Trace radioactivity from nuclear test era helps researchers measure growth of rare Antarctic plants
By Bob Berwyn
SUMMIT COUNTY —Some of the earliest explorers racing each other to reach the South Pole found fossil fragments showing that lush forests once grew on Antarctica, when it was part of the supercontinent, Gondwanaland.
In this era, it’s difficult to find any signs of vegetation in Antarctica, but a few sparse patches of moss suggest that climate change in recent decades is having an impact on the few plants that do grow in the short summer season.
Australian scientists say that, even though we tend to think of Antarctica as the last untouched wilderness preserved from human impact, it is still affected by anthropogenic climate change.
A paper to appear in the January issue of Global Change Biology describes how the growth rate of some of these “old-growth” moss beds has slowed since the 1980s. The results of the study suggest the moss beds are drying out as a result of increased wind speeds around Antarctica that are linked to the Antarctic ozone hole.
Up until now, measuring the seasonal growth rate of these plants has been extremely difficult and hence it was impossible to assess the impact of our changing climate.
But the research conducted by team of environmental scientists from the University of Wollongong and nuclear physicists from the Australian Nuclear Science and Technology Organisation used increased concentration of radiocarbon in the atmosphere resulting from nuclear weapons testing (mostly in the late 1950s and early 1960s, called the ‘the bomb spike’) to accurately date the age of the moss shoots along their stems in a similar way to tree-rings.
“This has allowed scientists to show that climate change has made the driest continent on Earth an even harsher environment for plant life,” said Professor Sharon Robinson, of UOW’s Institute for Conservation Biology and Environmental Management.
Most of the plants the team studied were growing 50 years ago, when nuclear testing was at its peak. In some species the peak of the radiocarbon bomb spike was found just 15 mm from the top of the 50 mm shoot suggesting that these plants may be more than 100 years old.
‘Accurate dating along the moss stem allows us to determine the very slow growth rates of these mosses (ranging from 0.2 to 3.5 mm per year). Remarkably, these plants were already growing during the heroic age of Antarctic exploration. In terms of age these mosses are effectively the old growth forests of Antarctica — in miniature,” Robinson said.