ATTENTION: Please note the date of this news release. You may be reading about findings that have changed significantly or about programs and faculty no longer at the university. To check if there is updated information available, search the Earth Institute website.

 

posted 06/06/00

Increasing Carbon Dioxide Levels Threaten Coral Reefs Worldwide
by Kurt Sternlof

Columbia University, NYC

New research indicates that rising carbon dioxide (CO₂) levels in the atmosphere pose a substantial, ever-increasing threat to one of the world's most important and delicate ecosystems -- it's coral reefs.

A research team led by marine biologist Christopher Langdon of Columbia's Lamont-Doherty Earth Observatory (LDEO) has been studying the problem for almost four years using a unique experimental coral reef growing in the 700,000-gallon artificial ocean of the university's Biosphere 2 Center in Oracle, Arizona.

Results Published in Global Biogeochemical Cycles

Based on their results published in the June issue of Global Biogeochemical Cycles, a journal of the American Geophysical Union, Langdon estimates that the rate of coral reef growth will have dropped 40 percent by 2065, the year scientists project that atmospheric CO₂ levels will have doubled relative to pre-industrial times. And the evidence suggests that the reefs will never be able to adjust to the increase in CO₂.

"This is really the first definitive evidence that rising CO₂ levels negatively impact a major Earth ecosystem," Langdon said. "And as much as we are excited by the quality of the data obtained from the experimental reef, the environmental implications are disturbing."

Reefs Threatened by Global Warming and Rising Sea Levels

In fact, rising CO₂ levels -- caused primarily by the burning of fossil fuels and the destruction of tropical forests -- threaten reefs with something of a one-two knockout punch. Carbon dioxide is the greenhouse gas considered largely responsible for global warming, which in turn is expected to result in rapidly rising sea levels over the coming century. Thus reefs, which live and grow only near the ocean's surface, could literally drown as sea levels rise and their ability keep pace with new growth diminishes.

"Other research has indicated that terrestrial ecosystems might actually benefit from elevated CO₂ levels, insofar as it's a necessary raw material of photosynthesis," Langdon said. "But that is clearly not the case with coral reefs."

Coral, and many other ocean creatures, build their hard, protective shells from calcium and carbonate ions that they extract from the water around them. A reef results as millions of individual coral build their homes around and on top of each other over time, like the slow construction of an apartment building, one story after another.

When excess atmospheric CO₂ dissolves into the shallow ocean, its natural chemical balance is disrupted and the water becomes more acidic. The ocean's natural buffering system responds by using carbonate ions to consume the acid. While this does keep the water from becoming too acidic, less carbonate is available for coral building and overall reef growth slows.

Many of the world's reefs are already weakened from the effects of over fishing, development and pollution. Slowing growth only makes them more vulnerable, Langdon said. And to make matters worse, it appears that coral will not able to adapt to these changing water chemistry conditions over time.

More Evidence against Fossil-fuel Consumption

"Langdon's team's results at Biosphere 2 provide another strong argument in favor of acting now to stem the long-term trend toward ever-higher CO₂ emissions," said Wallace Broecker, LDEO geochemist and climate expert. "The newly recognized risk to these all-important coral reef ecosystems is yet another alarm going off to warn us of the consequences of our short-sighted, fossil-fuel dependent ways."

Although they comprise a tiny fraction of Earth's surface, reefs are extremely important, Langdon explained. At least 10 million people directly depend on them for food and, as cradles of biodiversity at least as important as tropical rainforests, they wield an inordinate impact on overall ocean health. Reefs also provide an important coastal buffer against ocean storms in many areas, and provide the focus of an enormous tourism industry that drives the economy of many otherwise poor nations.

Research Continues

Research at Biosphere 2 into the coral reef/ CO₂ relationship continues, as Langdon and his team use the artificial ocean environment's unique capabilities to investigate how individual species of coral and coralline algae are affected. The capability there to precisely control the physical and chemical environment, and measure minute changes in the experimental reef system is unparalleled and makes such research, Langdon said.

"Research findings like those produced by the Langdon team demonstrate the true potential of the Biosphere 2 laboratory," says Harris. "We fully expect that other studies of global climate change issues already underway here, or planned for the near future, will continue the tradition of producing significant research results."

Columbia University of New York City established a western campus at Biosphere 2 in 1996. Trustees of the Ivy League school recently approved spending $50 million to enhance research capabilities inside the 3.13-acre, sealed glass laboratory and to expand undergraduate enrollment, develop new academic programs and construct new facilities on the Biosphere 2 campus.

About The Earth Institute
The Earth Institute at Columbia University is the world's leading academic center for the integrated study of Earth, its environment and society. The Earth Institute builds upon excellence in the core disciplines — earth sciences, biological sciences, engineering sciences, social sciences and health sciences — and stresses cross-disciplinary approaches to complex problems. Through research, training and global partnerships, it mobilizes science and technology to advance sustainable development, while placing special emphasis on the needs of the world's poor. For more information, visit www.earth.columbia.edu.