a wall would prevent plants from migrating, consider those hypothetical javelinas in the spring of 2036, wistfully regarding those mesquite pods from across the international boundary wall. Javelinas, a distant cousin of domestic swine, play a very important role in moving plant species such as cacti and leguminous desert trees from place to place. When a javelina gobbles up seed-packed fruits, then excretes the seeds some distance away, its taking part in the age-old process of plant migration. Without aid from dispersing animals like the fruit-eating javelinas, many plants wouldnt be able to scatter their progeny to potentially hospitable spots in the landscape.
Thats especially important as the planet warms, and habitats north of the border become better places for southern plants to live. During past periods of climate change, the earths plants have either found ways to move their progeny to more suitable new habitats, or theyve died out.
As weve written in previous articles on the proposed border wall, actual specifics about that walls dimensions are hard to come by. But if the loose talk about a border wall more than 50 feet tall comes to fruition, it wont just be plants that depend on javelinas that suffer. A wall that tall will block even many wind-borne seeds, and fruits dispersed by ground-dwelling birds like the Gambels quail that prefer not to fly that high if they can avoid it.
Arroyo toad | Photo: USFWS
The border wall would also impede the migration of genetic material, which is as important for long-term biodiversity health as the migration of individual animals. Thats true even for animals that dont spend a lot of time moving around, such as arroyo toads. An individual toad may not move more than a mile in her lifetime, except by accident. But arroyo toad genes move back and forth across the landscape as successive generations of new toads mate with toads on the edges of their home territory, and the resulting offspring mate with toads even farther away.
Put a 50-foot barrier across arroyo toad habitat and that gene flow stops. Again, in a warming world in which southern toads may possess genetic tolerance of higher temperatures, cutting off the flow of genes from south to north is especially counterproductive.
And then, of course, theres the kind of migration most of us are more likely to picture in the context of the proposed border wall: big animals seeking out new territory, or trying to migrate with the seasons, that come upon an impassible barrier. And the borderlands shared by the U.S. and Mexico have a lot of embattled big animals that dont need any more obstacles to migration than theyve already got. The borderlands are a zoological wonderland with unique charismatic megafauna. Those jaguars trying to get to Arizona, for instance, have company: five of North Americas six species of big cats
