With the prospect of a US-Mexico border wall looming, research and reporting on the ecological impacts of walls is both important and timely. Reporting in BioScience on such barriers’ known effects on wildlife, science journalist Lesley Evans Ogden describes the potential effects of the proposed structure along the 2000-mile US-Mexico border. “If the wall is completed, it will create a considerable biodiversity conservation challenge—one unlikely to disappear anytime soon,” she writes.