After the bushfires, we helped choose the animals and plants in most need. Here’s how we did it



Daniel Marius/AAP

John Woinarski, Charles Darwin University; Dale Nimmo, Charles Sturt University; Rachael Gallagher, Macquarie University, and Sarah Legge, Australian National University

No other event in our lifetimes has brought such sudden, drastic loss to Australia’s biodiversity as the last bushfire season. Governments, researchers and conservationists have committed to the long road to recovery. But in those vast burnt landscapes, where do we start?

We are among the wildlife experts advising the federal government on bushfire recovery. Our role is to help determine the actions needed to stave off extinctions and help nature recover in the months and years ahead.

Our first step was to systematically determine which plant and animal species and ecosystems needed help most urgently. So let’s take a closer look at how we went about it.

Plants and animals are recovering from the fires, but some need a helping hand.
David Crosling/AAP

Sorting through the smoke

One way to work out how badly a species is affected by fire is to look at how much of its distribution – or the area in which it lives – was burnt.

This is done by overlapping fire maps with maps or records showing the species’ range. The greater the overlap, the higher the potential fire impact. But there are several complicating factors to consider:

1. Susceptibility: Species vary in how susceptible they are to fire. For instance, animals that move quickly – such as red-necked wallabies and the white-throated needletail – can escape an approaching fire. So too can animals that burrow deeply into the ground, such as wombats.

Less mobile animals, or those that live in vegetation, are more likely to die. We also considered post-fire recovery factors such as a species’ vulnerability to predators and reproductive rate.

The white-throated needle tail can escape the flames.
Tom Tarrant/Flickr

2. What we know: The quality of data on where species occur is patchy. For example, there are thousands of records for most of Australia’s 830 or so bird species. But there are very few reliable records for many of Australia’s 25,000-odd plant species and 320,000-odd invertebrate species.

So while we can estimate with some confidence how much of a crimson rosella’s distribution burned, the fire overlaps for less well-known species are much less certain.

3. The history of threats: The impact of fires on a region depends on the extent of other threats, such as drought and the region’s fire history. The time that elapses between fires can influence whether populations have recovered since the last fire.

For instance, some plants reproduce only from seed rather than resprouting. Fires in quick succession can kill regrowing plants before they’ve matured enough to produce seed. If that happens, species can become locally extinct.


Authors supplied

4. Fire severity: Some areas burn more intensely than others. High severity fires tend to kill more animals. They also incinerate vegetation and can scorch seeds lying in the soil.

Many Australian plant species are exquisitely adapted to regenerate and resprout after fire. But if a fire is intense enough, even these plants may not bounce back.

5. Already threatened?: Many species affected by these bushfires were already in trouble. For some, other threats had already diminished their numbers. Others were highly vulnerable because they were found only in very limited areas.

The bushfires brought many already threatened species closer to extinction. And other species previously considered secure are now threatened.




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Which species made the list?

With these issues in mind, and with contributions from many other experts, we compiled lists of plant, invertebrate and vertebrate species worst-affected by the 2019-20 fires. A similar assessment was undertaken for threatened ecosystems.

Some 471 plant, 213 invertebrate and 92 vertebrate species have been identified as a priority for interventions. Most had more than half their distribution burnt. Many have had more than 80% affected; some had 100% burnt.

The purple copper butterfly is listed as a priority for recovery efforts.
NSW Department of Planning, Industry and Environment

Priority invertebrates include land snails, freshwater crayfish, spiders, millipedes, beetles, dragonflies, grasshoppers, butterflies and bees. Many species had very small ranges.

For example, the inelegantly named Banksia montana mealybug – a tiny insect – existed only in the foliage of a few individuals of a single plant species in Western Australia’s Stirling Range, all of which were consumed by the recent fires.

Some priority plants, such as the Monga waratah, have persisted in Australia since their evolution prior to the break-up of the Gondwanan supercontinent about 140 million years ago. More than 50% of its current range burned, much at high severity. During recovery it is vulnerable to diseases such as phytophthora root rot.




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Some priority vertebrates have tiny distributions, such as the Mt Kaputar rock skink that lives only on rocky outcrops of Mt Kaputar near Narrabri, New South Wales. Others had large distributions that were extensively burnt, such as the yellow-bellied glider.

The priority lists include iconic species such as the koala, and species largely unknown to the public, such as the stocky galaxias, a fish that lives only in an alpine stream near Cooma in NSW.

Half the Monga waratah’s range burned in the fires.
Wikimedia

What’s being done

A federal government scheme is now allocating grants to projects that aim to help these species and ecosystems recover.

Affected species need immediate and longer-term actions to help them avoid extinction and recover. Critical actions common to all fire-affected species are:

  1. careful management of burnt areas so their recovery isn’t compromised by compounding pressures

  2. protecting unburnt areas from further fire and other threats, so they can support population recovery

  3. rapid surveys to identify where populations have survived. This is also the first step in ongoing monitoring to track recovery and the response to interventions.

Targeted control of feral predators, herbivores and weeds is also essential to the recovery of many priority species.

In some rare cases, plants or animals may need to be moved to areas where populations were reduced or wiped out. Captive breeding or seed collection can support this. Such restocking doesn’t just help recovery, it also spreads the risk of population loss in case of future fires.

Feral animals such as cats threaten native species in their recovery.
Hugh McGregor, Threatened Species Recovery Hub

Long road back

The COVID-19 pandemic has led to some challenges in implementing recovery actions. Like all of us, state agency staff, NGOs, academics and volunteer groups must abide by public health orders, which have in some cases limited what can be done and where.

