In 1983 an interagency working group consisting of members from the Montana Department of Fish, Wildlife and Parks, Bureau of Land Management, and Lewis and Clark National Forest was formed to assess cumulative effects on grizzly bears in the area of a proposed exploratory natural gas well on the Lewis and Clark National Forest. A constituent map was developed by mapping landtypes that had been used by radio-collared grizzlies in previous studies. The influence zone, or area which a human activity influences directly or indirectly was mapped and used as a baseline to evaluate cumulative effects. Influence zones were based on research data, literature, and professional opinions of bear biologists.

Influence zones of 1 km were mapped around each open road open to four-wheeled vehicles, as well as around oil and gas drill site locations. Trails, snowmobile routes, timber activities, camping grounds, trailheads, and administrative sites were mapped with 0.5 km influence zones.Cumulative effects analyasis was done by Bear Management Zone and by constituent element.

A scoring system was used to determine the activities contribution to the cummulative effects. Each activity was evaluated for six potential effects, with each effect given a value of severity. Permanent loss of habitat was scored the most severe, direct mortality was next, lack of management potential was judged equal to reduced forage, followed by reduced cover and displacement the least severe of the activities. The effect score was then multiplied by the duration of the activity (in months) to get an impact score. The impact scores were then totaled to derive the final cumulative effect score. These numbers were ultimately used to develop a color-coded map to describe overall habitat effectivness.

Since the development of this manual system, a new generation of cumulative effect analyasis (cartographic modeling) fhas been developed that lends itself to easier updating and rapid anlyasis of alternatives. This model also includes a habitat equality factor absent from the Lewis and Clark model, and is designed for computer application through cartographic modeling. Therefore the Lewis and Clark has since stopped work on this analysis program.