UPDATE: An error in this story was corrected on 5/29/09.

Spaceships in science fiction movies, such as the new (and the old) Star Trek, often employ a defensive device known as the "shield" or "force field."

As any fan knows, when a spaceship activates its force field, it creates an impenetrable buffer zone extending outward from the ship, effectively blocking the enemy's approach and its weapons.

The same idea is deployed by the environmental movement in the West. In a classic example, a national park or wilderness area that is designated a "Class 1 Airshed" (a guarantee of air quality) effectively has a force field that can extend hundreds of miles. Environmentalists use it to try to block distant generators of pollution, such as coal-fired power plants. They argue that the pollution should not be allowed because it would drift into the Class 1 Airshed.

With force fields like that, environmentalists want to leverage protected areas, effectively extending their boundaries beyond the official lines on the map. Lately, they're doing it more often and on a larger scale.

In Arizona, there is an attempt to create a force field around Grand Canyon National Park, protecting it from uranium mining. President Bush's Bureau of Land Management approved more than 1,000 mining claims within 10 miles of the park, and Obama's BLM continued the practice, granting additional claims near the park in late April. Companies have rushed in to do exploratory drilling. Though the actual mining would be outside the park, it poses a threat because any radioactive runoff would flow down to the park's streams and ultimately into the Colorado River in the canyon bottom.

Three groups (the Center for Biological Diversity, Grand Canyon Trust and Sierra Club) are challenging the uranium claims with a lawsuit. They want Interior Secretary Ken Salazar to ban new mining claims in a huge buffer zone (1 million acres outside the park). They also helped persuade the U.S. House of Representatives Natural Resources Committee to pass an "emergency resolution" calling for the buffer zone last June 25. (Congressional committees and the Interior secretary have such power thanks to the 1976 Federal Land Policy and Management Act, environmentalists say.)

Meanwhile, Arizona Rep. Raúl Grijalva, D, wants Congress to pass the Grand Canyon Watersheds Protection Act to ban mining in the same 1 million-acre buffer zone. That could be a template for more laws creating similar force fields elsewhere. "This issue speaks to the need for substantive public-land law reform," says Taylor McKinnon of the Center for Biological Diversity.

In Utah, there is a force field around national parks, defending them against about a hundred oil and gas leases proposed last year by Bush's BLM. Like the uranium claims, the proposed leases were near (but outside) the parks' boundaries. And again the popularity of the parks was leveraged outward against industry.

If the oil and gas leases were developed, environmentalists argued, they would ruin the viewsheds -- the scenery visible from the parks -- as well as the airsheds, watersheds and natural quiet (silence-sheds). The leases were "right next to the crown jewels of the national park system," says Steve Bloch, a Southern Utah Wilderness Alliance leader. Seeing gas wells in the distance and hearing the noise "would've affected the experiences of people in the parks," says Bill Hedden, head of Grand Canyon Trust. So environmentalists and the National Park Service successfully pressured the BLM and Salazar to call off most of those leases.

Force fields are also being deployed against mine proposals near wilderness areas, and against wind and solar electricity lines proposed near wildlife refuges and other sensitive areas.

Environmentalists are also pushing legal actions that claim the ice-dependent polar bear and other endangered species are harmed by all generators of global-warming gases. They expect to win that argument in court, even though Salazar announced May 8 he doesn't want to apply the Endangered Species Act so broadly against climate change (continuing the Bush administration's reluctance). Basically, the enviros are trying to establish a planetwide buffer zone around a few vulnerable species that have limited ranges. That's an attempt to create an all-encompassing real-life force field.