Singarayer Florentine, Federation University AustraliaAustralian native plants are having a moment in the sun, with more of us seeking out and planting native species than in the past. Our gardens — and our social media feeds — are brimming with beautiful Australian native blooms.
But not all Australian native species belong in all Australian environments. In fact, many have become pests in places far from their original homes.
They can crowd out other native endemic species, affect the local balance of insects and other animals, wreck soils and even increase fire risk.
Here are three Australian native plants that have become invasive species after ending up in places they don’t belong.
Sydney golden wattle (Acacia longifolia subspecies longifolia)
Originally extending from East Gippsland in Victoria up about as far as Brisbane in Queensland, this species is undoubtedly photogenic. It’s also an invasive weed in parts of Victoria, South Australia and Western Australia.
It was spread across the nation by well-meaning gardeners who saw it as a charming ornamental plant. However, its seeds made their way into the wild and took off — it’s what’s known in my field as “a garden escapee”.
Like many weeds, this species can capitalise on a natural disaster; after fire it can send out shoots from its base. Acacias are often one of the first species to sprout following a bushfire. They’re now completely dominant and spreading in many areas.
Seeds of Sydney golden wattle can last in the soil for many decades, long after the parent plants have died. The heat from a fire cracks the hard seed coat, allowing water to enter and germination to take off.
In the Grampians, in Victoria, Sydney golden wattle is causing terrible soil problems. Many native plants endemic to this area don’t like high levels of soil nitrogen, but Acacia longifolia subsp. longifolia is a nitrogen-fixing plant.
In other words, it increases the nitrogen in the soil and changes the soil nutrient status and even physical aspects of the soil. It can grow tall and produce a lot of foliage, which reduces the amount of light coming to the ground. That makes it harder for native species lower to the ground to survive.
This is a major challenge, especially in biodiversity-rich places like the Grampians.
Coast wattle (Acacia longifolia subspecies sophorae)
The blooms on Acacia longifolia subspecies sophorae (Coast wattle) look more or less the same as many other wattles, but the leaves are a bit shorter and stubbier.
Originally, Coast wattle occurred along the east coast from western Victoria — up about as far as Brisbane and down south as far as Tasmania (where Sydney golden wattle did not occur naturally).
It was originally restricted to sandy sites at the top of beaches but has been deliberately planted as a “sand-binder” in other sites. It’s also naturally spread into heathlands inland of the beaches and is now causing huge problems around our coasts.
Like the earlier example, it dominates local ecosystems and displaces native species endemic to the area (particularly in our species-rich heathlands), which affects local insect habitats. It is also now modifying natural sand dune patterns.
It is increasing fire risk by changing heathland plant profiles from mostly short shrubs of limited bulk to tall, dense shrublands with much higher fuel levels.
Coast teatree (Leptospermum laevigatum)
As with Coast wattle, Coast teatree was formerly restricted to a narrow strip on sandy soils just above the beaches of south-eastern Australia. But it has now spread into nearby heathlands and woodlands. It’s even reached as far as Western Australia.
This teatree plant is now considered an invasive species in parts of Victoria and South Australia.
Although the mature plants are usually killed by fire, the seeds are abundant and very good at surviving; they pop out of their capsules after fires.
They are high-density plants that burn quickly in a fire. They are very quick to take over and push out endemic species.
For example, parts of the Wilson’s Prom National Park in Victoria, which was originally a Banksia woodland, have now been converted almost to a teatree monoculture. It is very sad.
A call to action
Authorities are trying their best to keep these and other native invasive species under control, but in some cases things may never go back to the way they were. Sometimes, the best you can hope for is just to strike a balance between native and invasive species.
When you do landcare restoration work or home gardening, I urge you to look up the plant history and see if the species you’re thinking of planting is listed as one that might cause problems in future.
When you go to purchase from a nursery or plant centre, be cautious. Think twice before you bring something into your garden. Too many species have “jumped the garden fence” and now cost us a great deal in control efforts and in native species loss.
Lots of apps, such as PlantNet, can help you identify plants and see what is native to your area.
Australia has spent billions trying to control invasive species and environmental weeds. Anything you can do to help is a bonus.
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In recent decades, has New Zealand lost forest (both native and exotic) or gained it, courtesy of the One Billion Trees programme? What about natural habitats like wetlands?
Apart from wetlands, land above the treeline, coastal dunes and a few other exceptions, New Zealand was once covered in forests from Cape Reinga to Bluff.
So was Europe, which basically consisted of a single forest from Sicily in southern Italy to the North Cape in Norway, before human intervention.
