Australian stinging trees inject scorpion-like venom. The pain lasts for days



Fig B Dexcelsa.

Irina Vetter, The University of Queensland; Edward Kalani Gilding, The University of Queensland, and Thomas Durek, The University of Queensland

Australia is home to some of the world’s most dangerous wildlife. Anyone who spends time outdoors in eastern Australia is wise to keep an eye out for snakes, spiders, swooping birds, crocodiles, deadly cone snails and tiny toxic jellyfish.

But what not everybody knows is that even some of the trees will get you.

Our research on the venom of Australian stinging trees, found in the country’s northeast, shows these dangerous plants can inject unwary wanderers with chemicals much like those found in the stings of scorpions, spiders and cone snails.

The stinging trees

In the forests of eastern Australia there are a handful of nettle trees so noxious that signs are commonly placed where humans trample through their habitat. These trees are called gympie-gympie in the language of the Indigenous Gubbi Gubbi people, and Dendrocnide in botanical Latin (meaning “tree stinger”).

A casual split-second touch on an arm by a leaf or stem is enough to induce pain for hours or days. In some cases the pain has been reported to last for weeks.

A gympie-gympie sting feels like fire at first, then subsides over hours to a pain reminiscent of having the affected body part caught in a slammed car door. A final stage called allodynia occurs for days after the sting, during which innocuous activities such as taking a shower or scratching the affected skin reignites the pain.




Read more:
‘The worst kind of pain you can imagine’ – what it’s like to be stung by a stinging tree


How do the trees cause pain?

Pain is an important sensation that tells us something is wrong or that something should be avoided. Pain also creates an enormous health burden with serious impacts on our quality of life and the economy, including secondary issues such as the opiate crisis.

To control pain better, we need to understand it better. One way is to study new ways to induce pain, which is what we wanted to accomplish by better defining the pain-causing mechanism of gympie-gympie trees.

How does these plants cause pain? It turns out they have quite a bit in common with venomous animals.

The plant is covered in hollow needle-like hairs called trichomes, which are strengthened with silica. Like common nettles, these hairs contain noxious substances, but they must have something extra to deliver so much pain.

Earlier research on the species Dendrocnide moroides identified a molecule called moroidin that was thought to cause pain. However, experiments to inject human subjects with moroidin failed to induce the distinct series of painful symptoms seen with a full Dendrocnide sting.

Finding the culprits

We studied the stinging hairs from the giant Australian stinging tree, Dendrocnide excelsa. Taking extracts from these hairs, we separated them out into their individual molecular constituents.

One of these isolated fractions caused significant pain responses when tested in the laboratory. We found it contains a small family of related mini-proteins significantly larger in size than moroidin.

We then analysed all the genes expressed in the gympie-gympie leaves to determine which gene could produce something with the size and fingerprint of our mystery toxin. As a result, we discovered molecules that can reproduce the pain response even when made synthetically in the lab and applied in isolation.

The genome of Dendrocnide moroides also turned out to contain similar genes encoding toxins. These Dendrocnide peptides have been christened gympietides.

A plant with a straight narrow green stem covered in fine hairs and large flat leaves.
The most toxic of the stinging trees, gympie-gympie or Dendrocnide moroides.
Edward Gilding, Author provided

Gympietides

The gympietides have an intricate three-dimensional structure that is kept stable by a network of links within the molecule that form a knotted shape. This makes it highly stable, meaning it likely stays intact for a long time once injected into the victim. Indeed, there are anecdotes reporting even 100-year-old stinging tree specimens kept in herbariums can still produce painful stings.

What was surprising was the 3D structure of these gympietides resembles the shape of well-studied toxins from spider and cone snail venom. This was a big clue as to how these toxins might be working, as similar venom peptides from scorpions, spiders, and cone snails are known to affect structures called ion channels in nerve cells, which are important mediators of pain.

Specifically, the gympietides interfere with an important pathway for conducting pain signals in the body, called voltage-gated sodium ion channels. In a cell affected by gympietides, these channels do not close normally, which means the cell has difficulty turning off the pain signal.




Read more:
Explainer: what is pain and what is happening when we feel it?


Better understanding may bring new treatments

The Australian stinging trees make a neurotoxin that resembles a venom in both its molecular structure and how it is deployed by injection. Taking these two things together, it would seem two very different evolutionary processes have converged on similar solutions to win the endgame of inflicting pain.

In the process, evolution has also presented us with an invaluable tool to understand how pain is caused. The precise mechanisms by which gympietides affect ion channels and nerve cells are currently under investigation. During that investigation, we may find new avenues to bring pain under control.The Conversation

Irina Vetter, Australian Research Council Future Fellow, The University of Queensland; Edward Kalani Gilding, Postdoctoral Research Officer, The University of Queensland, and Thomas Durek, Senior Research Fellow, The University of Queensland

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

Photos from the field: capturing the grandeur and heartbreak of Tasmania’s giant trees



Steve Pearce/The Tree Projects, Author provided

Jennifer Sanger, University of Tasmania

Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this new series, we’ve invited them to share their unique photos from the field.


Tasmania’s native forests are home to some of the tallest, most beautiful trees in the world. They provide a habitat for many species, from black cockatoos and masked owls to the critically endangered swift parrot.

But these old, giant trees are being logged at alarming rates, despite their enormous ecological and heritage value (and untapped tourism potential). Many were also destroyed in Tasmania’s early 2019 fires.




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Comic explainer: forest giants house thousands of animals (so why do we keep cutting them down?)


