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In Arctic, scientists see dire effect of ocean acidification
by Staff Writers
Ny-Aalesund, Norway (AFP) July 26, 2010

File image: Ny-Aalesund.

Climate change could spur Mexican migration to US: study
Washington (AFP) July 26, 2010 - Global warming could drive millions more Mexicans into the United States in search of work by 2080 due to diminishing crop yields in Mexico, a study released Monday showed. "Depending on the warming scenarios used and adaptation levels assumed... climate change is estimated to induce 1.4 to 6.7 million adult Mexicans (or two percent to 10 percent of the current population aged 15-65 years) to emigrate as a result of declines in agricultural productivity alone," the study said.

Researchers led by Michael Oppenheimer of the Woodrow Wilson School of Public and International Affairs at Princeton University estimated the sensitivity of migration to climate change and predicted the number of Mexicans who would migrate under a range of different climate and crop yield scenarios. In the worst-case scenario would occur if temperatures were to rise by one to three degrees Celsius (1.8 to 5.4 degrees Fahrenheit) by 2080, if farming methods had not been adapted to cope with global warming and if higher levels of atmospheric carbon dioxide had not spurred plant growth. This would mean crop yields in Mexico would fall by 39 to 48 percent, the study said. "In that case, the increase in Mexico's emigration as a share of population would be between 7.8 percent and 9.6 percent," said the study, which was published in the Proceedings of the National Academy of Sciences.

"Using today's population of 70 million as the base for the age 15-65 year population in Mexico, this percentage increase corresponds to an additional 5.5 to 6.7 million emigrants," it said. The study focused on Mexico because it is "one of the biggest migrant-source countries, because there exists state-level data on emigration, and because it has undergone diverse degrees of climate variability across regions." But the findings are relevant to the many countries in Africa, south Asia, and Latin America, and even to Australia, where the authors of the study predict migration will become a "significant issue" as climate change drives temperatures up and crop yields down.

The icy Arctic waters around Norway's archipelago of Svalbard may seem pristine and clear, but like the rest of the world's oceans they are facing the threat of growing acidity.

Oceans have always absorbed part of the carbon dioxide, or C02, present in the air, which in turn makes them acid. But with CO2 levels soaring, the scientific community is getting worried about acidification harming marine life.

Off the coast of Ny-Aalesund, a tiny coal mine village turned scientific outpost just 1,200 kilometres (745 miles) from the North Pole, researchers from nine European countries conducted in July an unprecedented effort to analyse the phenomenon.

To do so, they submerged nine tubes, each weighing two tonnes and the height of two double-decker busses, in the icy waters of the remote fjord framed by snow-capped mountains.

They then injected the water-tight tubes, called mesocosms, with CO2, to reproduce sea life under different acidity levels expected from now until 2150 with the aim of studying the potentially disastrous effects of acidification on marine life.

"It's here in the Arctic that the ocean will become corrosive the fastest," Jean-Pierre Gattuso, with France's National Center for Scientific Research, said, explaining why the researchers chose to turn these waters thick with icy slush into a laboratory.

The threat to the world's oceans is not so much the absolute concentration of acidity, but rather the pace at which it is changing, Gattuso explained, pointing out that "cold water swallow up gas faster than hot or temperate water."

Oceans absorb more than a quarter of the CO2 emitted by humans, which in one way is fortunate since this natural absorption mitigates the impact the gas has on the climate.

However the soaring levels of man-made CO2 in the atmosphere are proving devastating to the oceans themselves: since the beginning of the industrial era they have become 30 percent more acidic, reaching an acidity peak not seen in at least 55 million years, scientists say.

And with no sign of CO2 emissions slowing down, ocean acidification will likely keep increasing in the decades to come.

This is especially worrisome since higher acidity levels have been shown to sharply slow calcification in corals, shellfish and other species.

Corals, a source of rich biodiversity that prevents land area from being submerged and draws much-needed tourists to some of the world's poorest corners, might thus have trouble shaping their skeletons, while shellfish could lose their shells.

-- Adaptation is less likely --


Ulf Riebesell, a German oceanographer, said not all sea creatures were equal in their ability to adapt to their increasingly acid environment.

"For micro-organisims which have generation times of a few days, adaptation may happen during the next 100 years or so as the ocean continues to acidify to critical levels," explained the researcher from the IFM-Geomar centre, braving glacial winds in a bright yellow padded windbreaker and a woolen hat.

But for organisms with long life spans, like corals, "adaptation is much less likely because they need so many generations to change their genetic set-up," Riebesell said.

Scientists caution the current frantic increase of seawater acidity is already causing serious problems for the pteropod, a sort of sea snail vital for the Arctic food chain.

The tiny, translucent mollusc could end up naked in the near future, unable to shape its shell in an increasingly acid environment, explained Jan Buedenbender, another German researcher from the IFM-Geomar institute.

This could have far-reaching consequences, he warned.

"They're a key species for the Arctic food system because they're feeding on very small particles and on phytoplankton, and they're getting quite big and really big animals like whales and birds and fish can feed on them," he explained.

They are also key because their shell contributes to fighting climate change, since it helps the sea snail sink to the bottom when it dies, dragging down all the CO2 ingested over its short lifespan.

By doing so "they're helping the ocean take up more CO2," Buedenbender said.

There is still a chance to save species like the pteropod, according to Iris Menn, a marine biologist with Greenpeace which shipped the giant test-tubes up to Svalbard.

But there is no easy solution. To make a difference, industrialised countries will have to slash their CO2 emissions by 40 percent by 2020, she said.

"We can't stop the trend anyway. We will have a high level of acidity in the water no matter what," she said.

"But what we can do is stop CO2 emissions, so the effect will be reduced."


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