Extreme snowfall kept most plants and animals in one Arctic ecosystem from reproducing

When Jeroen Reneerkens stepped off the plane in Greenland, all he saw was white.

The avian ecologist at the University of Groningen in the Netherlands was expecting to find snowless tundra teeming with life, as he had each summer for nearly a decade. Reneerkens travels to Zackenberg Research Station in northeast Greenland to study sanderlings — slight, mottled-brown arctic shorebirds — as they and other migratory shorebirds noisily descend on the open tundra to breed each summer (SN: 11/13/18).

But when Reneerkens arrived in 2018, he found only snow and silence. “There were no birds singing, even the river was still frozen,” Reneerkens says. “I was shocked.”

A study published October 15 in PLOS Biology documents an ecosystem-wide reproductive collapse around Zackenberg in 2018. Most plants and animals, including everything from arctic foxes to tiny Dryas flowers, failed to reproduce that year, because an extremely snowy winter left much of the ground covered with snow well into summer, Reneerkens and colleagues found.

Climate scientists predict that, as the globe warms, parts of the Arctic will see more precipitation and more extreme seasonal fluctuations (SN: 9/25/19). If years like 2018 become more common, the authors warn that the consequences for the ecosystem could be drastic.

“To see failure at so many levels of the food web is highly unusual,” says Warwick Vincent, an arctic ecologist at Laval University in Quebec City who wasn’t involved in the study. “Climate change is all about extremes, and this is a compelling example of how we’re moving into a world that’s less and less predictable.” 

For more than two decades, researchers at Zackenberg have carefully tracked the rhythms of arctic life. “There’s no such thing as a normal arctic summer,” says study coauthor Niels Martin Schmidt, an ecologist at Aarhus University in Roskilde, Denmark. But the snow usually melts in early June. “It’s like the lid gets pulled off the ecosystem, and everything starts,” he says.

Plants peek out of the soil and open their flowers to the long days. Hordes of insects emerge, pollinating plants and becoming food for migratory birds. Arctic fox cubs prowl bird nests looking for eggs, and stolid musk oxen birth calves that quickly join the herd.

“It’s a highly interdependent ecosystem that is resilient to variability,” says Martin Schmidt, “but only to a point.” The extreme snowfall in 2018, more than double what many parts of the field site usually experience, proved too much for the ecosystem, the researchers found.

By late July 2018, when the tundra around the research station is usually in full swing, 45 percent of the landscape was still covered in snow, entombing many plants and insects. While many plants eventually did flower, their seeds didn’t have enough time to sprout before the first freeze in August, the team found. Insects eventually emerged, but mostly too late to be fed upon by migratory birds.

That meant that the sanderlings and other birds that had flown halfway around the globe from as far as Namibia expecting a feast arrived to slim pickings.

“Many birds must’ve turned back. We only saw about a quarter of what we normally see,” Reneerkens says. The birds that did arrive huddled close to the field station for food scraps. “They were skeletons with some feathers,” he says, “Just super, super lean.”

Reneerkens found just one sanderling nest that season, which hatched “ridiculously late” on August 5, he says. Normally, the eggs would hatch in mid-July. Other birds fared just as poorly, and the few young that did hatch probably weren’t healthy enough to survive the southward migration, starting in later August.

Mammals were hit hard, too. The researchers saw no arctic fox cubs, and almost no musk ox calves that season. The entire ecosystem essentially came to a reproductive halt, Martin Schmidt says. “I try not to be sentimental, but it was scary,” he says. “In nearly 25 years of monitoring, we’ve never seen anything like this.”

One bad year, even this bad, doesn’t spell disaster for an arctic ecosystem. Plants and animals can reproduce again the next year, with few consequences. But the following summer swung towards the opposite extreme: Record high temperatures led to a much earlier snowmelt and then drier conditions in Zackenberg. The researchers worry that, as extreme events become more common, one bad breeding year could extend to two or three. “How many years in between do we need before the system collapses for real?” Martin Schmidt asks. “That we don’t know.”