Tasmania’s salmon industry detonates underwater bombs to scare away seals – but at what cost?

Benjamin J. Richardson, University of TasmaniaAustralians consume a lot of salmon – much of it farmed in Tasmania. But as Richard Flanagan’s new book Toxic shows, concern about the industry’s environmental damage is growing.

With the industry set to double in size by 2030, one dubious industry practice should be intensely scrutinised – the use of so-called “cracker bombs” or seal bombs.

The A$1 billion industry uses the technique to deter seals and protect fish farming operations. Cracker bombs are underwater explosive devices that emit sharp, extremely loud noise impulses. Combined, Tasmania’s three major salmon farm operators have detonated at least 77,000 crackers since 2018.

The industry says the deterrent is necessary, but international research shows the devices pose a significant threat to some marine life. Unless the salmon industry is more strictly controlled, native species will likely be killed or injured as the industry expands.

pile of grey and white fish — Tasmanian salmon farming is a billion-dollar industry.
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Protecting a lucrative industry

Marine farming has been growing rapidly in Tasmania since the 1990s, and Atlantic salmon is Tasmania’s most lucrative fishery‑related industry. The salmon industry comprises three major producers: Huon Aquaculture, Tassal and Petuna.

These companies go to great effort to protect their operations from fur seals, which are protected in Australia with an exemption for the salmon industry.

Seals may attack fish pens in search of food and injure salmon farm divers, though known incidents of harm to divers are extremely rare.

The industry uses a number of seal deterrent devices, the use of which is approved by the government. They include:

lead-filled projectiles known as “beanbags”, which are fired from a gun
sedation darts fired from a gun
explosive charges or “crackers” thrown into the water which detonate under the surface.

In June this year, the ABC reported on government documents showing the three major salmon producers had detonated more than 77,000 crackers since 2018. The documents showed how various seal deterrent methods had led to maiming, death and seal injuries resulting in euthanasia. Blunt-force trauma was a factor in half the reported seal deaths.

A response to this article by the salmon industry can be found below. The industry has previoulsy defended the use of cracker bombs, saying it has a responsibility to protect workers. It says the increased use of seal-proof infrastructure means the use of seal deterrents is declining. If this is true, it’s not yet strongly reflected in the data.

salmon farm infrastructure in water — Seal deterrents are deployed to protect salmon farm operations.
Shutterstock

Piercing the ocean silence

Given the prevalence of seal bomb use by the salmon industry, it’s worth reviewing the evidence on how they affect seals and other marine life.

A study on the use of the devices in California showed they can cause horrific injuries to seals. The damage includes trauma to bones, soft tissue burns and prolapsed eye balls, as well as death.

And research suggests damage to marine life extends far beyond seals. For example, the devices can disturb porpoises which rely on echolocation to find food, avoid predators and navigate the ocean. Porpoises emit clicks and squeaks – sound which travels through the water and bounces off objects. In 2018, a study found seal bombs could disturb harbour porpoises in California at least 64 kilometres from the detonation site.

There is also a body of research showing how similar types of industrial noise affect marine life. A study in South Africa in 2017 showed how during seismic surveys in search of oil or gas, which produce intense ocean noise, penguins raising chicks often avoided their preferred foraging areas. Whales and fish have also shown similar avoidance behaviour.

The study showed underwater blasts can also kill and injure seabirds such as penguins. And there may be implications from leaving penguin nests unattended and vulnerable to predators, and leaving chicks hungry longer.

Research also shows underwater explosions damage to fish. One study on caged fish reported profound trauma to their ears, including blistering, holes and other damage. Another study cited official reports of dead fish in the vicinity of seal bomb explosions.

dolphin jumps out of waves — Man-made noise can disturb a variety of marine animals, including porpoises.
Shutterstock

Shining a light

Clearly, more scientific research is needed into how seal bombs affect marine life in the oceans off Tasmania. And regulators should impose far stricter limits on the salmon industry’s use of seal bombs – a call echoed by Tasmania’s Salmon Reform Alliance.

All this is unfolding as federal environment laws fail to protect Australian plant and animal species, including marine wildlife.

