1,600 years ago, climate change hit the Australian Alps. We studied ancient lake mud to learn what happened

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Zoë Thomas, UNSW; Haidee Cadd, University of Wollongong, and Larissa Schneider, Australian National UniversityIf you’ve ever visited Australia’s highest peak — Mount Kosciuszko — you might remember the long uphill trek to the summit past some of Australia’s most picturesque and rugged landscapes. Vibrant snow gums, boardwalks with meadows of exquisite alpine plants, and blinding patches of snow.

As you approach the summit, a quartet of stunning blue lakes appear, created by glaciers during the last ice age that carved new valleys out of the mountain.

Lakes like these are windows to the past, offering an opportunity to understand how our climate and environment has changed over hundreds to thousands of years. One such lake, Club Lake — so-named for its resemblance to a suit in a deck of cards — was the focus of our new study.

After studying the lake’s sediment, we learned the Australian Alps experienced a sudden climate change about 1,600 years ago that brought a long spell of warmer conditions. What makes this sudden warming event particularly interesting is that it bears striking similarity to today.

Climate change in the Australian Alps

The Australian alpine region is the traditional home of a number of Aboriginal groups, including the Ngarigo, Walgalu and Djilamatang people. It is also home to highly diverse flora and fauna that occur nowhere else, from billy buttons (Craspedia costiniana) known for their vibrant yellow rosette of tiny flowers, to the broad-toothed rat and its chubby cheeks.

But this unique wildlife is under immense threat from climate change.

By 2100, Australia may warm by at least 4℃, with bushfires becoming more frequent and devastating. The fragile alpine ecosystem will be hit particularly hard by these changes.

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Many of Australia’s alpine species are already near their climatic limits, and are constrained by altitude. They’re at risk of becoming regionally extinct if their climatic thresholds are exceeded. As the temperature warms, treelines move upslope to cooler temperatures, pushing alpine flora and fauna to higher elevations. At some point they can go no higher — they’re squeezed out of their niche.

The critically endangered mountain pygmy-possum, for example, relies on the seasonal snowpack for winter hibernation, but increased temperatures are limiting this habitat.

A dip into the past

Our study showed Club Lake holds vital clues to the link between rising temperatures, loss of native plant species and more frequent fires in the Snowy Mountains.

Lake sediments are used all over the world as indicators of climate and environmental change because of the unique way they trap material. A body of water can act as a seal that ensures sediments are largely undisturbed over time.

We extracted sediments from the bottom of Club Lake to a depth of 35 centimetres. This equates to about 3,500 years of history, approximately 100 years for each centimetre.

Club Lake in Mt Kosciuszko.
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To work out how temperatures have changed over this time, we looked for the presence of molecular fossils, called “lipid biomarkers”. Analysing these biomarkers in the laboratory can tell us what the temperature in the environment was like, hundreds or thousands of years ago.

In the 3,500 years we examined, we detected a gradual warming trend. Superimposed on this, we found a sudden warming event that started 1,600 years ago, and lasted about six centuries. We suspect it was due to an atmospheric phenomenon linking higher tropical sea surface temperatures to southeastern Australia.

We’re not yet sure how much of Australia was affected by this warming, but other research from 2018 measured similar temperature changes in stalagmites from the Yarrangobilly caves 50 kilometres away.

Alpine snow gums (Eucalyptus pauciflora)
Zoë Thomas

What happened during this climate change?

During this unusual warmth, alpine herbs and shrubs declined, while the abundance of trees, particularly eucalyptus, increased. We know this by looking at grains of pollen preserved at different depths within the lake sediment samples, which indicates what types of plants were growing nearby.

We also found small particles of charcoal, produced by bushfires, embedded within the sediment layers. This showed the changes in vegetation also coincided with greater fire activity.

What surprised us most, however, was discovering a large increase in mercury at this time.

Mercury, which occurs naturally in the environment, is the only metal that’s liquid at room temperature, and is particularly sensitive to temperature changes. Higher temperatures enhance mercury deposition from the atmosphere, and our study shows a five-fold increase in mercury flux 1,600 years ago.

Alpine herbfields.
Nicola Pain

Industrial activities over the last 150 years, such as burning coal, have increased the abundance of mercury significantly. Our findings suggest future climate change is likely to increase the risk of mercury exposure not just in cities, but also in the seemingly remote Australian alpine environment.

Mercury contamination is a significant public health and environmental problem. At certain levels it’s poisonous to the nervous system, and it does not easily degrade.

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What can we do?

Insights from the past can help governments, environmental agencies, and scientists come up with effective strategies to protect the vulnerable flora and fauna of the Australian Alps. But it’s not just changes in climate they’ll have to contend with in future.

There are other perils, such as soil erosion and habitat fragmentation from the legacy of sheep and cattle grazing, and tourism. Invasive pests and pathogens are likely to further reduce the resilience of these alpine ecosystems.

Feral horses are a significant threat to native wildlife in Australia’s alpine region.
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Restoration programs over the last 50 years have aimed to revitalise the natural vegetation in the Kosciuszko National Park following 135 years of grazing — finally banned in 1969 — and the environmental damage caused by the Snowy River Hydro-Electric scheme.

More recently, the federal government has committed A$3.5 million towards recovery from the devastating 2019-2020 bushfires. Incorporating Aboriginal knowledge into mainstream fire management is essential for tackling future crises.

