Road Ecology

The ecology of roads and their effects has been a primary area of emphasis for me. One of the most fundamental questions that ecologists and managers can ask is how to restore connectivity to fragmented landscapes. The solution in the U. S. and Canada lies not only with ecologists but with North American Departments of Transportation. There is perhaps no greater anthropogenic influence on landscape connectivity than roads. Roads have both direct (animal mortality) and indirect (loss of landscape permeability resulting in fragmentation) effects. In effect, how roads are constructed will in large measure determine if the landscape is permeable, semi-permeable, or impermeable to animal movement; in other words the degree of landscape fragmentation as perceived by individual organisms. Context sensitive road design and maintenance necessarily incorporate a linked mitigation effort at landscape scales. In addition to a co-authored book ROAD ECOLOGY: SCIENCE AND SOLUTIONS, published by the Island Press in 2003, my students and I have addressed the direct effects of roads through directed research, peer-reviewed publications and reports, and presentations at national and international conferences.

Road mitigation for large animal mortality has often taken the form of animal exclusion with the construction of high (often 2.4 m or higher) fences. Typically, fences are combined with underpasses or overpasses to allow deer and other animals to access other parts of their range and hence maintain some semblance of landscape connectivity and permeability. However, a common assumption is that fences, once constructed, are ‘deer-proof”. This is seldom the case. Lack of maintenance, as well as erosion, earth slumping, and illegal breeching all compromise the integrity of fences. Deer, elk and other animals do access the highway right-of-way (ROW) and are often killed. My students and I have investigated the effectiveness of the traditional steel one-way escape gates and compared them with newly developed and tested earthen escape ramps. We found that ramps were from 8-12 times more effective in allowing deer and elk to escape the ROW. A valuation of amortizing the costs associated with the retro-fit construction of earthen ramps (approximately $2000 each) suggested that even assuming a very conservative reduction in mortality (2%), costs would be amortized in little over 2 years. This work has been transmitted as a M.S. thesis (HAMMER, M. L. 2002. EFFECTIVENESS OF EARTHEN ESCPE RAMPS IN REDUCING GAME MORTALITY IN UTAH, M.S. THESIS, UTAH STATE UNIVERSITY, LOGAN 65 p., a final report, and a publication is in the last stages of preparation. This work is a continuation of work begun earlier that included 2 research efforts described and listed below.

My students and I conducted a study that addressed mitigation for direct mortality effects of roads. Highway mortality of deer (Odocoileus sp.) is a nationwide concern. In 1991, 538,000 verified deer-vehicle collisions occurred nationwide; the actual number could be twice that amount. Estimates from 1995 (Conover et al. 1995: Wildlife Society Bull. 23:407-414 suggested that as many as 1.5 million deer may be killed annually in the United States. Property damage to vehicles ($1500-1700 average per vehicle), human injuries (4,650 from Michigan, Wisconsin, Minnesota, Illinois, and Iowa in 2000 alone (Knapp, U. Wisconsin, personal communication – nationwide figures not available but very significant) and fatalities (~200 per year nationwide), as well as potential impacts to local deer populations occur from deer-vehicle collisions. This study was conducted at the site of the newly constructed Jordanelle Reservoir near Park City, Utah. Area roads were relocated due to inundation of existing highways. Preconstruction road-kill was documented to be 0.29 kills/km. Annual road-kill levels of 278 (5.9 kills/km) and 119 (2.5 kills/km) deer occurred post-construction along the new roads from October 1991 to October 1993. Even though there was a 64.2% reduction in observed deer density, second year mortality was still 9 times the pre-project kill. Traffic characteristics, road alignment, and vegetative and topographic features were described relative to mule deer kill locations and significantly suggest the need for context sensitive planning and road construction. Traffic volume, slope, and right-of-way (row) vegetation cover were positively correlated with kill locations. In this study we assessed the effects of vehicle mortality on deer population dynamics and concluded it was inversely density dependent and partially additive, removing between 5.6 and 17.4% of the population annually that would have survived otherwise. This information is being used by the Utah Division of Wildlife, the U.S.F.W.S., the Central Utah Project, and the Utah Department of Transportation as a basis for locating road crossing structures and was the basis for the project described below that involved an evaluation of the effectiveness of a newly-designed system of highway crosswalks at reducing mule deer (Odocoileus hemionus)-vehicle collisions. The following M.S. thesis resulted: (ROMIN, L. 1994. FACTORS ASSOCIATED WITH THE HIGHWAY MORTALITY OF MULE DEER AT JORDANELLE RESERVOIR, UTAH. M.S. THESIS, UTAH STATE UNIVERSITY, LOGAN 75 p.) Here is an executive summary. Additional papers and presentations are listed below.

The Utah Department of Transportation constructed and my students and I tested the effectiveness of the newly designed ‘at-grade’ big-game crosswalks and their associated structures. The experimental crosswalks were substantially cheaper than conventional overpasses and underpasses. If effective, they could find nationwide application in helping to minimize the human, economic, and environmental losses that result from deer-vehicle collisions at substantially lower cost than current mitigative measures. We team developed 3 competing simulation models in which highway losses operated in a strictly additive, partially compensatory/additive, and strictly compensatory manner. The partially compensatory/additive model most closely tracked observed population dynamics. Annual variation in demographic parameters offset the impacts of highway mortality at big population densities, however at low densities, highway mortality was severe enough to drive declining population trends. Monte Carlo error analyses were used to check results. The analyses suggested that with no reduction in highway mortality, there was a 90.7 % chance of population decline. With 40, 60, and 80% reductions in mortality, the likelihood of a declining population was 62.4, 41.8, and 22.8%, respectively. The influence of variable climatic conditions was also evaluated. We concluded that: a) mitigation efforts should target greater mortality reductions to help insure that desired population changes occur; and 2) at-grade crossing structures were not appropriate for other than relatively narrow secondary roads. The M.S. thesis resulting from this work was titled: (LEHNERT, M. E. 1996, MULE DEER HIGHWAY MORTALITY IN NORTHEASTERN UTAH: AN ANALYSIS OF POPULATION-LEVEL IMPACTS AND A NEW MITIGATIVE SYSTEM. M.S. THESIS, UTAH STATE UNIVERSITY, LOGAN 82 p). The data from these studies are being used currently by the Utah Department of Transportation in their mitigation measures for high deer kill areas.

John A. Bissonette
John A. Bissonette

Wildland Resources Dept. College of Natural Resources
Utah State University
Logan, Utah 84322-5290
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