Nature Divided, Scientists United

Human pressures on the natural world come in many forms. Top among these pressures are large-scale human development projects that impose barriers on species movement.

For example, physical barriers can dissuade animals from accessing food, water, mates, and other critical resources. These barriers can block annual or seasonal migration and dispersal routes. Fragmented populations may suffer from reduced genetic diversity and face greater extinction risks.

In a recent communication to government officials due to be published in the next issue of BioScience, a multitude of scientists and conservationists including E.O. Wilson highlighted these dangers with a specific focus on the wildlife barrier created by the wall being constructed on the border between Mexico and the United States.

“Like any large-scale development,” the authors write in the article spearheaded by Defenders of Wildlife, “construction of the wall and associated infrastructure, such as roads, lights, and operating bases, eliminates or degrades natural vegetation, kills animals directly or through habitat loss, fragments habitats (thereby subdividing populations into smaller, more vulnerable units), reduces habitat connectivity, erodes soils, changes fire regimes, and alters hydrological processes (for example by causing floods).”

The article, “Nature Divided: Scientists United,” highlights the dual concerns that the wall will harm wildlife populations by eliminating, degrading and fragmenting habitats and damage positive binational scientific collaborations. The new barrier threatens many contiguous habitat corridors, including the Sonora Desert, Sky Islands, Big Bend and Lower Rio Grande, and threatens ongoing scientific studies, including a binational aerial census of the endangered Sonoran pronghorn.

The article asks government officials to “mitigate as completely as possible any environmental harm resulting from projects,” including “foregoing physical barriers in places with high ecological sensitivity, such as cross-border corridors or critical habitats for endangered species.” To learn more visit

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