Daily Archives for June 1, 2019

How I stumbled on a lost plant just north of Antarctica


Nick Fitzgerald, University of Tasmania

Sign up to the Beating Around the Bush newsletter here, and suggest a plant we should cover at batb@theconversation.edu.au.

Sunny interludes punctuate showers of rain, hail and sleet as furious winds sweep clouds across the sky. It’s a typical summer day on Macquarie Island, a sliver of ocean floor that rose more than 2.5 km from the depths of the Southern Ocean, halfway between Tasmania and Antarctica, around 12 million years ago.

On this February day in 2013, my colleague Jennie Whinam and I are visiting monitoring sites for the critically endangered Macquarie Island cushion plant, Azorella macquariensis, which has been suffering extensive dieback.

It is a short walk from our cosy field hut to Skua Lake on the opposite side of the island – a mere four kilometres of steep off-track walking, head-first into the icy wind.

We make a small detour to the shoreline of Skua Lake, the only known location for perhaps the rarest plant on the island, the subantarctic bedstraw (Galium antarcticum). This small herb had not been seen since it was first recorded on Macquarie Island in the early 1980s, despite several searches in the subsequent 30 years.


The Conversation

It seemed likely the humble bedstraw was extinct on Macquarie Island, and we weren’t confident we’d see one that day. It is a small herb, growing to a few centimetres in size, with reddish leaves clustered on sprawling stems and tiny inconspicuous white flowers. Not the easiest plant to spot amongst the lush growth of a subantarctic meadow.

But within five minutes of arriving at the shoreline of Skua Lake, we spotted a reddish-coloured herb unlike any other plant there, partly hidden among dense mosses and grasses.

Excitedly, we set about searching for others, finding hundreds of the tiny plants!

But our celebratory feeling was soon blown away by a flurry of horizontal snow carried across the lake. Skua Lake is perched on the top of an escarpment 130 metres above the ocean with no shelter from the winds that travel unimpeded around the globe at these latitudes.

We were so cold we had to start moving again. And turning our backs to the wind, we marched across grassy hills dusted with fresh snow.

Hidden for three decades

Our rediscovery of this critically endangered species raised a couple of questions. Where had it been hiding for 30 years? And, given the abundance of apparently suitable habitat on the island, why was it restricted to one location?

These questions remain unanswered. But four years later, in 2017, botanists Cath Dickson and Alex Fergus stumbled upon a second population of subantarctic bedstraw on the opposite side of Skua Lake, comprising an estimated 1,000 plants. But why it is not even more widespread remains a mystery.

Perhaps the bedstraw was preferentially grazed by invasive rabbits, which have had a dramatic impact on the vegetation of Macquarie Island. Or, the plant could be a recent immigrant to the island yet to expand its range.

Galium is a large and widespread genus of herbs (commonly called bedstraw) in the Rubiaceae family, with several native and introduced species in Australia including the familiar garden weed cleavers or sticky weed. Many species have distinctive bristly hairs, whereas G. antarcticum is hairless.

With a total known population of 1,500 plants confined to a few square metres of windswept tundra, Galium antarcticum remains critically endangered in Australia.

Travelled across vast seas

Macquarie Island is a young and very remote landmass with an unusual cold maritime climate. Its flora was born from long-distance dispersal and largely composed of subantarctic specialists.

Subantarctic bedstraw is one such specialist, and is also found in Patagonia, South Georgia, the Falklands, Crozet and Kerguelen islands. This wide distribution throughout most of the Subantarctic, including islands separated by thousands of kilometres of ocean, suggests this species has been dispersed by seabirds.

The future prospects for the species on Macquarie Island are uncertain. It may benefit from the recent eradication of rabbits, expanding its range, or it may struggle to compete with taller growing plants as the short grassland transitions to a more closed vegetation community in the absence of grazing pressure. Or it may continue to be a mystery.

Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Nick Fitzgerald, PhD candidate, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Advertisement

Will the discovery of another plastic-trashed island finally spark meaningful change?


Jennifer Lavers, University of Tasmania and Annett Finger, Victoria University

Today we learnt of yet another remote and formerly pristine location on our planet that’s become “trashed” by plastic debris.

Research published today in Scientific Reports shows some 238 tonnes of plastic have washed up on Australia’s remote Cocos (Keeling) Islands.

It’s not the first time the world has been confronted with an island drowning under debris. Perhaps it’s time to take stock of where we’re at, what we’ve learnt about plastic and figure out whether we can be bothered, or care enough, to do something meaningful.



Read more:
This South Pacific island of rubbish shows why we need to quit our plastic habit

Taking stock

In 2017, the world was introduced to Henderson Island, an exceptionally remote uninhabited island in the South Pacific. It has the dubious honour of being home to the beach with the highest ever recorded density of plastic debris (more than 4,400 pieces per metre squared).

What’s more, a single photo taken in 1992 showed Henderson Island had gone from pristine to trashed in only 23-years.

