Scientists in the US are warning of the potential for serious ecological consequences if Donald Trump’s proposed border wall between the US and Mexico goes ahead.
The wall, which would span the majority of the border from the North Pacific Ocean to the Gulf of Mexico, will impede animal migration, shrink animal habitat and split populations of species into smaller, less viable groups, according to the 18 researchers who published their findings today in BioScience.
More than 2,500 scientists endorsed the article, which calls on the US government to “recognise and give high priority to conserving the ecological, economic, political and cultural value of the US-Mexico borderlands”.
The construction of a border fence between the US and Mexico began during George W Bush’s presidency. At the time Congress gave the Department of Homeland Security authority to waive laws that could slow construction of the border fence, including the endangered species act (ESA) and the national environmental policy act (NEPA).
And there has reportedly been very little assessment of the environmental impacts of the various sections of border fence — adding up to 1,200 kilometres — that have since been built. Now President Trump plans to extend these various sections into a continuous barrier.
Numerous species along the US-Mexico border are already threatened with extinction, according to study author Professor Bill Ripple from Oregon State University.
“There are currently 62 species that are threatened,” he said.
“The Mexican grey wolf, it’s threatened, and its range would be truncated [by the wall]. The jaguar, there’s only a small amount of its range in the United States and that would be cut off from its range in the south. And the same with the ocelot.”
The researchers identified 1,506 species with ranges on both sides of the border, including 163 mammals.
Although the border wall has garnered a lot of attention both locally and internationally, the ecological impacts have been mostly overlooked, the researchers said.
In publishing their research and petition, Professor Ripple is aiming to bring these issues to light.
“This is not just a small fence, this is a huge construction project that could span the entire border between Mexico and the United States.”
Restricting jaguars could trigger trophic cascade, similar to Australian dingo fence
Although there has been some discussion of leaving small holes in the fence for animals to pass through, this will not help larger species, Professor Tim Kiett from the University of Texas told the ABC’s Science Show recently.
“Things like jaguar, jaguarundi, the pronghorn, a number of larger-bodied species could still be impacted even if there are small passageways in the barrier,” Professor Kiett said.
“They move daily and seasonally. Some embark on largescale migration, but many just move about to forage, to find mates, and for other reasons, so if their movement ability is restricted that can impact their populations.”
Research has shown that the dingo fence here in Australia, which cuts across southern Australia from Queensland to Western Australia, has created a cascade of ecological impacts and changed the physical shape of the sand dunes on either side.
Restricting dingoes from the southern side of the fence has allowed feral cats and foxes to proliferate, which in turn suppress the numbers of small seed and shrub-eating marsupials and rodents.
This has allowed more shrubs to grow, reinforcing the dunes and enabling them to grow larger, researcher Dr Mitchell Lyons from the University of News South Wales, who was not involved with the US study, said.
Dr Lyons believes that similar trophic cascades could be triggered if an impermeable fence is built across America.
“A bunch of things that happened here with the dingo fence weren’t exactly predictable, but it’s only 20 or 30 years down the path that you realise what you’ve done.”
US world leaders in extinction
The United States already has the highest number of extinctions of any country in the world, and by a significant margin.
The latest International Union for the Conservation of Nature Red List, released earlier this month, names 237 species extinctions in the United States, with a further 214 listed as critically endangered.
Australia is ranked fourth in the world for extinctions, having wiped out 40 species, and with another 106 on the critically endangered list.
The consequences of building a wall across the US will likely hit endangered species the hardest, and may be complicated by the impacts of climate change, Professor Ripple warned.
It has been shown that species are moving poleward away from the equator at more than 15 kilometres per year on average, as global temperatures warm.
Dr Lyons agreed that building a wall across the US would, over the next decade or two, stop animals on the Mexico side of the border being able to move north.
“That’s a big risk, especially when the barrier runs approximately east-west,” he said.
“You’ve got species trying to migrate, and certainly if there’s a big fence in the way they won’t be able to do that.”