But since people arrived in New Zealand some 850 years ago, about three quarters of the country’s native forest area has been lost. About half of the loss happened before Europeans arrived, mostly through burning to clear large areas of native bush.
In recent decades, the loss of native forest has slowed down. For example, in the first decade of the 21st century, we lost roughly 16,000 hectares of native forest, which translates to a loss of about 0.2% of the remaining total area covered in native forest (about 7.5 million hectares). The error associated with such estimates is considerable, though, because land cover is complex and highly fragmented.
A billion trees
According to Global Forest Watch, the drivers behind the more recent losses of native forests include exotic plantation forests, urban developments and wildfires. Indeed, the total land area dedicated to exotic plantation forests increased by about 200,000 hectares per decade between 1990 and 2017.
So what has the One Billion Trees Programme achieved in comparison to these changes?
The project’s aim is to double the current planting rate and plant one billion trees between 2018 and 2028. The latest report shows about a quarter of this goal has been achieved in terms of the number of trees planted. In regards to forest area, 25,557 hectares have been reforested, about half of it with natives.
This is a remarkable achievement in light of the losses cited above and the short duration of the programme.
Saving remaining peat bogs
We think of forests as our guardians of carbon — and indeed, an aged New Zealand forest can hold about 350 tonnes of carbon per hectare. But intact peat bogs, such as the Kopuatai dome in the Waikato region, can hold up to 1,400 tonnes of carbon per hectare.
But peat bogs only store carbon if they remain wet. Once drained, they begin to emit carbon dioxide. Almost half of New Zealand’s peatlands are in the Waikato, but of a total of 89,000 hectares only 19,400 hectares remain in a natural state.
The Kopuatai bog itself is surrounded by dairy farms operating on drained peat. Collectively, the Waikato’s drained peatlands produce 10-33 tonnes of CO₂-equivalent emissions per hectare each year.
The draining of peatlands in the Waikato region did far more damage, in terms of carbon emissions, than a small loss of forest area.
But nevertheless, planting trees and increasing our forest area is an important and necessary contribution to climate mitigation, and often comes with a myriad of other benefits, far beyond carbon sequestration.
Sometimes it’s as easy as planting your own fruit trees around your house. They will capture carbon for years to come, and keep you from buying fruit that has been transported thousands of kilometres.
They might even motivate you to reduce food waste. Globally, about 25-30% of food goes to waste. If we reduced food waste, we could save agricultural land multiple times the size of New Zealand and plant trees there instead.
Benjamin Mayne, CSIROIdentifying the age of animals is fundamental to wildlife management. It helps scientists know if a species is at risk of extinction and the rate at which it reproduces, as well as determining what level of fishing is sustainable.
Determining the age of fish has been difficult in the past — primarily involving extracting the inner ear bone, also known as the “otolith”. Layers of growth in the otolith are counted like rings on a tree to reveal an individual’s age. Unless a dead specimen is available, this method requires killing a fish, making it unsuitable for use on endangered populations.
However a non-lethal DNA test developed by the CSIRO enables researchers to determine fish age for three iconic and threatened Australian freshwater species: the Australian lungfish, the Murray cod and the Mary River cod. We outline the technological breakthrough in our research just published.
Our fast, accurate and cost-effective test can be adapted for other fish species. We now hope to share this method to improve the protection of wild fish populations and help promote sustainable fisheries around the world.
Iconic species at risk
Human activity has led to the population declines of the three Australian fish species at the centre of our research.
The threatened Australian lungfish is found in rivers and lakes in southeast Queensland. It’s often referred to as a “living fossil” because its extraordinary evolutionary history stretches back more than 100 million years, before all land animals including dinosaurs.
Man-made barriers in rivers reduce the movement of water, which lowers lungfish breeding rates.
Older lungfish do not have hard otolith structures, which makes determining their age difficult. Bomb radiocarbon, which analyses carbon levels in organic matter, has been used to age Australian lungfish, but this method is too expensive to be widely used.
Habitat destruction and overfishing are major threats to Murray cod and Mary River cod populations.
Otoliths can be used to determine age for both these cod species, however this has only been done on a population-wide scale for the more prevalent Murray cod.
Our DNA breakthrough
When cells divide to make new cells, DNA is replicated. This can lead to DNA methylation, which involves the addition or the loss of a “methyl group” molecule at places along the DNA strand.
Research has found the level of DNA methylation is a reliable predictor of age, particularly in mammals, including humans.
