An overview of the seven year pest eradication programme on Tasmania's Macquarie Island. And a voice of dissent ...
Discovered accidentally on 11th July, 1810, by Australian/Briton Frederick Hasselborough. Macquarie Island was claimed and then annexed to the colony of New South Wales in 1810. The island was named after Governor Lachlan Macquarie.
Fabian Gottlieb von Bellingshausen, who explored the area for AlexanderI of Russia, produced the first map of Macquarie Island landed on the island in 1820, defined its geographical position and traded rum and food for Macquarie Island's fauna with sealers. Between 1810 to 1919, seals then penguins were hunted almost to the point of exctinction.
In 1890, New South Wales transferred the island to Tasmania, who in turn leased it to Joseph Hatch between 1902 and 1920 for his oil industry based on harvesting penguins.
The island became a base for the Australasia Antarctic Expedition between 1911 and 1914 under Sir Douglas Mawson.
In 1933, authorities declared the island a wildlife sanctuary under the Tasmania Animals and Birds Protection Act 1928. In 1972, the island was made a State Reserve under the Tasmanian National Parks and Wildlife Act 1970.
In 1948, the Australian National Antarctic Research Expeditions (ANARE) established its expedition headquarters on the island.
The island was listed as a World Heritage Site in December, 1997.
The island is a haven for many species, including fur seals, elephant seals, royal penguins, king penguins and Macquarie shags. The island also supports about 3.5 million breeding seabirds of 13 species.
From the beginning, the island's seals and penguins were killed for fur and blubber. Rats and mice that were inadvertently introduced from the ships prospered due to lack of predators. Cats were then introduced deliberately to keep the rodents from eating human food stores. Then in about 1870, rabbits were left on the island by sealers for food. By the 1970s, the then 130,000 rabbits were causing tremendous damage to vegetation.
The feral cats introduced to the island have had a devasting effect on the native seabird population, with an estimated 60,000 seabird deaths per year. In 2000, the last of the nearly 2,500 cats were culled in an effort to save the seabirds.
The rabbits rapidly multiplied before numbers were reduced to about 10,000 in the early 1980s when myxomatosis was introduced. Rabbit numbers then grew again to over 100,000 by 2006.
On 4th June, 2007, Malcolm Turnbull, then Australian Federal Minister for the Environment and Water Resources, announced that the Australian and Tasmanian Governments to jointly fund the eradication of rodent pests, including rabbits to protect Macquarie Island's World Heritage values. Based on mass baiting follow-up dog hunting teams and an estimated cost of $24 million the programme would cover a period of up to seven years. (Other species impacted by the baits included giant petrels, black ducks and skuas. Higher death levels than expected of kelp gulls caused a temporary suspension of the programme.)
So, was this programme a monumental success, as claimed. Or was it, as former physicist John Reid puts it ... an environmental disaster?
In an opinion piece for Quadrant Magazine Online in 2012 www.quadrant.org titled “Wrecking Macquarie Island to Save It”, Reid calls the programme “...an unmitigated disaster.”
Reid goes on to assert that “...changes began with the extermination of the feral cats between 1985 and 2000 in an attempt to restore the island and its bird population to its pristine state. This led to an explosion in the rabbit population once feline predators had been removed. Attempts to control the rabbits started as early as 1968, but with little success. It now appears that it was primarily the cats keeping them in check.”
Reid goes on to say: “The rabbits have devasted the island. The formerly copious tussock grasses which consolidated the steep slopes have been almost entirely denuded. This has resulted in a loss of habitat for nesting birds and an increased number of landslides. As a consequence, ten species of seabirds are now considered threatened.”
From a 2012 ABC Science Show Broadcast, Reid quotes Keith Springer, Project Manager for the Pest Eradication Project: “Rabbits to an extent, were controlled by the myxoma virus but the effectiveness gradually declined. The population really exploded in the last ten-or-so years, before a one-off hit of calcivirus and the big aerial baiting operation last year.”
Towards the end of the interview Springer says: “I think I've been sort of fortunate in a way because I have seen Macquarie over the last 12 years or so go from quite good vegetation as a result of myxoma virus controlling rabbits, and then really hammered and absolutely degraded … “
Also interviewed on the island was Dana Bergstrom, principal research scientist, Australian Antarctic Division. In 2009, Bergstrom was lead author of a paper in the “Journal of Applied Ecology: Effects of Invasive Species Removal Devastate World Heritage Island.”
The key paragraph from the abstract reads: “Using a combination of population data from an invasive-herbivore, plot-scale vegetation analyses and satellite imagery, we show how a management intervention to eradicate a mesopredator has inadvertently and rapidly precipitated landscape-wide change on sub-Antarctic Macquarie Island. This happened despite the eradication being positioned within an integrated pest management framework. Following eradication of cats (Felis catus) in 2001, rabbit (Oryctolagus cuniculus) numbers increased substantially although a control action was in place (Myxoma virus) resulting in island-wide ecosystem effects.”
In other words, according to Reid: “ …the rabbit plague, which has so far cost $25 million to fix, was a direct consequence of the removal of feral cats from Macquarie Island. This was well known to at least one of the people interviewed. It was neither mentioned nor even hinted at in the course of the [ABC programme].”
In his article, Reid goes on to say: “In discussing the 90% dieback of the cushion plant Azorella, observed over the last year or two, Antarctic Division ecologist Aleks Terauds ponders”:
“And to be honest we haven't got any solid leads at this stage. We do think that it's exacerbated by a change in climate on the island , we think that's definitely got something to do with it, and whether that's interacting with the changing climate, it's interacting with pthogens, or there are other interactions at play, we're still trying to work out the detail, but there's definitely something going on that isn't good for the Azorella on Macquarie Island.”
Reid reacts: “Perhaps the aerial broadcasting of hundreds of tons (yes hundreds of tons) of a very nasty rat poison called brodifacoum as part of the baiting programme could be a factor., Or is that particular explanation off-limits? Did anyone bother to research the possible effects of aerial baiting on the flora of the island?”
- Published: 23 June 2015
Attribution-NonCommercial-NoDerivs 3.0 Australia Licence