(CN) — The U.S. Fish and Wildlife Service on Monday declared the prostrate milkweed an endangered species and mandated new habitat protections for the plant, closing a chapter in a feud between environmentalists and those who advocate for unfettered border wall construction in South Texas.
The rare milkweed, which grows only in the Texas-Mexico borderlands, has for months been at the center of the fight between butterfly lovers and Texas officials. Texas Attorney General Ken Paxton, a Republican who supports new border wall construction, said last year that formally protecting the plant would create an "influx of illegal aliens" and endanger Texans. Environmental groups say the listing will help safeguard the charismatic migratory monarch butterfly, which has a deeply symbiotic relationship with the unassuming weed.
While the prostrate milkweed has a range of around 200 miles, only 24 populations of the species are known to still exist. Those are in Starr and Zapata counties in far South Texas, as well as in neighboring states of Nuevo León and Tamaulipas in northern Mexico.
It's the rarest species of milkweed, and it's a critical habitat for monarch butterflies as they head north from Mexico after the winter. Monarch caterpillars can only eat milkweed, and female monarchs only lay their eggs on milkweed. Toxic compounds in the plant, which monarchs consume, help protect the butterflies from predators and give them their signature orange hue. In turn, monarchs help pollinate and spread the plants.
Historically, the FWS said in its final rule on Monday, patches of prostrate milkweed along the Texas-Mexico border were all geographically linked. They were separated and are "very unlikely" to reconnect, the agency said, due to what it called "disturbance" in the region.
That disturbance has included herbicides, oil and gas pipelines and, most notably, border wall construction green-lit by former President Donald Trump.
The Trump administration spurred a firestorm in 2017 when it began bulldozing habitat at the National Butterfly Center in South Texas, damaging habitat used by monarchs and other species. Officials with the center said they weren't properly notified about construction and publicly criticized the Trump administration. The situation pulled some butterfly lovers into an unlikely partisan battle, and the center was later forced to temporarily close following threats and conspiracies about human trafficking.
While Trump is no longer in office, Texas Governor Greg Abbott, a fellow Republican, has repeatedly said he also wants to build a wall. This year, he appointed a state border czar with a goal of speeding up that project.
In the process, the Texas state government became one of the biggest opponents of plans to list the prostrate milkweed as endangered, submitting multiple comments to the FWS. Among them was a comment from the state attorney general's office warning the designation would have "a significant impact on national security by preventing Texas’s efforts to address the border crisis." In response, the FWS said in its rule that prostrate milkweed is currently in danger of extinction and that the agency is therefore required to list the species as endangered.
While hardly charismatic plants in their own right, milkweed has important symbiotic relationships with some of the world's most charismatic insects, including bees and butterflies — and especially the monarch. Various species of milkweed exist throughout Americas, and many of them provide food and habitat for monarchs on their multi-generational journey north and south across the continents.
Because of its location, the prostrate milkweed is particularly critical: It's one of the first stops monarch butterflies make in the United States after spending their winters in Mexico, said Tierra Curry, a senior scientist at the Center for Biological Diversity. Monarchs born on prostrate milkweed in South Texas will eventually find their way north across the rest of the United States.
The monarch butterfly has also been struggling, with population numbers dropping by 99.9% in some areas. The International Union for Conservation of Nature last year listed the monarch as endangered, citing declining milkweed populations as a factor, though federal officials have so far held off on making a similar ruling.
There are many factors behind the decline in milkweed, but one of the biggest is border wall construction, said Curry, the Center for Biological Diversity scientist. Even after a section of wall is constructed, there is an "ongoing disturbance" as border officials keep clear land near the wall and drive vehicles along it.
"You don’t just put up the wall and leave it there," Curry said.
Now, environmentalists like Curry are hopeful that new milkweed protections will also help the monarch rebound. The species is remarkably charismatic for an insect, not only because of its vibrant wings but because of its unique migration patterns, which see generations of the butterfly move from the jungles of South America all the way to southern Canada and back.
It's a sad irony, Curry said, that a border wall has impacted an insect that depends on travel across the U.S.-Mexico border.
"Monarchs are this symbol of migration," she said. "They travel all across America. The barrier to migration is what’s jeopardizing their host plant."
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