There are an estimated 1 billion domesticated dogs in the world. Most are owned animals – pets, companions or working animals who share their lives with humans. They are the most common large predator in the world. Pet cats trail far behind, at about 220 million.

We are all too aware of the negative effects of cats, both owned and feral, on wildlife. Feral dogs too are frequently seen as threats to biodiversity, although dingoes can have a positive role. By contrast, our pet dogs often seem to get a free pass.

This is, unfortunately, based more on feelings than data. Our beloved pet dogs have a far greater, more insidious and more concerning effect on wildlife and the environment than we would like to be the case.

In our new research, we lay out the damage pet dogs do and what can be done about it.

Dogs are predators. They catch many types of wildlife and can injure or kill them. Their scent and droppings scare smaller animals. Then there’s the huge environmental cost of feeding these carnivores and the sheer quantity of their poo.

We love our pet dogs, but they come with a very real cost. We have to recognise this and take steps to protect wildlife by leashing or restraining our animals.

The predator in your home

Dogs are domesticated wolves, bred to be smaller, more docile and extremely responsive to humans. But they are still predators.

Pet dogs are responsible for more reported attacks on wildlife than are cats, according to data from wildlife care centres, and catch larger animals.

Pet dogs off the leash are the main reason colonies of little penguins are nearing collapse in Tasmania.

In New Zealand, a single escaped pet dog is estimated to have killed up to 500 brown kiwis out of a total population of 900 over a five-week period.

Once off the leash, dogs love to chase animals and birds. This may seem harmless. But being chased can exhaust tired migratory birds, forcing them to use more energy. Dogs can kill fledglings of beach-nesting birds, including endangered birds such as the hooded plover.

The mere presence of these predators terrifies many animals and birds. Even when they’re on the leash, local wildlife are on high alert. This has measurable negative effects on bird abundance and diversity across woodland sites in eastern Australia.

In the United States, deer are more alert and run sooner and farther if they see a human with a leashed dog than a human alone.

Several mammal species in the United States perceived dogs with a human as a bigger threat than coyotes.

Dogs don’t even have to be present to be bad for wildlife. They scent-mark trees and posts with their urine and leave their faeces in many places. These act as warnings to many other species. Researchers in the US found animals such as deer, foxes and even bobcats avoided areas dogs had been regularly walked compared to dog exclusion zones, due to the traces they left.

Keeping dogs healthy and fed has a cost

The medications we use to rid our pet dogs of fleas or ticks can last weeks on fur, and wash off when they plunge into a creek or river. But some of these medications have ingredients highly toxic to aquatic invertebrates, meaning a quick dip can be devastating.

Researchers have found when birds such as blue tits and great tits collect brushed-out dog fur to line their nests, it can lead to fewer eggs hatching and more dead hatchlings.

Then there’s the poo. In the US, there are about 90 million pet dogs, while the UK has 12 million and Australia has 6 million.

The average dog deposits 200 grams of faeces and 400 millilitres of urine a day. This translates to a tonne of faeces and 2,000 litres of urine over a 13 year lifespan. Scaled up, that’s a mountain of waste.

This waste stream can add to nitrogen pollution in waterways, alter soil chemistry and even spread diseases to humans and other wildlife. More than 80% of the pathogens infecting domesticated animals also infect wildlife.

Dogs largely eat meat, meaning millions of cows and chickens are raised just to feed our pets. Feeding the world’s dogs leads to about the same emissions as the Philippines and a land use “pawprint” twice the size of the UK.

No one likes thinking about this

People love their dogs. They’re always happy to see us. Their companionship makes us healthier, body and mind. Many farms couldn’t run without working dogs. We don’t want to acknowledge they can also cause harm.

Dogs, of course, are not bad. They’re animals, with natural instincts as well as the domesticated instinct to please us. But their sheer numbers mean they do real damage.

Many of us have a large dog-shaped blind spot. Little Brutus wouldn’t have done something like that, we think. But Brutus can and does.

Choosing to own a dog comes with responsibilities. Being a good dog owner means caring not just for the animal we love, but the rest of the natural world.

Bill Bateman, Associate Professor, Behavioural Ecology, Curtin University and Lauren Gilson, Research Associate, Behavioural Ecology, Curtin University

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

Have you ever sat with a cup of tea at the end of a weeding session, with a feeling close to happiness? Or returned from the local garden centre with a bag of potting mix and some plants – and soon the sight of your newly planted herbs or flowers makes your heart feel inexplicably lighter?

Perhaps you’re in hospital recovering from surgery, as I was only a little time ago. I regained consciousness in an advanced recovery unit, a dimly lit space with no windows where everything felt slightly surreal and too intense.

I was receiving the best possible care, yet I had a desperate sense of having been cut loose from my life, and even from my body, as it was monitored and medicated throughout the night. Who knows where things might go from here, I thought. Yet I almost didn’t care.

In the morning, I was wheeled away to a room on an upper floor. It was a space flooded with natural light and with a view of a wintry, cloudy sky and distant treetops.

When a friend arrived with a posy of flowers, I found myself smiling for the first time since leaving home. As well as the pleasure of her company, there was a surge of delight at the presence of flowers. Their soft colours soothed something in me that had been clutched tight in fear since my first glimpse of the stark, frankly terrifying operating theatre.

A history of healing

Perhaps now, more than ever, we could all use some green relief, as we deal with a world that seems to only grow more anxiety-inducing and uncertain.

In May, Australians will vote in what has been called “the cost-of-living election”. Housing prices (and homelessness) have soared, too, with one study putting the rise in housing value between March 2020 and February 2024 at 32.5%.

Elsewhere, war rages in Ukraine, Gaza, and other countries, and the world order is wobbling in the wake of the US elections – particularly this week, when Donald Trump’s tariffs sparked a stock market crash not seen since COVID (until he changed his mind yesterday and it recovered) and led to predictions of a recession.

What evidence is there that the natural world can have a healing effect?

In most cultures throughout history, medicine and botany have been closely entwined, and gardens have been associated with healing the body, mind, and spirit. From around the 4th century BCE, Greece had healing centres known as “asclepieia”, after the god of medicine, Asclepius.

In medieval Europe, monasteries kept medicinal gardens. In England, hospitals and asylums were set within landscaped grounds in the belief the tranquillity of the setting played an important role in lifting patients’ mood. Both male and female inmates of 19th-century asylums often worked in the gardens, in what was seen as a healing process administered by the place itself.

Inevitably, the creep of urbanisation saw the garden landscapes of many such institutions greatly reduced, yet the health benefits to patients of connecting with nature remains undiminished.

Flowers and healing

An explanation for the uplifting effect of those flowers in my hospital room may be found in numerous studies that have shown, post-surgery, patients in rooms with plants and flowers have shorter recovery times, require fewer analgesics, and experience lower levels of anxiety. Partly, it is a response to beauty.

As psychiatrist Sue Stuart-Smith writes in The Well Gardened Mind, the human response to beauty involves brain pathways “associated with our dopamine, serotonin, and endogenous opioid systems and damp down our fear and stress responses”. She continues: “Beauty calms and revitalises us at the same time.” We humans have an affinity for patterns and order, she writes. “The simple geometrics we find in nature are perhaps most concentrated and compelling in the beauty of a flower’s form.”

There has been a trend towards banning flowers from hospital wards, on health grounds. Reasons include a suspicion bacteria lurk in the flower water, as well as safety concerns around patients or nursing staff knocking over vases during night shifts.

Florence Nightingale, in her Notes on Nursing, commented on the beneficial effects of flowers on her patients. She added that they recovered more quickly if they could spend time outside, or at least had a room with adequate natural light. “It is a curious thing to observe how almost all patients lie with their faces turned to the light, exactly as plants always make their way towards the light.” Even if lying on a particular side caused pain, patients still preferred it, Nightingale noted – because “it is the side towards the window”.

Our compulsion to turn towards the natural world is known as “biophilia”. The term was first coined in the 1960s, by German–American social psychologist and psychoanalyst, Erich Fromm. He described it as “the passionate love of life and all that is alive”, speculating that our separation from nature brings about a level of unrecognised distress.

