Project 4312

The endemic cushion plant, Azorella macquariensis (AM), has recently undergone rapid, widespread dieback across Macquarie Island. It is now listed as Critically Endangered. The decline in the conservation status of this ecologically important species is thought to be a response to a climate change-related shift in weather conditions. Local drying of the environment impacts directly on AM, its interactions with other species, and on the structure of sub-Antarctic fellfield ecosystems. This project will provide the knowledge needed to manage the species and a predictive conservation framework for the fellfield ecosystem it typifies. It will use a combination of existing information and data, and conceptual and predictive models to forecast the future of fellfield ecosystems. We will use the rapid changes on Macquarie Island to better understand climate change-driven catastrophic regime shifts, a subject highly significant to the international science and conservation agenda.

The 2015/2016 first year on this project has involved planning and recruitement, including the appointment of Cath Dickson as PhD student on the project. Data collation is underway as is the appointment of a part-time postdoctoral fellow to model microrefugia for the critically endangered cushion plant on Macquarie Island Nature Reserve.

In December 2016 project team members Dr Dana Bergstrom (AAD), Dr Jennie Whinam (UTas) and Cath Dickson (PhD student, Monash) began field work on Macquarie Island to determine the distribution and abundance of potential refugia for Azorella macquariensis. December 2016 set three monthly weather records, which resulted in a very wet, windy start to the field season. However, despite the weather the team succesfully established half of the temperature and humidity data-loggers and piloted the field methods before the New Year. Throughout January and February, Cath and John Burgess (AAD) travelled across the island to finish establishing the microclimate data-loggers, take leaf samples and complete condition and microtopography assessments at all 62 sites. The site assessments were undertaken in four broad terrain classes, encompassing a diversity of microtopography. The sites ranged from very steep highly exposed slopes, to exposed fellfield peaks, to wetter short grassland turf on sheltered or gentle slopes. Azorella dieback was recorded across the island, and the severity and levels of recovery varied between sites. Cath has now returned to Monash University and together with Dr David Baker (Postdoctoral Research Fellow) and the project team will spend the next year analysing the data collected on Macquarie Island.

In November 2017 Cath Dickson (PhD Candidate) and Rowena Hannaford (Research Assistant) returned to Macquarie Island for two months for the final field season of AASP 4312 Nowhere to Hide? Conservation options for a subantarctic keystone species. The primary aim of the season was to retrieve the microclimate (temperature and humidity) data-loggers from each site, which had been established during the previous 2016/2017 season. Together the team also resurveyed the extent of cover and dieback in the Macquarie Island cushion plant (Azorella macquariensis), the proportion of growth classes affected by dieback and refined data on soil characteristics at the 82 sites across the extent of Macquarie Island. It was a highly successful field season, with a complete set of microclimate data recorded from all sites. The microclimate data set is currently in the initial phase of analysis. The team are looking forward to determining the relationship between microclimate and cushion dieback as the first step to understanding if and where microclimate holdouts (refuges) for this keystone plant species potentially occur on Macquarie Island.

Terrestrial biodiversity across the sub-Antarctic islands is highly vulnerable to climate change. The endemic cushion plant, Azorella macquariensis (AM), has recently undergone rapid, widespread dieback across Australia's Macquarie Island. It is now listed as Critically Endangered.

Addressing a recognised research priority, this project developed a long term monitoring approach and baseline for Azorella dieback and the associated ecosystem on Macquarie Island with an emphasis on informing conservation and management responses.

The key research results ware that dieback is present across the entire island, is active and ongoing, has moved southward and is now centred in the middle of the island. Dieback is caused by an interaction between climate and a yet to be identified plant pathogen. Generally warmer and wetter conditions, along with humidity extremes, are associated with higher dieback, whereas sites with more freezing days and dryer conditions are associated with less dieback.

Higher winter rainfall and high maximum temperatures are now considered to be the conditions driving dieback. There has been a significant loss of ecosystem functioning and plant biomass in some areas as a result of the dieback - particularly in the north of the island. There are however sites with potential to act as microrefugia for the species, and signs of a small amount of re-growth at some sites. Both cushion cover and dieback need to be monitored.

This project delivered the survey design as well as the baseline data against which to compare future change in the ecosystem - both in the cushion plant itself, as well as in microclimate across the island and other properties of the iconic fellfield ecosystem. Specific conservation and management options were provided to, and discussed with relevant stakeholders.