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The wall being constructed at the U.S.-Mexico border has cut through the heart of the Sky Islands, causing enormous environmental destruction — endangering springs, damaging waterways like the San Pedro River, and stopping wildlife in their tracks. It’s also harming public lands, Indigenous lands and culture, local communities, human rights, and civil liberties.  

This goes against everything we stand for at Sky Island Alliance, with our mission to protect and connect the region’s landscapes, people, and wildlife for the benefit of all. Read on to learn more about what we’re doing to protect our borderlands from this threat.

Here’s what we’re doing to protect our Sky Islands from the border wall: 

  1. Studying borderlands wildlife and ecosystems and sharing that vital information with the public and policymakers; 
  2. Advocating for new border policies to reinstate laws and stop wall building; and 
  3. Working to restore wildlife pathways and waterways across the border.  

Explore this page to learn more about the U.S.-Mexico border wall, law waivers that have enabled its construction, local impacts, and how you can join our crucial work. 

Photo by Frank Staub/Lighthawk.

The Border at a Crossroads

A major transformation of the U.S.-Mexico border is underway. For the first two centuries of American history, the border was delineated only by simple markers and cattle fencing. The boundary was first marked by just 52 short posts that were installed in 1848, following the Treaty of Guadalupe Hidalgo. In 1891, an array of 258 larger concrete and steel obelisks was installed from coast to coast during the International Boundary Survey. The movement to harden the border was catalyzed by the passage of the Real ID Act in 2005, which gave the Department of Homeland Security secretary the authority to waive federal laws and statutes at the border to enable fast barrier construction.

The current era of border walls began with the authorization of funding for 700 miles of border barrier in 2006, and by 2009 more than 600 miles of border wall and vehicle barrier had been built. During the first Trump administration, many new law waivers were issued and over 450 miles of border wall were built. Construction was largely paused during the Biden administration, but in 2025 the second Trump administration announced plans to complete a militarized barrier system across the entire southern border, including floating river buoys and double border walls across the land. National Defense Areas were established, and the military mobilized to aid the rapid proliferation of border walls that indiscriminately cut through borderland communities and public lands, and severed vital wildlife corridors. This continental-scale construction project is underway and is slated to be completed in 2028.

Video by Leslie Ann Epperson, SmallWheel Films. Music selections from “Monsoon Mirage” composed by Grégory Rolland, and soundscape created by Lise Tanfin.

Latest News 

Feb. 17, 2026: U.S. Customs and Border Protection completed the first five of 27 miles of new steel border wall in the San Rafael Valley, transforming the landscape and severing this important wildlife corridor. As an added deterrent, the wall is painted black (to make it hotter to the touch). Also, an updated “Smart Wall Map” on the agency’s website showed plans to finish the wall in Arizona, add buoys in the Colorado River, and install more double wall in certain sections of the border.

Dec. 12, 2025: Sky Island Alliance and 23 other border coalition organizations sent a formal complaint to U.S. Border Patrol, following the agency’s installation of concertina razor wire on the north side of the border road in the Huachuca Mountains, Guadalupe Canyon, Buenos Aires National Wildlife Refuge, and other areas. The concertina wire can injure and kill large animals when they become trapped within the sharp wires.

Nov. 20, 2025: U.S. Customs and Border Protection initiated a public comment period for the Tucson Sector, proposing 19 miles of new primary border wall near Sasabe and in the Pajaritos, Atascosa Highlands, Patagonias, and Peloncillos at the New Mexico line. The agency also proposed 42 miles of “double wall” for certain sections where wall already exists, as well as 222 miles of system attributes such as stadium lighting, sensors, and roads. Sky Island Alliance supporters submitted 996 comments in opposition.

Oct. 15, 2025: The U.S. Department of Homeland Security, in an unprecedented move, announced new border wall waivers along the entire the U.S.-Mexico border, rather than issuing a policy for a specific sector. The announcement unilaterally waives virtually all laws ensuring transparency and accountability with new border wall contracting and procurement. See statement from Earthjustice.

Aug. 25, 2025: The Trump administration began new border wall construction along a 24.7-mile stretch of the San Rafael Valley after bringing in heavy equipment and clearing new roads. On the same day, SIA staff traveled through the valley to share its beauty with local filmmakers and to meet with community leaders like Alma Guadalupe Téllez, the mayor of Santa Cruz, Sonora, our neighbors just south of the San Rafael Valley. Over sandwiches and burritos passed across barbed wire fence, Alma shared her convictions on taking care of our shared wildlife and water and on maintaining connections going back hundreds of years. She also shared that her community can host some of our Border Wildlife Study cameras, after we were told that border cameras in the construction zone will be removed.

June 5, 2025: U.S. Customs and Border Protection awarded a new contract for border wall construction to Fisher Sand & Gravel Co. for $309,463,000 to construct 27 miles of border wall in the San Rafael Valley of Santa Cruz County, Arizona, within the U.S. Border Patrol’s Tucson Sector. This contract is funded with CBP’s Fiscal Year 2021 funds. The projects are covered by the waiver issued by DHS Secretary Kristi Noem on June 4, 2025. Learn more about the threats to the San Rafael Valley in this Sky Island Alliance report.

April 8, 2025: The U.S. Secretary of Homeland Security Kristi Noem issued a new round of border law waivers in California to expedite border wall construction in Jacumba, Otay Mesa, and Smuggler’s Gulch areas. See notice in Federal Register.

Jan. 20, 2025: Following his reelection, President Donald Trump declared a national emergency at the U.S. southern border with Mexico, citing an “assault on the American people” by cartels, gangs, and “illegal aliens.” The declaration calls for the construction of additional border wall and the use of Armed Forces. The president also signed an executive order calling on the Secretaries of Defense and Homeland Security to “deploy and construct temporary and permanent physical barriers to ensure complete operational control” of the border.

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2021

How the Wall Harms the Sky Islands 

At least 84 federal and state laws and regulations, including the Endangered Species Act and the National Environmental Protection Act, were waived to advance border wall construction in California, Arizona, New Mexico, and Texas.  

Here are just a few ways the wall is doing specific harm: 

  • It has reduced the number of wildlife migration corridors, separating animals from food, habitat, and their core populations in the U.S. and Mexico. The wall especially hurts large mammals, low-flying birds, and endangered species like jaguars, ocelots, and Mexican gray wolves. 
  • At least 60 new roads have been graded for border patrol and for access to construction sites. In the process a lot of water has been wasted to keep dust down. Cacti, trees, and other plants have been bulldozed and removed. And vehicle traffic has created noise and light pollution that disturbs wildlife. 
  • Water has been pumped from underground aquifers and springs to mix with concrete for the wall, and sections have been built across waterways like the San Pedro River, which has dammed certain places or reduced flow. This harm to our rivers and aquifers is especially devastating during times of drought. 
Oak trees bulldozed near the border to make room for construction equipment.
  • New border lighting has disrupted nocturnal species that rely on the cover of darkness to travel and hunt. Through our Border Wildlife Study, we’ve found that a majority of all mammal sightings occurred between sunset and sunrise, and half of the mammal species we’ve photographed have only been seen at night. 
  • Indigenous communities and Tribal lands have been harmed by the border wall. Barrier construction has disturbed or destroyed graves and cultural sites and infringes on Native sovereignty. Sacred lands and springs have been torn apart by road grading and wall construction without meaningful consultation. Learn more about why the Tohono O’odham Nation opposes the wall. 

Key Articles