While the Arctic is the most climatically vulnerable human-inhabited environment, coral reefs will probably see the most comprehensive destruction in coming decades. According to the IPCC, it is highly likely that they will succumb to a combination of heat and oceanic acidification as temperatures rise in response to greenhouse gas emissions. It is estimated that the last 25 years have seen the loss of 30% of warm-water coral cover. The worst summers so far for coral bleaching have been 1998 and 2002: in which 42% and 54% of all reefs worldwide were affected. As much as 80% of Caribbean coral may already have died.
Coral bleaching occurs when the zooxanthella algae that live in coral tissues die. The report of Working Group II of the IPCC highlights high surface temperatures as “almost certain to increase the frequency and intensity of mass coral bleaching events.” Throughout the Third and Fourth Assessment Reports, coral reefs are highlighted as being especially vulnerable to climatic change, with low adaptive capability.
Oceanic acidification reduces the calcifying ability of corals, by making it more difficult for them to extract calcium from seawater. In cases of extreme acidity, existing structures could begin to dissolve. According to the IPCC “the progressive acidification of oceans is expected to have negative impacts on marine shellforming organisms.” Studies have demonstrated that projected future ocean acidity will reduce coral calcification and weaken coral skeletons.
The Fourth Assessment Report projects that most corals will be bleached by a temperature rise of 1 to 3°C, with increasing coral mortality at higher levels of temperature increase. Between 2.5 and 3.5°C above the pre-industrial mean temperature, a summary table in the WGII report predicts simply “Corals extinct, reefs overgrown by algae.” It warns further that: “It is important to note that these impacts do not take account of ancillary stresses on species due to over-harvesting, habitat destruction, landscape fragmentation, alien species invasions… or pollution.” Given the low probability of keeping further temperature increases below 2°C – even with the advent of relatively stringent new international obligations – it is fair to say that most of the world’s coral is doomed to die. That, in turn, will undermine much of the basis of coral reef ecosystems. This is a further burden to some small island states, as coral reefs can be the habitat for important fish stocks. Reefs are also the most diverse marine ecosystems: home to about 25% of all marine species.
One way to interpret the news is this: if you have always dreamed of SCUBA diving in the natural splendour of a coral reef, make sure you do it fairly soon. Your children might not be able to do it at all. To quote the IPCC once more: “Annual or bi-annual exceedance of bleaching thresholds is projected at the majority of reefs worldwide by 2030 to 2050.”
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The fate of coral
Not just a pretty polyp
Mar 22nd 2007
From The Economist print edition
IF YOU thought coral was just a basic form of rather pretty underwater life, think again. The diminutive reef-builders gave us oxygen to breathe, cooled the atmosphere down to a clement level and went on to build the only biological structure that is visible from space—the Great Barrier Reef.
God bless the primordial cyanobacteria, on this holiest of days.
“And the Lord said, ‘Let there be a photosynthetic bacterium of the class Coccogoneae or Hormogoneae, generally blue-green in color and in some species capable of nitrogen fixation.’, and it was good.”
it is fair to say that most of the world’s coral is doomed to die
Wow. Talk about being responsible stewards of the earth…
This is really sad. Coral reefs have probably existed for millions of years, and we wiped them out in a few hundred.
In tropical shallow waters, a temperature increase of up to
only 3° C by 2100 may result in annual or bi-annual bleaching
events of coral reefs from 2030–2050. Even the most optimistic
scenarios project annual bleaching in 80–100% of the World’s
coral reefs by 2080. This is likely to result in severe damage
and wide-spread death of corals around the World, particularly
in the Western Pacific, but also in the Indian Ocean, the Persian
Gulf and the Middle East and in the Caribbean.
As CO2 concentrations in the atmosphere increase so does
ocean assimilation, which, in turn, results in sea water becoming
more acidic. This will likely result in a reduction in the area
covered and possible loss of cold-water coral reefs, especially
at higher latitudes. Besides cold-water corals, ocean acidification
will reduce the biocalcification of other shell-forming organisms
such as calcareous phytoplankton which may in turn
impact the marine food chain up to higher trophic levels.
Key coral reefs ‘could disappear’
By Lucy Williamson
BBC News, Manado, Indonesia
The world’s most important coral region is in danger of being wiped out by the end of this century unless fast action is taken, says a new report.
The international conservation group WWF warns that 40% of reefs in the Coral Triangle have already been lost.
The area is shared between Indonesia and five other South East Asian nations and is thought to contain 75% of the world’s coral species.
It is likened to the Amazon rainforest in terms of its biodiversity.
