A third of reef-building corals threatened with extinction: scientists

Yahoo News 10 Jul 08;

A third of reef-building corals worldwide are threatened with extinction due to climate change and water pollution, according to the first global assessment on the marine creature by 39 scientists.

Destructive fishing and the degradation of coastal habitats also posed threats, said the study published Thursday involving the International Union for Conservation of Nature (IUCN) and Conservation International.

"The results of this study are very disconcerting," said Kent Carpenter, lead author of the study which examined 845 coral reef species.

"When corals die off, so do the other plants and animals that depend on coral reefs for food and shelter, and this can lead to the collapse of entire ecosystems," he added.

Roger McManus from Conservation International said that reef-building corals in particular were "most vulnerable to the effects of climate change".

Sea temperature rises bleach and weaken the algae that give the underwater sea life its vibrant colour, and make it more susceptible to diseases.

As they are home to over 25 percent of marine species -- including fish stocks -- loss of reefs could also impact coastal fishing communities.

"The loss of the corals will have profound implications for millions of people who depend on coral reefs for their livelihoods," said McManus.

According to the study, the Caribbean region has the highest number of highly threatened corals.

Due to huge human populations in the region, the Indo-Malay-Philippine archipelago also has the highest proportions of vulnerable and almost threatened species in the Indo-Pacific.

"We either reduce our CO2 emission now or many corals will be lost forever," warned Julia Marton-Lefevre, IUCN Director General.

'Alarming' plight of coral reefs
Richard Black, BBC News 10 Jul 08;

A third of the world's reef-building coral species are facing extinction.

That is the stark conclusion from the first global study to assess the extinction risks of corals.

Writing in the journal Science, researchers say climate change, coastal development, overfishing, and pollution are the major threats.

The economic value of the world's reefs has been estimated at over $30bn (£15bn) per year, through tourism, fisheries and coastal protection.

"The picture is frightening," said Alex Rogers from the Zoological Society of London, one of 39 scientists involved in the assessment.

"It's not just the fact that something like a third of all reef-forming corals are threatened, but that we could be facing the loss of large areas of these ecosystems within 50 to 100 years.

"The implications of that are absolutely staggering - not only for biodiversity, but also for economics."

The analysis shows that reef-building corals are more threatened than any group of land-dwelling animals except amphibians.

'Incredible' destruction

The most dramatic decline in recent years was caused by the 1997/8 El Nino event, which caused waters to warm across large swathes of the tropics.

When water temperatures rise, coral polyps - tiny animals that build the reefs - expel the algae that usually live with them in a symbiotic relationship.

The corals lose their colour, with reefs taking on a bleached appearance, and begin to die off because the algae are not there to provide nutrients.

The new analysis shows that before 1998, only 13 of the 704 coral species assessed would have been classified as threatened. Now, the number is 231.

"It was a devastating event in terms of the destruction of corals, with 16% of reefs irreversibly destroyed - an incredible amount," said Kent Carpenter from Old Dominion University in Norfolk, Virginia, in the US.

"The big problem is that if these bleaching events become more frequent as temperatures rise, as we suspect will happen, then we will see whole tracts of coral wiped out."

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See the effects of coral bleaching (Sea Web)

Adding to this, scientists have come to realise in recent years, is ocean acidification. The water absorbs some of the atmosphere's extra carbon dioxide, making it slightly more acid, enough to compromise the capacity of corals to build their skeletons, and snails to build their shells.

"We know that high sea surface temperatures are bad for coral, but we also have an idea that some might be able to adapt," said Professor Carpenter.

"But ocean acidification is a much more insidious thing. We don't know how bad it will be, but the evidence suggests it will be absolutely devastating, perhaps on the order of decades, perhaps on the order of years."

Complex web

But carbon dioxide is not the only culprit.

Overfishing in many regions - especially the use of dynamite to fish in East Asia and heavy trawls that reduce reefs to rubble - the excavation of building materials from reefs, coastal development, invasive species and pollution are all fingered in the new analysis.

The Caribbean shows how the threat jigsaw fits together.

Coastal development and farming produce effluent, which stimulates the growth of types of algae that smother growing coral.

Meanwhile, fishermen are catching fish that would usually graze on these algae.

In this stressed condition, coral then fall prey more easily to disease, such as white-band disease which has swept through elkhorn and staghorn corals in the region.

