Australasian Science: Australia's authority on science since 1938

There’s Value in our Island Arks

By Justine Shaw

Investing in conservation management on Australian islands yields a great return.

Australia’s islands have biodiversity values that can be dis­proportionate to their size. Consider Barrow Island, which lies off north-west Western Australia and is home to 24 species that occur nowhere else on Earth (of which five are mammals).

But the conservation value of islands extends beyond their indigenous species. Consider the case of Bald Island, off the coast from Albany in the south of Western Australia. Noisy scrub-birds had been presumed extinct until they were heard singing near a picnic area in Two Peoples Bay National Park near Albany. The rocky landscape had protected a small number of breeding pairs – perhaps fewer than 50 – from wildfires but the remaining population was under constant threat from fire and foxes. In the mid-1990s a few individuals were translocated to a series of nearby release sites, including Bald Island. Not long after, the mainland populations were devastated by a series of wildfires that killed 92% of the mainland population.

Bald Island has since also become home to the world’s second population of Gilbert’s potoroo, which previously existed as a single population restricted to an area of 5 km2. It too was threatened by wildfire.

Many of our islands, like Barrow Island, support rare and endemic taxa. And many, like Bald Island, offer a last refuge to species that have been wiped out on the mainland or provide opportunities for insurance populations to be established. The isolation and generally low human population of our islands has enabled some of Australia’s most successful conservation initiatives to date through pest eradications and species translocations.

For example, for the once-off investment of $250,000 by the Tasmanian state government, cats have now been eradicated from remote Tasman Island. This project, co-funded through private donations, has ended the annual predation of approximately 50,000 fairy prions, thereby ensuring the protection of Australia’s largest fairy prion colony. The effort has safeguarded many other sea bird colonies as well.

On Macquarie Island more than 150,000 rabbits have been reduced to just six individuals in 12 months through joint federal and state government funding. On Kangaroo Island around 1200 goats have been removed by a pair of local shooters.

Over 10,000 Lord Howe stick insects have been produced through a captive breeding program from a founder population of only two breeding pairs! This tiny population of this Lazarus species was rediscovered in 2001, clinging to a single melaleuca plant on a rocky outcrop 23 km from Lord Howe Island.

However, the attributes that make our islands so valuable are also their weakness. Despite their conservation potential, island conservation is often neglected because they are isolated in space and governance.

Indeed, most islands (and their taxa) are in a worse environmental state than their mainland counterparts. Yet while the biodiversity value of islands has long been acknowledged, it’s only been in the past few decades that their conservation profile has started to match their biodiversity assets.

Island Rescue Australia (http://islandarks.com.au/islandarks/Island_Rescue.html) is an alliance of people and organisations concerned about the future of Australia’s island environments and their people. In February it hosted the Island Arks II symposium in Canberra. The meeting highlighted that investing in Australian island conservation yields a great return to biodiversity, as well as good cultural, social and economic benefits.

A recurrent theme throughout the symposium was the importance of robust island biosecurity despite there being no standardised national protocols between states or even between regional archipelagos.

The complexity and range of the problems discussed at the symposium highlighted both the importance and the potential scope for furthering island conservation. The need for robust monitoring and adequate, sustained funding was reiterated by many speakers.

It is now critical to broaden our outlook to consider multiple species interactions prior to and following management actions, both within and between island ecosystems. The potential impacts of translocated populations to island ecosystems require assessment. Further considerations should be given to island management prioritisation, robust conservation planning and strong investment, as these are essential to ensure the future of Australian island conservation.

Justine Shaw is a research fellow at the University of Queensland, and is part of the Environmental Decisions Group.