A female bobcat who lives along the border between the U.S. and Mexico has figured out where she can pass and where she can't.

This bobcat lives near the fence that already stretches intermittently across 650 miles from California to Texas, and was mandated under President George W. Bush. She was collared for tracking by the U.S. Fish and Wildlife Service (USFWS), and roams an estimated 730 acres — along both sides of the fence.

A lone animal facing the fence that cuts through his habitat.Matt Clark/Defenders of Wildlife

But, if elected, Republican candidate Donald Trump proposes to expand this barrier to keep illegal immigrants out of the U.S. "A nation without borders is not a nation. There must be a wall across the southern border," Trump writes. He claims he will force Mexico to pay for the wall.

If this expansion of the barrier were to happen, the environmental effects would be devastating: This particular bobcat's very survival could be compromised — along with the lives of thousands of other wild animals, including endangered species, who call the contentious area home.

"It is important to ensure that animals have the ability to travel across wild landscapes," David Steen, assistant research professor at Auburn University Museum of Natural History, told The Dodo. "Movement is important to maintain gene flow among populations and it can also help species recolonize areas where they've gone locally extinct."

A North American bobcat in Southern TexasShutterstock

Some of the animals the U.S. and Mexico have teamed up to help have already started to make a comeback.

"Under the Endangered Species Act, the United States Fish and Wildlife Service and other agencies have reintroduced the endangered Mexican wolf to states like New Mexico, and they are monitoring the recovery of jaguar populations in the United States," Jon Beckmann, a scientist at the Wildlife Conservation Society's North America Program, wrote in an op-ed for the New York Times. "Ocelots, too, appear to be moving from Mexico back to ranges they once occupied north of the border."

Trump's proposed cement and concrete wall — which would stretch along the full 1,989-mile border, be as high as 55 feet and be built "very inexpensively" — would rewind this progress.

The Mexican wolf, an endangered species, has been making a comeback — but a border wall could change that.Shutterstock

"Many species undertake seasonal migrations to take advantage of changing conditions and find suitable areas for foraging or reproduction," Steen said. "It is easy to imagine how building a structure that restricts animal movement will result in numerous negative consequences for wild creatures."

The wall would greatly impact the animals who traverse the boundary to survive and have families. It's estimated that 111 endangered species could suffer as a result Trump's wall, as well as 108 species of migratory birds.

A section of the border fence in Arizona.Shutterstock

Also, when environmental hardship strikes — like drought — the animals need to be able to roam to find water. A wall wouldn't allow for that.

"In key locations … fencing seriously hampers the movement of predators and migratory animals," Beckmann wrote. "For species like wolves and jaguars, which need to range widely between habitats that are susceptible to drought, this is a grave threat to survival."

Drought is becoming more and more of a problem — and it indicates a global climate disaster. But Trump also denies larger environmental problems — like the ones affecting the entire planet.

(In fact, global warming threatens to wipe out thousands of species. The first mammal has already gone extinct due to climate change — and many more are on the brink.)

Trump has also suggested that, if elected, he'd dismantle the Environmental Protection Agency, the government sector that aims to protect human health by trying to reduce pollution. "Environmental protection — we waste all of this money," Trump said in February.

A family of javelinas trapped along a stretch of fence between Mexico and the U.S. built under President George W. Bush.Matt Clark/Defenders of Wildlife

"This election season, those of us who are concerned about conservation, who care about the quality of our air and water, who worry about climate change and who want to protect imperiled wildlife around the world and in our own backyards MUST make our voices heard at the ballot box," Jamie Rappaport Clark, president of Defenders of Wildlife, wrote recently.

Ocelots have started to repopulate the habitats where they'd been wiped out in the U.S., but a wall would stop this progress.Shutterstock

You can follow David Steen's commentary on politics from a biologist's perspective on Twitter and Facebook.

Matt Clark/Defenders of Wildlife