In the 1980s, biologist and ecologist Edward O. Wilson, in his book Biophilia, asserted that all humans share an affinity with the natural world. “The urge to affiliate with other forms of life is to some degree innate,” he wrote.

In hospital, as my body began its tentative recovery from the shock of surgery, I remembered a line popularly attributed to the French Impressionist painter, Claude Monet: “What I need most are flowers, always, and always.” Through his paintings, notably his studies of waterlilies, and the garden he established at Giverny, which welcomes visitors to the present day, Monet’s flowers continue to calm and revive us with their transcendent beauty.

Perhaps the simplest way to forge a connection with nature lies in our own suburban gardens, if we are lucky enough to have them. Aside from the pleasure of creating pleasing spaces, contact with the soil bacteria Mycobacterium vaccae has been shown to trigger the release of serotonin in the brain. Serotonin, a natural antidepressant, strengthens the immune system. An added bonus is that when we harvest edible plants, our brain releases dopamine, flushing our systems with a gentle rush of satisfaction and pleasure.

Regular doses of serotonin and dopamine were never more needed than during the pandemic, when lockdowns unleashed a sudden fervour for gardening.

In her book The Garden Against Time, Olivia Laing writes that “over the course of 2020, three million people in Britain began to garden for the first time, over half of them under forty-five”. And it wasn’t just in Britain, where garden centres ran out of plants and compost as people set to work transforming the spaces where they were confined.

Australia experienced a similar surge in interest, with the ABC reporting sales of herb and vegetable plants shot up 27%, joining toilet paper and pasta on the list of panic buys. In the United States, Laing writes, 18.3 million people started gardening, “many of them millennials”. American seed company W. Atlee Burpee “reported more sales in the first March of lockdown than at any other time in its 144-year history”.

Laing writes:

crouched on the threshold of unimaginable disaster, death toll soaring, no cure in sight – it was reassuring to see the evidence of time proceeding as it was meant to, seeds unfurling, buds breaking, daffodils pushing through the soil; a covenant of how the world should be and might again.

It is precisely this “evidence of time proceeding as it was meant to” that has the power to hold humans calmly in place. We may imagine we want more than this from life; despising dullness, we think we crave excitement and change. But given the option, few would choose to wake to an Orwellian “bright cold day in April” to find “the clocks were striking thirteen”, which is how it felt during those nightmarish early days of the COVID-19 crisis.

Life on earth does still feel somewhat bright and cold, its future somewhat bleak; it is as if Orwell’s dystopian vision is at last catching up with us.

Who would believe an activity so apparently humble as gardening could come to the rescue of millions of stressed and fearful people? Yet gardeners seem to know this instinctively.

Tending ourselves

In the book In Kiltumper: a Year in an Irish Garden, co-written with her husband, Niall Williams, Irish writer and gardener Christine Breen describes the ordeal of undergoing cancer treatment through the Irish healthcare system. Following an oncology appointment in Galway, the couple drives home towards west Clare, or as Christine puts it: “back to the garden, where there is safety”.

Christine’s husband Niall confirms that, although the medical community might dismiss the healing power of working in a garden as “airey-fairy”, in Christine’s case, even while weak from chemotherapy, “going about the flower beds, trying to do exactly the same work she had always done” meant continuity.

It represented “carrying on living, because that is one of the prime lessons any garden teaches you: the garden grows on”. He speculates that after many years together, garden and gardener become one: “when we tend it, we tend some part of ourselves”.

If we know this, we too often forget. Consequently, garden centres rarely top the list of most desirable destinations, and gardening has been traditionally represented as fussy and domestic. Weeding and mowing are seen as chores that, if possible, are to be avoided.

In her book Why Women Grow, Alice Vincent writes that gardening has “so many associations, of neatness and nicety; a prissiness that feels deeply removed […] from the sex and death and life on show in every growing thing.” She writes: “When we garden, we change how a small part of the world works.”

Doubtless, it was this sense of being able to change one’s world, of seizing control, that appealed to so many of us during the pandemic. And if we got our hands into the soil, we were rewarded with much-needed infusions of serotonin.