Former Greens leader Bob Brown recently launched a legal challenge to Tasmania’s native forest logging. And this year, Forestry Watch, a small group of citizen scientists, found five giant trees measuring more than five metres in diameter inside logging coupes. “Coupes” are areas of forest chopped down in one logging operation.

These trees are too important to be destroyed in the name of the forestry industry. This is why my husband Steve Pearce and I climb, explore and photograph these trees: to raise awareness and foster appreciation for the forests and their magnificent giants.

Climbing trees is not just for the young, but for the young at heart. Kevin is in his early 70’s and helps us with measuring giant trees.
Steve Pearce/The Tree Projects, Author provided

What makes these trees so special?

Eualypytus regnans, known more commonly as Mountain Ash or Swamp Gum, can grow to 100 metres tall and live for more than 500 years. For a long time this species held the record as the tallest flowering tree. But last year, a 100.8 m tall Yellow Meranti (Shorea faguetiana) in Borneo, claimed the title — surpassing our tallest Eucalypt, named Centrioun, by a mere 30 centimetres.

Centrioun still holds the record as the tallest tree in the southern hemisphere. But five species of Eucalypt also grow above 85 m tall, with many ranking among some of the tallest trees in the world.

It’s not only their height that make these trees special, they’re also the most carbon dense forests in the world, with a single hectare storing more than 1,867 tonnes of carbon.




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Our giant trees and old growth forests provide a myriad of ecological services such as water supply, climate abatement and habitat for threatened species. A 2017 study from the Central Highlands forests in Victoria has shown they’re worth A$310 million for water supply, A$260 million for tourism and A$49 million for carbon storage.

This significantly dwarfs the A$12 million comparison for native forest timber production in the region.

Chopped wood in a logging coupe.
Chopping down old growth trees doesn’t make economic sense.
Steve Pearce/The Tree Projects, Author provided

Tasmania’s Big Tree Register

Logging organisation Sustainable Timber Tasmania’s giant tree policy recognises the national and international significance of giant trees. To qualify for protection, trees must be at least 85 m tall or at least an estimated 280 cubic metres in stem volume.




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While it’s a good place to start, this policy fails to consider the next generation of big, or truly exceptional trees that don’t quite reach these lofty heights.

That’s why we’ve created Tasmania’s Big Tree Register, an open-source public record of the location and measurements of more than 200 trees to help adventurers and tree-admirers locate and experience these giants for themselves. And, we hope, to protect them.

Last month, three giant trees measuring more than 5 m in diameter were added to the register. But these newly discovered trees are located in coupe TN034G, which is scheduled to be logged this year.

Logging is a very poor economic use for our forests. Native forest logging in Tasmania has struggled to make a profit due to declining demand for non-Forest Stewardship Council certified timber, which Sustainable Timber Tasmania recently failed. In fact, Sustainable Timber Tasmania sustained an eye watering cash loss of A$454 million over 20 years from 1997 to 2017.




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Summer bushfires: how are the plant and animal survivors 6 months on? We mapped their recovery


The following photos can help show why these trees, as one of the great wonders of the world, should be embraced as an important part of our environmental heritage, not turned to wood chips.

A portrait of an entire tree captured. Its canopy breaches the clouds.

Steve Pearce/The Tree Projects, Author provided

It’s not often you get to see the entirety of a tree in a single photo. This tree above is named Gandalf’s Staff and is a Eucalyptus regnans, measuring 84 m tall.

While Mountain Ash is the tallest species, others in Tasmania’s forests are also breathtakingly huge, such as the Tasmanian blue gum (Eucalyptus globulus) at 92 m, Manna gum (Eucalyptus viminalis) at 91 m, Alpine ash (Eucalyptus delegatensis) at 88 m and the Messmate Stringybark (Eucalyptus obliqua) at 86 m.

A woman appears tiny standing against an enormous felled tree.

Steve Pearce/The Tree Projects, Author provided

This giant tree, pictured above, was a Messmate Stringybark that was felled in coupe, but was left behind for unknown reasons. Its diameter is 4.4 metres. Other giant trees like this were cut down in this coupe, many of which provided excellent nesting habitat for the critically endangered swift parrot.

Nine people sit across the trunk of an enormous tree.
The citizen science group Forestry Watch helps search for and measure giant trees in Tasmania.
Steve Pearce/The Tree Projects, Author provided

Old-growth forests dominated by giant trees are excellent at storing large amounts of carbon. Large trees continue to grow over their lifetime and absorb more carbon than younger trees.

A man wraps a measuring tape around a huge tree trunk, covered in moss.

Steve Pearce/The Tree Projects, Author provided

The tree in the photo above is called Obolus, from Greek mythology, with a diameter of 5.1 m. Names are generally given to trees by the person who first records them, and usually reflect the characteristics of the tree or tie in with certain themes.

For example, several trees in a valley are all named after Lord of the Rings characters, such as Gandalf’s Staff (pictured above), Fangorn and Morannon.

The tops of the giant tree canopies are higher than the clouds.

Steve Pearce/The Tree Projects, Author provided

Giant trees are typically associated with Californian Redwoods or the Giant Sequoias in the US, where tall tree tourism is huge industry. The estimated revenue in 2012 from just four Coastal Redwood reserves is A$58 million dollars per year, providing more than 500 jobs to the local communities.

