[Reader-list] GW and corals
nagraj.adve at gmail.com
Thu Sep 3 18:10:42 IST 2009
The debate on limiting emissions and global warming often ignores the fact
that over a quarter of all emissions get absorbed by the oceans. This has
already increased oceanic acidity by 30 per cent since the Indus Rev. WIth
disastrous effects for coral reefs. Piece from the Guardian below.
How global warming sealed the fate of the world's coral reefs
Destroyed by rising carbon levels, acidity, pollution, algae, bleaching and
El Niño, coral reefs require a dramatic change in our carbon policy to have
any chance of survival, report warns
- *David Adam* <http://www.guardian.co.uk/profile/davidadam>
- guardian.co.uk <http://www.guardian.co.uk/>, Wednesday 2 September
2009 16.53 BST
[image: Coral reef : An aerial view of teh coastline along Hawaii Kai on
the Hawaiian Island of Oahu]
An aerial view of the coastline along Hawaii Kai on the Hawaiian Island of
Oahu where organic sediment is one of the major threat to the reef.
Photograph: Ed Darack/Corbis
Animal, vegetable and mineral, a pristine tropical
coral<http://www.guardian.co.uk/environment/coral>reef is one of the
natural wonders of the world. Bathed in clear, warm water
and thick with a psychedelic display of fish, sharks, crustaceans and other
sea life, the colourful coral
rise from the sand are known as the rainforests of the oceans.
And with good reason. Reefs and rainforests have more in common than
Both have stood for millions of years, and yet both are poised to disappear.
If you thought you had heard enough bad news on the environment and that the
situation could not get any worse, then steel yourself. Coral reefs are
The situation is virtually hopeless. Forget ice caps and rising sea
the tropical coral reef looks like it will enter the history books as the
first major ecosystem wiped out by our love of cheap energy.
Today, a report from the Australian government agency that looks after the
nation's emblematic Great Barrier Reef reported that "the overall outlook
for the reef is poor and catastrophic damage to the ecosystem may not be
averted". The Great Barrier Reef is in trouble, and it is not the only one.
Within just a few decades, experts are warning, the tropical reefs strung
around the middle of our planet like a jewelled corset will reduce to
rubble. Giant piles of slime-covered rubbish will litter the sea bed and
spell in large distressing letters for the rest of foreseeable time: Humans
"The future is horrific," says Charlie Veron, an Australian marine biologist
who is widely regarded as the world's foremost expert on coral reefs. "There
is no hope of reefs surviving to even mid-century in any form that we now
recognise. If, and when, they go, they will take with them about one-third
of the world's marine biodiversity. Then there is a domino effect, as reefs
fail so will other ecosystems. This is the path of a mass extinction event,
when most life, especially tropical marine life, goes extinct."
Alex Rogers, a coral expert with the Zoological Society of
talks of an "absolute guarantee of their annihilation". And David Obura,
another coral heavyweight and head of CORDIO East
a research group in Kenya, is equally pessimistic: "I don't think reefs have
much of a chance. And what's happening to reefs is a parable of what is
going to happen to everything else."
These are desperate words, stripped of the usual scientific caveats and
expressions of uncertainty, and they are a measure of the enormity of what's
happening to our reefs.
The problem is a new take on a familiar evil. Of the billions of tonnes of
carbon dioxide spewed from cars, power stations, aircraft and factories each
year, about half hangs round in the thin layer of atmosphere where it traps
heat at the Earth's surface and so drives global
What happens to the rest of this steady flood of carbon
Some is absorbed by the world's soils and forests, offering vital respite to
our overcooked climate. The remainder dissolves into the world's oceans. And
there, it stores up a whole heap of trouble for coral reefs.
Often mistaken for plants, individual corals are animals closely related to
sea anemones and jellyfish. They have tiny tentacles and can sting and eat
fish and small animals. Corals are found throughout the world's oceans, and
holidaymakers taking a swim off the Cornish coast may brush their hands
through clouds of the tiny creatures without ever realising.
It is when corals form communities on the sea bed that things get
interesting. Especially in the tropics. Yes, Britain has its own rugged
coral reefs, but such deep-water constructions are too remote, cold and dark
to really fire the imagination. It is in shallow, brightly light waters,
that coral reefs really come to life. In the turquoise waters of the
Caribbean, Indian Ocean and Pacific, the coral come together with tiny algae
to make magic.
The algae do something that the coral cannot. They photosynthesise, and so
use the sun's energy to churn out food for the coral. In return, the coral
provide the algae with the carbon dioxide they need for photosynthesis, and
so complete the circle of symbiotic life.
Freed of the need to wave their tentacles around to hunt for food, the coral
can devote more energy to secreting the mineral calcium carbonate, from
which they form a stony exoskeleton. A second type of algae, which also
produces calcium carbonate, provides cement. Together, the marine
menage-a-trois make a very effective building site, with dead corals leaving
their calcium skeletons behind as limestone. For all their apparent beauty
and fragility, just think of coral reefs as big lumps of rock with a living
A fragile crust too. The natural world is a harsh environment for coral
reefs. They are under perpetual attack by legions of fish that graze their
fields of algae. Animals bore into their shells to make homes, and storms
and crashing waves break them apart. They may appear peaceful paradises, but
most coral reefs are manic sites of constant destruction and frantic
rebuilding. Crucially though, for millions of years, these processes have
been in balance.
