The ecological, economic and social issues created by habitat fragmentation by highways are well documented in a variety of sources. The Wildlife-Vehicle Collision Reduction Study: Report to Congress (FHWA 2008; online at: http://www.fhwa.dot.gov/publications/research/safety/08034/08034.pdf) provides an overview of the extent and serious implications of wildlife-vehicle collisions. The average cost of a single WVH with a deer was estimated to be over $6,600, with an estimated total annual cost of $8,388,000,000 for all WVCs. This cost does not address the additional and harder to define economic and social costs related to the effects of habitat fragmentation such as reduced or altered ecological functions, effects on plant and wildlife productivity and changes in biodiversity.
Table 5: Summary of Estimated Costs
Wildlife-Vehicle Collision for a Deer, Elk, and Moose
Description |
Deer |
Elk |
Moose |
Vehicle repair costs per collision |
$1,840 |
$3,000 |
$4,000 |
Human injuries per collision |
$2,702 |
$5,403 |
$10,807 |
Human fatalities per collision |
$1,671 |
$6,683 |
$13,366 |
Towing, accident attendance and investigation |
$125 |
$375 |
$500 |
Monetary value animal per collision |
$2,000 |
$3,000 |
$2,000 |
Carcass removal and disposal per collision |
$50 |
$100 |
$100 |
Total |
$8,388 |
$18,561 |
$30,773 |
Source: Wildlife-Vehicle Collision Reduction Study: Report to Congress (FHWA 2008).
The analysis of cost effectiveness for a mitigation measure attempts to determine if the investment is worth the cost in terms of the measures performance. Based on the data in Table 3 reducing WVCs has a direct economic return; however, practitioners need to understand if the return offsets the cost of implementing and maintaining the measures required to achieve that goal, and which measures may achieve that goal with the least cost. Unfortunately, cost-benefit analyses for mitigation measures are rare (Huijser et al, 2009).
The NCHRP Report 615 (2008) report examined the research priorities for the evaluation of wildlife crossings and discussed the need for the development of procedures for estimating the cost-benefit and effectiveness of crossing structures to reduce wildlife-vehicle collisions. Information regarding the cost effectiveness of various mitigation solutions to offset habitat fragmentation impacts has only recently been compiled to address wildlife permeability (connectivity). These measures, such as underpasses or overpasses, typically require large investments in highway infrastructure. A summary of the estimated cost-benefit of measures to reduce Deer-Vehicle Collisions (DVCs) and improve wildlife permeability was assembled as part of the Wildlife-Vehicle Collision Reduction Study (FHWA 2008) and is presented in Table 6. In general, under and over passes and fencing were found to be cost-effective methods to reduce DVCs.
Table 6: Summary Cost-Benefit of Mitigation Measures for Five DVCs per Km per Year |
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Mitigation measure |
Cost |
% DVC |
Benefit |
Balance |
Standard warning signs |
$18 |
0% |
$0 |
-$18 |
Enhanced wildlife warning signs |
$249 |
? |
? |
? |
Seasonal wildlife warning signs |
$27 |
26% |
$10,904 |
$10,878 |
Animal detection systems (ADS) |
$31,300 |
82% |
$34,391 |
$3,091 |
ADS linked to on-board computer |
?* |
82% |
$34,391 |
? |
On-board animal detectors |
$2,225* |
? |
? |
? |
Vegetation removal |
$500 |
38% |
$15,937 |
$15,437 |
Deer reflectors and mirrors |
$495 |
0% |
$0 |
-$495 |
Deer whistles |
$23.5* |
0% |
$0 |
? |
Carcass removal |
$250* |
? |
? |
? |
Population culling |
$2,508 |
50% |
$20,970 |
$18,462 |
Relocation |
$10,260 |
50% |
$20,970 |
$10,710 |
Anti-fertility treatment |
$61,702 |
50% |
$20,970 |
-$40,732 |
Fence (including dig barrier) |
$3,760 |
87% |
$36,488 |
$32,728 |
Boulders in right of way |
$2,461 |
? |
? |
? |
Long bridges |
$781,250 |
100% |
$41,940 |
-$739,310 |
Long tunnels or long bridges |
$1,500,000 |
100% |
$41,940 |
-$1,458,060 |
Fence with gap and warning signs |
$3,772 |
0% |
$0 |
-$3,772 |
Fence with gap and crosswalk |
$5,585 |
40% |
$16,776 |
$11,191 |
Fence with gap and ADS |
$9,930 |
82% |
$34,391 |
$24,461 |
Fence with underpasses |
$5,860 |
87% |
$36,488 |
$30,628 |
Fence with overpasses |
$26,485 |
87% |
$36,488 |
$10,003 |
Fence with under- and overpasses |
$7,510 |
87% |
$36,488 |
$28,978 |
Assumes 1 km with 5 DVCs per year.
* Costs not in dollars/km/year, but in a different unit; see text.
? = Unknown or uncertain.
Source: Wildlife-Vehicle Collision Reduction Study: Report to Congress (FHWA 2008).
Huijser et al (2009) presented a method for calculating the cost-benefit of thirteen mitigation measures (structures and other methods aimed at reducing wildlife-vehicle collisions) for large ungulates. The method incorporates cost factors such as construction and maintenance cost of structures and devices over their useful lifetime. The authors also address the effectiveness of types of approaches in terms of the percentage reduction in wildlife-vehicle collisions attributed to different approaches. This information was incorporated into Table 3 where appropriate to address estimated costs of mitigation solutions.
Similar studies of the cost effectiveness of patch-based mitigation approaches to reduce the effects of habitat fragmentation are not available, though the literature for assessing the success of wildlife habitat restoration and wetland mitigation in meeting performance standards is readily available.
While the long-term cost benefits and savings from reducing WVCs using different approaches alone is compelling, additional benefits and savings from habitat fragmentation impact reduction may be achieved. The value of the benefits derived from maintaining ecosystem services, biodiversity, aesthetics, and recreation use attributable to habitat fragmentation reduction are not as well defined as for WVCs and can be an area for further research.