Rising Seas

Rising Sea Levels
ENN, Dec 2, 1999

Florida's coastal forests are dying. Caught between rising sea levels and the development of inland areas for agriculture, silviculture and condominiums, the cabbage palms and other species occupying the coastal strand are being squeezed out of existence. Several years ago Florida residents noticed that cabbage palms - Florida's state tree - were dying along the state's Gulf Coast. This information landed on the desk of Dr. Francis Putz, a University of Florida professor of botany and forestry with an interest in the changes that global events bring to forests. His research showed that a rise in sea level is killing all the trees in Florida's coastal forests. "We're talking about forests that start out with 30 or 40 canopy tree species," he says. "By the time the cabbage palms die, the forest has lost all the other species, plus it's lost the ability to regenerate." Sea levels have risen and fallen in the historical past, and coastal forests worldwide have moved with them. But inland agriculture, forestry and development have squeezed Florida's coastal forests into a narrow ribbon, with no place to move.

Putz's research showed that a rise in sea level is killing all the trees in Florida's coastal forests."With inland areas under management, natural processes are prevented from occurring," Putz says. "In the past, the species that live on the coast could move up and down as the coast moved." Now the state's coastal areas are trapped between development and agriculture, and the rising water. "Globally, the rate of sea level rise is around 1.5 millimeters per year," Putz says. This rise in sea level began about 16,000 years ago, after the last glacial maximum. What concerns Putz and other scientists is that global warming - caused in part by the burning of fossil fuels and in part by widespread logging in the tropical forests he usually studies - is increasing the rate of sea level rise worldwide. "The primary cause of sea level rise is water expansion," Putz says. "It doesn't expand very much, but we have a lot of water on this blue planet, and increasing global temperatures will cause water expansion. You also get melting of polar ice caps, and they contribute together."

... For the foreseeable future, Putz says, scientists expect global temperatures to continue to rise, regardless of efforts to reduce the rate of deforestation and the production of greenhouse gases. Putz says that increasing sea level rise will have a dramatic and continuing effect on coastal conservation issues. "The rate of sea level rise may increase even more in the future," he says. "Globally, this means disaster. A huge proportion of the world's population lives within a few decimeters of sea level. For places like Bangladesh and the island nations of the Pacific, the consequences of this are astronomical."