To develop our test, we first worked with zebrafish. This species is useful when studying fish biology because it has a short lifespan and high reproductive rates. We took zebrafish whose ages were known, then removed a tiny clip of their fin. We then examined DNA methylation levels in the fin sample to identify the fish’s age.
Following this successful step, we transferred the method to Australian lungfish, Murray cod and Mary River cod. Again, we used fish of known ages, as well as bomb radiocarbon dating of scales and ages determined from otoliths.
We found despite the zebrafish and the study fish species being separated by millions of years of evolution, our method worked in all four species. This suggests the test can be used to predict age in many other fish species.
A conservation management boom?
In the same way human population demographers use census data to understand and model human populations, we now have the tools to do this with animals.
We are looking to expand this DNA-based method to determine the age of the endangered eastern freshwater cod and trout cod. We will also continue to test the method across other species including reptiles and crustaceans.
This work is part of CSIRO’s ongoing efforts to use DNA to measure and monitor the environment. This includes estimating the lifespan of vertebrate species such as long-lived fish and surveying biodiversity in seawater using DNA extracted from the environment.
We envisage that in the not too distant future, these methods may be used by other researchers to better understand and manage wild animal populations.
Philip Zylstra, University of Wollongong; Grant Wardell-Johnson, Curtin University; James Watson, The University of Queensland, and Michelle Ward, The University of QueenslandThe Black Summer bushfires burned far more temperate forest than any other fire season recorded in Australia. The disaster was clearly a climate change event; however, other human activities also had consequences.
Taking timber from forests dramatically changes their structure, making them more vulnerable to bushfires. And, crucially for the Black Summer bushfires, logged forests are more likely to burn out of control.
We believe these findings are too narrowly focused and in fact, misleading. They overlook a vast body of evidence that crown fire – the most extreme type of bushfire behaviour, in which tree canopies burn – is more likely in logged native forests.
Crown fires vs scorch
The Black Summer fires occurred in the 2019-20 bushfire season and burned vast swathes of Australia’s southeast. In some cases, fire spread through forests with no recorded fire, including some of the last remnants of ancient Gondwanan rainforests.
Tragically, the fires directly killed 33 people, while an estimated 417 died due to the effects of smoke inhalation. A possible three billion vertebrate animals perished and the risk of species extinctions dramatically increased.
Much of the forest that burned during Black Summer experienced crown fires. These fires burn through the canopies of trees, as well as the undergrowth. They are the most extreme form of fire behaviour and are virtually impossible to control.
Crown fires pulse with such intense heat they can form thunderstorms which generate lightning and destructive winds. This sends burning bark streamers tens of kilometres ahead of the fire, spreading it further. The Black Summer bushfires included at least 18 such storms.
And to our knowledge, every empirical analysis so far shows logging eucalypt forests makes them far more likely to experience crown fire. The studies include:
- A 2009 paper suggesting changes in forest structure and moisture make severe fire more likely in logging regrowth compared to undisturbed forest
- 2012 research concluding the probability of crown fires was higher in recently logged areas than in areas logged decades before
- A 2013 study that showed the likelihood of crown fire halved as forests aged after a certain point
- 2014 findings that crown fire in the Black Saturday fires likely peaked in regrowth and fell in mature forests
- 2018 research into the 2003 Australian Alps fires, which found the same increase in the likelihood of crown fire during regrowth as was measured following logging.
The findings of these studies are represented in the image below. The lines a, b and c refer to the 2013, 2014 and 2018 studies respectively.
Crown fires take lives
The presence of crown fire is a key consideration in fire supression, because crown fires are very hard to control.
However, the study released last week – which argued that logging did not worsen the Black Summer fires – focused on crown “scorch”. Crown scorch is very different to crown fire. It is not a measure of how difficult it is to contain the fire, because even quite small flames can scorch a drought-stressed canopy.
Forestry studies tend to focus more on crown scorch, which damages timber and is far more common than crown fires.
But the question of whether logging made crown scorch worse is not relevant to whether a fire was uncontrollable, and thus was able to destroy homes and lives.
Importantly, when the study said logging had a very small influence on scorch, this was referring to the average scorch over the whole fire area, not just places that had been logged. That’s like asking how a drought in the small town of Mudgee affects the national rainfall total: it may not play a large role overall, but it’s pretty important to Mudgee.
The study examined trees in previously logged areas, or areas that had been logged and burned by fires of any source. It found they were as likely to scorch on the mildest bushfire days as trees in undisturbed forests on bad days. These results simply add to the body of evidence that logging increases fire damage.
