Ecosystem Collapse on a Sub-Antarctic Island

Abstract

Sub-Antarctic Macquarie Island has been the location of a rapid ecosystem collapse in its most dominant vegetation assemblage, the Macquarie Island alpine mosaic, beginning around 2008 and continuing today. An ecosystem engineer and endemic, keystone species, the cushion plant, Azorella macquariensis (Apiaceae), and associated bryophyte species have undergone sudden and widespread dieback. Additional species, particularly the megaherb daisy, Pleurophyllum hookeri (Asteraceae), are currently also showing widespread mortality. Initially, water stress linked to long-term changes in climate appeared to be the primary pressure causing dieback, with a secondary putative pathogen emerging. However, over the last 10 years there has been a shift in fundamental