When infrastructure and habitat collide, there's trouble – not just for wildlife, but also for developers hoping to avoid regulatory conflict. That's why the Western Governors' Association created its Crucial Habitat Assessment Tool (CHAT), a West-wide map that ranks each state's habitat on a scale of 1 to 6 (with "1" most crucial). "If you're putting in transmission lines, siting pipelines, or building a wildlife overpass, you can find out where the most valuable habitat is before you begin planning," explains Carlee Brown, WGA's policy advisor.

Map users might notice a telling quirk: Because each state had near-total freedom in ranking its habitat, many boundary-spanning ecosystems appear far more valuable on one side of the line than the other. "Every state has different economic and political realities," says biologist Gary Vecellio of Idaho's Department of Fish and Game. "If you look at a Google Earth map of (Idaho's) Snake River Plain, you see a whole bunch of center pivots and then some tiny pockets of wildlife refugia." When that corridor hits Wyoming, however, the protected public lands around Yellowstone are shown as offering lots of high-quality habitat.

Brown says the border seams are a feature, not a bug: They demonstrate states' autonomy to set their own land-use priorities and steer developers in the right direction.