During the late 1930’s, Aldo Leopold witnessed a striking contrast along the narrow boundary between the United States and Mexico. He later described Mexican ecosystems as a “lovely picture of ecological health” and those same ecosystems north of the U.S. - Mexico border as “so badly damaged that only tourists and those ecologically blind, can look upon them without a feeling of sadness, and regret.” On this the hundredth centennial of Leopold’s arrival in the Southwest, the difference has waned but has not completely vanished. Within Mexico’s Janos – Casas Grande region lays the largest black-tailed prairie dog complex within North America, reminiscent of past ecosystems just north of the border. Now a Biosphere Reserve, collaborative efforts between Mexican and U. S. scientists are reconstructing the area’s ecological history and identifying key ecosystem properties maintaining grasslands and essential ecosystem services.