Arctic food web and the impacts of Climate Change
Climate change is having a rapid impact on the Arctic food web on land and on the ice. The Arctic is home to the polar bear, caribou, musk oxen, walrus, the beluga and bowhead whales. The creatures most at risk from a warming planet are those that permanently live in the Arctic and depend on sea ice for their survival. The species most at risk include polar bear, seals, walrus and the ivory gull.
The Sea Ice Food Web
When the sea ice begins to melt every Spring this is the signal for life to explode into action. As the ice melts away the sunlight hits the water giving energy to microscopic algae to grow. This algae becomes food for the tiny armies of zooplankton which become food for fish, birds and whales. The Arctic cod is a small fish that is a very important part of the food web. It eats mostly zooplankton and lives water between -2 and 0°C due to a type of antifreeze in its blood. It is the main source of food for some whales, seals and birds of the Arctic. Less ice and warmer water has a direct impact on this key part of the web – the Arctic cod.
Less ice and warming water means that life is far more difficult for polar bears, walrus and seals that rely on the sea ice to hunt and rest. Polar bears need to eat almost 50 seals a year to survive and they and only hunt from mid-spring, through summer and the start of autumn before the oceans freeze over again. Spring rains instead of spring snow can cause the collapse of snow dens and death of seal pups and polar bear cubs. In some places in the lower Arctic the ice is melting much earlier forcing polar bears to scavenge in human settlements before they can go out on the ice to hunt. This early melt causes them to miss out on their main source of spring food – seal pups. Mother polar bears are getting skinnier and fewer cubs are surviving in the southern regions. This drop in southern Arctic polar bears is not great news for the 20,000 polar bears in the rest of the Arctic. The US Geological Survey who studies polar bears noted, ‘projected changes in future sea ice conditions, if realised, will result in loss of two thirds of the world’s current polar bear population by the mid 21st century.’
Land Food Web
The plains in the Arctic are known as the tundra. Covered in snow during winter before plants return in the spring and summer. Warmer weather means the permafrost (frozen ground) is now melting in the southern Arctic turning dry ground into a bog. This is impacting on the caribou (similar to it’s Eurasian cousin the reindeer) migrations causing them to make many detours.
These detours impact on the hunting traditions of the indigenous Inuit people who depend on the caribou for food. In winter, caribou dig up snow to get at the shrubs and lichen below. When icy rain falls instead of the usual snow the food becomes impossible to get to and the caribou die.
This changing climate throws out the balance of nature and animals often arrive after the best of the food has come and gone. This is also affecting birds such as sandpipers and plovers.
In addition, the tree line has moved 10 kilometres north, meaning the southern tundra is getting bushier and the growing season is getting longer. This has meant that the the spruce beetle (previously unable to live so far north due to the cold) are now eating the bark of the pine trees and killing them in some regions.
As the permafrost continues to thaw out and melt roads, houses and sheds begin to buckle, break up and sink into the soft ground.
We can predict some of the impacts of these changes, but not all. There are many things that might or could happen, but even the smartest of scientists and the most accurate of models won’t be able to tell us how it will all play out.
