A review of the latest research on the Arctic says the accelerating loss of sea ice is kicking the legs out from under the entire northern dinner table with consequences for large animals and tiny plants alike.
“We’re losing all the things that life depends on,” said Ian Stirling, an adjunct professor at the University of Alberta and one of the co-authors of a study published Thursday in the prestigious journal Science.
The paper reviews dozens of recent studies on the Arctic in an attempt to provide a big-picture look at the overall ecological consequences of vanishing sea ice.
The conclusions are chilling.
“Primary producers dependent on sea ice as their habitat underpin the entire marine food web of the Arctic,” it says. “The loss of over two million square kilometres of Arctic sea ice since the end of the last century represents a stunning loss of habitat.”
Sea ice is home for algae and plankton, which together produce 57 per cent of all the food in northern oceans. Not only does melting ice shrink that habitat, changing seasons have altered when those tiny organisms at their greatest and fastest growth.
Instead of feeding animals hungrily swimming around the ice, the annual bloom of algae and plankton increasingly falls off and filters down to the sea floor. As well, normal types of plankton don’t grow as well in less salty waters around shrinking floes, reducing the benefit of higher growth from increased sunlight.
The effects wind all the way up to the top predators. The impact on polar bears, which use the ice as a hunting platform, has been well publicized, but the animals aren’t the only ones affected.
“Mass mortality among Pacific walrus along the coast of the Chukchi Sea in Alaska has been attributed to loss of sea ice cover over the continental shelf,” says the report.
The indirect effects may be just as dramatic.
Some animals such as wolves and foxes use sea ice to travel, which allows populations to mix and remain genetically healthy. Other animals are kept apart by the ice, such as polar bears and grizzly bears.
“Hybridization between polar bears and grizzly bears may be the result of increasing inland presence of polar bears as a result of a prolonged ice-free season,” the report concludes.
Scientists are now anticipating that a type of distemper common to eastern seals to spill over to the west. Late freeze-ups are likely to disrupt the migration of some caribou herds.
Oceans warmed after losing their sea-ice cover also are expected to promote warming permafrost as far as 1,500 kilometres inland. That warmer tundra is expected to lead to an earlier spring growth, disrupting delicate timing for caribou seeking extra food for their calves.
And much of that increased plant productivity comes in the form of shrubs now spreading across what used to be grassy tundra. Caribou can’t eat shrubs.
There will be winners.
Norwegian Arctic foxes, for example, could suffer less from rabies if Russian populations can no longer cross ice to infect them.
“We’re not saying all these are necessarily bad,” said Stirling. “But there are major changes.”
Sea ice — which Stirling said is as central to the Arctic as soil is to a forest — remains poorly understood by scientists and largely ignored by the public, he said.
“The sense that we’re losing sea ice has become fairly common knowledge,” he said. “I think it’s fairly understood that that is going to have an effect on polar bears.
“But they haven’t thought about it in an ecological sense. Hardly anybody has done that.”