Climate targets ‘will kill coral’
By Richard Black
Environment correspondent, BBC News website
Current climate targets are not enough to save the world’s coral reefs – and policymakers urgently need to consider the economic benefits they bring.
Those are two of the conclusions from a UN-backed project aiming to quantify the financial costs of damaging nature.
Studies suggest that reefs are worth more than $100bn (£60bn) annually, but are already being damaged by rising temperatures and more acidic oceans.
The study puts the cost of forest loss at $2-5 trillion annually.
Looking ahead to December’s UN climate conference in Copenhagen, study leader Pavan Sukhdev said it was vital that policymakers realised that safeguarding the natural world was a cost-effective way of protecting societies against the impacts of rising greenhouse gas levels.
“In time, it sent me searching for two other pieces of esoteric but existentially critical science news that emerged in 2008 and quickly vanished in the churning media sea of burst housing bubbles and flailing banks. The first was a concise policy paper released in August and signed by fourteen of the world’s top ocean researchers — Charlie Veron among them — under the title The Honolulu Declaration on Ocean Acidification and Reef Management. Their statement noted the imminent onset of levels of ocean acidity not seen in “tens of millions of years,” which would “compromise the long-term viability of coral reef ecosystems.” The crisis was phrased more bluntly in the accompanying press release: “In July 2008, scientists at the International Coral Reef Symposium in Florida declared acidification as the largest and most significant threat that oceans face today and conveyed that coral reefs will be unable to survive the projected increases in ocean acidification.””
Diversity of corals, algae in warm Indian Ocean suggests resilience to future global warming
Published: Tuesday, February 16, 2010 – 11:59 in Earth & Climate
Penn State researchers and their international collaborators have discovered a diversity of corals harboring unusual species of symbiotic algae in the warm waters of the Andaman Sea in the northeastern Indian Ocean. “The existence of so many novel coral symbioses thriving in a place that is too warm for most corals gives us hope that coral reefs and the ecosystems they support may persist — at least in some places — in the face of global warming,” said the team’s leader, Penn State Assistant Professor of Biology Todd LaJeunesse. According to LaJeunesse, the comprehensiveness of the team’s survey, which also included analysis of the corals and symbiotic algae living in the cooler western Indian Ocean and Great Barrier Reef area of Australia, is unparalleled by any other study.
World’s coral reefs could disintegrate by 2100
Researchers at Carnegie Institution say corals are being overwhelmed by rising carbon dioxide in the atmosphere
The world’s coral reefs will begin to disintegrate before the end of the century as rising carbon dioxide levels in the atmosphere make the oceans more acidic, scientists warn.
The research points to a looming transition in the health of coral ecosystems during which the ability of reefs to grow is overwhelmed by the rate at which they are dissolving.
More than 9,000 coral reefs around the world are predicted to disintegrate when atmospheric carbon dioxide levels reach 560 parts per million.
The amount of carbon dioxide in the atmosphere today stands at around 388ppm, but is expected to reach 560ppm by the end of this century.
Coral reefs are at the heart of some of the most biodiverse marine ecosystems in the world. They are home to more than 4,000 species of fish and provide spawning, refuge and feeding areas for marine life such as crabs, starfish and sea turtles.
“These ecosystems which harbour the highest diversity of marine life in the oceans may be severely reduced within less than 100 years,” said Dr Jacob Silverman of the Carnegie Institution in Stanford University, California.
Scientists put reef in deep freeze; Coral suspended in liquid nitrogen in effort to preserve Australian treasure
The arid plains fringing Australia’s desert centre are more suited to camels than blooms of coral, but here, hundreds of kilometres from the coast, a piece of the Great Barrier Reef has been put on ice.
Suspended in a liquid nitrogen chamber of -196 C, the 70 billion sperm and 22 billion coral embryos are part of an ambitious Australian project to preserve and perhaps one day regenerate the world-famous reef.
“We know the Great Barrier Reef is in deep, deep trouble because of a number of different things – global threats including climate change and acidification of waters as well as the warming of waters,” said the project’s director, Rebecca Spindler. “We will never have as much genetic diversity again as we do right now on the reef, this is our last opportunity to save as much as we possibly can.”
Spindler’s team is working with Hawaii-based Mary Hagedorn from the Smithsonian Institution to collect and freeze samples from the World Heritage-listed reef, a sprawling and vivid natural wonder visible from space.
In order to maximize the amount of reproductive cells – gametes – collected, the team cut away sections of the reef and took them back to land-based tanks to spawn, an event that only occurs for three days a year.
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