But the restrictions may also have an upside. For instance, fewer vehicles on the roads might reduce roadkill of recovering wildlife.

As states ease restrictions, more groups will be able to continue the recovery process.




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As well as action on the ground, much planning and policy response is still required. Many fire-affected species must be added to threatened species lists to ensure they’re legally protected, and so remain the focus of conservation effort.

Fire management methods must be reviewed to reduce the chance of future catastrophic fires, and to make sure the protection of biodiversity assets is considered in fire management planning and suppression.

Last bushfire season inflicted deep wounds on our biodiversity. We need to deal with that injury. We must also learn from it, so we can respond swiftly and effectively to future ecological disasters.


Many species experts and state/territory agency representatives contributed to the analyses of priority species. Staff from the Department of Agriculture, Water and the Environment (especially the Environmental Resources Information Network (Geospatial and Information Analytics Branch), the Protected Species and Communities Branch and the Threatened Species Commissioner’s Office) and Expert Panel members also contributed significantly to this work.The Conversation

John Woinarski, Professor (conservation biology), Charles Darwin University; Dale Nimmo, Associate Professor in Ecology, Charles Sturt University; Rachael Gallagher, Senior Lecturer/ARC DECRA Fellow, Macquarie University, and Sarah Legge, Professor, Australian National University

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

Climate explained: why higher carbon dioxide levels aren’t good news, even if some plants grow faster



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Sebastian Leuzinger, Auckland University of Technology

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

If carbon dioxide levels were to double, how much increase in plant growth would this cause? How much of the world’s deserts would disappear due to plants’ increased drought tolerance in a high carbon dioxide environment?

Compared to pre-industrial levels, the concentration of carbon dioxide (CO₂) in the atmosphere will have doubled in about 20 to 30 years, depending on how much CO₂ we emit over the coming years. More CO₂ generally leads to higher rates of photosynthesis and less water consumption in plants.

At first sight, it seems more CO₂ can only be beneficial to plants, but things are a lot more complex than that.




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Let’s look at the first part of the question.

Some plants do grow faster under elevated levels of atmospheric CO₂, but this happens mostly in crops and young trees, and generally not in mature forests.

Even if plants grew twice as fast under doubled CO₂ levels, it would not mean they strip twice as much CO₂ from the atmosphere. Plants take carbon from the atmosphere as they grow, but that carbon is going straight back via natural decomposition when plants die or when they are harvested and consumed.

At best, you might be mowing your lawn twice as often or harvesting your plantation forests earlier.

The most important aspect is how long the carbon stays locked away from the atmosphere – and this is where we have to make a clear distinction between increased carbon flux (faster growth) or an increasing carbon pool (actual carbon sequestration). Your bank account is a useful analogy to illustrate this difference: fluxes are transfers, pools are balances.




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The global carbon budget

Of the almost 10 billion tonnes (gigatonnes, or Gt) of carbon we emit every year through the burning of fossil fuels, only about half accumulates in the atmosphere. Around a quarter ends up in the ocean (about 2.4 Gt), and the remainder (about 3 Gt) is thought to be taken up by terrestrial plants.

While the ocean and the atmospheric sinks are relatively easy to quantify, the terrestrial sink isn’t. In fact, the 3 Gt can be thought of more as an unaccounted residual. Ultimately, the emitted carbon needs to go somewhere, and if it isn’t the ocean or the atmosphere, it must be the land.

So yes, the terrestrial system takes up a substantial proportion of the carbon we emit, but the attribution of this sink to elevated levels of CO₂ is difficult. This is because many other factors may contribute to the land carbon sink: rising temperature, increased use of fertilisers and atmospheric nitrogen deposition, changed land management (including land abandonment), and changes in species composition.

Current estimates assign about a quarter of this land sink to elevated levels of CO₂, but estimates are very uncertain.

In summary, rising CO₂ leads to faster plant growth – sometimes. And this increased growth only partly contributes to sequestering carbon from the atmosphere. The important questions are how long this carbon is locked away from the atmosphere, and how much longer the currently observed land sink will continue.




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The second part of the question refers to a side-effect of rising levels of CO₂ in the air: the fact that it enables plants to save water.

Plants regulate the exchange of carbon dioxide and water vapour by opening or closing small pores, called stomata, on the surface of their leaves. Under higher concentrations of CO₂, they can reduce the opening of these pores, and that in turn means they lose less water.

This alleviates drought stress in already dry areas. But again, the issue is more complex because CO₂ is not the only parameter that changes. Dry areas also get warmer, which means that more water evaporates and this often compensates for the water-saving effect.

Overall, rising CO₂ has contributed to some degree to the greening of Earth, but it is likely that this trend will not continue under the much more complex combination of global change drivers, particularly in arid regions.The Conversation

Sebastian Leuzinger, Professor, Auckland University of Technology

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

These plants and animals are now flourishing as life creeps back after bushfires


Flickr

Kathryn Teare Ada Lambert, University of New England

As the east coast bushfire crisis finally abates, it’s easy to see nothing but loss: more than 11 million hectares of charcoal and ash, and more than a billion dead animals.

But it is heartening to remember that bushfire can be a boon to some plants and animals. We’re already seeing fresh green shoots as plants and trees resprout. Beetles and other insects are making short work of animal carcasses; they will soon be followed by the birds which feed on them.

