Peirson's milk vetch flowering at Algodones Dunes, California. (USFWS Photo)

With support from Carlsbad Fish and Wildlife Office Project Leader, Jim Bartel, four biologists, Jeremiah D. Groom, Lloyd B. McKinney, Lianne C. Ball and Clark S. Winchell recently published a paper, Quantifying off-highway vehicle impacts on density and survival of a threatened dune-endemic plant, in the science journal Biological Conservation.

Maintaining science excellence and expertise within the Fish and Wildlife Service is critical to the Service’s missions.  This paper is one of many that have been published by Service biologists since the creation of the Office of Science Excellence and a concurrent reemphasis on supporting specific activities that help maintain scientific expertise. 

This study examines the impact of OHVs on Astragalus magdalenae var. peirsonii (Peirson’s milk-vetch), one of several species restricted within the United States to the Algodones Dunes, California. This dune system attracts many OHV enthusiasts annually, and there have been several investigations into determining the impact of OHVs on Peirson’s milk-vetch, some with seemingly contradictory conclusions. Groom, et al’s objectives were to quantify how much the plant’s densities differed between high- and low-OHV use areas and determine whether OHV impact was a credible factor for affecting plant density. The study found that density estimates from one of the study areas recently closed to OHVs were surprisingly large, which may suggest that periodic closure of occupied habitat during favorably wet years would assist in ensuring Peirson’s milk vetch productivity and persistence. The researchers indicate that an improved understanding of this phenomenon may point to a dunes-wide management strategy that would allow OHV activity to coexist with this plant.

In addition to furthering the Service’s goal of maintaining science excellence, the authors pursued a cross program and cross agency approach to conducting their study.  Working closely with Bureau of Land Management staff, the authors were able to gain useful comments on the study proposal and help with field logistics.  In addition, Daniel Gomez, Christopher Schoneman, and the rest of the staff at the Sonny Bono National Wildlife Refuge helped with the effort by providing OHVs to gain access to remote areas.