Horses and Packstock Unlikely to spread Invasive Plants Along Trails.

Dr. Stith T. Gower of the University of Wisconsin, Madison, prepared the following two studies with assistance from the American Endurance Riders Conference. 1) Dr. Gower’s study on “Horses and Invasive Plants, The Western USA Study” and 2) Are horses responsible for introducing non-native plants along forest trails?

Dr. Gower’s studies indicate that horses and pack stock are unlikely, if at all, to spread invasive weeds along trails under the conditions he studied in both eastern and western United States. For example, the 2013 study concludes the with the following:

“The 0% germination and establishment rate of weeds from hay, manure and hoof debris plots on the horse trails at the nine study sites illustrates the difficult physical and environmental conditions that seedlings experience during the critical germination and establishment phase.”

Consequently, although the science has found that horses and pack stock are capable of excreting seeds (both native and non-native) along backcountry trails, such seeds face harsh conditions and are highly unlikely to germinate. Based on conditions studied by Dr. Gower, the use of horses and pack stock should not be viewed as vectors for the spread of invasive or noxious weeds.

Click to view Dr. Gower’s study on Horses and Invasive Plants, The Western USA Study” reprinted from the April 2013 Endurance News or view the original document published by Dr. Gower here.

Stith Tom Gower Ph.D.
Area of Expertise: Whole-system Analysis of Forest Ecosystems; Education Innovation
B.S. Furman University (1980)
M.S. North Carolina State University (1983)
Ph.D. University of Washington (1987)