Australia’s worsening fire regimes are challenging even these tolerant species. But let’s take a look at exactly how life is returning to our forests now, and what to expect in coming months.

Life is returning to fire-ravaged landscapes.
Flickr, CC BY

The science of resprouting

Of course, bushfires kill innumerous trees – but many do survive. Most of us are familiar with the image of bright green sprouts shooting from the trunks and branches of trees such as eucalypts. But how do they revive so quickly?

The secret is a protected “bud bank” which lies behind thick bark, protected from the flames. These “epicormic” buds produce leaves, which enables the tree to photosynthesise – create sugar from the sun so the tree can survive.

Under normal conditions, hormones from shoots higher in the tree suppress these buds. But when the tree loses canopy leaves due to fire, drought or insect attack, the hormone levels drop, allowing the buds to sprout.

Insect influx

This summer’s fires left in their wake a mass of decaying animal carcasses, logs and tree trunks. While such a loss can be devastating for many species – particularly those that were already vulnerable – many insects thrive in these conditions.

For example, flies lay eggs in the animal carcasses; when the maggots hatch, the rotting flesh provides an ample food source. This process helps break down the animal’s body – reducing bacteria, disease and bad smells. Flies are important decomposers and their increased numbers also provide food for birds, reptiles and other species.




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Similarly, beetles such as the grey furrowed rosechafer, whose grubs feed on decaying logs and tree trunks, add nutrients to the soil when they defecate which helps plants grow again.

Insects also benefit from the mass of new leaves on trunks and branches. For example, native psyllids – an insect similar to aphids – feed on the sap from leaves and so thrive on the fresh growth.

Animal carcasses are a sad consequence of bushfire, but provide a boon to some insect species.
Sean Davey/AAP

Then come the birds

Once insects start to move back into an area from forested areas nearby, the birds that eat them will follow.

An increase in psyllids encourages honeyeaters – such as bell miners and noisy miners – to return. These birds are considered pests.

A CSIRO study after bushfires in Victoria’s East Gippsland in 1983 found several native bird species – flame and scarlet robins, the buff-rumped thornbill and superb fairy-wren – increased quickly to levels greater than before fire. As shrubs in the understorey regrow, other species will move in, slowly increasing biodiversity.




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Since the recent bushfire in woodland near Moonbi in New South Wales, numerous bird species have returned. On a visit over this past weekend, I observed currawongs landing in the canopy, saw fairy wrens darting in and out of foliage sprouting from the ground, and heard peep wrens in tufts of foliage on bark and high branches.

Honeyeaters moved between burnt and intact trees on the edge of the blackened forest and butterflies visited new plants flowering after recent rain.

The presence of the currawong, while a pest species, shows birdlife is returning to the bush.
Flickr, CC BY

Weeds can help

Weeds usually benefit when fire opens up the tree canopy and lets in light. While this has a downside – preventing native plants from regenerating – weeds can also provide cover for native animal species.

A study I co-authored in 2018 found highly invasive Lantana camara provided habitat for small mammals such as the brown rat in some forests. Mammal numbers in areas where lantana was present were greater than where it was absent.

Lantana often grows quickly after fire due to the increase in light and its ability to suppress other plant growth.

Lantana provides cover for animal species.
Flickr, CC BY

Is there hope for threatened species?

Generalist species – those that thrive in a variety of environments – can adapt to burnt forest. But specialist species need particular features of an ecosystem to survive, and are far less resilient.

The critically endangered Leadbeater’s possum lives only in small pockets of forest in Victoria.

It requires large fires to create a specific habitat: big dead trees provide hollows for shelter and nesting, and insects feeding on burnt wood and carcasses provide a food source.

But for the Leadbeater’s possum to benefit from the fire regime, bushfires should be infrequent – perhaps every 75 years – allowing time for the forest to grow back. If fires are too frequent, larger trees will not have time to establish and hollows will not be created, causing the species’ numbers to decline.

Similarly in NSW, at least 50% and up to 80% of the habitat of threatened species such as the vulnerable rufous scrub-bird was burnt in the recent fires, an environmental department analysis found.

Looking ahead

Only time will tell whether biodiversity in these areas is forever damaged, or will return to its former state.

Large fires may benefit some native species but they also provide food and shelter for predatory species, such as feral cats and foxes. The newly open forest leaves many native mammals exposed, changing the foodweb, or feeding relationships, in an ecosystem.

This means we may see a change in the types of birds, reptiles and mammals found in forests after the fires. And if these areas don’t eventually return to their pre-fire state, these environments may be changed forever – and extinctions will be imminent.




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The Conversation


Kathryn Teare Ada Lambert, Adjunct Lecturer/ Ecologist, University of New England

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

Yes, more carbon dioxide in the atmosphere helps plants grow, but it’s no excuse to downplay climate change



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Vanessa Haverd, CSIRO; Benjamin Smith, Western Sydney University; Matthias Cuntz, Université de Lorraine, and Pep Canadell, CSIRO

The alarming rate of carbon dioxide flowing into our atmosphere is affecting plant life in interesting ways – but perhaps not in the way you’d expect.

Despite large losses of vegetation to land clearing, drought and wildfires, carbon dioxide is absorbed and stored in vegetation and soils at a growing rate.

This is called the “land carbon sink”, a term describing how vegetation and soils around the world absorb more carbon dioxide from photosynthesis than they release. And over the past 50 years, the sink (the difference between uptake and release of carbon dioxide by those plants) has been increasing, absorbing at least a quarter of human emissions in an average year.

