Macquarie Island iconic species dying out
Cushion plants on Macquarie Island
Dr Dana Bergstrom
Our study has been looking at a rapid collapse of an alpine ecosystem on Macquarie Island. On the top of Macquarie Island there is a plateau and in that plateau are cushion plants that are endemic to the island, that means they only occur there and nowhere else.
What we found was rapid dieback of this endemic plant. Of 115 sites across the plateau, up to 90% of those sites had death in them in the cushion plants and up to 80% of death in mosses. This plant has been on the island for 10’s of thousands of years and so it was a really big shock.
And the first thing that we thought – is it a disease? And so after five years of study we can say what we suspect is happened is that the plants aren’t coping with recent changes to climate. They don’t have the capacity to cope with the changes that we’ve observed, which have gone from a very wet and misty environment to now one with lots and lots of drying. What happens on the Island is that a storm will come through, drop a large amount of rain, and then blow through. So the days after that are sunny and windy, and it’s that sunny and windy conditions which are putting the plants under stress.
What we are now looking at is all the plants on Macquarie Island to see how vulnerable they are to drying on the Island. So we are not just looking at the cushion plants and the mosses we are not extending it to other plants on the island to have an idea of their vulnerability to the current climate changes.
Old growth cushion plants and mosses on sub-Antarctic Macquarie Island are being decimated by recent climate change.
New research, published in the Journal of Applied Ecology today, reveals the cushion plants, Azorella macquariensis, estimated to be hundreds of years old, are dying due to windier and drier conditions.
Lead author and ecologist with the Australian Antarctic Division, Dr Dana Bergstrom, said the dieback of the cushion plants and mosses is rapid, progressive and widespread across the island.
“This is a plant that has survived for thousands of years, but it’s now struggling to cope with the rapid changes occurring on the Island,” Dr Bergstrom said.
“Over the past four decades the environment has altered dramatically from wet and misty to one subject to periods of drying.”
The study, undertaken by 18 scientists from 10 institutions, looked at 115 sites across the Macquarie Island alpine tundra.
Between 2008 and 2013 the researchers found that 88% of the study areas had dieback present, often leaving a desert-like landscape.
“The extent of the death of this keystone endemic cushion plant is so severe that it has been declared critically endangered,” she said.
The primary cause of the species’ collapse is suspected to be the failure of cushion plants and mosses to withstand changes in summer water availability.
“We found that for 17 years in a row there was not enough water available to the plants,” Dr Bergstrom said.
“Additionally, between 1967 and 2011, there has been uniform increases in sunshine hours, wind speed and water loss from the leaves of the plants and soil despite overall increases in precipitation from storm events.”
Australian Antarctic Division spatial ecologist, Dr Aleks Terauds, said the cushion plants and mosses are an important habitat for many other species on Macquarie Island.
“The cushions really act as a refuge for a whole range of spiders, mites and other plants, in what can be a very inhospitable environment,” Dr Terauds said.
“The dieback is essentially taking away that critical habitat and with annual growth of the plant rarely exceeding 5 mm, it will be difficult for the species to recover.”
An insurance population of 54 irrigated plants has been set up on the island as a growth trial.
“These plants are growing successfully in what is considered the best way to conserve the species until large quantities of seed can be harvested,” Dr Bergstrom said
“This rapid ecosystem collapse on Macquarie Island is giving us a window into the potential impact of climate-induced environmental change on vulnerable ecosystems elsewhere.”
Macquarie Island is a subantarctic island located in the Southern Ocean, approximately half way between Australia and Antarctica.
It is a Tasmanian State Reserve managed by the Tasmanian Parks and Wildlife Service and was inscribed on the World Heritage List in 1997.