Climate change means Arctic may no longer be a safe haven for nesting birds

Our planet is changing. So is our journalism. This story is part of a CBC News initiative entitled Our Changing Planet to show and explain the effects of climate change and what is being done about it.

Wildlife research scientist Paul Smith is a lot like the birds he studies: every spring, when the ice recedes, he migrates north to the Arctic. But while he's been able to adapt to the changing climate, the nesting birds have not been so lucky in the face of new threats.

Historically, in Cape Dorset, Nunavut, when migratory birds would sit on their nests in June and July to incubate their eggs, polar bears were still out on the ice eating seals.

These days, Smith has witnessed an earlier ice melt that leads to bears coming to shore sooner. That means the birds' breeding ground becomes a snack bar.

"The bears are swimming onto islands where there are nesting colonies of birds, and gobbling up thousands of eggs," said Smith, who works for the National Wildlife Research Centre at Environment and Climate Change Canada.

In recent years, Inuit elders have reported seeing more bears near their communities, which has led to deadly attacks in some cases. Smith and his fellow research scientists stopped sleeping in tents and now stay in small cabins, surrounded by electric fences. 

Birds such as eider ducks and thick-billed murres are struggling to adapt.

"One bear can eat a thousand eggs in a sitting, and wipe out an entire nesting colony island, and that's it for that year for those birds," Smith said. 

It's a lose-lose situation — the eggs are not enough to substitute a polar bear's traditional diet of seals, which they can't access once the ice melts — and yet the loss of all those eggs is a major blow to the local population of birds.

A recent qualitative review paper argues that the introduction of new predators is one example of how climate change is eroding the benefits of northward migration for birds, insects and other species around the world.

The authors suggest the Arctic is no longer the safe harbour for breeding and nesting that it once was.

The report, Animal migration to northern latitudes: environmental changes and increasing threats, explores how climate change is shifting Arctic and boreal habitats by contributing to the spread of parasites and diseases, an increase in predators, and timing gaps between when food supply is available and when offspring need to feed. 

"The [impact on] species could be like a domino," said co-author Tamás Székely, an evolutionary biologist and professor of biodiversity at the University of Bath in England.

He said it's difficult to know what will happen if climate change continues at this rate — some birds might stop migrating or migrate differently, while others may not be able to adapt.