The sink is getting larger because of a rapid increase in plant photosynthesis, and our new research shows rising carbon dioxide concentrations largely drive this increase.

So, to put it simply, humans are producing more carbon dioxide. This carbon dioxide is causing more plant growth, and a higher capacity to suck up carbon dioxide. This process is called the “carbon dioxide fertilisation effect” – a phenomenon when carbon emissions boost photosynthesis and, in turn, plant growth.

What we didn’t know until our study is just how much the carbon dioxide fertilisation effect contributes to the increase in global photosynthesis on land.

But don’t get confused, our discovery doesn’t mean emitting carbon dioxide is a good thing and we should pump out more carbon dioxide, or that land-based ecosystems are removing more carbon dioxide emissions than we previously thought (we already know how much this is from scientific measurements).

And it definitely doesn’t mean mean we should, as climate sceptics have done, use the concept of carbon dioxide fertilisation to downplay the severity of climate change.




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Rather, our findings provide a new and clearer explanation of what causes vegetation around the world to absorb more carbon than it releases.

What’s more, we highlight the capacity of vegetation to absorb a proportion of human emissions, slowing the rate of climate change. This underscores the urgency to protect and restore terrestrial ecosystems like forests, savannas and grasslands and secure their carbon stocks.

And while more carbon dioxide in the atmosphere does allow landscapes to absorb more carbon dioxide, almost half (44%) of our emissions remain in the atmosphere.

More carbon dioxide makes plants more efficient

Since the beginning of the last century, photosynthesis on a global scale has increased in nearly constant proportion to the rise in atmospheric carbon dioxide. Both are now around 30% higher than in the 19th century, before industrialisation began to generate significant emissions.

Carbon dioxide fertilisation is responsible for at least 80% of this increase in photosynthesis. Most of the rest is attributed to a longer growing season in the rapidly warming boreal forest and Arctic.

Ecosystems such as forests act as a natural weapon against climate change by absorbing carbon from the atmosphere.
Shutterstock

So how does more carbon dioxide lead to more plant growth anyway?

Higher concentrations of carbon dioxide make plants more productive because photosynthesis relies on using the sun’s energy to synthesise sugar out of carbon dioxide and water. Plants and ecosystems use the sugar both as an energy source and as the basic building block for growth.

When the concentration of carbon dioxide in the air outside a plant leaf goes up, it can be taken up faster, super-charging the rate of photosynthesis.




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More carbon dioxide also means water savings for plants. More carbon dioxide available means pores on the surface of plant leaves regulating evaporation (called the stomata) can close slightly. They still absorb the same amount or more of carbon dioxide, but lose less water.

The resulting water savings can benefit vegetation in semi-arid landscapes that dominate much of Australia.

We saw this happen in a 2013 study, which analysed satellite data measuring changes in the overall greenness of Australia. It showed more leaf area in places where the amount of rain hadn’t changed over time. This suggests water efficiency of plants increases in a carbon dioxide-richer world.

Young forests help to capture carbon dioxide

In other research published recently, we mapped the carbon uptake of forests of different ages around the world. We showed forests regrowing on abandoned agricultural land occupy a larger area, and draw down even more carbon dioxide than old-growth forests, globally. But why?

Young forests need carbon to grow, so they’re a significant contributor to the carbon sink.
Shutterstock

In a mature forest, the death of old trees balances the amount of new wood grown each year. The old trees lose their wood to the soil and, eventually, to the atmosphere through decomposition.

A regrowing forest, on the other hand, is still accumulating wood, and that means it can act as a considerable sink for carbon until tree mortality and decomposition catch up with the rate of growth.




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This age effect is superimposed on the carbon dioxide fertilisation effect, making young forests potentially very strong sinks.

In fact, globally, we found such regrowing forests are responsible for around 60% of the total carbon dioxide removal by forests overall. Their expansion by reforestation should be encouraged.

Forests are important to society for so many reasons – biodiversity, mental health, recreation, water resources. By absorbing emissions they are also part of our available arsenal to combat climate change. It’s vital we protect them.The Conversation

Vanessa Haverd, Principal research scientist, CSIRO; Benjamin Smith, Director of Research, Hawkesbury Institute for the Environment, Western Sydney University; Matthias Cuntz, Research Director INRAE, Université de Lorraine, and Pep Canadell, Chief research scientist, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRO

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

Fire almost wiped out rare species in the Australian Alps. Feral horses are finishing the job



Feral horses are destroying what little threatened species habitat was spared from bushfire.
Invasive Species Council

Jamie Pittock, Australian National University

On Friday I flew in a helicopter over the fire-ravaged Kosciuszko National Park. I was devastated by what I saw. Cherished wildlife species are at grave risk of extinction: those populations the bushfires haven’t already wiped out are threatened by thousands of feral horses trampling the land.

The New South Wales park occupies the highest mountain range in Australia and is home to plants and animals found nowhere else in the world. Many of these species are threatened, and their survival depends on protecting habitat as best we can.




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Kosciuszko National Park provides habitat for two species of corroboree frog (critically endangered), the alpine she-oak skink (endangered), broad-toothed rat (vulnerable) and stocky galaxias (a critically endangered native fish), among other threatened species.

As the climate has warmed, the cool mountain habitat of these species is shrinking; bushfires have decimated a lot of what was left. Feral horses now threaten to destroy the remainder, and an urgent culling program is needed.

