• The Biden administration on Tuesday will establish two new national monuments in the Southwest, a decision that will protect the Spirit Mountain area in Nevada and Castner Range in Texas from development.
• The president will make the announcement at a White House summit on conservation action at the Interior Department.
• The Spirit Mountain area, also known as Avi Kwa Ame, would be the largest protected area so far under the Biden administration.

The Biden administration on Tuesday will establish two new national monuments in the Southwest, a decision that will protect the Spirit Mountain area in Nevada and Castner Range in Texas from development.

The president will make the announcement at a White House summit on conservation action at the Interior Department. The proclamations are part of the administration's commitment to protect one-third of the country's lands and waters by 2030.

The Spirit Mountain area, also known as Avi Kwa Ame, would be the largest protected area under the administration so far and only the second monument designated to honor Indigenous tribes while conserving public land.

Avi Kwa Ame is considered sacred by tribes including Mojave, Chemehuevi and Paiute. The area is also home to one of the world's largest Joshua tree forests and provides habitat and migration corridors for species like desert bighorn sheep, desert tortoise and Gila monster.

The other designation, Castner Range, is located on Fort Bliss and served as a training and testing site for the U.S. Army during World War II, the Korean War and the Vietnam War until it closed in 1966.

Protecting Castner Range connects the area with the Franklin Mountains State Park, which will provide habitat for wildlife including the golden eagle, Texas horned lizard and western burrowing owl. The area also contains cultural sites documenting the history of Native tribes.

Once the area is remediated for safe public access, Castner Range will also expand access to nature for underserved communities that have historically had less access to public lands, the White House said in a statement.

The two new national monuments will collectively protect nearly 514,000 acres of public lands, the White House said. Last year, the president designated a World War II-era military site in Colorado, called the Camp Hale-Continental Divide National Monument, as his first national monument.

The Honor Avi Kwa Ame coalition said in a statement on Tuesday that the group was overjoyed to learn about the site's designation as a national monument.

"The president's action today will safeguard hundreds of thousands of acres of cultural sites, desert habitats, and natural resources in southern Nevada, which bear great cultural, ecological, and economic significance to our state," the group said.

Biden is using his authority under the Antiquities Act of 1906 to designate the new monuments. In 2021, the president also restored three monuments — Northeast Canyons and Seamounts, Bears Ears and Grand Staircase-Escalante — that were significantly reduced by the Trump administration.