The National Butterfly Center covers an expanse of cultivated gardens and wild landscape along the Texas-Mexico border, where all sorts of butterflies, birds and mammals frolic about in safeguarded habitats. But questions are now swirling about the future of the center; according to Hannah Waters of the Audubon, heavy construction machinery rolled up to the property on Monday, reportedly in preparation for building part of a border wall that will cut through the sanctuary.

This wall is not directly connected to the $5.7 billion partition that United States President Donald Trump wants to build along the U.S.-Mexico border—a plan that has divided Congress and recently ground the government into the longest shutdown in U.S. history. Last March, reports Nomaan Merchant of the Associated Press, Congress approved more than $600 million in funding for new stretches of wall in the Rio Grande Valley, one of the most biologically diverse regions in North America. This land between Texas and Mexico is home to 11 different habitats—including wetlands, thorn forests and arid lands—thousands of plant species, some 200 vertebrates and 300 butterfly species.

U.S. Customs and Border Protection (CBP) designs indicate that the wall will extend to the height of an existing flood control levee next to the Rio Grande river, and be crowned with 18-foot steel posts. CBP also intends to clear a 150-foot “enforcement zone” in front of the wall. Seventy of the National Butterfly Center’s 100 acres will lie south of this new barrier, as will much of the land belonging to the Bentsen-Rio Grande Valley State Park, which is home to more than 500 bird species, according to Waters.

The butterfly sanctuary is privately owned, and the CBP promised last December that staff and visitors “will continue to have access to the 70 acres on the south side of the existing levee.” But in a Facebook post published Sunday, the center said that a police officer told them they would not have access to this land, and that the authorities were ordered to stop anyone who tried to set foot on the levee. “Effective Monday morning, it is all government land,” the officer reportedly said.

Though the center had previously been informed that construction on the wall could start in February or March, staff did not know that equipment would be arriving on the property this weekend. Jeffrey Glassberg, president of the center, tells Waters that he was due to meet with an appraiser to discuss the government land seizure, leaving staff members confused as to whether or not the sudden presence of construction vehicles and law enforcement means that the seizure is already underway.

“Honestly, I have no idea what to expect,” Marianna Wright, the National Butterfly Center’s executive director, tells David Tarrant of Dallas News.

In its Facebook post, the center said it “will be taking legal action.” A coalition of environmental groups is already suing the Department of Homeland Security, which has waived 28 environmental regulations, including the Endangered Species Act and the Clean Air Act, to allow border wall construction to happen more quickly. That lawsuit, which is still pending, argues that the waivers exceed government authority and threaten wildlife by paving the way for construction to take place. Critics also say that the wall will push asylum seekers into increasingly dangerous territory as they try to enter the United States.

“Border walls are death sentences for wildlife and humans alike,” Amanda Munro of the Southwest Environmental Center, which restores and protects native wildlife and habitats, told the Guardian’s Samuel Gilbert in December. “They block wild animals from accessing the food, water and mates they need to survive. They weaken genetic diversity, fragment habitat, and trap animals in deadly floods. At the same time, they drive desperate asylum seekers to risk their lives in the unforgiving desert.”