In literature, too, people suffering physically or mentally, or both, have often sought refuge or found solace in a garden.

For many readers, their first encounter with the transformative nature of gardening was Frances Hodgson Burnett’s classic children’s book, The Secret Garden. In it, a spoilt yet neglected child, Mary Lennox, is orphaned in India when her parents and their servants succumb to cholera. She is bundled off to Yorkshire, England, to a daunting atmosphere of secrecy and neglect at Misselthwaite Manor, into the care of an uncle she has never met. There, Mary soon discovers the key to a garden that has been locked for years following her aunt’s death.

In her efforts to restore life to the neglected garden, Mary herself is restored, gradually shedding the lonely, helpless persona of her Indian childhood. When she discovers the manor’s other tightly held secret – her sickly, bedridden cousin, Colin – Mary manages to get him, too, out of the house and into the garden. The outcome is healing for the children, and eventually for Mary’s grieving uncle.

Green prescriptions

For a real-life example of green relief, in The Well Gardened Mind, Sue Stuart-Smith describes how her grandfather – a submariner in the first world war – was taken prisoner during the Gallipoli campaign. After a series of brutal labour camps in Turkey, the last of them in a cement factory, he eventually escaped.

But after the long journey home he was so severely malnourished he was given only a few months to live. Crucial to regaining his health was the devoted nursing by his fiancée, followed by a year-long horticultural course set up to rehabilitate ex-servicemen.

A psychiatrist as well as a gardener, Stuart-Smith writes of the therapeutic effects of working with our hands in a protected space. She describes how gardening allows our inner and outer worlds “to coexist free from the pressures of everyday life”.

Gardens, she writes, are an “in-between space which can be a meeting place for our innermost, dream-infused selves and the real physical world”. In a garden, we are able to hear and process our own, sometimes turbulent, thoughts.

In 1986, after being diagnosed HIV positive, the English artist and filmmaker Derek Jarman retreated to the Kent coast near the nuclear power station at Dungeness. In The Garden Against Time, Olivia Laing writes that at Prospect Cottage, Jarman

began with stones, not plants: the grey flints he called dragon’s teeth, revealed by the tide on morning walks.

Gradually he established a garden in the inhospitable soil, seeing it as “a therapy and a pharmacopoeia” – and “a place of total absorption”.

It was this capacity to slow or stop time, as much as its wild and sportive beauty, that made it such a paradise-haunted place.

The pandemic spread waves of turbulence across the globe. In April 2021, as part of its post-COVID recovery plan, the government of the United Kingdom launched a two-year green social prescription pilot.

Project-managed by the National Health Service, the program worked across seven test sites: areas disproportionately affected by the pandemic. These included people living in deprived areas and people with mental health conditions, many of them from ethnic minority communities.

Over the course of the two-year program, more than 8,500 people were referred to a green social prescribing activity. Green networks were established in all seven test sites. Findings showed positive improvements in mental health and wellbeing – and green social prescribing is ongoing, proof of the program’s lasting impact.

In recent times, doctors in some countries are writing green prescriptions, rather than scripts for medication. And not just for mental health problems, but for physical conditions such as high blood pressure, diabetes and lung diseases.

In the late 1990s, New Zealand became one of the first countries where GPs used green prescriptions to encourage patients to increase their levels of physical activity. Japanese clinicians have been advocating “shinrin-yoku”, or forest bathing for decades. In Finland, with its long dark winters, five hours a month is regarded as a “minimum dose” of contact with nature.

Aside from the physical benefits, time spent in a garden can provide a mood boost for those of us who feel oppressed by calendars, and by clock time’s relentless march. In her 2018 memoir Life in the Garden, Penelope Lively writes:

To garden is to elide past, present and future; it is a defiance of time. You garden today for tomorrow, the garden mutates from season to season, always the same but always different.

Perhaps no group of people stands in greater need of time-defiance than those of us entering the final decades of our lives. Time is short, and we know it. But as now 92-year-old Lively wrote seven years ago: “A garden is never just now; it suggests yesterday and tomorrow; it does not allow time its steady progress.”

