GUY RAZ, host:
From NPR News, this is All Things Considered. I'm Guy Raz. Our use of fossil fuels appears to be stunting the growth of coral on Australia's Great Barrier Reef. Scientists have predicted that the buildup of carbon dioxide in the atmosphere will be bad for coral, and as NPR's Richard Harris reports, a new study provides some of the strongest evidence yet that coral is already suffering.
RICHARD HARRIS: Living corals literally build the reefs that support some of the most diverse life on Earth. So, researchers at the Institute of Marine Science in Australia have taken a close look at corals along the Great Barrier Reef to check on their growth over the past several decades. Glenn De'ath explains they focused on big, round corals known as parieties.
Dr. GLENN DE'ATH (Researcher, Institute of Marine Science, Australia): They lay down the history of their growth in the skeletons of - just like tree rings.
HARRIS: As a result, scientists can measure the rings and see how fast they've been growing. As they report now in Science Magazine, coral growth slowed appreciably starting around 1990.
Dr. DE'ATH: There have been some other studies now which are showing similar effects, but this one covers basically the whole of the Great Barrier Reef, which is over 2,000 miles long, and that's a huge area, and we've found very consistent results.
HARRIS: Growth is slowing by about one percent per year. And if the trend continues, De'ath says, this critical species of coral could stop growing entirely across the Great Barrier Reef by the middle of this century. The big question is why this is happening. The scientist pointed two factors; one is increasing ocean temperatures apparently as a result of global warming. De'ath says the other factor is that the ocean has been getting more acidic, also as a consequence of all the carbon dioxide we're pumping into the atmosphere.
Dr. DE'ATH: So, the carbon dioxide dissolves in the water, the water becomes more acidic, and that increased acidity is what reduces the rate of growth of the corals.
HARRIS: That change in ocean chemistry makes it much harder for corals and other shell building organisms to build their skeletons. I called coral expert Joni Claipus(ph) at the National Center for Atmospheric Research in Colorado to ask her about the study. So, what does this portend for corals?
Dr. JONI CLAIPUS (Coral Expert, National Center for Atmospheric Research): Oh, it's not very good, is it? We've predicted this for a long time and I think most of us would like to be proven, and it seems like this paper is one more notch telling us that maybe this whole problem of climate change in coral reef is really true and we need to do something out it.
HARRIS: But what to do is the question. Carbon dioxide is building up rapidly in the Earth's atmosphere as we burn more and more fossil fuels. Even optimistic scenarios find that a whole lot more carbon dioxide is going into the air and the ocean in the coming decades.
Mr. RON SOLM (Advisor, Nature Conservancy, Hawaii): It looks pretty gloomy. I have to say it, it looks really gloomy for the Great Barrier Reef and I think there'll be major changes there.
HARRIS: That's Ron Solm(ph) in Hawaii, who advises the Nature Conservancy about coral-reef issues. He doesn't cheer the gloomiest scenario which is that corals in the Great Barrier Reef could die off entirely by the end of the century. But he expects the reef will soon be a very different place. Solm says, of course the world needs to reduce carbon dioxide emissions, but we also need to find and preserve reefs that are relatively resilient to the effects of global warming and ocean acidification. For example, there are some areas north of Australia, in the so-called coral triangle, that seemed to be doing relatively well right now.
Mr. SOLM: We need to put in place actions that we can take today to help safeguard the reefs. So, that by the time the carbon dioxide emissions are under control and are being rolled back to some acceptable level, that we've got to ensure that there's something that survives.
RAZ: Presuming we can someday repair our atmosphere, young sea born corals can then float throughout the ocean and repopulate the reefs. What's coming clear is that in the face of climate change, the conservation challenges for the ocean may turn out to be even more challenging than for ecosystems on land. Richard Harris, NPR News.