Where Has All The Seagrass Gone?

Seagrass in Belize. Photo courtesy mongabay.com

When most people think of seagrass, they think of algae – either the kind you eat or the ones that wash up on the beach with huge bladders that feel neat when you squish them between your toes.

Seagrass ecosystems are in decline. The results of an on-going study that started in 1879 (wow!) left a legacy of compiled data from 215 studies and 1,800 observations of seagrass habitat that an international team of scientists interpreted and released in a report. Among many other things, they found that 58% of seagrass meadows are declining. Since 1879, 29% of seagrass meadows have vanished entirely.



As with all environmental issues, the rate of decline has accelerated. In 1940, the annual seagrass loss was less than 1% per year; while, in 1990 the seagrass loss has risen to 7% per year.

"While the loss of seagrasses in coastal ecosystems is daunting, the rate of this loss is even more so," said co-author Dr. Robert Orth of the Virginia Institute of Marine Science. “The loss is on par with that of coral reefs and tropical forests.”

Seagrass ecosystems are made of submerged flowering plants. They provide many vital ecosystem services, including habitat for a large variety of marine life, alterations in water flow, mitigation of pollutants, and carbon sinks.

"With the loss of each meadow, we also lose the ecosystem services they provide to the fish and shellfish relying on these areas for nursery habitat. The consequences of continuing losses also extend far beyond the areas where seagrasses grow, as they export energy in the form of biomass and animals to other ecosystems including marshes and coral reefs," added Orth.

“A recurring case of ‘coastal syndrome’ is causing the loss of seagrasses worldwide," said co-author Dr. William Dennison of the University of Maryland Center for Environmental Science. "The combination of growing urban centers, artificially hardened shorelines and declining natural resources has pushed coastal ecosystems out of balance. Globally, we lose a seagrass meadow the size of a soccer field every thirty minutes."

A large part of the problem is the continual growth of human populations on the coast. "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," said co-author Dr. Tim Carruthers of the University of Maryland Center for Environmental Science. "As more and more people move to coastal areas, conditions only get tougher for seagrass meadows that remain."

A good short film describing seagrass and the problems it faces today: