Penguins

If ever one needed an excuse to post pictures of penguins, yesterday was World Penguin Day.

King penguins at Green Gorge
King penguins at Green Gorge
King penguins are much more graceful in the water than on land!
King penguins are much more graceful in the water than on land!

Four penguin species breed on Macquarie Island. King penguins (Aptenodytes patagonicus) can reach a metre tall and can dive to deeper than 300 metres. Royal penguins (Eudyptes schlegeli) are endemic to Macquarie Island, where they breed in colonies up to 1 km from the coast. Rockhoppers (Eudyptes chrysocome) and gentoos (Pygoscelis papua) breed in smaller numbers.

Royal penguins.
Royal penguins at Finch Creek.

What do penguins have to do with plants? Plants require nitrogen and penguins produce lots of nitrogen. Although nitrogen is an essential plant nutrient too much of it can be toxic to plants. Nitrophilous plants are well adapted to abundant nitrogen. On Macquarie Island the herbs Callitriche antarctica and Montia fontana and the grasses Poa annua and Poa cookii are frequently found in and around penguin rookeries and seal wallows where nitrogen concentrations are high. Studies on subantarctic Marion Island show that plant nutrients are derived mostly from the ocean, as aerosols and as excreta from seabirds and seals. Plants growing around penguin rookeries tend to have high concentrations of nitrogen and a characteristic bright green leaf colour. Animal-derived nitrogen is a key nutrient source for plants in the subantarctic, where nitrogen from other sources such as bedrock and nitrogen-fixing cyanobacteria is limited.

Gentoo penguin.
Gentoo penguin.

Macquarie Island’s penguin populations are still recovering from exploitation in the early 1900s when an estimated 150,000 penguins were slaughtered for oil every year. Many penguin species are listed as threatened on the IUCN Red List. A recent review of threats to penguin populations points to the need for an effective global network of marine reserves.

Penguin digestors at the Nuggets. Thousands of penguins were boiled alive in these to produce oil in the late 1800s and early 1900s. Royal penguin colony in the background.
Penguin digestors at the Nuggets. Thousands of penguins were boiled alive in these to produce oil in the late 1800s and early 1900s. High-rise royal penguin colony in the background.
Penguin city. The population of king penguins at Lusitania Bay is at least 350,000 and growing.
Penguin city. The population of king penguins at Lusitania Bay is at least 350,000 and growing.

Four years without bunnies

Walking is getting harder on Macquarie Island. Previously short-cropped grass only centimetres tall is now a knee-deep meadow of grass matted with mosses and herbs. This is one of the initial observations from last week’s field trip to the Subantarctic island.

Short grassland at Green Gorge study site has more than doubled in height since rabbits were removed.
Short grassland at Green Gorge study site has more than doubled in height since rabbits were removed. The previous day this was under snow but after overnight rain it became possible to do a vegetation survey.

Another obvious change is a shift in the dominant species. Under the rampant rabbit regime, one grass species in particular flourished – Agrostis magellanica. Now other native grasses which were present in lower numbers are now prominent, even dominating sites where rabbits had previously kept them in check. The mat-forming herb Acaena which thrived in heavily grazed grasslands is struggling to compete with the vigorous growth of grasses and sedges.

Many of the smaller herbs which favour bare ground and occupy openings amongst the grasses appear to be less common. In the absence of rabbit diggings and overgrazing they are now abundant only on creek banks and landslides, which is perhaps their original niche in a pre-grazing era.

Boggy short grassland at Bauer Bay on the west coast. The Macquarie Island cabbage plants which have appeared here since rabbits were removed have the potential to reach over 1 metre in height.
Boggy short grassland and herbfield at Bauer Bay on the west coast. The Macquarie Island cabbage plants which have appeared here since rabbits were removed have the potential to reach over 1 metre in height. Note the tussocks on the slopes in the background, most of which have appeared in the past four years.