Managing forests for all
For example during the Black Saturday fires in 2009, the Kilmore East fire north of Melbourne consumed all before it as a crown fire. Then it reached the old, unlogged mountain ash forests on Mount Disappointment and dropped to the ground, spreading as a slow surface fire.
The trees were scorched. But they were too tall to ignite, and instead blocked the high winds and slowed the fire down. Meanwhile, logged ash forests drove flames high into the canopy.
Despite decades of opportunity to show otherwise, the only story for eucalypt forests remains this: logging increases the impact of bushfires. This fact should inform forest management decisions on how to reduce future fire risk.
We need timber, but it must be produced in ways that don’t endanger human lives or the environment.
Philip Zylstra, Adjunct Associate Professor at Curtin University, Honorary Fellow at University of Wollongong, University of Wollongong; Grant Wardell-Johnson, Associate Professor, Environmental Biology, Curtin University; James Watson, Professor, The University of Queensland, and Michelle Ward, PhD Candidate, The University of Queensland
Jennifer Silcock, The University of Queensland; Jaana Dielenberg, Charles Darwin University; Roderick John Fensham, The University of Queensland, and Teghan Collingwood, The University of QueenslandAs far as odds go, things don’t look promising for the slender-nerved acacia (Acacia leptoneura), a spiky plant with classic yellow-ball wattle flowers. With most of its habitat in Western Australia’s wheat belt cleared for agriculture, it was considered extinct for more than 160 years.
Now, just two plants are known in the world, and they’re not even in the same place. This species is among many Australian plants that have come perilously close to extinction.
To help prevent the loss of any native plant species, we’ve assembled a massive evidence base for more than 750 plants listed as critically endangered or endangered. Of these, we’ve identified the 50 at greatest risk of extinction.
The good news is for most of these imperilled plants, we already have the knowledge and techniques needed to conserve them. We’ve devised an action plan that’s relatively easy to implement, but requires long-term funding and commitment.
What’s driving the loss?
There are 1,384 plant species and subspecies listed as threatened at a national level. Twelve Australian plant species are considered probably extinct and a further 21 species possibly extinct, while 206 are officially listed as critically endangered.
Australian plants were used, managed and celebrated by Australia’s First Nations people for at least 60,000 years, but since European colonisation, they’ve been beset by a range of threats.
Land clearing, the introduction of alien plants, animals, diseases, and interruptions to ecological processes such as fire patterns and flooding have taken a heavy toll on many species. This is particularly the case in the more densely populated eastern and southern parts of the continent.
Things aren’t improving. Scientists recently compiled long-term monitoring of more than 100 threatened plant species at 600 sites nationally. And they found populations had declined on average by 72% between 1995 and 2017.
This is a very steep rate of decline, much greater than for threatened mammal or bird populations.
On the brink
Many species listed as threatened aren’t receiving targeted conservation action or even baseline monitoring, so an important first step in preventing extinctions was identifying the species at greatest risk.
To find the top 50, we looked at the evidence: all available published and unpublished information and expert surveys of over 120 botanists and land managers.
They’re targeted by our Action Plan for Australia’s Imperilled Plants.
Thirty of the species in the plan have fewer than 50 mature individual plants remaining.
And 33 are known only from a single location, such as the Grampians pincushion-lily (Borya mirabilis), which occurs on one rocky outcrop in Victoria. This means the entire population could be destroyed by a single event, such as a major bushfire.
So how can we protect them?
Some of the common management actions we’ve proposed include:
- preventing further loss of species’ habitat. This is the most important action required at a national scale
- regularly monitoring populations to better understand how species respond to threats and management actions
- safely trialling appropriate fire management regimes, such as burning in areas where fires have been suppressed
- investing in disease research and management, to combat the threat of phytophthora (root-rot fungus) and myrtle rust, which damages leaves
- propagating and moving species to establish plants at new sites, to boost the size of wild populations, or to increase genetic diversity
- protecting plants from grazing and browsing animals, such as feral goats and rabbits, and sometimes from native animals such as kangaroos.
Another common issue is lack of recruitment, meaning there’s no young plants coming up to replace the old ones when they die. Sometimes this is because the processes that triggered these plants to flower, release seed or germinate are no longer occurring. This can include things like fire of a particular intensity or the right season.
Unfortunately, for some plants we don’t yet know what triggers are required, and further research is essential to establish this.
Now we need the political will
Our plan is for anyone involved in threatened flora management, including federal, state, territory and local government groups, First Nations, environment and community conservation groups, and anyone with one of these plants on their land.
