Ecological Effects of a Transportation Network on Wildlife: A Spatial Analysis of the Upper Missouri River Breaks National Monument

Thursday, January 1, 2009

The spectacular Upper Missouri River Breaks National Monument in north-central Montana, along the Wild and Scenic Upper Missouri River, was established to preserve the area's outstanding ecological, scientific, and cultural values — from its remote and undeveloped character and archaeological and historic sites to its remarkable wildlife, geologic, and paleontological resources.

Presidential Proclamation 7398, which designated the monument, requires the Bureau of Land Management (BLM) to develop a transportation plan as a component of the resource management planning process. The transportation plan is critical to protection of the monument's unique attributes. Although this monument appears to be a wild, relatively untrammeled place, hundreds of years of human travel and recreation, cattle grazing, mining, and hunting have carved innumerable roads, vehicle trails, and other linear transportation features across the landscape. Given their impacts on habitat quantity and quality, the spread of invasive plants, wildlife mortality, soil erosion, air quality, restoration projects, and archaeological and cultural sites, these transportation features must be carefully managed and minimized in accordance with the monument's preservation purpose. The immediate need to resolve transportation issues in this monument cannot be overstated. It reflects a key management challenge facing the BLM in other national monuments and conservation areas that the agency manages across the country.

Spatial analysis techniques can greatly assist the BLM and the public in the design of a transportation plan that minimizes impacts on the ecological and cultural resources of protected areas, while still allowing adequate access. Spatial analysis is predicated on the recognition that roads, vehicle trails, and other linear transportation features must be managed as a cohesive and interwoven system embedded within a landscape and not as a disjointed aggregation of individual access points.

This report presents three landscape fragmentation analysis methods that the BLM can — and should — use to plan ecologically viable transportation networks. The methods include density analysis of existing transportation network features, buffer analysis to examine the effect zone of the transportation network, and core area analysis to identify habitat that remains unaffected by the transportation network. We applied these analyses to Upper Missouri River Breaks and, in this report, discuss the implications of the results for management of the monument, emphasizing potential impacts on wildlife.

We found that wildlife populations are threatened by landscape fragmentation attributable to existing transportation features. Forty percent of occupied elk habitat in the monument is laced with routes at a density of 0.8 miles/mile. Scientific literature indicates that elk habitat is completely lost at this density. Nearly 100 percent of land in the monument is within two miles of a route. It is known that Greater Sage-grouse within two miles of features constructed by people, including routes, have lower nest initiation rates. More than 86 percent of the 791-mile monument lies within one mile of a transportation feature, leaving just 111 miles available as potential habitat for wildlife.

The results of our analyses point out the need for route closures to mitigate current and potential impacts of the transportation network on the monument's resources. This report does not make specific route closure recommendations, but it does present a list of actions to ensure that the transportation plan will enhance, not degrade, the values of the monument. Our recommendations include:

  • The BLM must develop a transportation plan as a key element of the monument's Resource Management Plan, emphasizing protection of the objects of interest articulated in the proclamation and key resources that provide an overall measure of the monument's health and integrity. The transportation plan should consist of two components:
  1. a baseline transportation network and
  2. an adaptive ecosystem management framework to guide all future transportation management decisions.
  • In developing the baseline transportation network, the BLM should conduct a habitat fragmentation analysis that overlays spatial data for objects of scientific and historic interest listed in the monument's proclamation and other key resources with transportation analysis layers similar to those generated for this report. "Wildcat" routes and roads or other transportation features that have adverse impacts on the objects and resources or otherwise cause unnecessary or undue degradation of the landscape must be closed.
  • Relevant literature concerning the impacts of routes on wildlife should be used to aid interpretation of the results of the habitat fragmentation analysis.
  • All routes designated as open should be geographically distributed in a manner that reduces habitat fragmentation and human contact with sensitive resources to an acceptable minimum threshold.
  • Once routes are identified for closure, the Resource Management Plan should include a detailed route closure and restoration strategy. Plan implementation should be consistent with the adaptive ecosystem management framework and include enforceable timelines and a stated commitment to devote a portion of staff time and annual budgets to restoration of closed routes.

Spatial analysis, using mapping software and up-to-date ecological data, is a manageable and essential part of crafting transportation plans that protect wildlife and recreation opportunities and other ecological, scientific, and cultural values. The use of spatial planning analysis in Upper Missouri River Breaks National Monument clearly demonstrates the dramatic impacts of the existing transportation network by illustrating how the network causes fragmentation of critical wildlife habitat. This important information can help guide the BLM and the public in making informed choices for transportation management. We believe it is essential for the BLM to incorporate spatial analysis as a standard step in transportation management planning.