The Mexican Environment and Natural Resources Secretariat (that's their EPA and Fish and Wildlife Service all rolled into one) released a study entitled "A Barrier to Our Shared Environment: The Border Wall between Mexico and the United States". According to the report, the border wall that is being constructed by U.S. government contractors could cause floods, the extirpation of 11 animal species with the interruption of their migration routes, and the fragmentation of flora and fauna populations. The jaguar, the Mexican gray wolf and the bison are among the species that would be adversely impacted.
h/t treehugger
see also, a Grist story from October on this same issue
