Our next speaker is Dr Justine Shaw who's going to talk to us about post-eradication monitoring of a sub-Antarctic ecosystem.
A conservation success story, nicely timed after hearing the environmental stewardship opening presentation to this session.
Justine holds a joint position between the Antarctic Division and the Queensland University
of Technology where she's a research leader within the SAEF program that is run by Steven.
Her interests include Antarctic and sub-Antarctic conservation, species
interactions, decision science and biodiversity monitoring.
She first went south in 1996 and works on policy, governance and ecosystem science.
Justine is also a passionately strong advocate for gender equity and inclusivity in STEM.
Thanks Nicole and hi everyone.
I've got the privilege today of talking to you about one of the greatest conservation successes
in Australia, due to one single management action and I'm taking you today to Macquarie Island.
It's a sub-Antarctic world heritage island, covered in hundreds of thousands of seabirds and seals and it
has an Australian Antarctic research station on it that's been there for over 70 years.
In 2001 cats were eradicated from this ecosystem
and in 2011 rabbits, rats and mice were all eradicated as well so we were really interested
as ecologists to understand what happens when you rip three species out of an ecosystem.
We're interested as scientists what's the new science learning, as managers we were interested
from management perspective of their new emergent management issues and also what's
the return on investment for 24.5 million dollars, which is what the program cost.
In order to understand how the ecosystem responded to this management action, we had
to work out what do you measure, how do you measure an ecosystem?
So we sat down and worked out what are we going to monitor. So what are the threatened species
was a really easy thing to understand. What was eaten, the predator prey dynamics, the cats, the
rabbits, the mice, the rats ate different things and what was directly impacted so we knew that
several hundred, over 500 seabirds, were poisoned through the eradication program and you can see
from the photo that there's a negative predatory bird and it's eating rabbits and rabbits
have become part of their diet, they're feral rabbits, and they are now part of their diet.
We had to work out what can we measure. If you're detecting change you need a time zero you need a
baseline and so we had to work out what we were actually going to measure.
We had the challenge of identifying and locating historic data sets and so we did some good old-fashioned
1970s and 1960s field ecology which can't be automated these days but we did look at where
there was uncertainty and where there was an opportunity to grow those past studies.
This is a small borrowing petrel and they nest in burrows under the ground and they only come out at night
and that's their habitat on the left with a field researcher.
So we had to work out how can we use new technology, how can we innovate and so we did.
We used infrared cameras and you can see them here that put outside burrows and they detected
the species that we got some information about breeding and occupancy of those burrows.
We used acoustic monitors to detect new species. We put little trackers on the back of those
predatory birds to see where are they going now that they've got no winter supply that the rabbits are gone.
We used isotopes, we use remote sensing and we also collected bird species and we extracted DNA out of that faeces
to understand what species have dropped that faeces at that burrow to try and understand what was happening.
And so what did we find?
It's a great success story. There's more birds. We found new species of seabirds are now breeding on Macquarie Island.
The island's greener. There's much more lush vegetation. You can have a look outside at some of the
recovery, at the posters out there.
We found more spiders and beetles that were eaten by rabbits. They're coming back and we've measured and quantified that.
And we found that that predatory bird I spoke about, the skua.
It was initially really impacted quite heavily so the breeding success was down. It's diet shifted, but now
over time we've been able to detect that it's on an upward trend and it's a positive story.
They're now eating lots of penguins but that's okay, the numbers work out.
If you look at this graph it's interesting to note though, and this
is probably the take home message, is that not every species responds the same way so recovery is nuanced.
It's a positive ecosystem story but for the purposes of management, it's important to understand that
different species respond differently and so on this graph we've got four species of petrel.
We've got the Antarctic petrel, the white-headed petrel, the blue petrel and the grey petrel.
And these are these small burrowing birds that were eaten by cats and rats.
And what it shows is that for those four species, their distribution is different on the island.
Their density of burrows in those locations, where they occur is different and their rate of recovery is different.
And so it's really important for managers, two of these species are threatened species, and it's important
to understand why that's happening and how it's happening.
And similarly for the vegetation, not every plant is coming back at the same rate because they've got different growth
rates and different mechanisms of seed dispersal and that has implications for the invertebrates
that live in them and the animals that use it as habitat.
So I spoke about collecting bird faeces, which is probably one of the least glamorous parts of our study but what that enabled us
understand is some of this nuances about species recoveries and if you look just at this one here,
this is the white-headed petrel and so we found that those scats we got the DNA out of the faeces
and we were able to show it was very closely related to the birds on Auckland Island,
which is an neighbouring island, and that helped us understand why the rate of recovery of white-headed petrels
might be driven driven by immigration on top of natural population growth.
This entire program and this entire management action will only be successful if we have ongoing biosecurity.
It'll only take one pregnant rat to reach Macquarie Island to undo this amazing,
good work and the 24.5 million dollars in investment.
The other challenge we have is to work out our endpoints.
What are we tracking for? Two species of land bird are extinct from Macquarie Island.
They're endemic species and they're gone now but they've got neighboring subspecies on nearby islands.
Are we prepared to think about introducing them to Macquarie Island to replace that function in the ecosystem?
And finally, I think the success of the program can really be captured by what I'm about to share with you.
And if you walk out in the dark of Green Gorge Hut on Macquarie Island now and
you step into the night, you'll hear something that hasn't been heard on the island for over 80 years.
And it's the sound of blue petrel's breeding, which hopefully will work.
Thanks