And the laws in Tasmania are far from perfect. In 2017, Tasmania’s Finfish Farming Environmental Regulation Act introduced opportunities for better oversight of commercial fisheries. However, as the Environmental Defenders Office (EDO) has noted, the director of Tasmania’s Environment Protection Authority can decide on license applications by salmon farms without the development necessarily undergoing a full environmental assessment.

Tasmania’s Marine Farming Planning Act covers salmon farm locations and leases. As the EDO has noted, the public is not notified of some key decisions under the law and has very limited public rights of appeal.

Two relevant public inquiries are underway – a federal inquiry into aquaculture expansion and a Tasmanian parliamentary probe into fin-fish sustainability. Both have heard evidence from community stakeholders, such as the Tasmanian Alliance for Marine Protection and the Tasmanian Conservation Trust, that the Tasmanian salmon industry lacks transparency and provides insufficient opportunities for public input into environmental governance.

The Tasmanian government has thrown its support behind rapid expansion of the salmon industry. But it’s essential that the industry is more tightly regulated, and far more accountable for any environmental damage it creates.

In a statement in response to this article, the Tasmanian Salmonid Growers Association, which represents the three producers named above, said:

Around $500 million has been spent on innovative pens by the industry. These pens are designed to minimise risks to wildlife as well as to fish stocks and the employees. We believe that farms should be designed to minimise the threat of seals, but we also understand that non-lethal deterrents are a part of the measures approved by the government for the individual member companies to use. If these deterrents are used it is under strict guidelines, sparingly, and in emergency situations when staff are threatened by these animals, which can be very aggressive.

Tasmania has a strong, highly regulated, longstanding salmon industry of which we should all be proud. The salmon industry will continue its track record of operating at world’s best practice now and into future. Our local people have been working in regional communities for more than 30 years, to bring healthy, nutritious salmon to Australian dinner plates, through innovation and determination.

Benjamin J. Richardson, Professor of Environmental Law, University of Tasmania

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

Bones and all: see how the diets of Tasmanian devils can wear down their sharp teeth to blunt nubbins

Tahlia Pollock, Monash University; Alistair Evans, Monash University; David Hocking, Monash University, and Marissa Parrott, The University of MelbourneTasmanian devils are expert scavengers, with strong jaws and robust teeth that give them the notorious ability to eat almost all of a carcass — bones and all.
Scientists have even found echidna spikes in their poo.

But regularly crunching through bone comes at a cost: extreme tooth wear. In our new study, we analysed the skulls of nearly 300 devils, and show how regularly crunching through bones wears a devil’s teeth down from sharp-edged weapons to blunt nubbins.

Tasmanian devils are endangered and their wild population is continuing to decline. A key part of conserving this marsupial is by maintaining healthy and happy devils in captivity.

Understanding how their food affects their teeth can help us see if captive devils have the same types of tooth wear as their wild counterparts, and look for signs of any unusual or harmful wear.

Is there anything a devil won’t eat?

Tasmanian devils are the largest marsupial carnivore alive today. As scavengers, they occupy a unique niche in the Australian ecosystem by disposing of dead animal carcasses.

Devil standing over a dead carcass — Captive Tasmanian devils are given a variety of foods to replicate what they’d find in the wild. This photo was taken during a carcass feed at Healesville Sanctuary.
Zoos Victoria, Author provided

Devils are highly opportunistic and can eat many different types of prey. While their favourites are the carcasses of native mammals such as wombats and wallabies, they’ll also eat reptiles, amphibians, birds, fish, and even insects.

We know this because we find hair, feathers, scales, small bones, claws and more in their poo.

Almost nothing is off limits to devils — they’ll even have a go at a stranded whale given the chance. Although devils prefer to scavenge, they’re also accomplished hunters.

But due to a transmissible cancer, devil facial tumour disease, wild numbers of these remarkable marsupials have plummeted by around 80%.

Right now, 45 Australian zoos and wildlife sanctuaries, plus an island and a fenced peninsula, are collaborating to maintain a healthy population of disease-free devils. It’s important for these institutions to provide captive animals with the right kinds of food for their health and to help make their future release back to disease-free wild locations successful.

Devils naturally wear their teeth down from sharp points and edges to blunt, almost flat surfaces by regularly eating bones.
Tahlia Pollock, Author provided

This is especially crucial for carnivores, who rely on tough foods to help them develop strong jaws.