Plants make Australian landscapes unique — over 90% of our plant species are found nowhere else in the world. They’re also the backbone of our ecosystems, creating the rich and varied habitats for our iconic fauna to live in. Plants underpin and enrich our lives every day.
Now we have an effective plan to conserve the Australian plants at the greatest risk of extinction. What’s needed is the political will and resourcing to act in time.
Jennifer Silcock, Post-doctoral research fellow, The University of Queensland; Jaana Dielenberg, University Fellow, Charles Darwin University; Roderick John Fensham, Associate Professor of Biological Sciences, The University of Queensland, and Teghan Collingwood, Research Technician, The University of Queensland
David Bowman, University of TasmaniaThe Black Summer bushfires shocked the world and generated enormous global media interest. Fire scientists like myself found themselves filling a role not unlike sport commentators, explaining the unfolding drama in real time.
Scientists who engaged with the media during the crisis straddled two competing imperatives. First was their duty to share their knowledge with the community while knowing their understanding is imperfect. Second was the ethical obligation to rigorously test hypotheses against data analysis and peer review – the results of which could only be known long after the fires were out.
One area where this tension emerged was around the influential idea that logging exacerbated the bushfire disaster. During the fire crisis and in the months afterwards, some scientists suggested logging profoundly affected the fires’ severity and frequency. There were associated calls to cease native forestry and shift wood production to plantations.
But there is no scientific consensus about the possible effects of logging on fire risk. In fact, research by myself and colleagues, published in Nature Ecology and Evolution today, shows logging had little if any effect on the Black Summer bushfires. Rather, the disaster’s huge extent and severity were more likely due to unprecedented drought and sustained hot, windy weather.
These findings are significant for several reasons. Getting to the bottom of the bushfires’ cause is essential for sustainable forest management. And, more importantly, our research confirms the devastating role climate change played in the Black Summer fires.
Looking for patterns
Our research focused on 7 million hectares of mostly eucalyptus forests, from the subtropics to temperate zones, which burned between August 2019 and March 2020.
There is some evidence to suggest logged areas are more flammable that unlogged forests. Proponents of this view say logging regimes make the remaining forests hotter and drier, and leave debris on the ground that increases the fuel load.
In our research, we wanted to determine:
- the relative roles logging and other factors such as climate played in fires that destroyed or completely scorched forest canopies
- whether plantations are more vulnerable to canopy scorch than native forests.
To do so, we used landscape ecology techniques that could compare very large areas with different patterns of land use and fire severity. We sampled 32% of the area burnt in three regions spanning the geographic range of the fires.
What we found
Fire intensity is classified according to the vertical layer of vegetation burnt. A scorched tree canopy suggests the most intense type of fire, where the heat extended from the ground to the treetops.
We found several predictors of canopy damage. First, completely scorched canopy, or canopy consumed by fire, typically occurred across connected swathes of bushland. This most likely reflected instances where the fire made a “run”, driven by localised winds.
Extreme weather fire conditions were the next most important predictor of canopy damage. The drought had created vast areas of tinder-dry forests. Temperatures during the fire season were hot and westerly winds were strong.
Southeast Australia’s climate has changed, making such extreme fire weather more frequent, prolonged and severe.
Logging activity in the last 25 years consistently ranked “low” as a driver of fire severity. This makes sense for several reasons.
As noted above, fire conditions were extraordinarily extreme. And there was mismatch between the massive area burnt and the comparatively small areas commercially logged in the last 25 years (4.5% in eastern Victoria, 5.3% in southern NSW and 7.8% in northern NSW).
Fire severity is also related to landscape features: fire on ridges is generally worse than in sheltered valleys.
Our research also found timber plantations were as prone to severe fire as native forestry areas. In NSW (the worst-affected state) one-quarter of plantations burned – than 70% severely. This counteracts the suggestion using plantations, rather than logging native forest, can avoid purported fire hazards.
A challenge awaits
Our findings are deeply concerning. They signal there is no quick fix to the ongoing fire crisis afflicting Australia and other flammable landscapes.
The crisis is being driven by relentless climate change. Terrifyingly, it has the potential to turn forests from critical stores of carbon into volatile sources of carbon emissions released when vegetation burns.
Under a rapidly warming and drying climate, fuel loads are likely to become less important in determining fire extent and severity. This will make it increasingly difficult, if not impossible, to lower fuel loads in a way that will limit bushfire severity.
A massive challenge awaits. We must find socially and environmentally acceptable ways to make forests more resilient to fire while the also produce sustainable timber products, store carbon, provide water and protect biodiversity.
