SACRAMENTO -- Federal guidelines released Thursday for protecting seasonal wetlands favor development over species protection in a handful of fast-growing California counties.

The U.S. Fish and Wildlife Service decided that protecting all areas containing the so-called vernal pools would be too costly to the state's economy. The agency's revised guidelines are the latest version of a federal critical habitat plan that an environmental group has successfully challenged in court.

They could lead to additional housing developments in a state where the median home price is about $450,000, 2½ times the national median.

The wildlife agency says it tried to strike a balance between the pressure to build more homes in California's quickly developing Central Valley and the well-being of 15 rare species that dwell only in the shallow and temporary pools.

The habitat boundaries set by the agency exclude 23 census tracts across 11 counties for economic reasons. The agency estimated that protecting the species on those 23 tracts would mean $740 million in increased development costs, nearly 80 percent of the total estimated price tag.

Home builders are "very appreciative that the economic impact was taken into account, because it was very substantial," said Dennis Rogers, senior vice president of the Building Industry Association of Superior California. "I think it would have had a very detrimental impact on development in our area," which runs from Sacramento north.

Builders will have to protect actual species where they exist, but not the habitat where they potentially could exist in areas that were excluded from the designation, he said.

The tracts opened for development are in Butte, Fresno, Madera, Monterey, Placer, Sacramento, Shasta, Solano and Stanislaus counties.