Devastation as far as the eye can see on the burnt western face of Kosciuszko National Park.
Jamie Pittock

Not a green leaf in sight

Australia’s plants and ecosystems did not evolve to withstand trampling by hard-hooved animals, or their intensive grazing. Unfortunately, the New South Wales government has allowed the population of feral horses in the park to grow exponentially in recent years to around 20,000.

I flew over the northern part of the park with members of the Invasive Species Council, who were conducting an urgent inspection of the damage. Thousands of hectares were completely incinerated by bushfires: not a green leaf was visible over vast areas. A cataclysm has befallen the western face of the mountains and tablelands around Kiandra and Mount Selwyn.




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Further north and east of Kiandra the fires were less intense and burnt patchily. On Nungar Plain the grassland and peat wetlands were only lightly burnt, and the first green shoots were already visible along the wetlands of the valley floor.

At first, I wondered if the fires may have spared two animals which live in tunnels in the vegetation on the sub-alpine high plains: the alpine she-oak skink and broad-toothed rat (which, despite the name is a cute, hamster-like creature).

The hamster-like broad toothed rat.
Flickr

But not only was their understory habitat burnt, a dozen feral horses were trampling the peat wetlands and eating the first regrowth.

On the unburnt or partially burnt plains a few ridges over, 100 or more horses were mowing down the surviving vegetation.

Precarious wildlife refuges

Next we flew over a small stream that holds the last remaining population of a native fish species, the stocky galaxias. A small waterfall is all that divides the species from the stream below, and the jaws of the exotic trout which live there.

The aftermath of the fires means the last refuge of the stocky galaxias is likely to become even more degraded.

Over the years, feral horses have carved terraces of trails into the land causing erosion and muddying the stream bank. As more horses congregate on unburnt patches of vegetation after the fires, more eroded sediment will settle on the stream bed and fill the spaces between rocks where the fish shelter. Ash runoff entering the stream may clog the gills of the fish, potentially suffocating them.

An Alpine she-oak skink.
Renee Hartley



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Many key wetland habitats of the southern and northern corroboree frogs have also been burnt. These striking yellow and black frogs nest in wetland vegetation.

A corroboree frog.
Flickr

We hovered over a key wetland for the northern corroboree frog that had not been burnt, deep in the alpine forest. A group of feral horses stood in it. They had created muddy wallows, trampled vegetation and worn tracks that will drain the wetland if their numbers are not immediately controlled.

Horses out of control

Five years ago a survey reported about 6,000 feral horses roaming in Kosciuszko National Park. By 2019, the numbers had jumped to at least 20,000.

We saw no dead horses from the air. Unlike our native wildlife, most appear to have escaped the fires.




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Flying down the upper Murrumbidgee River’s Long Plain, I saw large numbers of feral horses gathered in yet more wetlands. Displaced by the fires to the south and west, they were already trampling the mossy and heathy wetlands that store and filter water in the headwaters.

The Murrumbidgee River is a key water source for south-east Australia. The horses stir up sediment and defecate in the water. They create channels which drain and dry the wetlands, exposing them to fire.

One-third of Kosciuszko National Park has been burnt out and at the time of writing the fires remain active. Feral horses are badly compounding the damage.

If we don’t immediately reduce feral horse numbers, the consequences for Kosciuszko National Park and its unique Australian flora and fauna will be horrendous.

Responsible managers limit the numbers of livestock on their lands and control feral animals. The NSW government must repeal its 2018 legislation protecting feral horses in Kosciuszko National Park, and undertake a responsible control program similar to those of the Australian Capital Territory and Victorian governments.

Without an emergency cull of feral horses in Kosciuszko National Park, burnt vegetation may not fully recover and threatened species will march further towards extinction.The Conversation

Jamie Pittock, Professor, Fenner School of Environment & Society, Australian National University

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

Many of our plants and animals have adapted to fires, but now the fires are changing



Eucalypt seeds don’t fall far from the tree, meaning repopulating large areas of forest will be difficult.
from http://www.shutterstock.com

Cris Brack, Australian National University

Australia is a land that has known fire. Our diverse plant and animal species have become accustomed to life with fire, and in fact some require it to procreate.

But in recent decades the pattern of fires – also known as the fire regime – is changing. Individual fires are increasingly hotter, more frequent, happening earlier in the season and covering larger areas with a uniform intensity. And these changes to the fire regime are occurring too fast for our native flora and fauna to adapt and survive.




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Our fire-adapted plants are suffering

Many of Australia’s iconic eucalypts are “shade intolerant” species that adapted to exist within a relatively harsh fire regime. These species thrive just after a major fire has cleared away the overstory and prepared an ash bed for their seeds to germinate.

Some of our most majestic trees, like the alpine ash, can only regenerate from seed. Those seeds germinate only on bare earth, where the leaf litter and shrubs have been burnt away.

But if fire is so frequent the trees haven’t matured enough to produce seed, or so intense it destroys the seeds present in the canopy and the ground, then even these fire-adapted species can fail.

The current fires are re-burning some forests that were burnt only a decade ago. Those regenerating trees are too young to survive, but also too young to have started developing seed.

With the disappearance of these tree species, other plants will fill the gap. Acacias (wattles) are potential successors as they mature much earlier than alpine ash. Our tall, majestic forests could easily turn into shrubby bushland with more frequent fires.

Wattles mature early and could take over Eucalypts.
from http://www.shutterstock.com

Even within a burnt area, there are usually some unburnt patches, which are highly valuable for many types of plants and animals. These patches include gullies and depressions, but sometimes are just lucky coincidences of the terrain and weather. The patches act as reserves of “seed trees” to provide regeneration opportunities.