The next step is a real-world evaluation of management options. One idea worth exploring is whether the fire resistance of native forests can be improved in specific areas by altering tree density, vegetation structure or fuel loads, while sustaining biodiversity and amenity.
Commercial forestry could potentially do this, with significant innovation and willingness to let go of current practices.
Through collective effort, I’m confident we can sustainably manage of forests and fire. Our study is but a small step in a much bigger, zig-zagging journey of discovery.
It’s not often you get to cast your eyes on a creature feared to be long-gone.
Perhaps that’s why my recent rediscovery of the native bee species Pharohylaeus lactiferus is so exciting — especially after it spent a century eluding researchers.
But how did it stay out of sight for so long?
A creature overshadowed
Australia is home to 1654 named species of native bee. Unfortunately, these are often overshadowed in the eyes of public by the widespread and invasive European honeybee.
Scientific research on Australian native bees is lagging, compared to many other nations.
With this in mind, it may not be surprising to learn some native species can go unnoticed for many years. Although, when it’s the only representative of a whole genus, one might start to worry about losing something special.
In this case the genus is Pharohylaeus, where “pharo” means “cloaked”, as these bees’ first three abdominal segments overlay the others to resemble a cloak.
I found the cloaked bee P. lactiferus during a major east coast sampling effort of more than 225 unique sites. The discovery, and what I learnt from it, helped me find more specimens at two additional sites.
It also made me wonder why P. lactiferus had been missing for so long. Is it naturally rare, hard to find, or perhaps threatened?
Many Australian bees are very difficult to identify to a species level. In fact, some might be nearly impossible.
However, P. lactiferus is a relatively distinct black and white masked bee. Masked bees are those from the subfamily Hylaeinae, named so because they often have striking, bright facial patterns on an otherwise dark face.
With this distinctive appearance, identification issues weren’t a contributor to the mystery of P. lactiferus.
Still, despite having sampled extensively across sites and flowering plant species, I only found P. lactiferus on two types of plant: the firewheel tree and the Illawarra flame tree — both of which boast exuberant red flowers.
Bees generally don’t see shades of red, so such plants are usually pollinated by birds. It could be that bee researchers tend to avoid sampling these red flowering plant species for this reason.
Then again, bee vision and bee perception are not always the same. And bees are also guided by their keen sense of smell.
So far, I’ve only found P. lactiferus within about 200 metres of one major vegetation subgroup, which is tropical or sub-tropical rainforest.
The first specimens I collected were in Atherton, Queensland. I later found more in Kuranda and Eungella. Some of these specimens are now stored in the South Australian Museum.
The habitat specialisation of P. lactiferus may suggest it has an above-average level of vulnerability to disturbances, particularly if it needs a strict set of requirements to make it through its entire life-cycle.
It is one of myriad bee species that nest in narrow, wooden hollows. Some bees such as Amphylaeus morosus dig these themselves and may require specific plant species to make their nest in.
Others such as Exoneurella tridentata need to use holes made by weevil larvae in two particular tree species: western myall and bullock bush.
Rainforests are also notoriously hard to sample. If a bee species spends much of its time in the high canopy, finding it would be difficult.
That said, two early collectors managed to find six specimens of P. lactiferus between 1900 and 1923. So its rarity doesn’t necessarily come down to it being a canopy-dweller.
We know in the bioregions where P. lactiferus has been found that rainforests have undergone both habitat destruction and fragmentation since European colonisation. This threat hasn’t abated and Queensland is still a land-clearing hotspot.
We also know these rainforests burnt across Queensland every year between 1988 and 2016. The 2019-20 black summer megafires burnt nearly double the area of any previous year.
For some bee species this may not be a problem. But for a species that potentially requires specific foods, habitats and even other species, it could mean local extinction.
Only so many populations of a single species can disappear, before there are none left.
Where does this leave us?
P. lactiferus persists, which is wonderful. Unfortunately, we can’t yet say whether or not it is threatened.
To determine this confidently would require a robust, extensive and targeted survey regime.
We may not be able to undertake such a regime for all 1654 of the named bee species in Australia. But perhaps we could make that effort for the country’s only cloaked bee.
Humans have long been inspired and transfixed by the Moon, and as we’re discovering, moonlight can also change the behaviour of Australian wildlife.
A collection of recently published research has illuminated how certain behaviours of animals – including potoroos, wallabies and quolls – change with variation in ambient light, phases of the Moon and cloud cover.