Human impact has tipped that balance. Loaded with the agricultural nutrients
nitrates and phosphates, rivers now spill their polluted waters into the
sea. Sediment and sewage cloud the clear waters, while over-fishing plays
havoc with the finely tuned community of fish and sharks that kept the reef
nibbling down to sustainable levels. All of this is enough to wreck coral
without any help from climate
Global warming, predictably, has made the situation worse. Secure in their
tropical currents, coral reefs have evolved to operate within a fairly
narrow temperature range, yet, in the late 1970s and 1980s, coral scientists
got an unpleasant demonstration of what happens when the hot tap is left on
too long. "The algae go berserk," said Rogers. Scientists think the algae
react to the warmer water and increased sunlight by producing toxic oxygen
compounds called superoxides, which can damage the coral. The coral respond
by ejecting their algal lodgers, leaving the reefs starved of nutrients and
deathly white. Such bleaching was first observed on a large scale in the
1980s, and reached massive levels worldwide during the 1997-98 El Niño
weather event <http://www.guardian.co.uk/environment/elnino>.
On top of a human-warmed climate, the 1997-98 El
caused by pulses of warming and cooling in the Pacific, drove water
temperatures across the world beyond the coral comfort zone. The mass
bleaching event that followed killed a fifth of coral communities worldwide,
and though many have recovered slightly since, the global death toll
attributed to the 1997-98 mass bleaching stands at 16%. "At the moment the
reefs seem to be recovering well but it's only a matter of time before we
have another [mass bleaching event]," says Obura.
With its striking images of skeletal reefs stripped of colour and life,
coral bleaching offers photogenic evidence of our crumbling biodiversity,
and has placed the plight of coral reefs higher on the world's
consciousness. Head along to your local swimming pool for diving lessons
these days, and chances are that you will be offered a coral conservation
course as well.
Katy Bloor, an instructor at Sub-Mission Dive School in Stoke-on-Trent, says
many divers are not aware of the problems corals face, particularly as
holiday operators tend to visit reefs in better condition. "Most have
probably dived on a coral reef that they thought was a bit rubbish, but they
haven't considered why," she said.
If anyone knows what they are missing out on, it should be Charlie Veron. So
what does it feel like to dive on a pristine reef? "I have not seen many
reefs that can be called pristine, and none exist now," he says. "But if I
had to take a punt, I was diving on the Chesterfield Reefs, east of New
Caledonia [in the southwest Pacific] about 30 years ago and was staggered by
the wealth of life, especially big fish which were so thick that I was
hardly ever able to photograph coral. That place made even remote parts of
the Great Barrier Reef look second rate.
"I can only describe it like walking through a rainforest dripping with
orchids, crowded with birds and mammals of bewildering variety and trees
growing in extreme profusion."
Can the coral be helped? If planting more trees can regrow a forest, can
coral be introduced to bolster failing reefs? There are a handful of groups
working on the problem, many of which have reported encouraging results. Off
Japan, scientists are farming healthy coral on hundreds of ceramic discs,
which they plan to transplant onto the badly-bleached Sekisei Lagoon reef
within two years. In 30 years or so, they hope the reef can recover fully.
A similar, if more low-tech, exercise is under way in the Philippine coastal
community of Bolinao, where local people have broken off chunks from the
healthy section of their local reef and have crudely wedged them into cracks
in bleached sections. Others have cultured corals in swimming pools,
in the Maldives are using giant sunken
connected to a low level electric current, to help coral form their chalky
But the problem with all these efforts, according to Rogers at the ZSL, is
that they cannot address the looming holocaust that reefs face. A new,
terrible curse that comes on top of the bleaching, the battering, the
poisoning and the pollution.
Remember the carbon dioxide that we left dissolving in the oceans? Billions
and billions of tonnes of it over the last 150 years or so since the
industrial revolution? While mankind has squabbled, delayed, distracted and
dithered over the impact that carbon
on the atmosphere, that dissolved pollution has been steadily turning
the oceans more acidic. There is no dispute, no denial, about this one.
Chemistry is chemistry, and carbon dioxide plus water has made carbonic acid
since the dawn of time.
As a result, the surface waters of the world's oceans have dropped by about
0.1 pH unit – a sentence that proves the hopeless inadequacy of scientific
terminology to express certain concepts. It sounds small, but is a truly
jaw-dropping change for coral reefs.
For reefs to rebuild their stony skeletons, they rely on the seawater
washing over them to be rich in the calcium mineral aragonite. Put simply,
the more acid the seawater, the less aragonite it can hold, and the less
corals can rebuild their structure. Earlier this year, a paper in the
journal Science reported that calcification rates across the Great Barrier
Reefs have dropped 14% since
The researchers said more acidic seas were the most likely culprit, and
ended their sober write-up of the study with the extraordinary warning that
it showed "precipitous changes in the biodiversity and productivity of the
world's oceans may be imminent".
Rogers says carbon dioxide levels in the atmosphere are already over the
safe limits for coral reefs. And even the most ambitious political targets
for carbon cuts, based on limiting temperature rise to 2C, are insufficient.
Their only hope, he says, is a long-term carbon concentration much lower
than today's. The clock must somehow be wound back and carbon somehow sucked
out of the air<http://www.guardian.co.uk/environment/2009/sep/01/geo-technology-testing>.
If not, then so much more carbon will dissolve in the seas that the reefs
will surely crumble to dust. Given the reluctance to reduce emissions so
far, the coral community is not holding its breath.
"I just don't see the world having the commitment to sort this one out,"
says Obura. "We need to use the coral reef lesson to wake us up and not let
this happen to a hundred other ecosystems."
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