MARRAKESH, Morocco, Nov 25 (Thomson Reuters Foundation) -
When nearly all the young oyster crop died two years in a row at
shellfish farms in the U.S. Pacific Northwest, workers at first
suspected a virus.
But the real culprit was a new worry: a change in the
acidity of the sea water feeding the oyster tanks.
As the world's oceans absorb carbon dioxide that is building
up in the atmosphere, seas have become 30 percent more acidic
than they were before the industrial era, said Carol Turley, a
senior scientist at Britain's Plymouth Marine Laboratory.
The increasingly corrosive water threatens a wide range of
sea life, particularly shellfish such as oysters and scallops,
making it hard for them to form and maintain shells.
Warming of the world's oceans, as they absorb rising heat
associated with climate change, also is killing coral reefs and
driving more fish species toward cooler seas and away from the
regions where they have traditionally lived and been caught,
Turley said on the sidelines of the recent U.N. climate talks in
Another effect of warming is a reduction in the amount of
oxygen in the sea, threatening fish, said Ulf Riebesell, a
German ocean researcher who works on acidification, among other
"The ocean is under a major challenge. It's not only heating
up, it's also acidifying and losing oxygen. The three stressors
come simultaneously and they play out worldwide," he said in
That is fuelling new challenges for both rich and poor
communities around the world, from small-scale fishermen who can
no longer bring in a catch, to conservationists watching fish
move out of hard-won reserves, and coastal and island states
fearful their tourist industries will collapse with their ailing
"It's happening too fast for organisms and ecosystems to
develop strategies to cope," said Hans Pörtner, a scientist with
the German-based Alfred Wegener Institute and a contributor to
the work of the Intergovernmental Panel on Climate Change.
"There's a high risk of losing up to 90 percent of coral
reefs in a 1.5-degree Celsius warmer world by the end of the
century. This is a system that has already gone beyond its
tolerance limits," he said.
ADAPTING TO CHANGE
Rapidly cutting planet-warming emissions is the surest way
to deal with the problem and limit potential damage, scientists
say. But with a global shift to clean energy happening more
slowly than is needed so far, fishing communities around the
world will have to find ways to adapt to the changes - and some
are already trying out ideas, scientists say.
At oyster farms in the U.S. Pacific Northwest, for instance,
monitors now check the acidity level of ocean water coming into
the tanks of young oysters. If levels begin to rise, as a result
of upwellings of acidic ocean water, intakes are shut off or can
be adjusted to draw water from different levels, Turley said.
At least one big oyster operation, after major losses due to
ocean acidity in 2007 and 2008, shifted production to Hawaii,
where upwellings of acid water are less of a problem, she said.
Poorer fishing communities may be able to adopt early
warning systems too, said Ana Queirós, a marine ecologist at the
For instance, they could quickly harvest a bigger number of
fish if satellite monitoring of currents showed warm, low-oxygen
water that could kill fish moving toward fishing grounds, she
"These are real-life adaptation measures - though they are
also temporary solutions," Queirós said, particularly if more of
the oceans become regularly inhospitable for fish and other sea
Turley believes poor communities that risk losing their
reefs could also turn to "carbon farming" by growing and
harvesting seaweed, which takes up ocean carbon.
Turning seaweed into anything from food to drugs, fertiliser
and roof thatching could help bring in an income to supplement
or replace fishing, she said, and communities may be able to
earn money from carbon credits as well.
"We've been looking at impacts (of climate change), but now
we also need to look at solutions, for both the short term and
the long term," she said.
Mayrah Shaltout of Morocco's National Institute of
Oceanography and Fisheries said coastal communities in Africa
are already seeing declines in fish catches - and not just
because of competition from industrial trawlers.
Two thirds of the countries most vulnerable to fishing
declines are in Africa, she said.
In other parts of the world, Atlantic cod are moving north
toward the Arctic, seeking cooler waters, while young barnacles
off the British coast are gradually moving north as well,
"The species will go if they can," she warned. "Science
tells us the changes are going to happen, and they're going to
be much more prevalent than what we're seeing now."
(Reporting by Laurie Goering; editing by Megan Rowling; Please
credit the Thomson Reuters Foundation, the charitable arm of
Thomson Reuters, that covers humanitarian news, climate change,
women's rights, trafficking and property rights. Visit news.trust.org/climate)