Recent fires, burning in hotter and drier conditions, are tending to be severe over large areas with fewer unburnt patches. Without these patches, there are no trees in the fire zone to spread seeds for regeneration.

Eucalypt seed is small and without wings or other mechanisms to help the wind disperse it. Birds don’t generally disperse these seeds either. Eucalypt seed thus only falls within 100 – 200 metres of the parent tree. It may take many decades for trees to recolonise a large burnt area.

That means wind-blown or bird-dispersed seeds from other species may fully colonise the burnt area well before the Eucalypts. Unfortunately many of these windblown seeds will be weed species, such as African Love Grass, which may then cover the bare earth and exclude successful Eucalypt regeneration while potentially making fires even hotter and more frequent.

Animals have fewer places to hide

Young animals are significantly more vulnerable to disturbances such as fire than mature individuals. So the best time to give birth is a season when fire is rare.

Spring in the southern zones of Australia has, in the past, been wetter and largely free from highly destructive fires. Both flora and fauna species thus time their reproduction for this period. But as fire seasons lengthen and begin earlier in the year, vulnerable nestlings and babies die where they shelter or starve as the fires burn the fruits and seeds they eat.

Australian fauna have developed behaviours that help them survive fire, including moving towards gullies and depressions, climbing higher, or occupying hollows and burrows (even if not their own) when they sense fire.

Many native animals have learnt to sense fire and take cover, but with greater areas burning, there are fewer places to hide.
from http://www.shutterstock.com

But even these behaviours will fail if those refuges are uncharacteristically burning under hotter and drier conditions. Rainforest, marshes and the banks of watercourses were once safe refuges against fire, but we have seen these all burn in recent fires.




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What can be done?

All aspects of fire regimes in Australia are clearly changing as a result of our heating and drying climate. But humans can have a deliberate effect, and have done so in the past.

Indigenous burning created a patchwork of burnt areas and impacted on the magnitude and frequency of fires over the landscape. These regular burns kept the understory under control, while the moderate intensity and patchiness allowed larger trees to survive.




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There have been repeated calls of late to reintroduce Indigenous burning practices in Australia. But this would be difficult over vast areas. It requires knowledgeable individuals to regularly walk through each forest to understand the forest dynamics at a very fine scale.

More importantly, our landscapes are now filled with dry fuel, and shrubs that act as “ladders” – quickly sending any fire into tree canopies to cause very destructive crown fires. Given these high fuel conditions along with their potentially dangerous distribution, there may be relatively few safe areas to reintroduce Indigenous burning.

The changed fire conditions still require active management of forests, with trained professionals on the ground. Refuges could be developed throughout forests to provide places where animals can shelter and from which trees can recolonise. Such refuges could be reintroduced by reducing forest biomass (or fuel) using small fires where feasible or by mechanical means.

A Kangaroo Island landscape devastated by fire.
David Mariuz/AAP

Biomass collected by machines could be used to produce biochar or other useful products. Biochar could even be used to improve the soil damaged by the fires and excess ash.

Midstory species could be cut down to prevent the development of fire ladders to tree crowns. Even the overstory could be thinned to minimise the potential for crown fires. Seed could also be collected from thinned trees to provide an off-site bank as ecological insurance.

Such active management will not be cheap. But using machinery rather than fire could control biomass quantity and distribution in a much more precise way: leaving some biomass on the ground as habitat for insects and reptiles, and removing other patches to create safer refuges from the fires that will continue to come.The Conversation

Cris Brack, Associate Professor, Fenner School of Environment and Society, Australian National University

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

Yes, native plants can flourish after bushfire. But there’s only so much hardship they can tak



Bulbine lilies flowering and eucalypts resprouting after fire in the Victorian high country.
Heidi Zimmer

Lucy Commander, University of Western Australia and Heidi Zimmer, Southern Cross University

In a fire-blackened landscape, signs of life are everywhere. A riot of red and green leaves erupt from an otherwise dead-looking tree trunk, and the beginnings of wildflowers and grasses peek from the crunchy charcoal below.

Much Australian flora has evolved to cope with fire, recovering by re-sprouting or setting seed. However, some plants are sensitive to fire, especially when fires are frequent or intense, and these species need our help to recover.




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After announcing a A$50 million wildlife and habitat recovery package, the Morrison government recently met with Australia’s leading wildlife experts to steer recovery efforts.

Encouraging native flora to bounce back from these unprecedented fires requires targeted funding and actions to conserve and restore plants and ecological communities, including seed banking.

How do plants naturally recover from fire?

Many plants from fire-prone ecosystems have evolved strategies to survive, and even thrive, with fire. Some resprout after fire, with green shoots bursting from blackened stems. For others, fire stimulates flowering.

Some species are able to resprout from blackened stems following a fire.
Lucy Commander, Author provided

Fire can also trigger seed germination of hundreds of species, as seeds respond to fire “cues” like heat and smoke.

Seeds may wait in woody fruits stored on the plant. The fruits’ hard capsules shield the seeds from the fire, but the heat opens the capsules, releasing seeds into the soil below.

We can capitalise on this natural recovery by not disturbing the soil where the seeds are scattered, not clearing “dead” plants which may resprout and provide shelter for remaining wildlife, including perches for birds who may bring in seeds.

We should also stop vegetation clearing, especially unburnt vegetation home to threatened species and communities.

Some species, like this Banksia, have woody fruits that protect the seeds, then open after fire to release them.
Lucy Commander, Author provided

When do we need to intervene?

