Box ANT6 Rapid collapse of an alpine ecosystem through dieback

Old-growth cushion plants and mosses on subantarctic Macquarie Island are being decimated by recent climate change, with rapid, progressive and widespread death across the island. Endemic Macquarie cushions (Azorella macquariensis), estimated to be hundreds of years old in some areas, are dying because of windier and drier conditions (Bergstrom et al. 2015). For the past 4 decades, the environment has been altered dramatically—from continually wet and misty to periods of drying. From 2008 to 2013, researchers found that, in 88 per cent of the study areas, almost all plants had died, often leaving a desert-like landscape. The extent of the mortality of this keystone species is so severe that it has been declared critically endangered.

A remaining patch of healthy fellfield

A remaining patch of healthy fellfield

Photo: Dana Bergstrom, Australian Antarctic Division, all rights reserved

The primary cause of the species’ collapse is suspected to be the failure of cushion plants and mosses to withstand changes in water availability in summer. For 17 consecutive years (1992–2008), there was a reduction in water available to the plants. During this period, there were accompanying 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. An additional factor in the dieback appears to be the emergence of soilborne plant pathogens.

The cushion plants and mosses are an important habitat for many other species on Macquarie Island. The cushions act as a refuge for a range of spiders, mites and springtails. They also support other plants in what can be a very inhospitable environment. The species’ collapse is taking away that critical habitat, and it will be difficult for the species to recover because plant growth rarely exceeds 5 millimetres per year.

An ‘insurance’ population of 54 irrigated plants has been set up on the island as a growth trial, and these plants are growing successfully. This is considered the best way to conserve the species until large quantities of seed can be harvested.

This rapid ecosystem collapse on Macquarie Island highlights the potential impact of climate-induced environmental change on vulnerable ecosystems elsewhere.

A cushion plant, half of which is affected by dieback

A cushion plant, half of which is affected by dieback

Photo: Dana Bergstrom, Australian Antarctic Division, all rights reserved

Fellfield in which cushions have died and blown away exposing red brown peat

Fellfield in which cushions have died and blown away, exposing red-brown peat

Photo: Dana Bergstrom, Australian Antarctic Division, all rights reserved

Klekociuk A, Wienecke B (2016). Antarctic environment: Box ANT6 Rapid collapse of an alpine ecosystem through dieback. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/case-study/antarctic-environment/box-ant6-rapid-collapse-alpine-ecosystem-through-dieback, DOI 10.4226/94/58b65b2b307c0