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Early spring for some Arctic plants is bad news for caribous

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One plant species is now budding 26 days earlier than it did a decade ago

Eric Post / UC Davis

Some plant species in Greenland are experiencing early springs amid a changing Arctic. Global warming is throwing off some plants’ “natural” clocks, causing them to bud earlier than in the past, according to a new study. That can have consequences for herbivores, like caribous, that rely on the plants to survive.

The study, recently published in the journal Biology Letters, relied on 12 years of observations at a site in West Greenland. The researchers looked for signs of growth in individual plants from early May to late June each year. During that time, Arctic plants rely on warmer temperatures and receding ice to understand when it’s time to wake up from winter and start growing again.

The researchers found that some plant species budded earlier than in the past. One grassy sedge species, for instance, now buds 26 days earlier than it did a decade ago. That was a surprising finding. “When we started studying this, I never would have imagined we’d be talking about a 26-day per decade rate of advance,” lead author Eric Post, a polar ecologist in the UC Davis Department of Wildlife, Fish and Conservation Biology, said in a statement. “That’s almost an entire growing season. That’s an eye-opening rate of change.”

The changes were associated with diminishing sea ice cover, which means that the changing Arctic landscape due to global warming is having real effects on the area’s ecology. Not every plant experienced early spring, however. Some plants like a dwarf birch species is budding only five days earlier than it did a decade ago, while the gray willow hasn’t changed at all. The result is that the gap between early bloomers and late bloomers is widening, so there are now longer periods of time when no plants are blooming at all.

The consequences can be particularly strong for herbivores in the area that need the plants for nutrition. Previous studies by Post have shown that fewer caribou calves are born and more die early in years when spring plant growth doesn’t match the caribou calving season.

“That’s one example of the consequences of this for consumer species like caribou, who have a limited window to build up resources before going into the next winter,” Post said. “With the most recent study, we’re taking a step toward understanding how extensive and cryptic the effects of sea ice loss might be in the Arctic.”