Few Australians are aware of our own impressive trees. We could easily boost tourism to regional communities in Tasmania if the money was invested into tall tree infrastructure.The Conversation

Jennifer Sanger, Research Associate, University of Tasmania

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

‘Majestic, stunning, intriguing and bizarre’: New Guinea has 13,634 species of plants, and these are some of our favourites



Bulbophyllum alkmaarense: New Guinea is home to more than 2,400 species of native orchids.
Andre Schuiteman/CSIRO

Bruce Webber, CSIRO; Barry J Conn, University of Sydney, and Rodrigo Cámara-Leret, University of Zürich

Scientists have been interested in the flora of New Guinea since the 17th century, but formal knowledge of the tropical island’s diversity has remained limited.

To solve this mystery, our global team of 99 scientists from 56 institutions built the first ever expert-verified checklist to the region’s vascular plants (those with conductive tissue).

We found there are 13,634 formally described species of plants in New Guinea, of which a remarkable 68% are known to occur there and nowhere else. This richness trumps both Madagascar (11,488 species) and Borneo (11,165 species), making New Guinea the most floristically diverse island in the world.

From tarantula-like orchids to giant bananas, here we reveal some of the more mysterious plants on our checklist. Sadly, unsustainable logging and climate change threaten the conservation of many New Guinean species, and we highlight urgent solutions.




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People are ‘blind’ to plants, and that’s bad news for conservation


The majestic flora of New Guinea

New Guinea is a land of evocative contrasts. As the world’s largest tropical island – made up of Papua New Guinea to the east and two Indonesian provinces to the west – its biological diversity spans habitats from fringing mangroves to alpine grasslands.

The flora is diverse, filled with the majestic, stunning, intriguing and bizarre. However, very little is known about the conservation status of many species in New Guinea, which remains relatively unexplored by scientists.

The high hoop pine with thin branches and a full canopy
High hoop pines tower over forest canopy.
Wikimedia, CC BY

There are the few remaining forests of 60 metres high hoop pine (Araucaria cunninghamii) and klinkii pine (A. hunsteinii), that tower majestically up to 30 metres above the already tall rainforest canopy.

Figs, with their copious sap, are present in diverse forms, from small shrubs to vines, or large canopy trees.

And the strongly irritant black sap of the Semecarpus tree, a distant relative of the American poison ivy, causing severe dermatitis, is something naive botanists must learn to avoid!

Three panels showing different parts of Ryparosa amplifolia
Ryparosa amplifolia maintains an intimate association with ants via hollow stems and food bodies.
Bruce Webber, Author provided

Then there’s the Ryparosa amplifolia, a rainforest tree that provides swollen hollow stems for ant colonies to live inside. The tree also produces energy rich “food bodies” – granule-like structures on the leaves that mimic animal tissue and provide the ants with sustenance. In return, the ants act as bodyguards, chasing away insect herbivores, and leaf cleaners.

A giant banana tree with an umbrella-like canopy and a thick trunk towers in a rainforest
The giant banana tree holds the record of being the largest and tallest non-woody plant in the world.
Rodrigo Camara, Author provided

Some of our most popular foods were domesticated from New Guinea, including sugarcane and bananas. But the giant banana, Musa ingens is a a highlight in montane forests. Its leaves can stretch to a length of 5 metres, the tree can grow more than 20 metres tall, and its fruits are massive.

With more than 2,400 species of native orchid species, New Guinea is one of the most spectacular floral gardens in the world. It includes fascinating species such as Bulbophyllum nocturnum, which is the first and only known example of a night-flowering orchid, and Bulbophyllum tarantula, with appendages that resemble the iconic spider.

A close-up of a green orchid with pink blotches and furry leg-like bits
Bulbophyllum tarantula gets its name from its tarantula-like appearance.
Jan Meijvogel, Author provided

An uncertain future

Despite New Guinea’s seemingly high number of plant species, at least 3,000 species remain to be discovered and formally described. This estimate is based on the rate of description of new species in the past decades.

Much of New Guinea, particularly the Indonesian part, has been extremely poorly studied, with very few plant species collected. Even within Papua New Guinea, the distribution of many species is inadequately known. This means our findings should be viewed as a baseline upon which to prioritise further work.

The biggest impact on forest conservation is from logging, both clear-felling and degradation. As land is predominantly under customary ownership, addressing subsistence-related forest loss is a long-term challenge. Climate change adds yet further threats, including increased burning of degraded forest due to drier weather.

This means there’s a high risk of the world losing entire species before they are even known.

Looking down on the jungles of Papua New Guinea
Unsustainable logging and climate change are the biggest threats to the flora of New Guinea.
Shutterstock

To this end, in 2018 the governors of Indonesia’s two New Guinea provinces announced the Manokwari Declaration, a pledge to conserve 70% of forest cover for the western half of the island.

Reversing funding shortfalls and declining engagement

Our work builds on many decades of effort by plant collectors whose countless nights under leaking canvas, grass huts and bark shelters have led to thousands of plant discoveries.

Their stories are astounding. These fearless adventurers have sampled water plants by jumping from helicopters hovering low over Lake Tebera, swam in the Purari River rapids to haul a disabled dugout canoe full of botanists and cargo to safety, and have fallen into beds of stinging plants in the mountains of Wagau without subsequent access to pain relief.

Taxonomy – the discipline of identifying, classifying, and understanding relationships between plants – is the key to unlocking the value of this collecting effort.


A yellow flower with small brown spots and three appendages
Bulbophyllum nocturnum: the first known example of an orchid species in which flowers open after dark and close in the morning.
Jan Meijvogel, Author provided

But the discipline is suffering from global funding shortfalls and declining engagement. For instance, 40% of our co-authors on this work are 55 years or older.

Future opportunities for botanical research with local New Guineans at the helm is also vital – only 15% of the scientific publications on the New Guinean flora over the past 10 years involved local co-authors.

Improved collaboration between taxonomists, scientific institutions, governments and New Guinean scientific agencies could address these critical urgent priorities.

Undoubtedly, the conservation of New Guinea’s unique flora will be challenging and require work on many fronts that transcend single disciplines or institutions. From what we know already, a world of botanical surprises awaits in the last unknown.

After all, as 19th century naturalist J.B. Jukes wrote:

I know of no part of the world, the exploration of which is so flattering to the imagination, so likely to be fruitful in interesting results […] and altogether so well calculated to gratify the enlightened curiosity of an adventurous explorer, as the interior of New Guinea.




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The Conversation


Bruce Webber, Principal Research Scientist, CSIRO; Barry J Conn, Researcher, University of Sydney, and Rodrigo Cámara-Leret, Researcher, University of Zürich

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

Gabon’s large trees store huge amounts of carbon. What must be done to protect them



Ivanov Gleb/Shutterstock

John Poulsen, Duke University

Large trees are the living, breathing giants that tower over tropical forests, providing habitat and food for countless animals, insects and other plants. Could these giants also be the key to slowing climate change?

The Earth’s climate is changing rapidly due to the buildup of greenhouse gases, like carbon dioxide, in the atmosphere as a result of human activities. Trees absorb carbon from the air and store it in their trunks, branches, and roots. In general, the larger the tree, the more carbon it stores.

Globally, tropical forests remove a staggering 15% of carbon dioxide emissions that humans produce. Africa’s tropical forests – the second largest block of rainforest in the world – have a large role to play in slowing climate change.

But large trees are in trouble everywhere. I carried out research to examine the distribution, drivers and threats to large trees in Gabon. Gabon has 87% forest cover and is the second most forested country in the world.

By carrying out this project, I was able to identify areas with a wealth of large trees (and therefore key carbon stores and sinks), what needed to be done to better protect them and eventually recommend those areas as a priority for conservation.

National inventory

In 2012, the government of Gabon began a national inventory of its forests to measure the amount of carbon stored in its trees – one of the first nationwide efforts in the tropics.

An inventory of this scale isn’t easy, especially in a heavily forested country. Technicians from Gabon’s National Parks Agency travelled to every corner of the country, sometimes hiking more than two days crossing swamps and traversing rivers, to measure the diameter and height of trees in plots a bit larger in size than a soccer field.

Using Gabon’s new inventory of 104 plots, we calculated the amount of carbon in 67,466 trees, representing at least 578 different species. We did this by applying equations to the tree measurements.

The results indicated that the density of carbon stored in Gabon’s trees is among the highest in the world. On average, Gabon’s old growth forests harbour more carbon per area than old growth forests in Amazonia and Asia.

Most of this carbon is stored in the largest trees – those with diameters bigger than 70cm at 1.3 meters from the ground. Just the largest 5% of trees stored 50% of the forest carbon. In other words, 3,373 trees out of the 67,466 measured trees contained half of the carbon.

Drivers of forest carbon stocks

Next, we examined the drivers of carbon stocks. What determines whether an area of forest holds many large trees and lots of carbon? Do environmental conditions or human activities have the largest impact on forest carbon stocks?

Environmental factors – such as soil fertility and depth, temperature, precipitation, slope and elevation – often influence the amount of carbon in a forest. During photosynthesis, trees harness energy from the sun to convert water, carbon dioxide, and minerals into carbohydrates for growth. Therefore, forests with low levels of soil minerals or that receive little rainfall should store less carbon than areas with abundant minerals and water.

Human activities – like agriculture and logging – also influence carbon stocks. Cutting down trees for timber, to clear land for farming, or for construction reduces the amount of carbon stored in forests.

We examined the amount of carbon in each tree plot in relation to the environmental factors and human activities associated with the plot. Surprisingly, we found that human activities, not environmental factors, overwhelmingly affect carbon stocks.

The impact of human activities on forest carbon was largely unexpected because of Gabon’s high forest cover (the second highest of any country) and low population density (9 people per square kilometer), 87% of which is located in urban areas. If human impacts are this strong in Gabon, what must their effects be in other tropical nations?

Although we don’t know for sure, we believe past and present swidden (slash-and-burn) agriculture is the principle cause for low carbon stocks in some areas. Forests close to villages had lower levels of carbon, probably because forest clearing for farming converts old growth forest to secondary forest.

Interestingly, forests in logging concessions held similar amounts of carbon as old growth forests. It is too early to conclude that timber harvest doesn’t reduce carbon levels by cutting large trees, but this finding gives hope that logging concessions can be managed sustainably to conserve carbon stocks.

Importantly, forests in national parks stored roughly 25% more carbon than forests outside of parks. Thus, protecting mostly undisturbed forests can effectively conserve carbon and biodiversity.

Saving Gabon’s giants

The critical role of humans in diminishing carbon stocks is both a blessing and a curse. One one hand, the future of forests are in our hands, giving us the power to choose our fate. On the other hand, we cannot ignore the responsibility to act collectively to secure these resources while considering the interests of the countries that host them.

Gabon is taking laudable actions to conserve its forests, including a protected area network of 13 parks. In addition, Gabon is reforming its logging sector and developing a nationwide land use plan. These actions are a great start, yet continued action is necessary to curb the effects of swidden agriculture and ensure that growing industrial agriculture does not reverse Gabon’s achievements.