Like hyaenas, but stronger

The types of food an animal eats will wear their teeth down differently. For example, big cats such as lions prefer to eat the softer parts of a carcass, like flesh or organs, and leave the bones behind.

Spotted hyaenas, however, will happily eat the bones. As a result, hyaenas have incredibly high tooth wear compared with lions.

This might not hinder the hyaena or devil as much as you might think. Both have very strong jaws that can compensate for the loss of sharp teeth. In fact, devils have the strongest bite force per body weight of any living mammal.

In the interactive below, you can check out 3D models of devil skulls to get a better idea of how much their teeth wear down.

Toothwear in Tasmanian Devils by Evans EvoMorph Lab on Sketchfab

Comparing wild and captive diets

By comparing the tooth wear of wild and captive devils, we can see if captive animals are encountering enough hard foods in their diets.

In the Save the Tasmanian Devil Program — an initiative of the federal and Tasmanian governments — captive devils are given a variety of small and large foods at different times, replicating what they’d find in the wild.

We found no signs of different or harmful tooth wear in captive devils, and they showed much the same patterns and types of wear as wild devils.

However, we noticed captive devils wore their teeth more slowly than those in the wild. This may be due to eating higher quality food, such as carcasses that were fresh, whole, and yet to be scavenged.

This means captive institutions are doing a good job of providing devils with the right types of food for their teeth and encouraging wild behaviours.

Part of the health check for wild devils involves looking at their teeth. This particular devil has nice sharp tips and edges on their canines and molars.
Marissa Parrott/Zoos Victoria, Author provided

Collecting data about Tassie devils after they’ve been released confirms this. In 2012 and 2013, devils were released onto Maria Island in Tasmania after being born and raised for around a year in captivity.

Encouragingly, these devils kept the behaviours required to scavenge and hunt prey, and had diets similar to wild devils.

How you can help save Tasmanian devils

Our research is one small, but promising, piece in the overall puzzle. While captive research and breeding programs help conserve the Tasmanian devil, there are ways you can help, too.

Because they like to scavenge the carcasses of dead animals, road kill is especially tempting for devils. But being so close to the road is dangerous and road mortality is the second-biggest killer of wild devils.

So take care on the roads to help wildlife, especially if driving at night. And if you’re in Tasmania and see a devil that’s been hit on the road, log it in the Roadkill TAS app.

This will help identify road kill hotspots and protect this impressive, but endangered, species.

Tahlia Pollock, PhD candidate, Monash University; Alistair Evans, Associate Professor, Monash University; David Hocking, Curator of Vertebrate Zoology and Palaeontology at the Tasmanian Museum and Art Gallery (TMAG) | Adjunct Research Associate at Monash University, Monash University, and Marissa Parrott, Reproductive Biologist, Wildlife Conservation & Science, Zoos Victoria, and Honorary Research Associate, BioSciences, The University of Melbourne

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

Tasmania’s reached net-zero emissions and 100% renewables – but climate action doesn’t stop there

Rupert Posner, ClimateWorks Australia and Simon Graham, ClimateWorks AustraliaGetting to net-zero greenhouse gas emissions and 100% renewable energy might seem the end game for climate action. But what if, like Tasmania, you’ve already ticked both those goals off your list?

Net-zero means emissions are still being generated, but they’re offset by the same amount elsewhere. Tasmania reached net-zero in 2015, because its vast forests and other natural landscapes absorb and store more carbon each year than the state emits.

And in November last year, Tasmania became fully powered by renewable electricity, thanks to the island state’s wind and hydro-electricity projects.

The big question for Tasmania now is: what comes next? Rather than considering the job done, it should seize opportunities including more renewable energy, net-zero industrial exports and forest preservation – and show the world what the other side of net-zero should look like.

electricity transmission lines — Hydro-electric power and wind energy mean Tasmania runs on 100% renewable energy.
Shutterstock

A good start

The Tasmanian experience shows emissions reduction is more straightforward in some places than others.

The state’s high rainfall and mountainous topography mean it has abundant hydro-electric resources. And the state’s windy north is well suited to wind energy projects.

