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Arctic shorebirds face rising predation risk

November 13, 2018, by Tim Radford

The spoon-billed sandpiper, one Arctic shorebird in trouble. Image: By JJ Harrison (jjharrison89@facebook.com) via Wikimedia Commons

Rapid warning means rapid change in the north. That’s bad news for the hardy Arctic shorebirds and delicate plants that once found safety there.

LONDON, 13 November, 2018 – Vulnerable baby birds are no longer safe in their nests. New research shows that nest predation – the theft of the eggs of migrant Arctic shorebirds such as plovers and sandpipers in the high latitudes of the northern hemisphere – has risen threefold in the last 70 years.

A second study suggests that the very thing that encourages Arctic plant growth – the rapid warming of the north polar regions – also means a loss of vital snow cover for the delicate plants in the high mountains that depend on snow for winter insulation. This is bad news for the snow buttercup, mountain sorrel and mossplant.

British, Czech, Russian and |Hungarian researchers report in the journal Science that they compared rates of nest robbery over two timespans, from 1944 to 1999 and from 2000 to 2015, around the world.

Altogether the study covered 38,191 nests in 237 populations of 111 species in 149 locations. Nest predation in the tropics was always higher – perhaps because there are more predators – and tropical bird species tend to counter offspring loss by living longer to generate more.

But, the researchers found, nest predation in temperate Europe, Asia and North America had doubled. And in the Arctic, nestling loss by shorebirds had risen threefold.

“The future changes in northern species populations may be abrupt, giving rise to ecological surprises that are hard to predict”

In fact, certain species have always flown far north to breed because until the Arctic began to warm rapidly, as a consequence of ever higher levels of the greenhouse gas carbon dioxide in the atmosphere, the Arctic provided a relatively safe space for ground-nesting birds.

The reason for ever greater nest losses? This has yet to be established. But the guess is that as change comes to the plants and animal life of the Arctic, either predator species have changed, or the loss of familiar prey has forced a change of diet on hunters.

Because snow cover in the high Arctic has changed the lemming population has crashed, and the carnivores that hunted lemmings may now have turned to birds’ nests.

“These findings are alarming. The Earth is a fragile planet with complex ecosystems, thus changes in predator-prey relationships can lead to cascading effects through the food web with detrimental consequences for many organisms thousands of kilometres away,” said Tamás Székely, a biologist at the University of Bath, UK, with research posts at Hungarian and Chinese universities.

Final blow

“Migration of shorebirds from the Arctic to the tropics is now one of the largest movements of biomass in the world. But with increased nest predation, the babies are no longer making the journeys with their parents. This could be the last nail in the coffin for critically-endangered species such as the spoon-billed sandpiper.”

And Vojtěch Kubelka, of Charles University in Prague, who led the research, said the Arctic was no longer a safe harbour for breeding birds. “On the contrary, the Arctic now represents an extensive ecological trap.”

Rapid warming of the north polar regions also means a more rapid invasion of plants from further south and a change in plant response.

Finnish scientists report in the journal Nature Climate Change that changes in snow cover on the high ground may be an even greater danger to Arctic biodiversity than rising temperatures.

Snow cover crucial

They looked at satellite data and computer-based models of probable change as humans burn ever more fossil fuels to drive global warming and climate change, and applied the results to 273 flowering plants, mosses and lichens at 1200 locations in the mountains of northern Scandinavia.

Snow that now lingers until late spring provides vital protection for fragile growths and prevents hardier southern species from colonising the same habitat. In brief, it limits the competition.

The great unknown remains snowfall: while climate scientists can be sure of likely future temperatures at any latitude, it is much harder to predict changes in precipitation. But if the snow cover is reduced, then local extinction rates could accelerate. Plants that once maintained a precarious hold in extreme conditions could vanish with the snows.

“Our findings show that the future changes in northern species populations may be abrupt, giving rise to ecological surprises that are hard to predict, such as fast eradications of populations in some places and the invasion of flexible species into new places”, said Risto Heikkinen from the Finnish Environment Institute. – Climate News Network

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