Intact forests can pay returns. Norway recently committed to paying Gabon $150 million for stewardship of its forests. Conservation of forests requires sacrifice by the Gabonese people. Yet, this payment demonstrates that Gabon’s large trees are a national asset that can contribute to its development as well as an international resource requiring collective action to conserve.The Conversation

John Poulsen, Associate Professor of Tropical Ecology, Duke University

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

Are young trees or old forests more important for slowing climate change?



Jeremy Kieran/Unsplash, CC BY-SA

Tom Pugh, University of Birmingham

Forests are thought to be crucial in the fight against climate change – and with good reason. We’ve known for a long time that the extra CO₂ humans are putting in the atmosphere makes trees grow faster, taking a large portion of that CO₂ back out of the atmosphere and storing it in wood and soils.

But a recent finding that the world’s forests are on average getting “shorter and younger” could imply that the opposite is happening. Adding further confusion, another study recently found that young forests take up more CO₂ globally than older forests, perhaps suggesting that new trees planted today could offset our carbon sins more effectively than ancient woodland.

How does a world in which forests are getting younger and shorter fit with one where they are also growing faster and taking up more CO₂? Are old or young forests more important for slowing climate change? We can answer these questions by thinking about the lifecycle of forest patches, the proportion of them of different ages and how they all respond to a changing environment.




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Using forests to manage carbon: a heated debate


The forest carbon budget

Let’s start by imagining the world before humans began clearing forests and burning fossil fuels.

In this world, trees that begin growing on open patches of ground grow relatively rapidly for their first several decades. The less successful trees are crowded out and die, but there’s much more growth than death overall, so there is a net removal of CO₂ from the atmosphere, locked away in new wood.

As trees get large two things generally happen. One, they become more vulnerable to other causes of death, such as storms, drought or lightning. Two, they may start to run out of nutrients or get too tall to transport water efficiently. As a result, their net uptake of CO₂ slows down and can approach zero.

Eventually, our patch of trees is disturbed by some big event, like a landslide or fire, killing the trees and opening space for the whole process to start again. The carbon in the dead trees is gradually returned to the atmosphere as they decompose.

The vast majority of the carbon is held in the patches of big, old trees. But in this pre-industrial world, the ability of these patches to continue taking up more carbon is weak. Most of the ongoing uptake is concentrated in the younger patches and is balanced by CO₂ losses from disturbed patches. The forest is carbon neutral.

A misty forest scene.
New trees absorb lots of carbon, old trees store more overall and dead trees shed their carbon to the atmosphere.
Greg Rosenke/Unsplash, CC BY-SA

Now enter humans. The world today has a greater area of young patches of forest than we would naturally expect because historically, we have harvested forests for wood, or converted them to farmland, before allowing them to revert back to forest. Those clearances and harvests of old forests released a lot of CO₂, but when they are allowed to regrow, the resulting young and relatively short forest will continue to remove CO₂ from the atmosphere until it regains its neutral state. In effect, we forced the forest to lend some CO₂ to the atmosphere and the atmosphere will eventually repay that debt, but not a molecule more.

But adding extra CO₂ into the atmosphere, as humans have done so recklessly since the dawn of the industrial revolution, changes the total amount of capital in the system.

And the forest has been taking its share of that capital. We know from controlled experiments that higher atmospheric CO₂ levels enable trees to grow faster. The extent to which the full effect is realised in real forests varies. But computer models and observations agree that faster tree growth due to elevated CO₂ in the atmosphere is currently causing a large carbon uptake. So, more CO₂ in the atmosphere is causing both young and old patches of forest to take up CO₂, and this uptake is larger than that caused by previously felled forests regrowing.

The effect of climate change

But the implications of climate change are quite different. All else being equal, warming tends to increase the likelihood of death among trees, from drought, wildfire or insect outbreaks. This will lower the average age of trees as we move into the future. But, in this case, that younger age does not have a loan-like effect on CO₂. Those young patches of trees may take up CO₂ more strongly than the older patches they replace, but this is more than countered by the increased rate of death. The capacity of the forest to store carbon has been reduced. Rather than the forest loaning CO₂ to the atmosphere, it’s been forced to make a donation.

So increased tree growth from CO₂ and increased death from warming are in competition. In the tropics at least, increased growth is still outstripping increased mortality, meaning that these forests continue to take up huge amounts of carbon. But the gap is narrowing. If that uptake continues to slow, it would mean more of our CO₂ emissions stay in the atmosphere, accelerating climate change.

Overall, both young and old forests play important roles in slowing climate change. Both are taking up CO₂, primarily because there is more CO₂ about. Young forests take up a bit more, but this is largely an accident of history. The extra carbon uptake we get from having a relatively youthful forest will diminish as that forest ages. We can plant new forests to try to generate further uptake, but space is limited.

But it’s important to separate the question of uptake from that of storage. The world’s big, old forests store an enormous amount of carbon, keeping it out of the atmosphere, and will continue to do so, even if their net CO₂ uptake decreases. So long as they are not cut down or burned to ashes, that is.The Conversation

Tom Pugh, Reader in Biosphere-Atmosphere Exchange, University of Birmingham

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

Click through the tragic stories of 119 species still struggling after Black Summer in this interactive (and how to help)



Shutterstock

Anthea Batsakis, The Conversation and Wes Mountain, The Conversation

This article is part of Flora, Fauna, Fire, a special project by The Conversation that tracks the recovery of Australia’s native plants and animals after last summer’s bushfire tragedy. Explore the project here and read more articles here.