What’s more, almost half the state’s 6.81 million hectares comprises forest, which acts as a giant carbon “sink” that sucks up dioxide (CO₂) from the atmosphere.

Given Tasmania’s natural assets, it makes sense for the state to go further on climate action, even if its goals have been met.

The Tasmanian government has gone some way to recognising this, by legislating a target of 200% renewable electricity by 2040.

Under the target, Tasmania would produce twice its current electricity needs and export the surplus. It would be delivered to the mainland via the proposed A$3.5 billion Marinus Link cable to be built between Tasmania and Victoria. The 1,500 megawatt cable would bolster the existing 500 megawatt Basslink cable.

But Tasmania’s climate action should not stop there.

artist impression of marinus link — The Marinus Link would provide a second electricity connection from Tasmania to the mainland.
http://www.marinuslink.com.au

Other opportunities await

Tasmania can use its abundant renewable electricity to decarbonise existing industrial areas. It can also create new, greener industrial precincts – clusters of manufacturers powered by renewable electricity and other zero-emissions fuels such as green hydrogen.

Zero-emission hydrogen, aluminium and other goods produced in these precincts will become increasingly sought after by countries and other states with their own net-zero commitments.

Tasmania’s vast forests could be an additional source of economic value if they were preserved and expanded, rather than logged. As well as supporting tourism, preserving forests could enable Tasmania to sell carbon credits to other jurisdictions and businesses seeking to offset their emissions, such as through the federal government’s Emissions Reduction Fund.

The ocean surrounding Tasmania also presents net-zero economic opportunities. For example, local company Sea Forest is developing a seaweed product to be added to the feed of livestock, dramatically reducing the methane they emit.

logs on a truck — Retaining, rather than logging, Tasmania’s forests presents an economic opportunity.
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Concrete targets are needed

The Tasmanian government has commissioned a review of its climate change legislation, and is also revising its climate change action plan.

These updates give Tasmania a chance to be a global model for a post-net-zero world. But without firm action, Tasmania risks sliding backwards.

While having reached net-zero, the state has not legislated or set a requirement to maintain it. The state’s current legislated emission target is a 60% reduction by 2050 on 1990 levels – which, hypothetically, means Tasmania could increase its emissions in future.

Also, despite reaching net-zero emissions, Tasmania still emits more than 8.36 million tonnes of CO₂ each year from sources such as transport, natural gas use, industry and agriculture. Tasmania’s emissions from all sectors other than electricity and land use have increased by 4.5% since 2005.

Without a net-zero target set in law – and a plan to stay there – these emissions could overtake those drawn down by Tasmania’s forests. In fact, a background paper prepared for the Tasmanian government shows the state’s emissions may rise in the coming years and stay “positive” until 2040 or later.

The legislation update should also include a process to set emissions targets for each sector of the economy, as Victoria has done. It should also set ambitious targets for “negative” emissions – which means sequestering more CO₂ than is emitted.

Industrial plant billowing smoke — Tasmania must cut emissions from industry and other sectors.
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Action on all fronts

Under the Paris Agreement, the world is pursuing efforts to limit global warming to 1.5℃ this century. For Australia to be in line with this goal, it must reach net-zero by the mid-2030s.

Meeting this momentous task requires action on all fronts, in all jurisdictions. Bigger states and territories are aiming for substantial emissions reductions this decade. Tasmania must at least keep its emissions net-negative, and decrease them further.

Tasmania has a golden opportunity. With the right policies, the state can solidify its climate credentials and create a much-needed economic boost as the world transitions to a low-carbon future.

Rupert Posner, Systems Lead – Sustainable Economies, ClimateWorks Australia and Simon Graham, Senior Analyst, ClimateWorks Australia

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

Australia: Salmon Farming

Deer in Tasmania

Tasmanian devils look set to conquer their own pandemic

Hamish McCallum, Griffith University and Austin H. Patton, University of California, Berkeley

In the midst of a human pandemic, we have some good news about a wildlife one: our new research, published today in Science, shows Tasmanian devils are likely to survive despite the infectious cancer that has ravaged their populations.

