The Trump administration says it will avoid environmental laws to build its $21 billion border wall

In November, US Customs and Border Protection will start building the first part of President Trump's border wall through a Texas wildlife refuge and a 15-mile area in San Diego, using money it has already received from Congress.

But in order to do that, the Trump administration will need to circumvent a number of environmental reviews and regulations.

Under a law that grants the government the ability to waive legal requirements to expedite border infrastructure, the Department of Homeland Security (DHS) said on August 1 that it will bypass dozens of environmental rules in California. In 2005, Congress also passed the Real ID Act, which allows the Department of Homeland Security to waive environmental regulations that would normally halt construction in any wildlife area along the US-Mexico border.

Since February, the CBP has been preparing to build a nearly 3-mile border through the Santa Ana National Wildlife Refuge, according to The Texas Observer. The New York Times also recently reported that the US Army Corps of Engineers has started drilling and soil testing in California and New Mexico for the wall.

Some scientists worry that the wall, which would likely thwart some animal migration, could devastate wildlife habitats along the border. As Vox notes, the area is home to species including the bobcat, mountain lion, barred tiger salamander, Texas earless lizard, and Rio Grande chirping frog.

The 2,088-acre Santa Ana refuge, located along the Rio Grande south of McAllen, Texas, contains more than 400 species of birds. It's also home to two endangered wildcats, the ocelot and jaguarundi, and some of the last surviving sabal palm trees in South Texas, according to ProPublica. The Rio Grande Valley is one of the most biodiverse places in North America, and the migratory paths of several tropical bird species converge there.

Continuous noise and traffic from the Border Patrol, which can deter animals from migrating, could also the wildlife there, according to some studies. Free movement is important for animal populations, especially after droughts, flooding, or other natural disasters. In April, NPR reported that some Mexican engineers are worried that the Trump administration's border wall, which could essentially act as a dam, will increase flooding in some areas as well.

In July, the House of Representatives granted $1.6 billion toward the wall. That would pay for 74 miles of barriers along the southwest border. Construction is not expected to begin until January 2017.

The DHS has estimated that the wall would cost approximately $21.6 billion in total. Over 650 miles of border fencing exists in Texas, New Mexico, Arizona, and California.

Environmental experts told The Texas Tribune that the barriers make it harder for animals to find food, water, and mates. Many of them, like jaguars and gray wolves, are already endangered.

The research on the environmental impacts of the border fence are still new and limited in scope. The federal government has also provided little funding for independent studies, according to The Tribune.

Though Senate Democrats and some Republicans are expected to oppose the next spending bill for the wall, the Trump administration plans to start its construction soon, at least in San Diego and Texas.

"The sector remains an area of high illegal entry for which there is an immediate need to improve current infrastructure and construct additional border barriers and roads," the DHS said in a press release.