Fast-Growing Moss Is Turning Antarctica Green

Rising temperatures have boosted the growth rates of seasonal moss on the southern continent over the last 50 years.

The icy landscape of Antarctica is getting decidedly greener.

By drilling down into layers of moss that have accumulated on the southern continent over the last 150 years, researchers discovered that those diminutive plants have done more growing than usual in the last five decades.

The driving force, they say, is warmer global temperatures—as Antarctica’s ice melts, more water is available to moisten the mosses, and the rising heat provides longer growing seasons for the plants. 

"Temperature increases over roughly the past half century on the Antarctic Peninsula have had a dramatic effect on moss banks growing in the region," Matthew Amesbury, a paleoclimate researcher at the University of Exeter in the U.K., said in a statement.

"If this continues, and with increasing amounts of ice-free land from continued glacier retreat, the Antarctic Peninsula will be a much greener place in the future."

SEE THE EXTREME CHANGES NEAR THE ANTARCTIC PENINSULA Join the Extreme Ice Survey team on an expedition to South Georgia Island near the Antarctic Peninsula.

Mosses, in general, grow very slowly, and in cold polar regions, they accumulate rather than decompose at the end of the growing season. This provides researchers with growth records going back thousands of years, similar to peat accumulations in other regions of the world.

Led by Dan Charman of the University of Exeter, the team took moss core samples at three sites across a 400-mile swath of the Antarctic Peninsula. Jutting north toward South America, the peninsula is the northernmost portion of the Antarctic mainland, an area that would be among the first on the continent to display evidence of shifting climate patterns.

Until about 50 years ago, the two species that dominate the moss banks on the peninsula grew one millimetre or less a year, on average, the team reports this week in the journal Current Biology. Since then, though, the mosses have averaged three or more millimetres a year.

Reliable meteorological records began in the middle of the 20th century, so it’s not possible to correlate temperature and other weather trends with moss layer accumulations prior to then. But a key point is that moss growth and accumulation trended consistently upward since at least the 1950s, even across geographically distant sites, meaning the root cause is widely dispersed. Carbon isotope accumulation—an indication of more photosynthetic activity—and microbial activity also increased.

Based on these patterns, the researchers surmise that further warming could quickly tip the region into a very different ecological landscape—much as how the Arctic region has become more verdant over the last several decades.

“The sensitivity of moss growth to past temperature rises suggests that ecosystems will alter rapidly under future warming, leading to major changes in the biology and landscape of this iconic region," Charman said in the statement. "In short, we could see Antarctic greening parallel to well-established observations in the Arctic."

The globe’s southernmost continent hasn’t always been ice-bound. The discovery of fossil ferns, pines, and ginkgoes from the Cretaceous Era shows that it was once a warm place, and that many plant and animal species lived quite comfortably very near to the South Pole. This renewed greening is, in a way, a step back in time. 

“Change is the pulse of our planet,” Robin Bell, a geophysical researcher with Columbia University’s Lamont-Doherty Earth Observatory, says via email. “So change is not a surprise. But the change caused by humans and the rate of change are both new.”

Though it’s unclear what that means for the planet as a whole, for now, it does represent a new opportunity for research and discovery, Bell says.

“With less ice, more of the continent’s rock will be uncovered, and there will be so many new things to learn,” she says. “It’s so important to leverage all the observations of this remote place we can get our hands on.”

Header Image: Icebergs dot the sea off the moss-covered coast of Green Island in Antarctica. PHOTOGRAPH BY MATT AMESBURY

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