Tasmanian devils have been devastated by a bizarre transmissible cancer. Devil facial tumour disease, or DFTD for short, was first detected in 1996 in northeast Tasmania. Transmitted via biting, DFTD has spread over almost the entire state, reaching the west coast in the past two or three years. It has led to a decline of at least 80% in the total devil population.

Tasmanian devil with facial tumour — The infectious tumours are spread by biting.
CREDIT, Author provided

Ten years ago, we thought there was a real chance DFTD would drive the Tasmanian devil to extinction. Our concern arose not just because the cancer was almost inevitably lethal, but also because the transmission rate did not appear to slow down, even as devils became very rare.

Our new research has some good news: by pioneering application of genomic analysis typically used for viruses, we have discovered the curve has flattened and the rate of increase of infections has slowed. This means while the disease is probably not going away, neither are Tasmanian devils.

Genomics is a relatively new field of science that uses the vast amounts of data available from modern genetic sequencing techniques to answer some of the most difficult and important questions in biology.

The genomic approach we used is called phylodynamics. It uses sophisticated mathematical analysis of small changes in DNA to reconstruct the evolution and spread of the tumour through devil populations. This is the same method used to track the COVID-19 pandemic, and it was first developed to study the influenza virus. Viruses have small genomes and evolve rapidly. This is the first time the method has been used for a pathogen with a much more complex and slowly evolving genome.

Screening more than 11,000 genes, we found the R number (the average number of secondary cases for each primary case, now familiar from COVID-19) has fallen from about 3.5 at the peak of the epidemic to about one now. This suggests some sort of steady state has been reached, and the disease and devils are now coexisting.

Reproduction number RE of DFTD from 1990 to the present.
CREDIT, Author provided

This discovery backs up a paper we published last year, in which we reached a similar conclusion using mathematical models based on marking and recapturing Tasmanian devils at a single study site, without taking genetics into account.

Our new study is based on samples collected across Tasmania since the early 2000s. Given the very different nature of the two methods, the agreement between the results lends us increased confidence in our conclusions.

This paper, in addition to several we have published recently, shows there have been rapid evolutionary changes in Tasmanian devils and in the tumours themselves since the emergence of this transmissible cancer. Already, frequencies of gene variants known to be associated with immune function in humans have increased in Tasmanian devil populations, suggesting the devils are evolving and adapting to the threat.

We also now know a relatively small number of genes has a large influence on whether devils become infected, and whether they survive if they do.

Finally, and perhaps most encouragingly of all, we have now seen tumours shrink and disappear — something that was unheard of when the disease first emerged. What’s more, we also know this has a strong genetic basis, again suggesting the devils are genetically adapting to their foe.

Together, all of these discoveries show wild Tasmanian devils can evolve very rapidly — over just five generations or so — in response to this disease. This has profoundly encouraging implications for their likely future survival.

Baby Tasmanian devil — Tasmanian devils now have much better genetic defences against the disease.
Rodrigo Hamede, Author provided

There is still much more to learn about the evolution of the devils and their tumours. But meanwhile, our results provide a warning that a strategy of reintroducing captive-reared animals to supplement diseased wild devil populations is likely to be counterproductive.

When devils from populations that have never been exposed to the disease interbreed with wild animals in diseased populations, the evolution we have seen in wild populations is likely to slow down or even reverse, endangering those populations.

What’s more, the slowing rate of disease transmission may be partly a consequence of reduced devil population densities, resulting in fewer bites. Artificially boosting population densities might accelerate disease transmission, the opposite of the intended effect.

With the growing body of evidence showing extinction of devils is quite unlikely even over the next 100 years, we have time for careful consideration of management strategies. Specifically, models can be developed to assess the evolutionary and epidemiological consequences of reintroductions or translocations.

One possibility would be to captively breed devils that have the right genes to boost their chance of surviving the disease. More broadly, our research underlines the vital importance of taking evolutionary considerations into account when managing endangered species. We now have the genomic tools to do so.

Many thanks to Andrew Storfer at Washington State University, Menna Jones and Rodrigo Hamede at the University of Tasmania, and Paul Hohenlohe at the University of Idaho for their contributions to this article and the research it describes.

