The Mega-Herbs of Macquarie Island are Back in Bloom!

I feel as though I have been writing about the effect of pest species on the Sub-Antarctic Islands a lot as of late and so when I saw the topic for this blog post, I couldn’t help but share it. Who doesn’t love good news?

ECOS Magazine recently reported that the large-scale operation to eradicate rabbits from Australia’s only Sub-Antarctic Island, Macquarie Island, is already doing good things for its wild inhabitants.

The article, Macquarie Island is Back in Bloom, tells of ecstatic scientists who have watched the islands mega-herb populations take over the island quicker than anyone had expected.

Rabbits have been a problem on Macquarie Island for a number of years, but have become most troublesome recently. As I mentioned in my previous post on pest species, rabbits are most dangerous in large numbers, especially to local vegetation.

The last estimate of the population size of rabbits on Macquarie Island was around 100,000 and in such large numbers, they can certainly mow through the vegetation. These mega-herbs are crucial for a number of invertebrate and sea-bird species that are, in many cases, endemic to the island. What’s more is that Macquarie Island has peat soil that is easily eroded without the support that these mega-herbs provide.

So how did they achieve it? Eradicating such a virulent species from an isolated island is no easy task. The snippet below from the ECOS Magazine article sums it up nicely, but I highly recommend having a look at the full article and doing a little dance for the mega-herbs of Macquarie Island.

“Three months before aerial baiting resumed in 2011, rabbit calicivirus was introduced to the island to reduce the rabbit population. This step was part of a risk management strategy to minimise the number of poisoned rabbit carcases above ground that could be eaten by predatory or scavenging seabirds.

By last July, the last of the poisoned bait had been dropped from helicopter-slung buckets. Teams of hunters, accompanied by highly trained sniffer dogs and handlers, then arrived on the island to ‘mop up’ remaining pests. While they initially managed to flush out 13 rabbits, none have been detected on the island since December.”

Mega Herbs – The Giants of the Sub-Antarctic

Meet Lorna Little. She has been studying at the University of Otago for the past 7 years. After receiving a scholarship to travel to the Sub-Antarctic Islands she was hooked on the region and swore she would get back there one day. After doing an honours project on invasive species in the mountain of New Zealand and then the Certificate in Antarctic Studies (which saw her visit Scott Base in Antarctica), she decided that the polar regions were for her. Find out what led Lorna to research Sub-Antarctic mega-herbs and what she has discovered about this group of amazing, yet over-looked plants.Tell me about yourself – where do you come from & how did you come to study mega-herbs?

I’m Lorna Little. I’m originally from Whangarei and have been studying in Dunedin for the past 7 years. I decided to do my PhD and emailed some one at the University Centre in Svalbard about plants in the region. She wrote back and is now my supervisor! I also spoke to an old lecturer and she said “hey, I’m going down to the Sub-Antarctic Islands – do you want to do a project on flower colour?” Eventually I realised that I could make it all fit together. In Svalbard, there is a poppy that comes in different variations – there’s a white one and a yellow one. Similarly, the Gentians on Campbell Island come in purple and white so that’s how I came to find my research topic.

My main question had come from the purple and white flowers in the Sub-Antarctic Islands, but I thought okay – maybe I could do something on what the point of having purple flowers is, because it seems to pop up a lot. Then I asked myself well why have purple AND white flowers, then I thought why have yellow AND white flowers? This could be a perfect chance to test in the field and the lab what the effect of these different colours have. So I set up a project looking at flower colour in polar regions! And here I am today, 2 years down the track. So I have finished all my field work now and am in to the writing phase. It’s been a bit of a roller-coaster.

Lorna on Campbell Island (Photo: Lorna Little)

Is this the first kind of research that has been done on flower colour in polar regions? I had a look around and I couldn’t find a lot.

There is quite a bit of research on flower colour in general – because you’ve got the idea of pollinator recognition. When it comes to the Sub-Antarctic Islands, there really isn’t much. The main focus of research has been mega-herb restoration, general ecology, and biomass allocation. There has also been a lot of work done on the evolution of mega-herbs, so looking at if they’re related to ancient Antarctic or mainland New Zealand plants. I don’t know if it’s because they’re so far away or if there’s just not enough people who know where the islands are! I get the impression that the general public think “it’s 800 kilometers away – why should we care?” which is really sad because these islands are amazing and worth protecting. It’s also a huge process to get a project up and running down there. Logistics are a massive hurdle. If you go down you have to stay there to do your research. You know you can’t just collect a whole bunch of plants to bring back to New Zealand. That’s not really in line with the Department of Conservations’ non-destructive research methods.

What is the first thing people associate with mega-herbs?

Pleurophylum speciosum is the first species that springs to mind. It’s the poster child of Campbell Island. The way I generally describe it to people is to have them imagine a daisy on their garden lawn and then times it by 100. Then they’re getting close to the size of this -. It’s got huge hairy, corrugated leaves and it was interesting to do thermal images of these because I found that the valleys of the corrugations and the top of the corrugations had different temperatures – the images really look like corrugated cardboard.

Their flowers are best described as bright purple daisies on top of a huge stalk. The Pleurophyllum speciosum “presents” its pollen inside the dark purple centre. When there is enough sun you will see these flowers covered with yellow spots. We actually sat and watched this one day and basically each of the pollen sacs will just burst open and release this bright yellow pollen, and then the next one, and so on. It’s really quite an amazing thing to see

Pleurophyllum speciosum flower (left) and leaves (right) (Photos: Kimberley Collins)

What are some of the challenges that plants might face on Sub-Antarctic Islands?

To begin with, the soil is very peaty and acidic because there are a lot of sphagnum bogs on the island. The climate itself is very cool – the average temperature is about 4 degrees in winter and 8 or 9 in summer. I was there for 2 weeks in December 2010. It was getting in to summer and so we had three or four days of beautiful clear skies. Then we had a few days of very low-lying cloud, mist, and really high winds – up to 100 knots an hour. At one point I was being blown down the boardwalk and literally had to hold on to the ground to stop myself being blown away. We also had snow for two days – and this is all in the space of 2 weeks. It’s such a huge range of weather and I think that having snow in what we consider summer is quite impressive. So that’s the kind of thing that these plants have to deal with

So explain the thermal imaging technology you were using.

I have a fluke infrared camera, which is a thermal imaging camera. You just point it at the plant, focus on it, and squeeze the trigger so that it takes a picture. Each pixel in the photo equals a temperature so you can analyze it and detect where the hot-spots are and why they might be hot there. The main aim of the research is to look at how much warmer above air temperature (ambient temperature) the plants are.

What can you deduct from the images?

My data shows that when there is a short burst of sunshine, the temperature will rocket and stay quite warm until the next burst of sunshine, when the temperature is boosted up again. I have some thermal time course over a few hours – the longest is 4 or 5 hours. The ambient (air) temperature will stay the same, but the temperature of the flowers is clearly correlated with the amount of sunshine.

Thermal imaging of Pleurophyllum speciosum (Photo: Lorna Little)

So why do you think there is such a big difference between flower temperature and ambient temperature?

The Sub-Antarctic Islands have a very cool, windy, and wet climate. A plant’s growing season is non-existent – there’s not much difference between summer and winter when it comes to temperature. Basically they need to maximize the sunlight oppourtunities they get because it’s so cloudy all the time.

Lorna’s research does a great job in promoting the region as a biodiversity hot-spot. Sub-Antarctic mega-herbs are found nowhere else in the world and I look forward to reading Lorna’s final thesis on this compelling and important topic.