In Organ Pipe Cactus National Monument, Arizona, you can find more than 30 species of cactus, including the saguaro, desert giants that tower over the landscape and live for centuries. Desert specialists like endangered Sonoran pronghorn and Sonoyta mud turtles thrive there on just a few inches of rain per year.

This UNESCO Biosphere Reserve lies right on the United States-Mexico Border, previously demarcated only by a short three-foot-tall fence running through the wilderness, one that allowed animals to move freely. But in early 2020 construction began on President Trump’s signature project: a 30-foot-tall wall of steel and concrete.

Now that wall is almost entirely complete, along all 30 miles of the reserve.

Organ Pipe is not alone. The border wall is going