Hamish McCallum, Professor, Griffith School of Environment and Science, Griffith University and Austin H. Patton, Postdoctoral Associate, University of California, Berkeley

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

‘Like trying to find the door in a dark room while hearing your relatives scream for help’: Tasmania’s whale stranding tragedy explained

Olaf Meynecke, Griffith University

A desperate rescue effort is underway after hundreds of long-finned pilot whales (Globicephala melas) became stranded in Macquarie Harbour on Tasmania’s west coast.

Yesterday, more than 250 pilot whales were reported to have stranded, with one-third presumed dead. And this morning, rescuers found another 200 pilot whales stranded up to ten kilometres away from the first group — most are likely dead.

This brings the total number of stranded pilot whales in Tasmania to more than 450, and it’s believed to be the biggest ever recorded in the state. The Greens are calling on federal Environment Minister Sussan Ley to launch a national response.

The rescue mission aims to refloat the pilot whales that appear to still be in reasonable health. But their behaviour hampers rescue efforts: many pilot whales re-strand themselves to be with their family. This event likely means a number of generations of the local population will be lost.

How did they become stranded?

Despite its name, the long-finned pilot whale is actually a large oceanic dolphin. They cover vast areas of the Southern (Antarctic) Ocean, reaching between four and six metres in length and weighing up to one tonne.

They are well adapted to deeper oceans where they hunt for various species of squid in depths of between 600-1,000m, using echolocation to find their prey. Echolocation is a way of using sound to navigate in complete darkness.

They generally spend most of their lives offshore and it’s not well understood what conditions drive them close to shore, and to enter shallow embayments.

Some theories suggest food shortages are to blame, or changes in electromagnetic fields that disorient them. They may also be following a sick or distressed pod leader. And in some past cases strandings were related back to active sonar from ships and naval sonar interrupting their echolocation.

But once in shallow waters, it’s difficult to swim back out. As these whales mostly navigate with echolocation it’s not possible for them to use sonar effectively in shallow and muddy embayments.

It’s extremely distressing for the whales, a lot like trying to find the door in a dark room while hearing your relatives scream for help.

In fact, the stress is what many die from in the end. Other causes of death are overheating from sun exposure and drowning if they can’t move their bodies up to breach the surface in shallow water.

The rescue efforts

There are a number of strategies to refloat whales. In Macquarie Harbour, rescuers are using slings to tow the whales to deeper water, before releasing them.

Other options include multiple people pushing them off the beach during high tide into deeper water.

In this case, albeit potentially dangerous for the helpers, people power can make a big difference. After all, time is of immense importance for success, and to stop more whales beaching.

However, chances of survival plummet with long exposure to sun and extended periods of stress. What’s more, Macquarie Harbour is relatively remote and difficult to access, further complicating rescue efforts.

Dying together

But the biggest obstacle rescuers face is the whales’ social bonding. Long-finned pilot whales are highly intelligent and live in strong social units.

So when dealing with mass strandings, it’s important to realise the emotions and bonding between the whales are very likely beyond what humans can feel. One well-documented example of their emotional depth is the pilot whale seen carrying its dead calf for many days.

Mother pilot whale grieves over her dead calf.

This makes the stranding process extremely complex, as it unfolds over several hours to several days — the whales don’t all strand at the same time.

We know from killer whales, which also have strong social bonding, that if a close member of the group strands, others will attempt to join to die together.

The situation for pilot whale pods can be similar, but more complex as a result of having much larger pods. Pilot whale pods have multiple sub-units, which can consist of friends as well as family and they don’t have to be genetically related.

Social units get mixed up when they’re in shallow bays. This means individuals can become disconnected from their social units before the actual stranding occurs, causing stress and confusion prior the beaching.

Fewer pilot whales in the gene pool

There are an estimated 200,000 long-finned pilot whales in the Southern Ocean and Antarctica, but mass strandings like this can have a profound impact on sub-populations.

In Tasmania alone, 1,568 long-finned pilot whales have stranded between 1990 and 2008 in 30 stranding events.

Many similar sad events occured in New Zealand: hundreds of long-finned pilot whales stranded in 2018 and 2017, and the majority died.

To make matters worse, studies suggest the long-finned pilot whales in the Southeastern Pacific have low genetic diversity. There are similarities between this species found in Chile and New Zealand, but with surprisingly distinct differences between New Zealand and Tasmania.

