Straight from the horse’s, er, scientist’s mouth

Free-roaming horse advocates claim that feral horses cause no ecological damage, and are even good for the environment. Nothing could be further from the truth. Feral horses cause extensive damage to native habitats and wildlife. Credible info is readily available from scientific journals and respected wildlife organizations, and it’s worth seeking out. Here’s a quick look at just some of it:

  • A study by research ecologists at the USGS Northern Rocky Mountain Science Center found that, “high numbers of feral horses reduce vegetation cover and plant diversity, fragment shrub canopies, alter soil characteristics, and increase the abundance of invasive species, thus reducing the quality and quantity of habitat.”1
  • At the Sheldon National Wildlife Refuge in Nevada, which, like Placitas, is a fragile, high desert ecosystem, field monitoring by researchers documented that feral horse and burro populations caused severe degradation of 44 percent of the refuge’s riparian zone and 80 percent of its springs.According to the Refuge, “conflicts over scarce water in this desert environment include trampling of vegetation along stream banks and at springheads, physical exclusion of other species by dominant stud horses and burros, and contamination from feces and urine. Horses and burros also cause habitat degradation by trampling and destroying vegetation in the upland areas…Removal of this natural cover allows native predators to more easily locate and kill the species that depend upon that cover to hide…”3
  • A study in Anza-Borrego Desert State Park in California found that the hooves of feral horses compact the soil, which reduces rainwater filtration and root growth of plants.4 This leads to increased rainwater run-off and soil erosion. This is particularly harmful for desert soils, in which the nutrients needed by plants are concentrated within the top few centimeters. Ultimately, the combination of soil compaction, erosion, trampling, and vegetation loss harms many plant, bird, small mammal, and macroinvertebrate (insect and crustacean) communities.

There’s little debate in scientific circles. When free-roaming horses are allowed to overpopulate and overgraze, it comes at the expense of native wildlife—large and small, winged, clawed, scaled and furred.

A tip of the hat to Jon Couch of Coronado Soil and Water Conservation District, who provided information for this post.


1 Beever E, Tausch RJ, Brussard PF. Characterizing grazing disturbance in semiarid ecosystems across broad spatial scales using multiple indices. Ecological Applications. 2003;13:119-136.

2 Sheldon National Wildlife Refuge. Implementation of CCP Decision to Remove Feral Horses and Burros. Questions and Answers. August 2013. US Fish and Wildlife Service. Available at:

3 Sheldon National Wildlife Refuge. Horse and Burro Management. July 11, 2014. US Fish and Wildlife Service. Available at:

4 Ostermann-Kelm SD, Atwill EA, Rubin ES, et al. Impacts of feral horses on a desert environment. BMC Ecology. 2009;9:22.