Climate change is the big wild card when it comes to the survival of many Arctic species. A new study shows that climate change will be both good and bad for Svalbard barnacle geese populations — although the balance may tip depending upon the severity of future temperature increases and how other species react.
Life over the last half century has been pretty good for populations of Svalbard barnacle geese. A hunting ban implemented in the 1950s in their overwintering area in Scotland has led to explosive population growth — from roughly 2800 birds in 1960 to more than 40000 birds today.
But what will happen to these birds and others like them, which migrate to Arctic nesting grounds, as the climate grows warmer?
You might think that a warmer climate in the Arctic would only be beneficial, but shorter winters with earlier springs — as has already been recorded in places like Svalbard — are not necessarily good for birds that migrate there. Birds can arrive too late to match their breeding period with peak availability of their food.
And that’s just one possible issue raised by climate change. Another problem is that even when the birds can benefit from earlier springs, their predators can benefit from climate change, too.
Now, a team of researchers from Norway and the Netherlands has put together the puzzle of just how climate change affected a local Svalbard barnacle geese population. They’ve found that so far, climate change has been both good and bad for the birds — with a net zero effect.
“When you consider the earlier springs, it’s good news so far,” says Kate Layton-Matthews, a PhD candidate at the Norwegian University of Science and Technology’s Centre for Biodiversity Dynamics and the first author of the new study. “But the predation part outbalances the benefits from climate change.”
3487 birds over 28 years
The researchers relied on data on from 3487 geese that have been collected since 1990 from Ny-Ålesund, a small town in the Svalbard archipelago.
Over that period, senior author Maarten Loonen at the University of Groningen in the Netherlands collected sightings and physical data from the birds — their number of eggs, number of hatchlings and much more — and also put rings on the birds’ legs so they could be re-identified, year after year.
That wealth of information allows the researchers to be able to track overall population changes and to combine population data with other measurable variables, such as temperatures, time of snowmelt, start of growing season and the like. Co-author Eva Fuglei at the Norwegian Polar Institute also collected annual data on the abundance of the main predator, the Arctic fox.
“I have been studying this goose population for more than 30 years, and have seen increasing complexity in explaining population trends. Too many factors were changing at the same time, including climate change,” Loonen said. “The beauty for me in working with the team in Norway is that they could bring many of these factors together, especially related to climate change all along the flyway. The long data series from the Arctic is unique in its detail, but also the spatial scale on which these migratory birds operated and are affected by climate change.”
In short, this huge complex dataset gives a detailed picture of the birds’ lifecycles and how and why this has changed over the years, especially as the climate has warmed.
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Contrasting consequence of climate change for migratory geese: predation, density dependence and carryover effects offset benefits of high-arctic warming. Global Change Biology 2019. Kate Layton-Matthews, Brage Bremset Hansen, Vidar Grøtan, Eva Fuglei and Maarten JJE Loonen.DOI: 10.1111/gcb.14773
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