Christmas came a few days late for conservationists, but the presents were welcome nevertheless: Today President Obama used his authority under the Antiquities Act to establish two new national monuments in the Southwest. Together, the designation of the Bears Ears National Monument in Utah and the Gold Butte National Monument in Nevada gives added protections to some 1.6 million acres of land and, in the process, helps to complete a landscape-scale wildlife corridor north of the Colorado River.

Bears Ears National Monument will cover some 1.35 million acres of high desert in southern Utah that an unprecedented coalition of Native American nations has been campaigning to protect. According to archaeologists, the pinyon and juniper-covered canyons and buttes of the area may be home to as many as 100,000 cultural sites. In recent years, the area has suffered from an uptick in looting and vandalism. That spurred the Navajo, Hopi, Pueblo of Zuni, Ute, and Mountain Ute to set aside long-standing differences and join together to push for the monument.

“Today’s actions will help protect this cultural legacy and will ensure that future generations are able to enjoy and appreciate these scenic and historic landscapes,” the president said in a statement.

While President Obama’s monument designation is less than the 1.9 million acres the Bears Ears Coalition had sought, it does include the sort of Native American consultation that the coalition wanted. The designation establishes a “Bears Ears Commission” tasked with ensuring that Indian knowledge and cultural practices help inform the monument’s management. This sort of federal-tribal comanagement of a national monument is unique, and marks an important victory for a resurgent Native sovereignty movement.

In Nevada, the new Gold Butte National Monument will protect 300,000 acres of Mojave Desert that includes Joshua tree forests, twisting slot canyons, sandstone outcroppings, and, at the highest elevations, huge stands of ponderosa pine. Due to its mix of ecosystems and habitats—and the risk posed by development from sprawling Las Vegas— Gold Butte has long been a priority for desert conservation activists. It has also been an important cause for outgoing Senator Harry Reid, who has campaigned hard for the monument designation.

The creation of two national monuments comes on the anniversary of the passage of the Endangered Species Act; the newly protected lands are some of the last big pieces needed to knit together a vast wildlife corridor across the Southwest. From the outskirts of Las Vegas eastward to the foothills of the Rocky Mountains, a chain of wildlands preserves—Gold Butte National Monument, Grand Canyon-Parashant National Monument, Grand Canyon National Park, Grand Staircase-Escalante National Monument, Canyonlands National Park, and Bears Ears National Monument—protect millions of acres of land.

Environmental organizations and tribal leaders were thrilled with the new monuments. “We are just elated that we have this amount of land being designated,” Russell Begaye, president of the Navajo Nation, said in a telepress conference this afternoon.

“These designations, a response to strong tribal advocacy and years of work by local people, is a welcome reminder of the power of positive action and a chance to continue building the inclusive future we want to see in our public lands,” Sierra Club executive director Michael Brune said in a statement.

Congressional Republicans had a different take. Utah senator Orrin Hatch called the monuments' designations “an astonishing and egregious abuse of executive power,” while Utah’s other senator, Mike Lee, vowed to reverse it: "This arrogant act by a lame duck president will not stand. I will work tirelessly with Congress and the incoming Trump administration to honor the will of the people of Utah and undo this designation.”

But fulfilling that promise will be a tough lift. There is no precedent of undoing the creation of a national monument; federal officials conducted multiple public hearings to receive input about each of the proposed monuments; and popular sentiment in both Nevada and Utah appears to support them. A poll this spring showed that 71 percent of Utahans were in favor of a Bears Ears National Monument, while 63 percent of Las Vegas area residents support Gold Butte.

The president sought to underscore such facts in his signing statement: “Following years of public input and various proposals to protect both of these areas, including legislation and a proposal from tribal governments in and around Utah, these monuments will protect places that a wide range of stakeholders all agree are worthy of protection.”

The creation of two new national monuments helps cement Obama’s presidency as one of the most consequential in history for lands protection. He has used the Antiquities Act more than any of his predecessors—29 times—and in the process has protected or expanded protections for 553 million acres of public lands and waters.