Before the summer bushfires destroyed vast expanses of habitat, Australia was already in the midst of a biodiversity crisis. Now, some threatened species have been reduced to a handful of individuals – and extinctions are a real possibility.

The Kangaroo Island dunnart, a small marsupial, was listed as critically endangered before the bushfires. Then the inferno destroyed 95% of its habitat.

Prospects for the Banksia Montana mealybug are similarly grim. This flightless insect lives only on one species of critically endangered plant, at a high altitude national park in Western Australia. The fires destroyed 100% of the plant’s habitat.




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And fewer than 100 western ground parrots remained in the wild before last summer, on Western Australia’s south coast. Last summer’s fires destroyed 40% of its habitat.

Fish, crayfish and some frogs are also struggling. After the fires, heavy rain washed ash, fire retardants and dirt into waterways. This can clog and damage gills, and reduces the water’s oxygen levels. Some animals are thought to have suffocated.

Here, dozens of experts tell the stories of the 119 species most in need of help after our Black Summer.

How can I help?

Recovery from Australia’s bushfire catastrophe will be a long road. If you want to help, here are a few places to start.

Donate

Australian Wildlife Conservancy

Bush Heritage Australia

WWF

Birdlife Australia

Also see this list of registered bushfire charities

Volunteer

Parks Victoria

NSW National Parks and Wildlife Service

Queensland Parks and Wildlife Service

Conservation Volunteers Australia

Landcare

The Conversation

Anthea Batsakis, Deputy Editor: Environment + Energy, The Conversation and Wes Mountain, Multimedia Editor, The Conversation

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

Summer bushfires: how are the plant and animal survivors 6 months on? We mapped their recovery


Anthea Batsakis, The Conversation; Nicole Hasham, The Conversation, and Wes Mountain, The Conversation

Australia roared into 2020 as a land on fire. The human and property loss was staggering, but the damage to nature was equally hard to fathom. By the end of the fire season 18.6 million hectares of land was destroyed.

So what’s become of animal and plant survivors in the months since?

Click through below to explore the impact Australia’s summer of fires had on an already drought-ravaged landscape and the work being done to rescue and recover habitats.


The Conversation

Anthea Batsakis, Deputy Editor: Environment + Energy, The Conversation; Nicole Hasham, Section Editor: Energy + Environment, The Conversation, and Wes Mountain, Multimedia Editor, The Conversation

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

After last summer’s fires, the bell tolls for Australia’s endangered mountain bells



Darwinia nubigena also known as the Success Bell or Red Mountain Bell.
A.T Morphet, Author provided

Kingsley Dixon, Curtin University

This article is a preview from Flora, Fauna, Fire, a multimedia project launching on Monday July 13. The project tracks the recovery of Australia’s native plants and animals after last summer’s bushfire tragedy. Sign up to The Conversation’s newsletter for updates.


Hidden in the Stirling Range national park in Western Australia – an area so diverse, so ecologically important, I’ve described it as a “coral reef out of water” – are Australia’s spectacular mountain bells.

When Western botanists encountered these predominantly bird-pollinated plants, they found them so intriguing and so unlike anything they knew (Britain has no bird pollination), they named them Darwinia after Charles Darwin’s grandfather, Erasmus Darwin.

These breathtaking native Australian flowers are now at grave risk from recent fires, with many species listed on the government’s provisional list of plants requiring urgent management intervention. The Stirling Ranges were ravaged by this summer’s fires, and three-quarters of this WA national park now experience fire cycles twice as frequent as species recovery rates.

If it sounds grim, that’s because it is. There’s hope yet for the mountain bell, though, thanks largely to the efforts of concerned community members.

Darwinia collina, the yellow mountain bell, is listed as endangered.
A. T. Morphet, Author provided

Why are mountain bells so special?

With an astonishing range of colours, the Stirling Range mountain bells are the glamour plants in WA’s floral bouquet.

Standing up to 60cm tall, these glorious shrubs are a gardener’s dream. They have neat foliage and pendulous, bell-like flowers in colours ranging from yellow, to greens, to striking reds and multicoloured variegated blooms.

Darwinia has just 70 species – a modest number compared with some plant genera in Australia.

They occur in southeastern and southwestern Australia. Darwinia split from their ancestral lineage 16 million years ago with the southwest, including the Stirling Ranges – a cradle of the genus. The chance dispersal of seed to southeastern Australia meant the two nodes of diversity were separated by the Nullarbor and central desert, and evolved in splendid isolation. How these heavy-seeded plants managed such an epic journey across the Australian deserts remains a mystery.




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Nectar-hungry Australian birds found the rewards in the rain-protected, bell-like flowers irresistible.

In what was a blink of evolutionary time, mountain bells capitalised on birds as a better system for pollination than offered by insects, and new species appeared across the peaks of the Stirlings.

Today, there are ten species of mountain bells. All but one are only found in the Stirling Ranges, often on single peaks or in highly restricted locations. And many feature on the provisional list of plants requiring urgent management.

Virtually each peak could have its very own mountain bell. I recall my first encounter with the mountain bells years ago. I’d spotted the delicate cherry-coloured blooms of Wittwer’s bell nestled in a small wooded hollow, midway along the main drive through the Stirlings. I eagerly sought out other mountain bell species and, soon enough, realised I had an untreatable case of “bell fever”.