Now, the Cocos (Keeling) Islands off the coast of Australia are set to challenge that record, despite being sparsely populated and recognised for having one of Australia’s most beautiful beaches.

A recent, comprehensive survey of the Cocos (Keeling) Islands revealed mountains of plastic trash washed up on the beaches.



Read more:
Plastic warms the planet twice as much as aviation – here’s how to make it climate-friendly

While the density of debris on Cocos (a maximum of 2,506 items per square metre) was found to be less than that on Henderson Island, the total amount of debris Cocos must contend with is staggering: an estimated 414 million debris items weighing 238 tonnes.

A quarter of the identifiable items were found to be “single-use”, or disposable plastics, including straws, bags, bottles, and an estimated 373,000 toothbrushes.

At only 14 kilometres squared, the entire Cocos (Keeling) Island group is a little more than twice the size of the Melbourne CBD. So it’s hard to envision 414 million debris items in such a small area.

Lessons learned

Islands “filter” debris from the ocean. Items flow past and accumulate on beaches, providing valuable information about the quantity of plastic in the oceans.

So, what have these two studies of remote islands taught us?

South Island. A quarter of the identifiable items were found to be disposable plastics.
Cara Ratajczak, Author provided

On Cocos, the overwhelming quantity of debris you can see on the surface accounts for just 7% of the total debris present on the islands. The remaining 93% (approximately 383 million items) is buried below the sediment. Much like the proverbial iceberg, we’re only seeing the very tip of the problem.

Henderson Island, on the other hand, highlighted the terrifying pace of change, from pristine, tropical oasis to being inundated with 38 million plastic items in just two decades.

In the past 12 months alone, scientists have made other, ground-breaking discoveries that have emphasised how little we understand about the behaviour of plastic in the environment and the myriad consequences for species and habitats – including ourselves.



Read more:
Eight million tonnes of plastic are going into the ocean each year

Here are a few of the shocking discoveries:

  • microplastics were reported in bottled water, salt and beer

  • chemicals from degrading plastic in the ocean were found to disrupt photosynthesis in marine bacteria that are important to the carbon cycle, including producing the oxygen for approximately every tenth breath we take

  • degrading plastic exposed to UV sunlight (such as those on beaches) was reported to produce greenhouse gas emissions, including methane. This is predicted to increase significantly over the next 20 years in line with plastic production trends

  • microplastic particles are ingested by krill at the base of the marine food web, then fragmented into nano-sized particles

  • plastic items recovered from the ocean were found to be reservoirs and potential vectors for microbial communities with antibiotic resistant genes

  • tiny nanoplastics are transported via wind in the atmosphere and deposited in cities and even remote areas, including mountain tops

Meaningful action

Clean-ups on near-shore islands and coastal areas around cities are fantastic.

The educational component is invaluable and they provide an important sense of community. They also prevent large items, like bottles, from breaking up into hundreds or thousands of bite-sized microplastics.

But large-scale clean-ups of the Cocos (Keeling) Islands, and most other remote islands, are challenging for a variety of reasons. Getting to these locations is expensive, as would be shipping the plastic off for recycling or disposal.

There are also serious biosecurity issues relating to moving plastic debris off islands. Even if we did somehow manage to clean these remote islands, it would not be long before the beaches are trashed again, as it was estimated on Henderson Island that more than 3,500 new pieces of plastic wash up every single day.

As Heidi Taylor from Tangaroa Blue, an Australian initiative tackling marine debris, puts so aptly:

if all we ever do is clean up, that is all we will ever do.

For our clean-up efforts to be effective, they must be paired with individual behaviour change, underpinned by legislation that mandates producers to take responsibility for the entire lifecycle of their products.

Single-use items, such as razors, cutlery, scoops for coffee or laundry powder and toothbrushes were very common on the beaches of Cocos. Clearly this is an area where extended product stewardship laws (following the principles of a circular economy), coupled with informed consumer choices can lead to better decisions about the types of products we use and how and when we dispose of them.



Read more:
There’s no ‘garbage patch’ in the Southern Indian Ocean, so where does all the rubbish go?

The global plastic crisis requires immediate and wide-ranging actions that drastically reduce our plastic consumption. And large corporations and government need to adopt a leadership role.

In the EU, for instance, governments voted in March 2019 to implement a ban on the ten most prolific single-use plastic items by 2021. The rest of the world urgently needs to follow suit. Let’s stop arguing about how to clean up the mess, and start implementing meaningful preventative actions.The Conversation

Jennifer Lavers, Research Scientist, University of Tasmania and Annett Finger, Adjunct Research Fellow, Victoria University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Vic Stockwell’s Puzzle is an unlikely survivor from a different epoch


Andrew Thornhill, University of Adelaide

Sign up to the Beating Around the Bush newsletter here, and suggest a plant we should cover at batb@theconversation.edu.au.

On the western side of Mount Bartle Frere, the tallest mountain in Queensland, grows a tree that shares an ancient link to Australia’s most dominant plant group.

