For 18 years, whenever the U.S. Fish and Wildlife Service had to decide whether a proposed development violated the Endangered Species Act, the agency applied a basic standard: Will it affect the survival of an endangered species? From now on, that’s not good enough, two federal courts have ruled.

Instead, the Fish and Wildlife Service must also consider whether developments will affect the long-term "recovery" of endangered species. The rulings came in August, in a district court case over off-road traffic in Mojave desert tortoise habitat, and a 9th Circuit Court of Appeals case over logging in spotted owl habitat.

Both environmental and property-rights activists say the rulings could fundamentally alter the way the Endangered Species Act is implemented. "A lot more projects will need to be modified, or simply not done, because they’re slowly whittling away at many species’ ability to recover," says Michael Lozeau, an Earthjustice attorney involved in the tortoise case.

"The (appeals) court took a very broad-brushed view of a very nuanced matter," says Joe Nelson, legal counsel for the National Endangered Species Act Coalition, a pro-industry group. It will put "a much higher burden on the property owner," he adds, and makes development within critical habitat "awfully difficult."

The Fish and Wildlife Service is considering whether to continue the court battle with another appeal.