The Antarctic Peninsula is not only getting warmer, it’s getting dramatically greener with a sharp increase in plant growth over the past 50 years.
A study of moss cores sampled from along the eastern side of the peninsula has provided a unique record of how temperature increases over the last 150 years have affected plant growth.
The results, published today in Current Biology, show an unprecedented surge in growth all the way along a 600-kilometre stretch of the coastline, particularly since the 1950s.
The Antarctic Peninsula, which juts out towards South America, is one of the most rapidly warming places on Earth.
Study leader Dr Matthew Amesbury said direct climate records for the Antarctic Peninsula only went back around 50 years, whereas the moss cores provided a record that went back several thousand years.
“We can’t measure temperature or any other aspect of climate directly in these moss banks, but we can measure things that respond to temperature,” said Dr Amesbury, a paleoclimatologist at the University of Exeter.
These ‘proxies’ for temperature change include the vertical growth rate of the moss, how much mass it accumulates, and the amount of microbial activity — all of which tell researchers how that moss is responding to changes in temperature and water availability.
What they reveal is that the moss has been growing more and showing more microbial activity as the temperature increases, which means that if the temperatures in the area continue to warm, the Antarctic Peninsula is likely to get a lot greener, in line with what is happening in the Arctic.
“What we’re also seeing concurrently with climate change are other physical processes such as glacier retreat particularly,” Dr Amesbury said.
“What that does is it frees up new ice-free land that can then be colonised by plants, particularly mosses which are very effective colonisers of new bare ground.”
The study by Dr Amesbury and his colleagues builds on earlier work by the group which looked at moss cores from one site. This new paper reports from three more sites, stretching from the very northern Elephant Island to Lazarev Bay.
“The benefits of our work and our sites that we’ve been able to study is that we can make conclusions about a wide area,” Dr Amesbury said.
Professor Sharon Robinson, a climate change biologist at the University of Wollongong said the study by the UK researchers reaffirmed that mosses were a sensitive proxy for climate change in Antarctica.
“We don’t have many coastal proxies and so they show great potential for places which lack weather stations, which is most of Antarctica,” said Professor Robinson, who studies moss in East Antarctica.
Professor Robinson said the increase in the growth rates of moss seen in the study is dramatic if compared to growth at the scale of trees.
“Imagine that was a tree and it was growing four times as fast.”
Professor Robinson said while the rate of growth increase was surprising, it wasn’t unexpected, given the rate of warming in the Antarctic Peninsula.
Annual temperatures in the region have increased by up to 0.56 degrees Celsius per decade since the 1950s.
“If the temperatures are below 0C, it doesn’t matter if they change by 1 or 2 degrees, because all the water is still locked away as ice,” she says.
“But as soon as you get above 0C, every day above 0C, every hour above 0C potentially means that there’s more water available for growth, and so that increases the season.”
While the prospect of more plant growth might sound like a good thing from a greenhouse gas perspective, Professor Robinson said the warming could potentially release greenhouse gases from the ancient buried moss, which has so far remained frozen.
Dr Amesbury and his colleagues are now examining even older moss cores, going back 1,500 and 4,000 years, to build up an even more detailed picture of how the moss responds to changes in temperature.
“What we’re going to be doing next is trying to understand more about the relationships between the proxies that we measured in the mosses, how they’ve changed over longer time scales, before the advent of the human influence on climate,” he said.
Green Island was one of the sites used in the study. (Supplied: Matt Amesbury)