Steve Hillebrand, US Fish and Wildlife Service

The proposed wall along the U.S.-Mexico border would significantly affect wildlife (see “On the web”). Most animals cannot get past walls that are hundreds of miles long and many meters tall. Some species along parts of the border where a wall already exists, such as jaguars and ocelots, suffer from dwindling populations and difficulty finding mates.

Daily access to food and water can be disrupted by walls, and wildlife populations need to migrate freely to find viable habitat as climate conditions change. Researchers worry that an expanded wall would increase the number of threatened and endangered species requiring protection under the U.S. Endangered Species Act.

Besides walls, other human activities fragment wildlife habitat, including, for example, building houses in a forest, converting tallgrass prairie to cornfields, and laying highways along mountainsides. While such activities may not always substantially shrink the overall size of a habitat, they do break it into smaller, more isolated fragments.

Fragmentation disrupts plants and animals alike. When plans arose to expand the border wall in 2006, Arizona park and wildlife managers’ pointed out that “…building a wall, along with the roads and support facilities it necessitates, would not only plow under saguaros and other fragile desert plants but scare Sonoran pronghorn and other wildlife from important sources of food and water” (Cohn 2007).

Border walls going up in other parts of the world are having similar effects. A study in Slovenia found that the over 100 miles of fence built along the border with Croatia has fragmented habitat for large carnivores, such as wolves, bears, and lynx, which rely on intact territories. “These fences represent a major threat to wildlife because they can cause mortality, obstruct access to seasonally important resources, and reduce effective population size” (Linnell et al. 2016).

Classroom activities
To start, have students read an online article with photographs and a video about wildlife and border walls (see “On the web”). Next, in Modeling the Effects of Habitat Fragmentation, students pose as members of the Habitat Fragmentation task force. They determine specific effects of habitat fragmentation on four animal species using provided data (see “On the web”). In a lesson from Penn State, students learn about the key components of habitat and the suitability of habitats for particular wildlife species.

If you can dedicate a full week to habitat fragmentation, I recommend the Ecological Society of America’s lab activity. Students are introduced to concepts of fragmentation and species assemblages (nestedness) with a focus on birds breeding in forest fragments. The lab activity culminates with poster presentations (see “On the web”).

As the planned border wall takes shape, many wildlife species will be watching.

Amanda Beckrich (aabeckrich@gmail.com) is the Upper School assistant director, International Baccalaureate (IB) diploma program coordinator, and an environmental science teacher at Christ Church Episcopal School in Greenville, South Carolina.

On the web
Biodiversity and fragmentation lab: http://bit.ly/2ldcfb6
Border wall and wildlife articles: http://wapo.st/2lY9xum, http://wapo.st/2mz95PX, http://bit.ly/2kTsewt, http://bit.ly/2jVJsZL
Ecological Society of America’s lab activity: http://bit.ly/2lnxSq7
Modeling the effects of habitat fragmentation activity: http://bit.ly/2lnsVh8
Penn State College of Agricultural Sciences wildlife habitat activity: http://bit.ly/2lnsyTL
Wildlife article and video: http://bit.ly/2kZzQkx, http://bit.ly/2lnO1f5

References
Cohn, J.P. 2007. The environmental impacts of a border fence. BioScience 57 (1): 96. https://doi.org/10.1641/B570116
Linnell, J., A. Trouwborst , L. Boitani, P. Kaczensky, D. Huber, S. Reljic, et al. 2016. Border security fencing and wildlife: The end of the transboundary paradigm in Eurasia? PLoS Biol 14 (6): e1002483. http://bit.ly/Slovenia-habitat

Editor’s Note

This article was originally published in the April 2017 issue of The
Science Teacher journal from the National Science Teachers Association (NSTA).

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