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Pictured at left is the typical coral reef today on the southern Great Barrier Reef, which has endured a rise of 1 degree C and 375 parts per million of atmospheric carbon dioxide concentration. The middle frame shows what a reef would look like if global temperatures rise one more degree and CO2 concentrations increase, as predicted. The right frame shows what a reef would like if temperatures and CO2 levels rise even more.

If world leaders do not immediately engage in a race against time to save the Earth's coral reefs, these vital ecosystems will not survive the global warming and acidification predicted for later this century. That is the conclusion of a group of marine scientists from around the world in a major new study published in the journal Science on Dec. 13.

"It's vital that the public understands that the lack of sustainability in the world's carbon emissions is causing the rapid loss of coral reefs, the world's most biodiverse marine ecosystem," said Drew Harvell, Cornell professor of ecology and evolutionary biology and head of the Coral Disease Research Team, which is part of the international Coral Reef Targeted Research (CRTR) group that wrote the new study.

The rise of carbon dioxide emissions and the resultant climate warming from the burning of fossil fuels are making oceans warmer and more acidic, said co-author Harvell, which is triggering widespread coral disease and stifling coral growth toward "a tipping point for functional collapse."

The 17 marine scientists who authored the new study argue that "drastic action" is needed from world leaders to turn around the trend in rising levels of atmospheric carbon dioxide (CO2) to protect coral reefs. They based their conclusions on the forecasts for rising global temperatures and levels of CO2 announced recently by the Intergovernmental Panel on Climate Change, a United Nations body.

"Coral reefs have already taken a big hit from recent warm temperatures, but rapid rises in carbon dioxide cause acidification, which adds a new threat: the inability of corals to create calcareous skeletons," said Harvell. "Acidification actually threatens all marine animals and plants with calcareous skeletons, including corals, snails, clams and crabs. Our study shows that levels of CO2 could become unsustainable for coral reefs in as little as five decades."

In the short term, better management of overfishing and local stressors may increase resilience of reefs to climate threats, but rising global CO2 emissions will rapidly outstrip the capacity of local coastal managers and policy-makers to maintain the health of these critical ecosystems if the emissions continue unchecked, the authors stress.

At stake, added Ove Hoegh-Guldberg, director of the Center for Marine Studies at the University of Queensland, Australia, and the study's senior author, are ecosystems that play vital roles in providing habitats for a vast array of marine species that are essential to the oceans' complex food chain. They also provide livelihoods to 100 million people who live along the coasts of tropical developing countries. Diving tourism in the Caribbean alone is estimated to generate more than $100 billion a year. The loss of coral reef ecosystems also is exposing people to flooding, coastal erosion and the loss of food and income from reef-based fisheries and tourism, he added.

The CRTR is a leading international coral reef research initiative that provides a coordinated approach to credible, factual and scientifically proven knowledge for improved coral reef management. It is a partnership of the Global Environment Facility, the World Bank, the University of Queensland, Australia, the U.S. National Oceanic and Atmospheric Administration and approximately 40 research institutes and other third parties around the world.