The Columns

Greer Examines Climate Change and Coral Reefs

— by on October 22nd, 2008

When Lisa Greer, assistant professor of geology, traveled to Houston, Texas, in early October, the impact of Hurricane Ike was still being felt in the region where the storm caused an estimated $31.5 billion in damage.

Greer was in Houston to present her research on coral reefs and climate at the 2008 Joint Annual Meeting of the Geological Society of America and four other professional societies. The conference theme was celebrating the International Year of Planet Earth, but the location begged the question about possible relationships global warming and stronger hurricane systems.

Greer’s research also touches on issues of global warming. In this case, she is examining the impact that climate change might have on coral reefs.

Like a canary in a coal mine, Greer says coral reefs are an important barometer of our oceans’ health.

“The coral species that I presented on is one of two listed on the endangered species list,” she said. “Staghorn coral (Acroporoa cericonis) has been a major reef builder for more than 500,000 years, but starting in the 1980s it has been dying off. We’ve seen a very serious, dramatic population decline in the Caribbean and Atlantic oceans. The condition of this particular species is perhaps an indicator of things to come.”

Greer’s research compares fossilized specimens of Staghorn coral that grew somewhere between 9,000 to 5,000 years ago to small samples harvested off the Barbados shore last summer. Examining the chemical composition of each provides a snapshot of environmental conditions from the two geological eras.

“Staghorn is a very hardy species and has lived for thousands of years without interruption during a time that was very hot, with temperatures very similar to 1980s,” she noted. “In this environment the reefs were exposed to potentially harsh conditions, such as huge storms and dramatic changes in salinity. But now it is dying off. Our question is why? What is it that is impacting this coral? Our research data suggest that it’s not as simple as global warming. It’s not just a change in ocean temperature that’s causing this die-off.”

Greer believes a much more complex scenario is to blame, including disease, pollution and overfishing, in addition to climate change. “Studies have shown that when coral reefs are overfished, the dynamics of the ecosystem are significantly altered. For example, when there are no fish to graze on the algae, then the algae outcompetes the corals for space that the corals need to colonize.”

On a recent trip to Barbados, Greer was disheartened by the state of the coral reefs. “There are many reasons to be concerned about losing this species to extinction—from a biodiversity standpoint, from an economic standpoint and from a biomedical standpoint.” She notes that the Caribbean region depends upon reefs for ecotourism and that the local fisheries may also suffer if coral reefs die. Moreover, coral reefs act as a wave break, so in the event of a hurricane those reefs can actually break the force of the incoming tidal surge. And, like the Amazon rainforest, coral reefs may offer biomedical solutions that have yet to be discovered.

This summer, Greer hopes to be back in the Caribbean waters with several Washington and Lee undergraduates in the R. E. Lee Research Program to gather more coral specimens from a longer-lived species.

“My research in Barbados will be more focused on obtaining longer records of tropical Atlantic climate variability to extend our understanding of climate in this region beyond the instrumental record. We’ll be taking core samples from the coral reefs so we can look at the chemical composition of coral over time, sort of a climate archive,” she explained. “Perhaps this can lead to a better understanding of how the Caribbean marine environment since the 1980s has been different compared to a period 9,000-5,000 years ago.”