Greenland’s Lost Summer

Written by Daniel Ackerman on July 16, 2018. Posted in Current News

Instead, a record late snowpack—lingering into July—sealed the birds off from food and nesting sites. Without these key resources avian migrants to the region will not reproduce in 2018, experts say. Breeding failures like this may grow more common because some climate change models predict increased springtime snow in the shorebirds’ nesting habitat.

Snowmelt usually allows shorebirds to begin nesting on eastern Greenland’s treeless tundra during the first half of June, says Jeroen Reneerkens, an avian ecologist at the University of Groningen who has studied these birds since 2003. However, when he arrived this year at Zackenberg Station on June 14 to survey sanderlings, a species of Arctic-breeding shorebird, he found they had nowhere to construct their nests. “The tundra was 100 percent covered in snow, and it was a very deep layer,” he says, estimating an average depth of about one meter. “It was a big shock to see the place like that,” he adds.

Most years, mid-June is also a time of song in eastern Greenland—shorebirds croon to attract mates and defend breeding territory. But this year the tundra was “truly silent,” Reneerkens says. “That was very unusual.” The few shorebirds he did encounter, including sanderlings, ruddy turnstones and red knots, wandered the snow-free patches outside the station’s buildings in search of food. “They were just starving,” he says. “I realized these birds were not getting ready to breed at all. They’re just in survival mode.”

Reneerkens’s research team weighed the sanderlings and found they were 20 percent lighter than normal for this time of year. In such condition the birds can neither reproduce nor escape to better feeding grounds. “They got trapped at Zackenberg,” he says. “They couldn’t just fly south without the [fat] reserves to do so.” His group discovered three carcasses of sanderlings that had apparently starved. Researchers elsewhere along Greenland’s east coast also report extensive snow cover and hungry birds. The region’s tundra was still 80 percent covered in snow as of July 10, according to observations provided by a staff member at Zackenberg.

Although shorebird breeding success fluctuates by 20 percent or more from one year to the next, a nonbreeding summer appears to be unprecedented. “This year broke all records,” Reneerkens says. “I know my literature about Arctic shorebirds very well and I have never come across something like this.” He is uncertain how this “disastrous” incident will affect the overall populations of these shorebird species. But “given the scale that this happening [on],” he says, “I do expect that this will have large consequences.” He estimates the record-late snowmelt impacted half of the global breeding area for sanderlings, red knots and ruddy turnstones.

Nathan Senner, an ornithologist at University of Montana–Missoula not affiliated with Reneerkens’s research, agrees this summer’s reproductive crash in Greenland is exceptional: “A nonbreeding year is pretty extreme.” Senner says the case is reminiscent of 1992, when shorebirds suffered poor reproductive success after Mount Pinatubo in the Philippines erupted the prior year. The tropical volcano belched atmosphere-cooling particles over the planet—including the far north, causing cold summer temperatures in the Arctic. Nevertheless, a study of the eruption showed some birds did successfully reproduce that year.

Researchers elsewhere in the Arctic are also reporting unusually late snowmelt this year, with repercussions for shorebirds. Richard Lanctot, a researcher for the U.S. Fish and Wildlife Service, believes record late snowmelt inhibited nesting near Utqiavik (formerly Barrow) on the northern coast of Alaska. His group’s nest count this summer so far is among the lowest since they began monitoring in 2003. Shiloh Schulte, an avian ecologist who works in northeastern Alaska for the conservation nonprofit Manomet, says snowmelt was more than two weeks later than normal in his region. He noticed flocks of long-billed dowitchers and American golden plovers gathering to migrate south without breeding. “Everything needs to be timed perfectly for these birds to be successful,” Schulte says of the short Arctic summer. On Southampton Island in the Canadian Arctic Archipelago, shorebirds nested at less than half their typical densities due the late snowmelt, according to research scientist Paul Smith of Environment and Climate Change Canada. Even with similar trends throughout the North American Arctic, nowhere has been hit harder than eastern Greenland.

The region’s reproductive failure this summer exacerbates a global nosedive in migratory shorebird numbers. North American populations have halved since the 1970s. Climate change and hunting have contributed to this decline, Senner says. But he emphasizes the single biggest threat to shorebirds is the destruction of “stopover” habitat—areas where the birds rest and refuel while migrating between their Arctic breeding grounds and their southern wintering habitats. One study found that in the past 50 years, 65 percent of tidal flats have been lost to development around the Yellow Sea in east Asia, which had previously served as key stopover point. Climatic challenges like late snowmelt in their breeding grounds only compound the birds’ plight.

Senner fears this nonbreeding year in eastern Greenland could herald an alarming trend. Climate models predict the Arctic atmosphere will hold more moisture as global temperatures rise, he notes. A wetter atmosphere means more snow in winter and spring, potentially causing late snowmelt to interfere with shorebird reproduction. He says the bird populations should be resilient to a single poor breeding year like 2018 but worries what might happen if this year’s catastrophe becomes standard. “Even though things aren’t normally as extreme as the current situation in Greenland,” he says, “this is the kind of thing that seems to be happening more and more frequently across the Arctic”—which is probably bad news for birds.

Read more at www.scientificamerican.com

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