A _Darwinia macrostegia or Mondurup Bell on Mondurup Peak.
A.T Morphet, Author provided

A biodiversity hotspot at a crossroads

Traditional owners revered the Stirling Ranges as sacred land that had endured countless ice ages and climate ravages. But today, the Stirling Ranges are at a crossroads.

The discovery of dieback disease (Phytophthora cinnamomi) in 1974, as well as fires both prescribed and natural, have taken a heavy toll on the plants and animals in the park.

Last summer’s cataclysmic fires scorched half of the Stirling Ranges national park, and the danger the mountain bells now face is emblematic of the broader problem of biodiversity loss.

Many plants and animal species here may never recover. Yes, many Australian plants evolved to cope with bushfire – but not with how frequently these fires are reoccurring.

The Stirling Ranges national park is like no other, with an astonishing 1,500 plant species, eclipsing the flora of the British Isles.

Threats abound

Contemporary fire is now one of the single greatest threats to what remains of this extraordinary ecosystem.

The mountain bells need more than 15 years or more to rebuild their soil seed bank, as these plants are killed by even the mildest of fire.

We knew this was coming. Dire predictions by conservation scientists as early as 2015 warned the Stirling Ranges faced a biodiversity meltdown, and that mountain bells were particularly at risk of extinction.




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Though the fires have retreated, the once thriving populations of mountain bells are reduced to blackened stems. It is indescribably sad to see.

For some species, the 2020 bushfires came hot on the heels of an out-of-control prescribed burn in 2018, and few species can survive such short interval fire. Scientists are surveying the damage, to see if parts of the soil seed bank survived to grow the next generation of mountain bells. But it may be too late for some species. Time will tell.

The endemic grass tree Kingia australis absorbs ethylene gas from bushfire to initiate flowering within months.
Keith Bradbury, Author provided

Community action

Is there a future for mountain bells? I like to think so. I have grown them in wildflower gardens from cuttings handed down from wildflower gardeners over decades. Through temperamental and often unpredictable to grow, mountain bells are remarkably easy to propagate.

A key part of saving our mountain bells is, I believe, intimately linked to the community of wildflower enthusiasts. These passionate, committed community members stand ready to help save the last bells.

The Stirling Ranges national park in Western Australia.
Trevor Dobson, CC BY-NC-ND

The way we’ve done conservation in the past needs a reboot. For the mountain bells and many other threatened species to have a future, we need to embrace a new way of engaging with community volunteers and particularly our traditional owners.

Everyone I have spoken to is ready to roll up their sleeves and help our plants, and animals struggling to come out of the fires. Such an approach will need trust, training and support – but it may be our only hope.




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The Conversation


Kingsley Dixon, John Curtin Distinguished Professor, Curtin University

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

Planting non-native trees accelerates the release of carbon back into the atmosphere



native forest.

Lauren Waller and Warwick Allen, University of Canterbury

Large-scale reforestation projects such as New Zealand’s One Billion Trees programme are underway in many countries to help sequester carbon from the atmosphere.

But there is ongoing debate about whether to prioritise native or non-native plants to fight climate change. As our recent research shows, non-native plants often grow faster compared to native plants, but they also decompose faster and this helps to accelerate the release of 150% more carbon dioxide from the soil.

Our results highlight a challenging gap in our understanding of carbon cycling in newly planted or regenerating forests.

It is relatively easy to measure plant biomass (how quickly a plant grows) and to estimate how much carbon dioxide it has removed from the atmosphere. But measuring carbon release is more difficult because it involves complex interactions between the plant, plant-eating insects and soil microorganisms.

This lack of an integrated carbon cycling model that includes species interactions makes predictions for carbon budgeting exceedingly difficult.




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How non-native plants change the carbon cycle

There is uncertainty in our climate forecasting because we don’t fully understand how the factors that influence carbon cycling – the process in which carbon is both accumulated and lost by plants and soils – differ across ecosystems.

Carbon sequestration projects typically use fast-growing plant species that accumulate carbon in their tissues rapidly. Few projects focus on what goes on in the soil.

Non-native plants often accelerate carbon cycling. They usually have less dense tissues and can grow and incorporate carbon into their tissues faster than native plants. But they also decompose more readily, increasing carbon release back to the atmosphere.

Our research, recently published in the journal Science, shows that when non-native plants arrive in a new place, they establish new interactions with soil organisms. So far, research has mostly focused on how this resetting of interactions with soil microorganisms, herbivorous insects and other organisms helps exotic plants to invade a new place quickly, often overwhelming native species.

Invasive non-native plants have already become a major problem worldwide, and are changing the composition and function of entire ecosystems. But it is less clear how the interactions of invasive non-native plants with other organisms affect carbon cycling.




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Planting non-native trees releases more carbon

We established 160 experimental plant communities, with different combinations of native and non-native plants. We collected and reared herbivorous insects and created identical mixtures which we added to half of the plots.

We also cultured soil microorganisms to create two different soils that we split across the plant communities. One soil contained microorganisms familiar to the plants and another was unfamiliar.

Herbivorous insects and soil microorganisms feed on live and decaying plant tissue. Their ability to grow depends on the nutritional quality of that food. We found that non-native plants provided a better food source for herbivores compared with native plants – and that resulted in more plant-eating insects in communities dominated by non-native plants.

Similarly, exotic plants also raised the abundance of soil microorganisms involved in the rapid decomposition of plant material. This synergy of multiple organisms and interactions (fast-growing plants with less dense tissues, high herbivore abundance, and increased decomposition by soil microorganisms) means that more of the plant carbon is released back into the atmosphere.