While Australian plants and ecosystems have evolved to embrace bushfires, there’s only so much drought and fire they can take.

Many plants and ecosystems, including alpine and rainforest species, are not resilient to fire, especially if drought persists or they have been burnt too frequently. Too frequent fires deplete the seed bank and put recovery at risk.

Fires which are intense and severe will outright kill other plants, or the plants will be very slow to recover – taking years or decades to reach maturity again. We need comprehensive monitoring to detect which species are not returning, with systematic field surveys starting immediately, and continuing after the first rains to identify which species emerge from the soil.

Some ecosystems are adapted to fire, with trees resprouting and seeds germinating from the soil seed bank. Even so, fencing and weed control may be required.
Lucy Commander, Author provided

Invasive plants such as blackberry or veldt grass can also impede recovery after a fire by out-competing the natives. Feral herbivores – such as rabbits, goats and horses – can overgraze the native regrowth. So controlling the weeds and feral grazers with, for instance, temporary fencing and tree guards, is a priority post-fire.

And when ecosystems aren’t able to repair themselves, it’s up to us to intervene. For instance, land managers, supported by volunteer community groups, could sow seeds or plant seedlings in fire-affected areas. This act of restoring ecosystems can be an important healing process for those affected by the fires.

Do we have enough seeds?

But for that to happen, we need enough seeds to supply restoration efforts. With millions of hectares already burnt, few areas may be left for seed collection.

This means unburnt areas are at risk of over-collection from commercial and volunteer seed collectors. Stopping this from happening is possible, however. The agencies giving out permits for seed collection must record where seeds are being sourced and how much is collected. This ensures areas aren’t stripped of seeds, rendering them less resilient.




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Another, more controversial issue, is whether seeds should be collected locally (perhaps within 20km or within the catchment), or from somewhere much further away and more suited to a potential future climate.

And what should we do if we lose a population of a threatened plant species? Establishing a new population or replacing a lost one using translocation is one option. Similar to capture-and-release or zoo breeding programs for reintroduction of threatened animals, translocation refers to deliberately moving plants or seeds to a new location.

How can we better prepare for next time?

With potentially more unprecedented bushfire seasons in our future, it’s important land managers are prepared.

They need data on the distribution of species and the fire frequency, severity and season they can tolerate. A nationwide database could identify which species and ecosystems are most at risk, and could be incorporated into fire and restoration planning – including seed collecting – to ensure plant material is available if species fail to recover.




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Botanic gardens have a special role to play as many already have conservation seed banks of threatened species, and their living collections provide additional genetic material. Across Australia there is already a network of seed banks collaborating through the Australian Seed Bank Partnership that collect, store and undertake research to better support plant conservation.

A restoration seed bank in Utah, USA. These banks hold huge amounts of seeds, but the Australian equivalents operate on a smaller scale.
Lucy Commander

However, restoration seed banks operate on a much larger scale than botanic gardens, and it’s important both approaches are conducted collaboratively. We need more ongoing investment in seed banks, particularly for threatened species and ecosystems least likely to recover from repeat fires like rainforests. Investment in skilled staff to run them is also critical, as well as national guidelines for seed use and training programs for staff and volunteers.

The recent bushfires will push many plant species to their limits. If we want to keep these species around – and the animals depend on them for food and habitat – we need to monitor their recovery and intervene where necessary.The Conversation

Lucy Commander, Adjunct Lecturer, University of Western Australia and Heidi Zimmer, Research associate, Southern Cross University

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

Plants are going extinct up to 350 times faster than the historical norm



Plant extinctions have skyrocketed, driven in large part by land clearing and climate change.
Graphic Node/Unsplash, CC BY-SA

Jaco Le Roux, Macquarie University; Florencia Yanelli, Stellenbosch University; Heidi Hirsch, Stellenbosch University; José María Iriondo Alegría, Universidad Rey Juan Carlos; Marcel Rejmánek, University of California, Davis, and Maria Loreto Castillo, Stellenbosch University

Earth is seeing an unprecedented loss of species, which some ecologists are calling a sixth mass extinction. In May, a United Nations report warned that 1 million species are threatened by extinction. More recently, 571 plant species were declared extinct.

But extinctions have occurred for as long as life has existed on Earth. The important question is, has the rate of extinction increased? Our research, published today in Current Biology, found some plants have been going extinct up to 350 times faster than the historical average – with devastating consequences for unique species.




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Measuring the rate of extinction

“How many species are going extinct” is not an easy question to answer. To start, accurate data on contemporary extinctions are lacking from most parts of the world. And species are not evenly distributed – for example, Madagascar is home to around 12,000 plant species, of which 80% are endemic (found nowhere else). England, meanwhile, is home to only 1,859 species, of which 75 (just 4%) are endemic.

Areas like Madagascar, which have exceptional rates of biodiversity at severe risk from human destruction, are called “hotspots”. Based purely on numbers, biodiversity hotspots are expected to lose more species to extinction than coldspots such as England.

But that doesn’t mean coldspots aren’t worth conserving – they tend to contain completely unique plants.

We are part of an international team that recently examined 291 modern plant extinctions between biodiversity hot- and coldspots. We looked at the underlying causes of extinction, when they happened, and how unique the species were. Armed with this information, we asked how extinctions differ between biodiversity hot- and coldspots.