This is the critical time for climate action to protect this unique and iconic Australian landscape.

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Double trouble as feral horse numbers gallop past 25,000 in the Australian Alps

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Zoë Thomas, ARC DECRA Fellow, UNSW; Haidee Cadd, Research associate, University of Wollongong, and Larissa Schneider, DECRA fellow, Australian National University

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

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This bird’s stamina is remarkable: it flies non-stop for 5 days from Japan to Australia, but now its habitat is under threat

David Bassett, Author provided

Birgita Hansen, Federation University AustraliaImagine having to fly non-stop for five days over thousands of kilometres of ocean for your survival. That’s what the Latham’s Snipe shorebird does twice a year, for every year of its life.

This migratory shorebird, similar in size to a blackbird, completes this gruelling migration to warmer climes, where it prepares itself for its return flight and the next breeding season.

Unfortunately, their wetland habitat is now being lost to development and other pressures, putting this tough little bird at risk.

The Latham’s Snipe arrives at its destination severely malnourished and spends the Australian summer months build up its strength and body fat to complete its long return flight.
David Sinnott/instagram.com/birdsbydave/, Author provided

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A feat of incredible endurance

Latham’s Snipe breeds in northern Japan and parts of eastern Russia during May-July and spends its non-breeding season (September to March) along Australia’s eastern coast.

Like other migratory shorebirds, it has incredible endurance, undertaking a non-stop, over-ocean flight between its breeding and non-breeding grounds.

It arrives at its destination severely malnourished and spends the Australian summer months building up its strength and body fat to complete its long return flight.

Unlike many other migratory shorebird species in Australia, you won’t find Latham’s Snipe in large flocks enjoying picturesque estuaries and bays. Instead, it hides away in thickly vegetated wetlands during the day to avoid local predators.

Their characteristic brown mottled feathers help them hide in wetlands.

Large eyes high on their heads allow them to see far and wide. Their exceptional eyesight helps them constantly scan for dangers at night, when they forage for food in open wet and muddy areas.

Latham’s Snipe is the ultimate sun-seeker. It breeds in the northern hemisphere when the snows have melted and the weather is warm, then returns to the southern hemisphere to take advantage of spring rains, warmer weather and food-rich wetlands.

It spends its entire time in Australia feeding, resting and growing new flight feathers in preparation for the long haul back to Japan in autumn.

The Latham’s Snipe’s characteristic brown mottled feathers help it hide in wetlands.
Mark Lethlean, Author provided

No food and nowhere to rest

Latham’s Snipe, formerly known as the Japanese Snipe, was once a popular game bird. Hunting and wetland loss during the 20th century have contributed to a decline in Latham’s Snipe in south-eastern Australia.

The signing of the Japan Australia Migratory Bird Agreement in 1981 has stopped snipe hunting in both countries. However, their wetland habitat continues to be lost due to land development and drying of wetlands.

Imagine flying for five days straight, arriving at your destination emaciated and exhausted, only to find your habitat has disappeared. No food and nowhere to rest. This is the crisis facing Latham’s Snipe and many other migratory shorebird species.

No formal protection for many of its wetlands

Under the Australian government Environment Protection and Biodiversity Conservation Act, any grouping of 18 or more snipe at a wetland site is considered nationally important. Unfortunately, however, development on snipe habitat still occurs.

In 2014 — triggered by a plan to allow housing construction on an important snipe wetland area — a team of passionate researchers and citizen scientists banded together to initiate a monitoring program of Latham’s Snipe in south-west Victoria.

After the first year of the monitoring, the Latham’s Snipe Project expanded to other parts of the country with help from a large number of dedicated volunteers and professionals.

The story from this monitoring is still unfolding but two clear patterns are emerging:

1. Latham’s Snipe often congregate in urban wetlands; and
2. the majority of these important wetlands have no formal protection from development or disturbance.

7,000km, non-stop, in three days

Between 2016 and 2020, the Latham’s Snipe Project started tagging snipe with small electronic devices to try and learn about their migratory routes.

The team uncovered an amazing migration from a female snipe captured in Port Fairy. She left her breeding grounds in northern Japan and flew directly to south-east Queensland in three days, a non-stop flight of around 7,000km. A trip that might normally take around five days, this incredible individual did in three.

This is one of the fastest bird migrations on record and highlights how demanding these over-ocean migrations are. It also shines the spotlight on the critical importance of good quality wetland habitat when the snipe return to Australia.

Urban development continues to threaten Latham’s Snipe habitats. Several snipe sites in eastern Australia are at risk from housing developments and large infrastructure projects.

However, a different way of doing things is possible.

Eco-friendly developments like the Cape Paterson Ecovillage in Victoria provide hope. Here, researchers and citizen scientists have worked with the developer to help design conservation areas within the development to protect and restore wetlands for snipe.

Such progress is heartening, but a critically important next step is to make changes to local planning schemes that explicitly recognise wetlands for Latham’s Snipe.

Imagine flying for five days straight, arriving at your destination emaciated and exhausted, only to find your habitat has disappeared.
Mark Lethlean, Author provided

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Birgita Hansen, Senior Research Fellow, Federation University and Better Data for Better Decisions Constellation Leader, Food Agility CRC, Federation University Australia

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