In a practical sense, these soil treatments (soils with microorganisms familiar vs. unfamiliar to the plants) mimic the difference between reforestation (replanting an area) and afforestation (planting trees to create a new forest).

Reforested areas are typically replanted with native species that occurred there before, whereas afforested areas are planted with new species. Our results suggest planting non-native trees into soils with microorganisms they have never encountered (in other words, afforestation with non-native plants) may lead to more rapid release of carbon and undermine the effort to mitigate climate change.The Conversation

Lauren Waller, Postdoctoral Fellow and Warwick Allen, Postdoctoral fellow, University of Canterbury

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

The coastal banksia has its roots in ancient Gondwana



John Tann/Flickr, CC BY

Gregory Moore, University of Melbourne

If you fondly remember May Gibbs’s Gumnut Baby stories about the adventures of Snugglepot and Cuddlepie, you may also remember the villainous Big Bad Banksia Men (perhaps you’re still having nightmares about them).

But banksias are nothing to be afraid of. They’re a marvellous group of Australian native trees and shrubs, with an ancient heritage and a vital role in Australian plant ecology, colonial history and bushfire regeneration.

The genus Banksia has about 173 native species. It takes its name from botanist Sir Joseph Banks, who collected specimens of four species in 1770 when he arrived in Australia on board Captain Cook’s Endeavour.




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One of the four species he collected was B. integrifolia, the coastal banksia. This can be a small to medium tree about 5m to 15m tall. In the right conditions, it can be quite impressive and grow up to 35m.

It’s found naturally in coastal regions, growing on sand dunes or around coastal marshes from Queensland to Victoria. These can be quite tough environments and, while B. integrifolia tends to grow in slightly protected sites, it still copes well with sandy soils, poor soil nutrition, salt and wind.

In the right conditions, coastal banksia can grow to 35m tall.
Shutterstock

From ancient origins

Coastal banksia – like all banksias – belong to the protea family (Proteaceae). But given the spectacular flowering proteas are of African origin, how did our Australian genera get here?

The members of the Proteaceae belong to an ancient group of flowering plants that evolved almost 100 million years ago on the southern supercontinent Gondwana. When Gondwana fragmented more than 80 million years ago, the proteas remained on the African plate, while the Australian genera remained here.




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The spikes of woody fruits on the Australian banksia, sometimes called cones, are made up of several hundred flowers. The flower spikes are beautiful structures, soft and brush-like. But with B. integrifolia, they are pale green, similar to the foliage, and can be hard to see within the canopy at a distance.

Up close, these fruit spikes can look quite spooky, almost sinister, especially when wasps have caused extensive gall formation. Galls are swellings that develop on plant tissues as a result of fungal and insect damage, a bit like a benign tumour.

Maybe this is what led May Gibbs to cast them as the baddies in her Gumnut Baby stories. While the galls may look unsightly, they rarely do serious harm to banksias.

Banksias were depicted as the Big Bad Banksia Men in May Gibbs’s Gumnut stories.
May Gibbs/The Northcott Society and Cerebral Palsy Alliance

Indigenous use

Given the fruit spikes of coastal banksia look like brushes, it’s not surprising Indigenous people once used them as paint brushes.

The flowers are very rich in nectar, which attracts insects and birds. If you run your hand along the flower spike you, like generations of Aboriginal people before you, can enjoy the sweet taste if you lick the nectar off your hand. You can also soak the flowers in water and collect a sweet syrup.

In the garden, B. integrifolia is wonderfully attractive to native insects, birds and ringtail possums. It’s easy to establish and, until it grows more than a few metres high, can be successfully moved and transplanted.

Coastal banksia doesn’t need fire to release its seed.
Shutterstock

Unlike many other banksia species, coastal banksias don’t need fire to release their seed. For many Australian species, the woody fruits remain solid and sealed, and it’s only when fire comes through that they burn, dry, crack open and release their seed.

This can happen with B. integrifolia too, but in a garden setting the fruits will mature, dry and crack open and release the seeds, which germinate readily. This makes propagating coastal banksia easy work.

In touch with its roots

Perhaps one of the more important, but less obvious, attributes of B. integrifolia are its roots. These are a special type of root possessed by members of the protea family.

The roots form a dense, branched cluster, a bit like the head of a toothbrush, that can be 2-5cm across. They greatly increase the absorbing surface area of the roots, as each root possesses thousands of very fine root hairs.




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Proteoid roots can be very handy in sandy and other poor soils, where water drains quickly and nutrients are scarce.

These roots, also described as cluster roots, are often visible in a garden bed just at the interface of the soil with the humus or mulch layer above it. They’re very light brown, almost white, in colour.

Rainbow lorikeets love hanging around in banksias.
Flickr/Salihan, CC BY-NC-ND

B. integrifolia, like other banksias, also has the ability to take in nitrogen and enrich the soil, which can be very handy in soils low in nitrogen. It’s like a natural living and decorative fertiliser.




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Proteoid roots are unfortunately very well suited to the presence of Phytophthora cinnamomii (the cinnamon fungus). It causes dieback in many native plant species, but can be particularly virulent for banksias.

But B. Integrifolia is one of the more resistant species to the fungus. Promising experiments have been done on grafting susceptible species onto the roots of B. integrifolia to improve their rates of survival.

This could be important, as banksias have a role in bushfire regeneration in many parts of Australia, so the occurrence of the fungus can compromise fire recovery.The Conversation

Gregory Moore, Doctor of Botany, University of Melbourne

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