Southern Arizona is known for its scenic landscapes, diverse ecosystems and dark night skies.
But conservationists say that those skies could be blotted out by a system of stadium lights on the border.
A report by the Center for Biological Diversity found that government contractors have installed 1,800 lights on conservation lands near the border.
So far, the lights have not been turned on, but conservationists say they could disrupt wildlife navigation, migration and reproduction.
Emily Burns of the Sky Island Alliance, a Tucson-based nonprofit, says that in some areas the lights are still being wired.
"If those lights get turned on it will be a huge problem, for the dark sky quality that many of these birds and bats need in order to follow their historic migration routes," she said.
The lights have been installed at Cabeza Prieta National Wildlife Refuge, Organ Pipe Cactus National Monument, the San Pedro River Riparian National Wildlife Refuge, the San Bernardino
Valley and San Bernardino National Wildlife Refuge.