The construction of physical barriers along the U.S.–Mexico border, including proposed expansions through southern Arizona, has raised concerns among scientists, conservationists and local communities because of its potential effects on wildlife, ecosystems and natural migration patterns.
“It’s super concerning that with the technology we have available today we are using a type of border security that is so detrimental to wildlife,” said Susan Malusa, a Catholic biogeographer in an interview with Inside Climate News.
A key issue is that sections of border fencing and walls can sever wildlife migration corridors that many species rely on to move between habitats in the United States and Mexico. The San Rafael Valley in southeastern Arizona, for example, is recognized as one of North America’s most biodiverse regions and a crucial pathway for species like jaguars, ocelots, pronghorn, mountain lions and other mammals, according to Inside Climate News. If new wall segments replace low vehicle barriers or open terrain, animals may be unable to cross from one side to the other, fragmenting populations and isolating genetic diversity.
Research from 2024 shows that border wall barriers significantly reduce wildlife crossings compared with more permeable barriers. One study found that only about 9% of wildlife interactions with a border wall resulted in successful crossings, compared to much higher rates where vehicle barriers existed. This evidence suggests that the presence of a continuous wall greatly hinders natural movement patterns for large animals, including bears and mountain lions.
Across the broader U.S.–Mexico border region, scientists have documented that barrier structures affect hundreds of species by reducing access to food, mates and seasonal habitat transitions.
“As many as 40 species have been absent in the last year there as the additive effects of border wall construction, pumping, and dynamiting exacerbated other long-term stressors, like climate change, and pushed the ecosystem to the breaking point,” ecologist Gary Nabhan stated in Audubon magazine’s winter 2020 Edition.
In some cases, pollinating insects and ground-level birds, which cannot easily fly over tall and densely constructed walls, may see disruptions to their life cycles, potentially affecting broader ecosystem services such as plant pollination and soil health.
The environmental impacts are not limited to animal movements. Infrastructure associated with wall construction often involves clearing vegetation, extracting groundwater for concrete production or construction processes and building access roads. In sensitive desert and grassland areas, water sources that support diverse wildlife can become restricted or depleted, altering the natural distribution of species and further stressing ecosystems in a region already affected by drought and climate variability.
Due to the expedited building process authorized by the Trump administration, concerns persist regarding how comprehensive assessments of ecological harm are being conducted before construction begins.
The combined effects of barriers and their supporting infrastructure illustrate how large physical fences and walls intersect with ecological systems, potentially changing the way species interact with their environments over long time spans. Scientific literature on international border barriers generally notes that such large linear obstacles tend to fragment habitat, reduce gene flow among populations and restrict access to important resources, all of which can increase the risk of local extinctions and decrease biodiversity if not properly mitigated.