The line taken by many scientists and campaigners is that these problems should be easier to tackle than the rising tide of greenhouse gas emissions; so this is where attention should be concentrated.

Along Australia's Great Barrier Reef, protected areas have been established in the sea, and the use of fertilisers controlled on land to reduce pollution.

Recent research there has also shown that algae-munching fish can clean up smothered coral.

But there is another view; that these measures can only reduce and delay the inevitable impacts of rising greenhouse gas emissions.

The political response to climate change, said Alex Rogers, could be likened to "fiddling while Rome burns".

"Could you imagine if a single event wiped out 16% of the Amazon forest, or 16% of ecosystems in the UK?" he asked.

"I don't think politicians and the public are aware of the gravity of the situation we're in regarding coral reefs and other marine ecosystems."

Beyond value?

About one quarter of marine species are believed to depend on coral at some stage of their development. Many fish live their entire lives on reefs, while others use them as nurseries; presumably if the coral dies out, so do the fish.

The economic impact of losing coral is also significant.

Estimating the monetary value of natural ecosystems is far from being an exact science.

But one assessment published two years ago by the UN Environment Programme (Unep) concludes reefs provide services worth on average between $100,000 and $600,000 (£50,000 and £300,000) per square kilometre each year.

That gives a total global value between $30bn and $180bn (£15bn and £90bn) annually. In some regions, such as Sri Lanka, the value has been estimated to be 10 times the global average.

The same assessment concluded that protecting areas of reef costs about 0.2% of the value they bring.

The new assessment forms one element of a major project to measure threats to ocean ecosystems, the Global Marine Species Assessment, a joint initiative of the International Union for the Conservation of Nature (IUCN) and Conservation International (CI).

It will form part of the new IUCN Red List of Threatened Species, due to be published in October.

The IUCN's director general, Julia Marton-Lefevre, said world leaders faced a stark choice.

"We either reduce our CO2 emissions now, or many corals will be lost forever."

Acidifying oceans pose danger to coral reefs
Michael Christie, Reuters 10 Jul 08;

FORT LAUDERDALE, Florida (Reuters) - Like a tooth dipped in a glass of Coca-Cola, coral reefs, lobsters and other marine creatures that build calcified shells around themselves could soon dissolve as climate change turns the oceans increasingly acidic.

The carbon dioxide spewed into the atmosphere by factories, cars and power plants is not just raising temperatures. It is also causing what scientists call "ocean acidification" as around 25 percent of the excess CO2 is absorbed by the seas.

The threat to hard-bodied marine organisms, such as coral reefs already struggling with warming waters, is alarming, and possibly quite imminent, marine scientists gathered this week for a coral reef conference in Fort Lauderdale, Florida, said.

"The threshold for (corals) could be approached by the middle of this century ... when they'll reach a point where they may no longer be able to reproduce themselves as fast as they're being destroyed," said Chris Langdon, am associate professor at the University of Miami's Rosenstiel School of Marine and Atmospheric Science.

"It's not going to be instant. They're not going to disappear that year. It may take another 50 or 100 years."

It was only recently that scientists woke up to the fact that global warming would reduce the pH value of the oceans due to a chemical reaction of water with CO2. The pH scale is a measure of alkalinity or acidity, with 7 being neutral.

The pH value of the oceans has been around 8.2 for hundreds of thousands of years, but since the start of the industrial age in 1800, it has dropped by 0.1.

REEF COLLAPSE?

The U.N.'s Intergovernmental Panel of Climate Change projects it will drop further to 7.8 by the end of the century and some scientists fear the fall could be more precipitous.

A recent study of a natural CO2 vent in the waters off Italy suggests calcifying organisms, like coral, cannot exist in conditions where pH values go below 7.6, said Maoz Fine of Israel's Interuniversity Institute for Marine Science.

"It's like tossing a tooth into a glass of Coke," Fine told reporters at the conference in Fort Lauderdale.

Where pH values dropped to 7.6 at the vent there was a "complete shift from calcifying organisms to none," he said. "It was really quite dramatic, it was very obvious. You don't have to be a specialist to see it."

Stone-hard corals became soft as a sea anemone as their skeletons slowly dissolved in the acidic waters, he said.

