With global warming threatening to raise sea levels, environmental groups are challenging the wisdom of spending millions of dollars to put sand on area beaches -- especially if it is only going to wash back out to sea.

The world's oceans rose throughout the last century as the planet gradually warmed and the warmer sea waters expanded, scientists say.

And the melting ice sheets on Greenland and elsewhere are expected to dramatically accelerate the rate of rise between now and 2100.

It is against that backdrop that the San Diego Association of Governments, a regional planning agency, is launching an environmental study this summer to set the stage for a 2012 beach restoration project.

That project would be patterned after one in 2001 that pumped enough sand onto a dozen San Diego-area beaches -- including 10 in North County -- to fill Qualcomm Stadium.

Then, it cost $17.5 million. The price tag for the sequel is expected to reach $25 million or more.

Then, as now, the goal was to widen the region's thinning beaches to make coastal communities more attractive and to attract tourists so that they continue pumping billions into the local economy.

Proponents also say that the extra sand can buffer vulnerable coastal bluffs against destructive winter swells.

Whatever the goal, said Mark Massara, coastal programs director for the Sierra Club, it will seem as if public officials are merely throwing money into the Pacific, because the ocean will soon reclaim the sand.

Indeed, just a few months after residents and tourists frolicked on broad, freshly nourished beaches in the summer of 2001, a powerful Thanksgiving Day storm scoured Torrey Pines State Beach back to its normal thin strip.

And within five years, the other beefed-up beaches had largely returned to the condition they were in before the SANDAG project.

"This (new) project makes no sense at all in light of the 2001 failure," Massara said. "You would think we would have learned from what happened in 2001, but some of these sand lobbyists didn't get the memo. We cannot continue to act like ostriches here and put our heads in the sand -- because there isn't any."

Lessons learned

Sand replenishment proponents counter that they have, in fact, learned something.

Solana Beach Councilman Joe Kellejian, who sits on SANDAG's shoreline preservation committee, said regional officials found that coarse sand stays on beaches longer than finer sand.

And they learned some of the best offshore locations to dredge sand from the ocean bottom.

True, the sand didn't last as long as officials had hoped, Kellejian said.

But he said not all of it washed into the ocean, either.

He said some of it stayed nearby and, for several years, swept back on shore in summer.

Not only do replenishment opponents consider it foolish to pump sand onto the shore in the current economic climate, they say it is particularly unwise to artificially widen beaches when a more quickly rising sea is likely to scour away the sand at a much faster rate.

"You're playing God," said Fay Crevoshay, a spokeswoman for Wildcoast, an environmental group based in Imperial Beach. "You're taking out sand, you're deciding where the sand is going to go. But the sea is going to take it back."

And, said Mark Rauscher, assistant environmental director of the Surfrider Foundation in San Clemente, a flurry of recent state and regional reports suggests that the sea will take the sand back much faster in the future because of global warming.

"These things are happening much faster than they (scientists) originally thought," Rauscher said. "And at some point we are going to have to ask, 'How much money do you keep throwing in the ocean? How long can you keep that up?' What that number is, I don't know. But it's something that needs to be asked, and I don't think it is being asked."

To be sure, Kellejian said, local officials will have to confront the rising sea.

But he said, "It's going to be a long, long time before that sea level rise is going to affect the San Diego coastline to the extent that we would not have sand on our beach."

And with the scenic shoreline being the centerpiece of the region's tourist-oriented economy, Kellejian said beefing up beaches will continue to be a worthwhile investment for some time.

Visitors come to San Diego County from all over the world, he said.

"They want to go to SeaWorld. They want to go to the Wild Animal Park. And they may want to experience a Padres game," Kellejian said. "But I can guarantee you they want to be near or on the beach."

According to a recent state Department of Boating and Waterways report, 8 million people annually visit the shoreline from Del Mar to Oceanside and pump $6 billion into the North County economy, even with area beaches as narrow as they are.

We have ourselves to blame

Industrial civilization is largely to blame for the beaches' condition.

"We've paved over San Diego. We've dammed up the rivers. We've blocked up the lagoons with highway bridges and railroad trestles," Kellejian said.

Indeed, said San Diego County Supervisor Pam Slater-Price, chairwoman of the shoreline preservation committee, one need only take a trip to the Del Mar Fairgrounds to see why the beaches aren't as big as they were historically.

There, large piles of sand are blocked from heading out to sea through the mouth of the San Dieguito River.

"All of that sand is just sitting there. It can't get through because of that railroad bridge there," Slater-Price said.

With all of the man-made barriers, scientists figured the source of most present-day sand was the Santa Margarita and San Luis Rey rivers of North County, said Neil Driscoll, geology professor for UC San Diego's Scripps Institution of Oceanography.

But in the past five years, Driscoll said, scientists have discovered the bluffs generate most of the sand that spreads along the shore.

It turns out most of the sand coming down the rivers is flushed so far out to sea by storms it never reaches the shore, he said.

As the sea rises still faster, scientists think those bluffs will be pummeled much more frequently by storms.

The elusive equilibrium

But even though humans have dramatically altered the natural systems that gave birth to the region's once-wide beaches, that doesn't mean regional leaders shouldn't try to fix the mess, Slater-Price said.

Slater-Price said some beaches are holding up better today, in part because of that project eight years ago.

"Cardiff was just rocks, and now it's a sandy beach," she said.

Shelby Tucker coordinates SANDAG's beach planning and says that part of fixing the mess entails restoring the amount of sand that experts believe used to be on the shore long ago.

Tucker said it is believed that if the region eventually can pump 30 million cubic yards of sand into that near-shore area, a sort of equilibrium will be created and a wider strip of sand will remain on the beaches.

"Right now we're trying to play catch-up," she said. "Once you get enough sand in the system, you just have to maintain it."

Still, even maintaining the system would require adding 400,000 cubic yards annually, Tucker said.

By comparison, SANDAG put 2 million cubic yards on the beach in 2001.

Jim Jaffee, a Solana Beach engineer and co-chairman of a Surfrider Foundation committee, said restoring historical amounts of sand along the shore probably is needed.

But Jaffee said a much more comprehensive approach is needed to ensure wider beaches, including a plan to stop the proliferation of man-made sea walls that block natural processes and to gradually abandon coastal buildings that are immediately in the path of the approaching sea.

"We're just living in a dream thinking that laying sand down is the only solution that is going to work," he said.

Gary Murphy, a long-time Encinitas resident and surfer, suggested that it is also crucial to restore the near-shore kelp beds, which when healthy can help diffuse some of the biggest waves that tend to cause the most erosion.

Call staff writer Dave Downey at 760-745-6611, ext. 2623.