FAIRHOPE, Ala. — Scientists have issued a warning that the rapidly increasing loss of seagrass meadows is an immediate threat to the health and sustainability of coastal ecosystems. A study, published in the Proceedings of the National Academy of Sciences, indicates a worldwide acceleration of annual seagrass loss from less than 1 percent per year prior to 1940 to 7 percent per year since 1990.

Based on more than 215 studies and 1,800 observations dating back to 1879, the assessment shows that seagrasses are disappearing at rates similar to coral reefs and tropical rainforests.

This has become a serious problem, according to Dr. Ken Heck, senior marine scientist at the Dauphin Island Sea Lab and a co-author of the report. He said, “With 45 percent of the world’s population living on the 5 percent of land adjacent to the coast, pressures on remaining coastal seagrass meadows are extremely intense. As more and more people move to coastal areas, conditions only get tougher for seagrass meadows that remain.”

Heck said more studies are being conducted on the issue, but researchers already know the loss of these underwater nurseries has a direct impact on the population of a number of species, including shrimp, blue crabs, several varieties of snapper, red drum, speckled trout and gag grouper.

“They grow up in there as juveniles and use them for food,” he said. “If you’re a living organism, you need shelter or there’s a good chance you won’t survive.”

The team estimates that seagrasses have been disappearing at a rate of 42.4 square miles per year since 1980.

During this, the first comprehensive global assessment of seagrass observations, they also found that 58 percent of the world’s seagrass meadows are currently declining.

Another study co-author, Dr. William Dennison of the University of Maryland Center for Environmental Science, put it in terms easier to wrap the mind around. He said, “Globally, we lose a seagrass meadow the size of a soccer field every 30 minutes.”

Heck said one of the main causes of the loss is runoff created by expanding coastal development, which creates suspended sediment, therefore blocking much-needed sunlight from penetrating the water column and reaching the seagrasses.

D’Olive Creek (in Daphne) is a poster child for what runoff does,” he said.

Also to blame, Heck added, is the release of nutrients through sewage overflows. The result is essentially the same because algae thrives under those conditions, shading the subsurface meadows, which then die off in growing numbers.

He pointed out that seagrass requires 10 to 20 percent more light than algae, and as water quality plummets, so do the meadows.

“Any time a plant is overgrown by something that’s taller, that kills it out,” Heck said. “Although often seen from the surface, seagrasses are rooted on the bottom. Sunlight needs to make it to the bottom.”

In addition to providing critical habitat for aquatic life, the unique group of submerged flowering plants also alter water flow and can actually help mitigate the impact of nutrient and sediment pollution. But, it’s a Catch-22 situation. They have to be there in the first place.

Public awareness and involvement are vital components in reversing the damage, Heck said, adding seagrasses are important to each of us for a variety of reasons.

“The real connection people have with seagrass are the crabs, the shrimp and the fish that use the seagrass as a nursery. They like to eat them and they like to catch them,” he said, also noting that the harvest of shrimp is more successful in areas where seagrass is abundant. “There’s a positive relationship. The number of shellfish and fin fish is greatly reduced when the seagrasses diminish.”

Property owners also benefit from healthy seagrass meadows, he said, because they stabilize the bottom and help prevent erosion.

Heck stressed that better land use management, resulting in less runoff and erosion, is one key to solving the problem. It can be done, he said, by planting vegetation around property to prevent runoff. He said, “You have to have a lot of people doing it to make a difference.”

Grass beds also are damaged by powerboats crisscrossing outside navigational channels in areas such as Perdido Pass. Heck urges boaters to learn where the critical habitats are located and avoid them while under power.

“You can see the damage in aerial photography,” he said. “We worked with the state Department of Conservation to put up signage to let people know where the grass beds are. We’re trying to do an educational campaign. There’s a lot of production of shellfish that’s not taking place because (the seagrass) is gone.”

The article regarding the findings, “Accelerating loss of seagrasses across the globe threatens coastal ecosystems,” appeared in the June 29th edition of the scientific journal. It was authored by 14 scientists from the United States, Australia and Spain, including Drs. Michelle Waycott (lead author), Carlos Duarte, Tim Carruthers, Bob Orth, Bill Dennison, Suzanne Olyarnik, Ainsley Calladine, Jim Fourqurean, Ken Heck, Randall Hughes, Gary Kendrick, Jud Kenworthy, Fred Short and Susan Williams.

Information about seagrasses in the Gulf of Mexico region is included in the larger survey.

The assessment was conducted as a part of the Global Seagrass Trajectories Working Group, supported by the National Center for Ecological Analysis and Synthesis in Santa Barbara, Calif., through the National Science Foundation.