Coral specimens had managed to survive without their skeletons in benign laboratory conditions for up to two years, Fine said. But in their natural environment they would be vulnerable to predators, like parrot fish, and suffer increased damage from threats like storms.

Entire reefs would eventually collapse as they lost the mortar holding them together, scientists said.

The threat of ocean acidification is not as immediate to coral as the danger posed by bleaching, which occurs when environmental stresses, like heat, break down the symbiotic relationship between coral polyps and the unicellular algae that give them color.

But it would likely be much harder for coral to adapt to, and would affect coral all over the planet, said Langdon.

Researcher Simon Donner of the University of British Colombia said it was far too late already for the world to avoid climate change.

What coral scientists needed to do was develop ways to help coral reefs adapt to a changing environment so as to buy them another 40 of 60 years of existence before hoped-for cuts in industrial pollution begin to have an impact.

"The climate is like this big ship. In our case the ship's the Titanic and we're going to hit the iceberg. It's almost impossible for us not to hit the iceberg," Donner said.

"What we need to do is everything we can to put the brakes on, to slow the ship down, and then do whatever we can -- hopefully the coral will help us with this -- to move the iceberg a little bit."

(Editing by Jane Sutton and Sandra Maler)

A Third of Reef-Building Corals at Risk of Extinction
Brian Handwerk, National Geographic News 10 Jul 08;

A third of the world's major reef-building coral species are in danger of extinction, an international team of scientists warns in a study published today.

Because coral reefs are home to more than a quarter of all marine species, their loss could be devastating for biodiversity in the world's oceans.

"If corals themselves are at risk of extinction and do in fact go extinct, that will most probably lead to a cascade effect where we will lose thousands and thousands of other species that depend on coral reefs," said the study's lead author Kent Carpenter, a zoologist at Old Dominion University in Norfolk, Virginia.

The rate at which reefs have been besieged is most troubling, the scientists say.

Of the 704 corals classified in the study, 231 were listed as "vulnerable," "endangered," or "critically endangered" according to the International Union for Conservation of Nature's Red List.

A decade ago just 13 species met the same criteria.

The study appears in the online journal Science Express.

On The Brink?

Studies around the globe have made the news of coral reef declines distressingly commonplace, the researchers say.

"What we did was use that information about decline to ask the question, What is the consequence of this on the potential loss of biodiversity?" Carpenter said.

"It's easy for people to understand that coral reefs are at risk, but it's gotten to the point now where the risk of extinction is a reality for the actual species that form the coral reefs. That could be devastating to biodiversity in the ocean."

Some reef locales are faring worse than others, the paper said.

"Caribbean reefs appear to be the worst off in terms of numbers of important species that have a very high risk of extinction," Carpenter reported.

By contrast the "Coral Triangle" region of the Indo-Malay Philippine Archipelago—an area of high marine biodiversity—has the highest number of species appearing on the list, but many are at a lower level of extinction risk.

"It's potentially the next big problem area," Carpenter said. "If conditions worsen, we're talking about the most important marine biodiversity area in the world potentially becoming a big problem."

Meanwhile, areas of the Pacific Ocean stood out as regions where corals are faring better. Reefs among the Pacific's tens of thousands of isolated islands are scattered and relatively unaffected by human activity.

What is Killing Coral?

Experts generally agree that large scale die-offs from bleaching and disease have increased in frequency during recent decades—due at least in part to warming sea-surface temperatures linked to global climate change.

When sea temperatures rise for a sustained period of time by even a small amount, corals may expel their symbiotic food-producing algae, which turns reefs a sickly white.

A massive bleaching event in 1998 related to the El Niño weather phenomenon was the worst coral die-off ever observed. In the succeeding years such events have occurred with increasing frequency and severity.

The impact of disease or bleaching events is even worse when corals are weakened by local impacts such as overfishing, which sometimes targets species that protect reefs. Sedimentation and pollution from coastal development also harm coral health.

Corals do show some capacity to bounce back from bleaching and other destructive events. But if their overall declines are to be reversed, people must address the threats that have landed so many species on the IUCN list, scientists stress.

Related links

One Third of Reef-Building Corals Face Extinction
IUCN Press Release on the IUCN website, 10 Jul 08;

IUCN Global Reef-Building Coral Assessments
Some assessments for the individual coral species on the Old Dominion University website soon to be uploaded on the IUCN website in Oct 08.