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The ice sea sentinels and climate change

Benoît Hervieu
Benoît Hervieu
Journalist at Usbek & Rica

Global warming is disrupting the climate-regulating role played by the North and South Pole ice sheets. It also compromises ecosystems that local predators depend on. To understand its impact on this environment, in 2017 the SENSEI project (Sentinels of the Sea Ice) was launched with funding from the BNP Paribas Foundation’s Climate & Biodiversity Initiative programme.

Its originality lies in collecting information from animals that are now threatened, as Christophe Barbraud, researcher at the Centre for Biological Studies in Chizé (CNRS - University of La Rochelle), explained during the September 23rd conference which is part of the Climate & Biodiversity Initiative conference cycle organised by the BNP Paribas Foundation.

Measuring the impact of global warming on species that inhabit the Arctic and Antarctic regions

States have been slow to face the challenge of global warming and the polar regions are among the first to suffer. In the Arctic, the ice pack has shrunk by nearly 20% over the past three decades. Some forecasts predict that within 20 years it will simply vanish during the summer. The trend seems less pronounced in Antarctica, despite the rise in southern ocean temperatures precipitating the melting of coastal ice. From one continent to another, the cold storage reservoir, which is crucial for global climate regulation, has a reduced capacity that satellites, submarines, ships and smart buoys have already measured. But what do we know about the impact of climate change under the surface of the sea ice where exists this rich ecosystem vital for the survival of marine mammals and birds? What will be their demographic and behavioural responses to changes caused by global warming?

To answer these questions, the SENSEI project, conducted on both polar continents and now involving 15 universities from six countries, has taken the unprecedented step of enlisting help from predators in the local ecosystem.  

"The reverse side of sea ice is a high generator of biomass and primary production," says Barbraud. 

 "Phytoplankton is consumed by a cold water shrimp, krill, which in turn is eaten by fish.  The feeding and movement of birds and phocids depend on this chain.  Hence the interest in obtaining information through these animals.”

The reverse side of sea ice is a high generator of biomass and primary production.

Several species have become scientific helpers equipped with mini-cameras, sensors and GPS beacons. Black-legged kittiwake, thick-billed murres, black guillemot and hooded seals have been enlisted in the Arctic. In Antarctica, where a 10-week mission is set to start in November, the emissaries are snow petrels, Adelie penguins, Weddell seals, sea elephants and emperor penguins. "The seals and sea elephants carry mini-radars emitting an echo that allows the thickness of the ice to be measured from below," says Barbraud. "The same process is being developed on penguins.  It’s relatively easy to equip diving birds and mammals that regularly return to land.”  

Adaptation to climate change

The impact of climate change is modelled from their migration to the pack areas, in other words to the drifting sea ice where they feed.  "Variations in behaviour within the same population, particularly between young and old or male and female, must also be taken into account," adds Barbraud.  Should the threat to this icy hunting and breeding ground now give rise to fears for its residents’ future?  

"Global warming has serious consequences on the habitat and reproduction of species such as the emperor penguin," said Barbraud. "An entire colony has gone extinct on the Antarctic Peninsula." The same warming effects can be seen among some populations of hooded seals or Adelie penguins. In the Arctic, the forecast is gloomier for the black guillemot, which is highly affected in terms of diet by the decrease in ice and is subject to polar bear predation. “Unfortunately, local extinctions cannot be ruled out within the next 10 years,” warns the researcher.

Other factors add to the tragedy. One of them is overfishing, reducing both fish and krill stocks. "Here, there is a paradoxical effect," notes Barbraud. "The decrease in krill, fished at an annual rate of 500 million tonnes, favours longer carbon sequestration by phytoplankton. The effect is positive in the short term but negative in the long term." And just like the animals that eat them, krill and phytoplankton absorb pollutants. Mercury and chemical molecules circulate in the Poles as elsewhere.  Blood samples taken from some animals have explained their lower fertility and declining survival rates. “Seventeen kinds of plastic have been found in Antarctica, where DDT has also been found in penguins,” says Christophe Barbraud. "The combination of warming and pollutants and their cumulative effects remain to be studied.  But why ban some pollutants while allowing others?"

Once again, the survival of species will depend on their ability to adapt.  "Almost all of them have experienced it, but the rate of global warming has never been so high," Barbraud warns.  In four generations, birds and phocids from the Poles will have to develop genetic changes that would have previously occurred over thousands of years.  Time is short. The equation calls for action.  

Photo Credits - SENSEI Project Research Team 

Climate & Biodiversity Initiative

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