Unsurprisingly, we found hotspots to lose more species, faster, than coldspots. Agriculture and urbanisation were important drivers of plant extinctions in both hot- and coldspots, confirming the general belief that habitat destruction is the primary cause of most extinctions. Overall, herbaceous perennials such as grasses are particularly vulnerable to extinction.

However, coldspots stand to lose more uniqueness than hotspots. For example, seven coldspot extinctions led to the disappearance of seven genera, and in one instance, even a whole plant family. So clearly, coldspots also represent important reservoirs of unique biodiversity that need conservation.

We also show that recent extinction rates, at their peak, were 350 times higher than historical background extinction rates. Scientists have previously speculated that modern plant extinctions will surpass background rates by several thousand times over the next 80 years.

So why are our estimates of plant extinction so low?

First, a lack of comprehensive data restricts inferences that can be made about modern extinctions. Second, plants are unique in – some of them live for an extraordinarily long time, and many can persist in low densities due to unique adaptations, such as being able to reproduce in the absence of partners.

Let’s consider a hypothetical situation where we only have five living individuals of Grandidier’s baobab (Adansonia grandidieri) left in the wild. These iconic trees of Madagascar are one of only nine living species of their genus and can live for hundreds of years. Therefore, a few individual trees may be able to “hang in there” (a situation commonly referred to as “extinction debt”) but will inevitably become extinct in the future.

Finally, declaring a plant extinct is challenging, simply because they’re often very difficult to spot, and we can’t be sure we’ve found the last living individuals. Indeed, a recent report found 431 plant species previously thought to be extinct have been rediscovered. So, real plant extinction rates and future extinctions are likely to far exceed current estimates.

There is no doubt that biodiversity loss, together with climate change, are some of the biggest challenges faced by humanity. Along with human-driven habitat destruction, the effects of climate change are expected to be particularly severe on plant biodiversity. Current estimates of plant extinctions are, without a doubt, gross underestimates.




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However, the signs are crystal clear. If we were to condense the Earth’s 4.5-billion-year-old history into one calendar year, then life evolved somewhere in June, dinosaurs appeared somewhere around Christmas, and the Anthropocene starts within the last millisecond of New Year’s Eve. Modern plant extinction rates that exceed historical rates by hundreds of times over such a brief period will spell disaster for our planet’s future.The Conversation

Jaco Le Roux, Associate Professor, Macquarie University; Florencia Yanelli, Researcher, Stellenbosch University; Heidi Hirsch, Postdoctoral research fellow, Stellenbosch University; José María Iriondo Alegría, Catedrático de universidad en el área de Botánica, Universidad Rey Juan Carlos; Marcel Rejmánek, Emeritus professor, University of California, Davis, and Maria Loreto Castillo, PhD Candidate, Stellenbosch University

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

Climate explained: why plants don’t simply grow faster with more carbon dioxide in air



Fast-growing plantation trees store less carbon per surface area than old, undisturbed forests that may show little growth.
from http://www.shutterstock.com, CC BY-ND

Sebastian Leuzinger, Auckland University of Technology


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

Carbon dioxide is a fertiliser for plants, so if its concentration increases in the atmosphere then plants will grow better. So what is the problem? – a question from Doug in Lower Hutt

Rising atmospheric carbon dioxide (CO₂) is warming our climate, but it also affects plants directly.

A tree planted in the 1850s will have seen its diet (in terms of atmospheric carbon dioxide) double from its early days to the middle of our century. More CO₂ generally leads to higher rates of photosynthesis and less water consumption in plants. So, at first sight, it seems that CO₂ can only be beneficial for our plants.

But things are a lot more complex than that. Higher levels of photosynthesis don’t necessarily lead to more biomass production, let alone to more carbon dioxide sequestration. At night, plants release CO₂ just like animals or humans, and if those respiration rates increase simultaneously, the turnover of carbon increases, but the carbon stock doesn’t. You can think of this like a bank account – if you earn more but also spend more, you’re not becoming any richer.

Even if plants grow more and faster, some studies show there is a risk for them to have shorter lifespans. This again can have negative effects on the carbon locked away in biomass and soils. In fact, fast-growing trees (e.g. plantation forests) store a lot less carbon per surface area than old, undisturbed forests that show very little growth. Another example shows that plants in the deep shade may profit from higher levels of CO₂, leading to more vigorous growth of vines, faster turnover, and, again, less carbon stored per surface area.




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Water savings

The effect of CO₂ on the amount of water plants use may be more important than the primary effect on photosynthesis. Plants tend to close their leaf pores slightly under elevated levels of CO₂, leading to water savings. In certain (dry) areas, this may indeed lead to more plant growth.

But again, things are much more complex and we don’t always see positive responses. Research we published in Nature Plants this year on grasslands around the globe showed that while dry sites can profit from more CO₂, there are complex interactions with rainfall. Depending on when the rain falls, some sites show zero or even negative effects in terms of biomass production.

Currently, a net amount of three gigatons of carbon are thought to be removed from the atmosphere by plants every year. This stands against over 11 gigatons of human-induced release of CO₂. It is also unclear what fraction of the three gigatons plants are taking up due to rising levels of CO₂.

In summary, rising CO₂ is certainly not bad for plants, and if we restored forested land at a global scale, we could help capture additional atmospheric carbon dioxide. But such simulations are optimistic and rely on conversion of much needed agricultural land to forests. Reductions in our emissions are unavoidable, and we have very strong evidence that plants alone will not be able to solve our CO₂ problem.




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The Conversation


Sebastian Leuzinger, Associate Professor, Auckland University of Technology

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