HOUSTON – A Rice University biology expert is asking what are the ecological and evolutionary consequences of President Donald Trump's proposed wall along the U.S.-Mexico border.
Scott Egan, an assistant professor of ecology and evolutionary biology at Rice, said evolutionary effects from the wall can change the balance of nature along the border, which could put wildlife in the area, including more than 100 endangered species, at risk.
"Some of the larger animals that will be threatened by the border wall are the jaguar, ocelot, jaguarundi, Mexican gray wolf, desert big horn sheep and pronghorn antelope," Egan said.
Egan said there are two important phenomena to consider when building any type of barrier that interrupts animal or plant movement:
The Florida panther is one example of human-induced isolation of an animal population, which has led to a population bottleneck and inbreeding depression, Egan said.
"The species historically lived across the southeastern United States, but due to overhunting and habitat destruction, a small remnant set of populations lives in southern Florida isolated from all other panther populations," Egan said. "Just as evolutionary biologists predicted, Florida panthers experienced a reduction in genetic diversity and an increase in homozygosity. This has led to increased heart defects, low sperm counts and increased susceptibility to infection consistent with increased expression of deleterious mutations."
Egan said evidence reveals negative impacts also on humans.
"One highly relevant comparison comes from a border wall that was built between India and Pakistan in the Kashmir region," Egan said. "The border wall interrupted the natural movement of Asiatic black bears and leopards in this region, which decreased their access to natural prey and increased their movement into villages, sometimes targeting humans as prey. This then increased the frequency of humans killing the animals to prevent further attacks, or to retaliate against previous attacks."
Egan is also concerned by two other potential effects: cutting off natural migration routes and future range expansions driven by climate change.
"There are many animals that naturally migrate across the border each year, such as the black bears in West Texas, or the pronghorn antelope across the Southwest. Interrupting these natural movements could have devastating effects on these species on both sides of the border," Egan said. "Similarly, the border wall will trap populations that continue to move north in response to a warming and changing planet, potentially killing individual animals and populations, or resulting in the future extinction of entire species unable to find habitats south of the border to survive."