Humans are spectacular architects. Some of the most prominent and renowned architectural works in history have been in the form of walls designed to separate people and delineate the borders of different countries. The Great Wall of China, for example, is the longest man-made structure in the world, measuring over 13,000 miles in total length. It was constructed to fortify China’s northern border. Parts of the wall are nearly 3,000 years old (Britannica). The wall transects various habitat types, including deserts, grasslands, mountains, and plateaus.
Border walls are a predictable side effect of an increasingly globalized world. If not designed with wildlife and habitat conservation in mind, they can contribute to serious environmental degradation. For some species, walls can be just as detrimental as pollution, sea level rise, and deforestation. In a study published in 2003, a team of Chinese scientists found that The Great Wall of China impeded gene flow between plant species (Nature). It stands to reason that the natural movements of plants and animals are inhibited by the construction of large walls that render surrounding habitats impassable.
The U.S.-Mexico border stretches a length of 1,954 miles, and about 40% of it has some kind of physical barrier. The expansion and reinforcement of the U.S.-Mexico border wall has been one of President Donald Trump’s main agenda items during his campaign and presidency. He has ordered the construction of a “great wall” consisting of an impenetrable barrier made of concrete and steel (BBC). He has pledged to build at least 500 miles of new barriers by early next year. The U.S.-Mexico border wall is one of the largest federal infrastructure projects in U.S. history (The Washington Post). So far, only five miles of new walls have been added during the Trump administration (San Antonio Express-News).
The expansion of the U.S.-Mexico border wall spells disaster for many animals. Breeding and migratory patterns will be disrupted, genetic diversity will be reduced, and critical habitat will be fragmented and destroyed. The seasonal migration patterns of wildlife can be critical to their survival. A study by the Center for Biological Diversity identified 57 endangered species, 24 threatened species, 10 species under consideration for protection, and two species of concern (the golden and bald eagle) that have ranges near or crossing the U.S.-Mexico border. According to the EPA, more than 700 migratory species of birds, mammals, and insects use the borderlands during their migrations. Many species like Mexican gray wolves, jaguars, and ocelots may be driven to extinction (Animal Legal Defense Fund). The bottom line is that ecological boundaries rarely align with political boundaries, and biodiversity tends to suffer as a result.
There are many other areas in the world where border fencing has been erected across hundreds of miles of habitat space. Between India and Bangladesh, India is constructing a barbed wire fence about 2,000 miles long. Saudi Arabia built a 550-mile wall between Saudi Arabia and Iraq. Between Morocco and Western Sahara, a 1,700-mile sand wall is surrounded by millions of land mines (USA Today). In addition to the habitat destruction and fragmentation caused by the walls themselves, there are also indirect environmental effects resulting from the enforcement roads, noise, light, pollution, and increased levels of human disturbance and infrastructure in border areas.
There are a number of ways to construct border walls so they are less damaging to the environment. Ideally, we would allow natural ecological barriers, such as rivers and mountain ridges, to mark our boundaries whenever possible. Wildlife crossings and bridges can be incorporated to allow animals to pass safely. Planning for the largest wildlife crossing in the world, the Liberty Canyon Wildlife Crossing, is currently underway to create a safe passage for mountain lions and other wildlife near Highway 101 in California (National Wildlife Federation). This crossing can serve as a global model for urban wildlife conservation and the technique can be applied to border walls. Wildlife crossings can be combined with technologies such as drones, cameras, and sensors to reinforce border security without the need for a physical barrier in many areas. Going a step further, neighboring countries should work together across political lines to develop border projects that support wildlife and habitat conservation and ecosystem connectivity.