Gardening as defiance

My mother pottered in her garden until she was in her early 90s, pruning roses, pulling weeds, planting annuals and throwing down fertiliser. She’d wrestle her walker across the lawn to perch on its seat while she did the watering, before retreating to an armchair in the back room of her house, from where she could admire her achievements.

Gardening in extreme old age was, for her, an act of defiance – against time, and against her children, who nagged about the possibility of a fall and insisted she wear an emergency call button. It was a defiance, too, of the common view that old people should relinquish their homes with gardens and move into something more manageable.

On the face of it, not having a garden to maintain in old age makes perfect sense, but it may come at the expense of our human impulse to seek connection with living things, specifically those in the natural world. So ingrained is our instinct to connect with nature, it appears to survive even when other systems and connections have broken down.

A friend whose Alzheimer’s-afflicted husband is in residential care reports he is constantly finding odd containers, filling them with soil, and planting cuttings gathered from the care home’s garden. He crams them onto his windowsill, even planting in teacups when there is nothing else to hand.

Accustomed to gardening throughout his adult life, his impulse to work with living things persists in defiance of dementia. My friend reflects her mother used to do the same, only she would take pieces from the home’s fake indoor plants, then complain bitterly when they did not grow.

In the care facility my friend visits daily, women pick flowers in the grounds to decorate their walkers, and when there are no flowers they’ll use pictures of flowers cut from magazines. Cutting out paper flowers seems like the action of someone whose garden has been lost, but who still feels a powerful desire to connect with beauty and the natural world.

Imagined gardens

The theories of 20th-century historian Theodore Roszak, in his book The Voice of The Earth, founded the ecopsychology movement.

He believed “humans connect with nature through the ecological unconscious, which is the core of human identity”. Human nature, he wrote, is “densely embedded in the world we share with animal, vegetable, mineral”. He believed reconnecting with nature helps people become more aware of their connection to all living things.

So what are we to do if the garden has been lost?

The French writer Colette, whose books were full of botanical detail, did not cease gardening even when age and arthritis kept her bedridden. Rather than physical gardens, Colette roamed imagined gardens.

There is nothing so terrible about not having a garden any more. The worrying thing would be if the future garden, whose reality is of no importance, were beyond my grasp. But it is not.

Colette planned her “tomorrow garden”, specifying pansies “with wide faces, beards, and moustaches – that look like Henry VIII”. Nothing is too difficult for the imaginative gardener. “An arbour? Naturally I shall have an arbour. I’m not down to my last arbour yet.”

Imagining a garden may seem fanciful. Yet it is less so if considered in the context of embodied semantics – a process where brain connectivity during a thought-about action mirrors the connectivity that occurs during the actual action. (For example, thinking about running or swimming can trigger some of the same neural connections as the physical actions.)

It’s been shown that habitual negativity rewires the brain. Ultimately, it damages it by shrinking the hippocampus: one of the main areas destroyed by Alzheimer’s disease.

But gardens, with their earth-centred sense of time and season, are optimistic places. Watching things grow, deadheading spent flowers and saving seed for the return of spring, are just some of the forward-looking aspects of gardening and perhaps it works as well if the plants and flowers are imagined.

It is logical to go further and ask whether a positive habit, such as imagining a garden, has the potential to help rewire one’s brain in a good way. Imagined gardening is really a form of self-guided imagery, a practice with many applications in the treatment of pain, stress, anxiety and depression.

As we age, ideally we would find ways of getting our hands into the healing soil. Suggestions for gardening in old age, and extreme old age, include introducing raised beds to reduce bending, or working with potted plants.

A friend in her late 70s, with an enviable garden, swears by her Garden Group. Around a dozen friends come together for working bees in each other’s gardens. “You can get a huge amount done in an hour-and-a-half,” she says. Afterwards, they share morning tea – so it is a social as well as practical endeavour. My own best tip is to garden little and often. Committing to half an hour a day, or even 15 minutes, adds up nicely over the course of a week.

American poet May Sarton wrote of gardening as “an instrument of grace”. She regarded the natural world as the great teacher. From the Benedictine Monastery of Saint Paul de Mausole at Saint-Remy-de-Provence, Vincent Van Gogh wrote to his mother: “But for one’s health, as you say, it is very necessary to work in the garden and see the flowers growing.”

