SACRAMENTO (AP) — Protecting 15 rare species that survive only in seasonal pools across California will have an economic impact estimated at nearly $1 billion, mostly for the lost value of building about 1,600 homes, the U.S. Fish and Wildlife Service estimated Monday.

The agency said it is considering removing protections from areas that account for 80 percent of the projected economic loss.

Nearly 260,000 homes likely will be built over the next 20 years within habitat currently designated as critical in 35 California counties and one in Oregon. That designation is intended to protect four tiny freshwater shrimp species and 11 vernal pool plant species.

But the protections mean that about 1,600 homes will not be built, according to a draft analysis prepared for the service by CRA International, an Oakland-based consulting firm.

Overall, the protections will cost $992 million in economic loss over 20 years. Of that, $965 million relates to lost development opportunities, the consultant projected. There also would be $19.9 million in costs for transportation projects and a $10 million cost to the new University of California, Merced.

The analysis states that about half the economic cost is for protecting less than 5 percent of the critical habitat. The bulk of the cost is from lost housing development in just three counties, with an estimated impact of $374 million in Sacramento County, $154 million in Butte County and $120 million in Placer County.

Developers have long fought protections for the rare species that spring to life during winter rains and hide in the dry mud of the shallow ponds during the hot, dry summers. They argue that the protections are hindering vital housing in the fast-growing Central Valley and coastal regions. A spokesman for the California Building Industry Association had no immediate comment Monday.

The analysis discounts the many benefits of vernal pools, said Butte Environmental Council Executive Director Barbara Vlamis. The pools hold storm water and filter pollutants, she said. They also are crucial for migratory water fowl, while their organisms fulfill part of nature's food chain.

She said her organization will file its own economic projections during an upcoming public comment period.

The service has a July 31 deadline to decide whether to designate critical habitat in five counties that were dropped from a 2003 decision — Butte, Madera, Merced, Sacramento and Solano. Vlamis' organization sued to force a reconsideration and won a court order in October.

The Fish and Wildlife Service now says it will consider dropping protections in areas where development is most intense and the economic cost the highest.

The decision to drop protections in the five counties drew national attention because Deputy Assistant Interior Secretary Julie MacDonald altered the previous analysis the night before it was due, using calculations she later acknowledged to The Associated Press were flawed.

Assistant Secretary for Fish and Wildlife and Parks Craig Manson excluded the five counties using some of MacDonald's reasoning word-for-word. MacDonald later told the AP that using the correct numbers wouldn't have altered her recommendation to eliminate the five counties.

On the Net:

Read the analysis at http://sacramento.fws.gov