To get there, you must find a track hidden by rainforest and then walk for around an hour up and down a dirt path, until you reach cathedral-like giant red barked trees. This is Stockwellia quadrifida, also known as “Vic Stockwell’s puzzle”: a close but anciently separated relative of the eucalypts.



Read more:
A detailed eucalypt family tree helps us see how they came to dominate Australia

This ancient tree is best suited for wetter and warmer environments, a throwback to when this continent was still connected to South America and Antarctica 40-50 million years ago, in the supercontinent Gondwana.

But this rare plant is now at risk by an introduced threat, myrtle rust, a plant disease that was accidentally introduced to Australia from South America.

Photos courtesy of Stuart Worboys and CSIRO.

Sister to the eucalypts

In my opinion, Stockwellia trees are in the same league as California Redwoods – they’re both old, with very few close living relatives. In fact, they are probably more special, as only around 400 Stockwellia trees remain.

Some of the trees I saw in Queensland have large buttressed roots and are hollowed out so you can walk inside the tree and stare upwards. Their bark is strikingly red, and their enormous size means you have to crane your neck to see the top.

Stockwellia takes its name from a Queensland forest ranger named Victor Stockwell who worked in the Boonjee area on Mount Bartle Frere where the trees grow. While the species wasn’t officially scientifically described until 2002, it had been known to botanists for many decades.

The trees were first identified using aerial photography. For Vic Stockwell, the tree was a “puzzle” because despite his vast experience in the forests of Far North Queensland, he was surprised to come across a species of tree he didn’t recognise.

Ancient rainforest groups

In the early 2000s, a DNA study found Stockwellia belonged to a group of rainforest trees called the “mesicalypts”, a name coined by my colleagues and I.

Mesicalypts are a sister group to Australian eucalypts, and are made up of four species of rainforest plants, including Stockwellia. Eucalypts, on the other hand, have more than 800 species growing all over Australia, in much drier conditions.

DNA results suggest there is also another evolutionary group in between mesicalypts and eucalypts which only grows in New Caledonia, a species called Arillastrum gummifera. We have informally named this single species group “newcalypt” – New Cal-(edonian) (eucal)-ypt – because we didn’t want to make it feel left out from getting a new informal name.


The Conversation/Andrew Thornhill

Puzzling history

Molecular dating of these groups revealed some even more enigmatic things about the divergence of the mesicalypts and the newcalypt from the eucalypts.

The sole New Caledonian species is estimated to have had a common ancestor with the eucalypts around 59 million years ago. This poses an interesting question. How did a plant that old end up on a land mass that we think is only 30 million years old?

We don’t really know yet, and botanists still debate about where it came from and how it got there.



Read more:
How Earth’s continents became twisted and contorted over millions of years

Mesicalypts are also around 60 million years old and we estimate Stockwellia diverged from its nearest living relative around 30-40 million years ago. This was in an epoch called the late Eocene when the world was much wetter and warmer, and when Australia was still connected to South America and Antarctica.

With no fossil record of any ancient mesicalypts, it’s unclear how diverse and widespread they were back then. If we assume more species of mesicalypts once existed, then the ones we see today are the last living survivors from a very different past.

Their history is also the tale of two different fortunes.

The mesicalypts are better suited to live in wetter and warmer environments, and their relatives – the eucalypts – are better suited to drier and hotter conditions.

When Gondwana finally split and Australia started drifting north, one group had to hang on as their suitable growing conditions began to shrink, while the other hit the jackpot and became the dominant vegetation of the continent.

An extinction threat

Once, the main threat to the small number of Stockwellia populations appeared to be only white cockatoos eating their seeds.

But now they are menaced by something more sinister than birds. More than a decade after the species was officially named, I was taken to see the Stockwellia by Stuart Worboys from the Australian Tropical Herbarium.



Read more:
Invasive species are Australia’s number-one extinction threat

On this trip Stu found leaves of Stockwellia with myrtle rust on them – the first such recording for the tree.

Myrtle rust is a disease of the Myrtaceae family, and was accidentally introduced from South America in the late 2000s. It attacks plant leaves, fruit and, in some cases, kills the plant outright.

The Australian Myrtaceae have had no time to adapt to myrtle rust. What is happening now could cause the extinction of some extremely unique Australian plants – including Stockwellia.

It is sad to think a plant group that has hung on for so long, in a secluded part of Australia, minding its own business, now faces an introduced threat.

The hunch is that the myrtle rust was introduced to Stockwellia from the shoes of one of its human visitors. Unfortunately, we may have loved the tree to death.

Let’s hope it’s tough enough to withstand the rust and live for many more millions of years. If it is lost, it would take with it 40 million years worth of evolutionary history in Myrtaceae. And after surviving so much tumultuous history of changing continental climates, cyclones, and everything else that a tropical environment could throw at it, that would be a very sad thing.

Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Andrew Thornhill, Research botanist at the Botanic Gardens and State Herbarium of South Australia/Environment Institute, University of Adelaide

This article is republished from The Conversation under a Creative Commons license. Read the original article.