Like Monet, Van Gogh needed flowers. We all do. It’s just that many of us forget this during the push and pull of daily life. And in forgetting, we lose touch with our biophilic natures.

Carol Lefevre, Visiting Research Fellow, Department of English and Creative Writing, University of Adelaide

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

The Coalition has announced it would, if elected to government, weaken a scheme aimed at cutting car emissions.

The scheme, known as the New Vehicle Efficiency Standard (NVES), was introduced by the Albanese government and was due to take effect in July. It involved issuing penalties to automakers that breach an emissions ceiling on their total new car sales.

The new Coalition plan, announced this week, would see such penalties abolished.

But the penalties are crucial. Without penalties, automakers have limited incentive to supply fuel efficient, low or zero-CO₂ emitting vehicles to the Australian market.

If this plan became government policy, it would make Australia an international outlier – and put at risk Australia’s ability to meet its obligations under the Paris climate agreement.

An international outlier

More than 85% of the international car market is covered by fuel efficiency standards.

Without a robust New Vehicle Efficiency Standard scheme, complete with penalties for automakers that break the rules, Australia would join Russia in the tiny minority of developed countries without strong fuel efficiency standards for new vehicles.

Abolishing the penalties embedded in the scheme also risks making Australia the world’s dumping ground for inefficient vehicles.

That’s because the penalties embedded in the scheme are there to incentivise automakers to sell more efficient vehicles in Australia.

The current scheme, as it is, is not particularly punitive. Automakers that breach their cap of emissions are given up to two years to fix their mistakes before being issued with a financial penalty.

Weakening the scheme won’t help make it easier for Australians to buy fuel-efficient cars.

Decarbonising Australian roads

The 2015 Paris Agreement, to which Australia is a signatory, requires developed nations to decarbonise their transport by as much as 80% by 2050.

Carbon emissions from Australian transport accounts for 21.1% of the nation’s emissions (to June 2023).

It represents the third largest source of greenhouse gas emissions in Australia.

Without measures aimed at making cars more fuel efficient, Australia’s CO₂ emissions will continue to rise. It will be harder to meet our commitments under the Paris Agreement.

It’s regulation, not a tax

The Coalition, which is hoping to pick up votes in outer-ring suburbs, has called the penalties embedded in the New Vehicle Efficiency Standard scheme a “car tax”.

Liberal leader Peter Dutton said this week:

This is a tax on families who need a reliable car and small businesses trying to grow. Instead of making life easier, Labor is making it harder and more expensive […] We want cleaner, cheaper cars on Australian roads as we head towards net zero by 2050, but forcing unfair penalties on carmakers and consumers is not the answer.

But these penalties are not a tax; they are a form of regulation. Automakers that meet the rules wouldn’t have to pay penalties, under the current scheme.

If the goal is to reduce people’s hip-pocket pain at the bowser, the focus should be on ensuring Australians can buy fuel-efficient vehicles.

That means incentivising automakers to bring fuel-efficient vehicles to the Australian market. It also means avoiding any policy that encourages carmakers to see Australia as a dumping ground for gas-guzzling vehicles.

Anna Mortimore, Lecturer, Griffith Business School, Griffith University

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

Swim along the edge of a coral reef and you’ll often see schools of sleek, torpedo-shaped fishes gliding through the currents, feeding on tiny plankton from the water column.

For decades, scientists assumed these plankton-feeding fishes – or planktivores – shared specialised traits: forked tails and streamlined body forms for speed, large eyes for spotting small prey, and small extendable jaws for suction-feeding.

But our new study, published in Reviews in Fish Biology and Fisheries, shows there is more nuance to this story. We found plankton-feeding fishes don’t follow a single uniform design. To our surprise, they display the widest range of body forms of any feeding group among reef fishes.

Evolving similar traits

A core idea in evolutionary theory since Charles Darwin is that species facing the same problem often evolve similar traits. This is a process known as convergent evolution. It explains the pattern we see among dolphins, sharks, and tunas – distantly related lineages unified in their streamlined body shape used for fast swimming.