How big is the Moon? Let me compare …
One study found small mammals were more active on cloudy nights. Another found variation in moonlight led to differing amounts of species captured in non-lethal traps. And a study on willie wagtails found males just love singing on a full moon.
These findings are interesting from a natural history perspective. But they’ll also help ecologists and conservation scientists better locate and study nocturnal animals, and learn how artificial light pollution is likely changing where animals can live and how they behave.
Moonlit predator-prey games of hide and seek
Most of Australia’s mammals are nocturnal, and some smaller species are thought to use the cover of darkness to avoid the attention of hungry predators. However, there’s much we don’t know about such relationships, especially because it can be difficult to study these interactions in the wild.
In the relatively diverse mammal community at Mt Rothwell, Victoria, we examined how variation in ambient light affected species’ activity, and how this might influence species interactions. Mt Rothwell is a fenced conservation reserve free of feral cats and foxes, and with minimal light pollution.
Over two years, we surveyed the responses of predator and prey species to different light levels from full, half and new moon phases.
Potential prey species in our study included eastern barred and southern brown bandicoots, long-nosed potoroos, brushtailed rock-wallabies, and brushtail and common ringtail possums. Eastern and spotted-tailed quolls are their potential predators.
Just as we predicted, we found that while there does appear to be relationships between cloud cover, Moon phase and mammal activity, these interactions depend on the sizes and types of mammals involved.
Both predators and prey generally increased their activity in darker conditions.
Smaller, prey species increased their activity when cloud cover was higher, and predators increased their activity during the half and new moon phases.
This suggests their deadly game of hide and seek might intensify on darker nights. And prey might have to trade off foraging time to reduce their chances of becoming the evening meal.
What happens in the wild?
It’s important to acknowledge that studies in sanctuaries such as Mt Rothwell might not always reflect well what goes on in the wild, including in areas where introduced predators, such as feral cats and red foxes, are found.
Another recent study, this time of small mammals in the wilds of Victoria’s Mallee region, sheds further light on the situation. The authors tested if variation in weather and Moon phase affected the numbers of five small mammal species – Bolam’s mouse, common dunnart, house mouse, southern ningaui, and western pygmy possum – captured in pitfall traps.
Pitfall traps are long fences small animals can’t climb over or through, so follow along the side until they fall into a bucket dug in the ground. Ecologists typically use these traps to capture and measure animals and then return them to the wild, unharmed.
At more than 260 sites and over more than 50,000 trap nights, they found wind speed, temperature and moonlight influenced which species were caught and in what numbers.
For example, captures of a small native rodent, Bolam’s mouse, and carnivorous marsupial, southern ningaui, decreased with more moonlight, whereas captures of pygmy possums were higher with more moonlight.
Moonlight songbird serenades
Research from last month has shown even species normally active by day may change their behaviour and activity by night.
It’s not uncommon to hear bird song by night, including the quintessentially Aussie warbling of magpies. Using bioacoustic recorders and song detection software, these researchers show the willie wagtail – another of Australia’s most recogisable and loved birds – is also a nighttime singer, particularly during the breeding season.
While both male and female wagtails sing by day, it is the males that are most vocal by night. And it seems the males aren’t afraid of a little stage-lighting either, singing more with increasing moonlight, with performances peaking during full moons.
This work provides insight into the importance and potential role of nocturnal song for birds, such as mate attraction or territory defence, and helps us to better understand these behaviours more generally.
Moonlight affects wildlife conservation
These studies, and others, can help inform wildlife conservation, as practically speaking, ecological surveys must consider the relative brightness of nights during which work occurred.
Depending on when and where we venture out to collect information about species, and what methods we use (camera traps, spotlighting, and non-lethal trapping) we might have higher or lower chances of detecting certain species. And this might affect our insights into species and ecosystems, and how we manage them.
As dark skies become rarer in many places around the world, it also begs a big question. To what extent is all the artificial light pollution in our cities and peri-urban areas affecting wildlife and ecosystems?
Pipistrelle bats, for example, will be roughly half as active around well-lit bridges than unlit bridges. They’ll also keep further away from well-lit bridges, and fly faster when near them.
This means artificial light might reduce the amount and connectivity of habitat available to some bat species in urban areas. This, in turn could affect their populations.
Research is underway around the world, examining the conservation significance of such issues in more detail, but it’s another timely reminder of the profound ways in which we influence the environments we share with other species.
We would like to acknowledge Yvette Pauligk, who contributed to our published work at Mt Rothwell, and that the traditional custodians of this land are the Wathaurong people of the Kulin nation.
Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University; Courtney Marneweck, Postdoctoral Researcher in Carnivore Ecology, Clemson University , and Grant Linley, PhD Candidate, Charles Sturt University
The New South Wales government plans to release two million native fish into rivers of the Murray-Darling Basin, in the largest breeding program of its kind in the state. But as the river system recovers from a string of mass fish deaths, caution is needed.
Having suitable breeding fish does not always guarantee millions of healthy offspring for restocking. And even if millions of young fish are released into the wild, increased fish populations in the long term are not assured.
For stocking to be successful, fish must be released into good quality water, with suitable habitat and lots of food. But these conditions have been quite rare in Murray Darling rivers over the past three years.
We research the impact of human activity on fish and aquatic systems and have studied many Australian fish restocking programs. So let’s take a closer look at the NSW government’s plans.
According to the Sydney Morning Herald, the NSW restocking program involves releasing juvenile Murray cod, golden perch and silver perch into the Darling River downstream of Brewarrina, in northwestern NSW.
Other areas including the Lachlan, Murrumbidgee, Macquarie and Murray Rivers will reportedly also be restocked. These species and regions were among the hardest hit by recent fish kills.
Fish restocking is used worldwide to boost species after events such as fish kills, help threatened species recover, and increase populations of recreational fishing species.
Since the 1970s in the Murray-Darling river system, millions of fish have been bred in government and private hatcheries in spring each year. Young fish, called fingerlings, are usually released in the following summer and autumn.
There have been success stories. For example, the endangered trout cod was restocked into the Ovens and Murrumbidgee Rivers between 1997 and 2006. Prior to the restocking program, the species was locally extinct. It’s now re-established in the Murrumbidgee River and no longer requires stocking to maintain the population.
In response to fish kills in 2010, the Edward-Wakool river system was restocked to help fish recover when natural spawning was expected to be low. And the threatened Murray hardyhead is now increasing in numbers thanks to a successful stocking program in the Lower Darling.
After recent fish kills in the Murray Darling, breeding fish known as “broodstock” were rescued from the river and taken to government and private hatcheries. Eventually, it was expected the rescued fish and their offspring would restock the rivers.
Words of caution
Fish hatchery managers rarely count their fish before they hatch. It’s quite a challenge to ensure adult fish develop viable eggs that are then fertilised at high rates.
Once hatched, larvae must be transported to ponds containing the right amount of plankton for food. The larvae must then avoid predatory birds, be kept free from disease, and grow at the right temperatures.
When it comes to releasing the fish into the wild, careful decisions must be made about how many fish to release, where and when. Factors such as water temperature, pH and dissolved oxygen levels must be carefully assessed.
Introducing hatchery-reared fish into the wild does not always deliver dramatic improvements in fish numbers. Poor water quality, lack of food and slow adaptation to the wild can reduce survival rates.
In some parts of the Murray-Darling, restocking is likely to have slowed the decline in native fish numbers, although it has not stopped it altogether.
Address the root cause
Fish stocking decisions are sometimes motivated by economic reasons, such as boosting species sought by anglers who pay licence fees and support tourist industries. But stocking programs must also consider the underlying reasons for declining fish populations.
Aside from poor water quality, fish in the Murray Darling are threatened by being sucked into irrigation systems, cold water pollution from dams, dams and weirs blocking migration paths and invasive fish species. These factors must be addressed alongside restocking.
Fish should not be released into areas with unsuitable habitat or water quality. The Darling River fish kills were caused by low oxygen levels, associated with drought and water extraction. These conditions could rapidly return if we have another hot, dry summer.
Stocking rivers with young fish is only one step. They must then grow to adults and successfully breed. So the restocking program must consider the entire fish life cycle, and be coupled with good river management.
The Murray Darling Basin Authority’s Native Fish Recovery Strategy includes management actions such as improving fish passage, delivering environmental flows, improving habitat, controlling invasive species and fish harvest restrictions. Funding the strategy’s implementation is a key next step.
After recent rains, parts of the Murray Darling river system are now flowing for the first time in years. But some locals say the flows are only a trickle and more rain is urgently needed.
Higher than average rainfall is predicted between July and September. This will be needed for restocked fish to thrive. If the rain does not arrive, and other measures are not taken to improve the system’s health, then the restocking plans may be futile.
Lee Baumgartner, Professor of Fisheries and River Management, Institute for Land, Water, and Society, Charles Sturt University; Jamin Forbes, Freshwater Ecologist, Charles Sturt University, and Katie Doyle, Freshwater Ecologist, Charles Sturt University