Thanks to global warming, Antarctica is starting to turn green

Researchers in Antarctica have discovered rapidly growing banks of mosses. Photo / Matt Amesbury via Washington Post

Researchers in Antarctica have discovered rapidly growing banks of mosses on the ice continent's northern peninsula, providing striking evidence of climate change in the coldest and most remote parts of the planet.

Amid the warming of the past 50 years, the scientists found two species of moss undergoing the equivalent of growth spurts, with mosses that once grew less than 1mm a year, now growing more than 3mm a year on average.

"People will think of Antarctica quite rightly as a very icy place, but our work shows that parts of it are green, and are likely to be getting greener," said Matthew Amesbury, a researcher with the University of Exeter in the UK and lead author of the study.

"Even these relatively remote ecosystems, that people might think are relatively untouched by human kind, are showing the effects of human-induced climate change."

The study was published Thursday in Current Biology, by Amesbury and colleagues with Cambridge University, the British Antarctic Survey, and the University of Durham.

Less than 1 per cent of present-day Antarctica features plant life. But in parts of the peninsula, Antarctic mosses grow on frozen ground that partly thaws in the summer - when only about the first 30cm of soil thaws.

The surface mosses build up a thin layer in the summer, then freeze over in winter. As layer builds on top of layer, older mosses subside below the frozen ground, where they are remarkably well preserved because of the temperatures.

Amesbury said that made them "a record of changes over time".

Soil samples from a 650km area along the northern part of the Antarctic peninsula found dramatic changes in growth patterns going back 150 years.

The Antarctic peninsula has been a site of rapid warming, and has more days a year where temperatures rise above freezing. The consequence, the study found, was a four- to fivefold increase in the amount of moss growth in the most recent part of the record.

"This is another indicator that Antarctica is moving backwards in geologic time, which makes sense, considering atmospheric CO2 levels have already risen to levels that the planet hasn't seen since the Pliocene, three million years ago, when the Antarctic ice sheet was smaller, and sea levels were higher," said University of Massachusetts glaciologist Rob DeConto, who was not involved in the study but reviewed it for the Washington Post.

"If greenhouse gas emissions continue unchecked, Antarctica will head even further back in geologic time. Perhaps the peninsula will even become forested again someday, like it was during the greenhouse climates of the Cretaceous and Eocene, when the continent was ice free," DeConto continued.

The authors agree the observed changes are probably just the beginning. "These changes, combined with increased ice-free land areas from glacier retreat, will drive large-scale alteration to the biological functioning, appearance, and landscape of the [Antarctic peninsula] over the rest of the 21st century and beyond," they write.

The moss growth is still modest compared to what's happening in the Arctic, where a large-scale greening trend has even been captured by satellite. There's so much plant growth there that scientists hope it will at least partially offset the loss of carbon from thawing permafrost beneath those plants.

Those days are probably very far off for the Antarctic, but it's clear the continent used to be a very different landscape.

"We're starting back on a journey towards that sort of environment," said Amesbury. "Certainly, Antarctica has not always been the ice place it has been now on very long timescales."