Cross-border or transboundary conservation happens when countries sharing natural resources, plants, and animals work together to research and manage these valuable resources. Cross-border conservation is relevant on a huge scale. There are over 165,000 miles of national land boundaries worldwide. That’s enough to circle the Earth almost seven times! Just under 2,000 of those miles are shared by Mexico and the United States.

We don’t just share a lot of land along those 2,000 miles, we share some very important ecoregions too. Two of the world’s most unique and biodiverse regions, known as biodiversity hotspots, cross over the U.S.-Mexico border. An immense number of species span across our border. For example, of all the native plant species growing in the state of Baja California, Mexico, about three-quarters of them also grow in the United States.

Physical barriers along borders can have devastating consequences for species but these barricades are not the only issue. Conservation measures are often restricted to administrative boundaries.

What does it mean for a plant, animal, or watershed to be more protected on one side of the border than the other? Asymmetry in cross-border conservation can put species and ecosystems at risk through loss of habitat connectivity and by diluting effort and investment. Climate change further complicates the situation as species ranges continue to shift.

Research and conservation approaches that are geographically limited give us an incomplete picture that will lead us to an incomplete solution. While there are formidable challenges to cross-border collaboration such as differing policy, languages, governance, and resources, we also know that it works.

For example, collaboration between botanists in San Diego and Baja California has been crucial to understand the distribution of rare plants such as San Diego thornmint (Acanthomintha ilicifolia). Thanks to binational collaboration, this species was recently registered in the municipality of Tijuana for the first time in four decades. These new thornmint records will help create more compatible conservation strategies for the plant on both sides of the border. And as a huge bonus, one of these trips even led to the discovery of a new species (Astragalus tijuanensis) and new variety (Astragalus brauntonii var. lativexillum) of Astragalus, which are plants in the pea family.

The California red-legged frog (Rana draytonii) was once a common species in Southern California—until it wasn’t. Pressures including land-use change, non-native predators, and disease contributed to the disappearance of this species from the region. Cross-border collaboration has given hope for the return of this frog to SoCal. This effort has relied on Baja California collaborators to restore habitat to build resilience and bolster frog populations in Baja so that frog eggs can be translocated across the border to Southern California.

Cross-border collaboration isn’t just for researchers and government officials. The quality of life of people on all sides of borders depends on the same things—healthy ecosystems, clean air and water, and the participation of everyone is key.

Fortunately, there are simple things anyone can do to contribute. Apps like iNaturalist connect us despite physical borders. People spending time outdoors can snap and upload photos of plants, fungi, and animals from their smartphones, and their photos will be identified by experts and added to a global database. Sharing your observations creates quality data for researchers working to better understand and protect nature. Scientists can’t be everywhere, so sharing your observations from areas along the border will help them learn more about the binational distribution of species, and we will be a little closer to achieving their protection.

Authored by:
Michelle E. Thompson, Ph.D., Exequiel Ezcurra Director of Conservation Biology, San Diego Natural History Museum
Mariana Delgado Fernández, Ph.D., Environmental Consultant, Ecotono Consultoría Ambiental

Read the blog in Spanish. 

Posted by Dr. Michelle E. Thompson, Exequiel Ezcurra Director of Conservation Biology.