Considering they can live up to 50 years and the fact only few survive when multiple generations strand, such events not only destroy entire generations but also remove them from the gene pool.

This puts local populations at further risk. Inbreeding is one consequence, but the biggest problem is their decreasing general fitness and ability to adapt to changes.

How to help

In the past, significant numbers of stranded whales have been successfully released, making it worth the effort. For example, in one of largest mass strandings in New Zealand in 2017, volunteers helped about 100 whales refloat, and made a human chain to try to stop them restranding.

Still, such events are likely to be more frequent in the future due to changing ocean conditions and increasing human activity such a noise pollution, commercial squid fisheries and deep sea mining.

Climate change shifts ocean currents as sea temperature rises. And with this, squid availability will change. A lack of food offshore can cause stress and drive them closer to shore.

We can help the whales not only by actively supporting rescue organisations such as ORRCA, but also by helping reduce carbon emissions, foster sustainable fisheries, reduce plastic pollution and advocate for marine sanctuaries.

Olaf Meynecke, Research Fellow in Marine Science, Griffith University

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

Tasmanian Whale Deaths

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

Steve Pearce/The Tree Projects, Author provided

Jennifer Sanger, University of Tasmania

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

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

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

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

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

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

What makes these trees so special?

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

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

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

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

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

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

Tasmania’s Big Tree Register

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

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

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

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

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

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

A portrait of an entire tree captured. Its canopy breaches the clouds. — Steve Pearce/The Tree Projects, Author provided

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

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

A woman appears tiny standing against an enormous felled tree. — Steve Pearce/The Tree Projects, Author provided

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

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

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

A man wraps a measuring tape around a huge tree trunk, covered in moss. — Steve Pearce/The Tree Projects, Author provided

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

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

The tops of the giant tree canopies are higher than the clouds. — Steve Pearce/The Tree Projects, Author provided

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

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

Jennifer Sanger, Research Associate, University of Tasmania

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

The Tasmanian tiger was hunted to extinction as a ‘large predator’ – but it was only half as heavy as we thought

Smithsonian Institution/colourised by D.S. Rovinsky

Douglass Rovinsky, Monash University; Alistair Evans, Monash University, and Justin W. Adams, Monash University

Until it was hunted to extinction, the thylacine – also known as the Tasmanian tiger or Tasmanian wolf – was the world’s largest marsupial predator. However, our new research shows it was in fact only about half as large as previously thought. So perhaps it wasn’t such a big bad wolf after all.

Although the thylacine is widely known as an example of human-caused extinction, there is a lot we still don’t know about this fascinating animal. This even includes one of the most basic details: how much did the thylacine weigh?

An animal’s body mass is one of the most fundamental aspects of its biology. It affects nearly every facet of its biology, from biochemical and metabolic processes, reproduction, growth, and development, through to where the animal can live and how it moves.

For meat-eating predators, body mass also determines what the animal eats – or more specifically, how much it has to eat at each meal.

Catching and eating other animals is hard work, so a predator has to weigh the costs carefully against the benefits. Small predators have low hunting costs – moving around, hunting, and killing small prey doesn’t cost much energy, so they can afford to nibble on small animals here and there. But for bigger predators, the stakes are higher.

Almost all large predators – those weighing at least 21 kilograms – focus their efforts on prey at least half their own body size, getting more bang for the buck. In contrast, small predators below 14.5 kg almost always catch prey much smaller than half their own size. Those in between typically take prey less than half their size, but sometimes switch to a larger meal if some easy prey is there for the taking – or if the predator is getting desperate.

The mismeasure of the thylacine

Scan of article from Launceston Examiner — The March 14, 1868 edition of the Launceston Examiner featured tales of a ‘hyena’ that managed to kill 25 sheep.
trove.nla.gov.au

Few accurately recorded weights exist for thylacines – only four, in fact. This lack of information has made estimating their average size difficult. The most commonly used average body mass is 29.5kg, based on 19th-century newspaper accounts.

This suggests the thylacine would probably have taken relatively large prey such as wallabies, kangaroos and perhaps sheep. However, studies of thylacine skulls suggest they didn’t have strong enough skulls to capture and kill large prey, and that they would have hunted smaller animals instead.