Tussock grass (Poa foliosa) is clearly increasing in abundance and in height, signalling a future shift in vegetation type from short grassland to tall tussock grassland. And the Macquarie Island cabbage, which was virtually eliminated from much of the island by rabbits, is popping up as young plants throughout many grasslands. In a few years time it is likely to outgrow the short grasses and take over. The tall tussock grass and Stilbocarpa vegetation described in Nineteenth Century accounts might be making a comeback. The return of the megaherbs seems imminent.

Goodbye Macca

Vegetation monitoring site with two converging landslides, covered in snow. Even with the snow cover it is obvious that tussock grasses (Poa foliosa) are colonising this site.
Vegetation monitoring site with two converging landslides, covered in snow. Even with the snow cover it is obvious that tussock grasses (Poa foliosa) are colonizing this site.

Just arrived back at the station via helicopter. Unfortunately we lost about half of our planned fieldwork time: operations on the island are winding up early due to forecast bad weather, and earlier in the week we had two days where the island was blanketed in snow – sure looked nice, but hopeless for studying plants! Nevertheless we managed to complete 4 of our 6 long term vegetation change study sites and made lots of other observations. The plants are certainly getting taller without rabbit grazing.

Vegetation monitoring plot at Brothers Point under snow. Toe of landslide has flattened grass but not the marker stake.
Vegetation monitoring plot at Brothers Point under snow. Toe of landslide has flattened grass but not the corner marker stake.

Another unfortunate but interesting thing is that a few of the 35 year old monitoring plots have been impacted by some of the numerous landslides and debris flows which occurred during the unprecedented heavy rains in January this year. Getting on the ship and heading back to Hobart soon. Full report and pictures to come…

Into the field!

We landed on Macquarie Island yesterday and spent a few hours setting up and testing an automatic weather station. Now it is ready to be airlifted to over 300 m elevation on the plateau, ready for installation. We’ll find out just how windy it is up there!

The station is hectic with resupply activity. But we’re heading off for a few days to look at the vegetation. Already from the ship we could see the bright green tussocks of Poa foliosa creeping up the previously rabbit-grazed hillsides.

My colleague Micah and I are kitted out with warm waterproof clothing and ready to get out there.

First clear glimpse of Macca on Friday morning. It was a shadow in the mist when we arrived Thursday afternoon.
First clear glimpse of Macca on Friday morning. It was a shadow in the mist when we arrived Thursday afternoon.

Ferrying people ashore from the ship, 60 seconds by air.
Ferrying people ashore from the ship, 60 seconds by air.

Electronics 101. Luckily Micah knows about electronics because I don't!
Electronics 101. Luckily Micah knows about electronics because I don’t!

Weather station datalogger, wired up and wateprroofed, ready to face the elements.
Weather station datalogger, wired up and waterproofed, ready to face the elements.

Expedition begins

Helicopter landing on the Aurora prior to departing Hobart.
Helicopter landing on the Aurora prior to departing Hobart.

How much has the vegetation changed in the past two years? We’ll soon see.

Finally it’s time to do some field work. The Aurora Australis is loaded up and heading south. In 3 days time we will be at Macquarie Island. The main aim of my fieldwork is to revisit the vegetation monitoring sites which were established at six locations in the early 1980s. We will record the abundance of all the vascular plant species in these plots to determine which are the winners and losers in this new era of rabbit-free ecosystem.

Hope we don't need these...
Hope we don’t need these…
Departing Hobart on a grey autumn afternoon.
Departing Hobart on a grey autumn afternoon.

The Project

My research project is looking at vegetation change on Macquarie Island. Since rabbits were eradicated from the island in 2012 the plants which had been subject to intensive grazing by these pest animals are now growing back. Nobody knows what the original vegetation of the island looked like before rabbits were introduced int he late 1800s. What will it look like in 5 years, 10 years, 100 years?

To manage the island in the future we need to understand the vegetation. What grows where and why? What are the key factors determining which plants dominate in different environments?

IMG_7489 sml