This presented a problem: if the thylacine was as big as we thought, it shouldn’t be able to live solely on small prey. But what if we’ve had the weight wrong the whole time?

Weighing an extinct animal

Man taking a scan of a stuffed thylacine — Ben Myers of Thinglab scans a Museums Victoria thylacine.
CREDIT, Author provided

Our new research, published today in Proceedings of the Royal Society B, addresses this weighty issue. Our team travelled throughout the world to museums in Australia, the United States, the United Kingdom and Europe, and 3D-scanned 93 thylacines, including whole mounted skeletons, taxidermy mounts, and the only whole-body ethanol-preserved thylacine in the world, in Sweden.

Based on these scans, we created new equations to estimate a thylacine’s mass, based on how thick their limbs were – because their legs would have had to support their entire weight.

We also compared the results of these equations with a new method of digitally weighing 3D specimens. Based on a 3D scan of a mounted skeleton, we digitally “filled in the spaces” to estimate how much soft tissue would have been present, and then used our new formula to calculate how much this would weigh. Taxidermy mounts were easier as there was no need to infer the amount of soft tissue. The most artistic member of our team digitally sculpted lifelike thylacines around the scanned skeletons, and we weighed them, too.

Building and weighing a thylacine. Scanned skeletons (lop left) were surrounded by digital ‘convex hulls’ (top right), which then had their volume and mass calculated. The skeletons were then used in digitally sculpting lifelife models (bottom left), each with their own unique stripes (bottom right).
Rovinsky et al.

Our calculations unanimously told a very different story from the 19th-century periodicals, and from the commonly used estimate. The average thylacine weighed only about 16.7 kg – not 29.5 kg.

Tall tales on the tiger trail

This means the previous estimate, based on taking 19th-century periodicals at face value, was nearly 80% too large. Looking back at those old newspaper reports, many of them in retrospect have the hallmarks of “tall tales”, told to make a captured thylacine seem bigger, more impressive and more dangerous.

It was based on this suspected danger that the thylacine was hunted and trapped to extinction, with private bounties already placed on them by 1840, and government-sponsored extermination by the 1880s.

Graphic showing the size of thylacines relative to a woman — Thylacines were much smaller in stature than humans or grey wolves.
Rovinsky et al., Author provided

The thylacine was much smaller than previously thought, and this aligns with the smaller prey size suggested by the earlier studies. Predators below 21 kg – in which we should now include the thylacine – all tend to hunt prey smaller than half their size. The “Tasmanian wolf” probably wasn’t such a danger to Tasmanian farmers’ sheep after all.

By rewriting this fundamental aspect of their biology, we are closer to understanding the role of the thylacine in the ecosystem – and to seeing exactly what was lost when we deliberately hunted it to extinction.

Douglass Rovinsky, PhD Candidate, Monash University; Alistair Evans, Associate Professor, Monash University, and Justin W. Adams, Senior Lecturer, Department of Anatomy and Developmental Biology, Monash University

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

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Environment, Wildlife and Wilderness – Articles and News

Tag Archives for Tasmania

Tasmania’s salmon industry detonates underwater bombs to scare away seals – but at what cost?

Protecting a lucrative industry

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Shining a light

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The rescue efforts

Dying together

Fewer pilot whales in the gene pool

How to help

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

What makes these trees so special?

Tasmania’s Big Tree Register

The Tasmanian tiger was hunted to extinction as a ‘large predator’ – but it was only half as heavy as we thought

The mismeasure of the thylacine

Weighing an extinct animal

Tall tales on the tiger trail

Protecting a lucrative industry

Piercing the ocean silence

Shining a light

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Is there anything a devil won’t eat?

Like hyaenas, but stronger

Comparing wild and captive diets

How you can help save Tasmanian devils

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A good start

Other opportunities await

Concrete targets are needed

Action on all fronts

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How did they become stranded?

The rescue efforts

Dying together

Fewer pilot whales in the gene pool

How to help

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What makes these trees so special?

Tasmania’s Big Tree Register

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The mismeasure of the thylacine

Weighing an extinct animal

Tall tales on the tiger trail

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