We set out to test whether the same phenomenon was true for plankton-feeding reef fishes. Planktivores are an ideal group to study in this case.

For one, plankton-feeding is the most common feeding group among reef fishes – giving us many distantly related species to compare. For another, they all share the same challenge of having to spot and suck out small prey from the water column.

So we asked: do plankton-feeding fishes have a distinct body shape? And do patterns of convergence hold true across a diversity of plankton-feeding reef fishes?

The broadest range of body shapes

To answer these questions, we collected shape data from nearly 300 species of reef fishes from 12 globally distributed families – including surgeonfishes, wrasses, snappers, and damselfishes. We measured 15 feeding, swimming, and vision-related traits such as jaw length, tail shape, and pupil size.

By combining these measurements with evolutionary trees, we tested whether plankton-feeding fishes were distinct in shape to their counterparts.

But what we found surprised us. Plankton-feeding fishes aren’t converging on a specific body shape. It is quite the opposite – they display the broadest range of body shapes among reef fishes. Some species – such as the schooling fusiliers – truly fit the typical “plankton-feeding” model. They exhibit traits such as a forked tail, torpedo-shaped body, large eyes, and small, extendable jaws.

But most others break the mould entirely. For example, tiny gobies – just three centimetres long – cling onto whip corals and adopt a sit-and-wait approach for plankton to pass by.

Other deep-bodied damselfishes depart a small distance from their coral hosts to feed on plankton. But how can we explain this diversity of planktivore body shapes?

An innate ability

The answer lies in the vast diversity of their behaviours and environments.

Their body shape isn’t dictated by plankton-feeding alone – it’s shaped by where, when and how they feed. Some planktivores feed during the day, others at night. Some inhabit deep reefs, others are mere metres below the surface of the water. Some are restricted to rubble slopes while others prefer the reef edge. Some even target specific sizes and types of the plankton itself.

This diversity in activity patterns, habitat use, and prey preferences places different demands on their body forms – explaining why we see such a range of shapes and sizes among plankton-feeding fishes.

Even species we don’t typically think of as planktivores will feed on plankton when the chance arises. Just last year, while on Lizard Island, we watched yellowmask surgeonfishes – normally feeding on algae and detritus – swimming high above the reef, targeting plankton.

Perhaps this flexibility shouldn’t surprise us. After all, all reef fishes begin their lives as plankton feeders, floating in the open ocean before settling on the reef. The ability for fishes to feed on plankton is likely innate.

Challenging a longstanding assumption

Our findings challenge the longstanding assumption that planktivorous reef fishes are distinct in form and are converging towards an optimum body type.

Instead, plankton-feeding is a highly accessible and flexible feeding strategy on coral reefs – available to fishes of many shapes, sizes, evolutionary histories, and even different feeding groups.

This has important implications for how we think about reef fish ecology and evolution. It shows that broad feeding categories like “planktivore” can mask the diversity of other behavioural and ecological traits.

Rather than converging on a single solution, reef fishes highlight something different: that there is more than one way to be a planktivore.

Isabelle Ng, PhD candidate, College of Science and Engineering, James Cook University and Alexandre Siqueira, Vice-Chancellor's Research Fellow, School of Science, Edith Cowan University

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

Australia’s relationship with its regional neighbours could be in doubt under a Coalition government after two Pacific leaders challenged Opposition Leader Peter Dutton over his weak climate stance.

This week, Palau’s president Surangel Whipps Jr suggested a 2015 gaffe by Dutton, in which he joked about rising seas lapping at the door of Pacific islanders, had not been forgotten. Speaking at a clean energy conference in Sydney, Whipps said the Pacific’s plight was “not a metaphor or a punchline. It’s our fear and reality.”

And Tuvalu’s Climate Change Minister, Maina Talia, this month criticised Dutton for suggesting a joint Australia–Pacific bid to host global climate talks next year was “madness”. Talia said Dutton’s comments caused Pacific leaders to “question the nature of our friendship” with Australia.

Both Labor and Coalition governments have worked hard this decade to cement Australia as a security partner of choice for Pacific nations, as China seeks to expand its influence. Australia’s next government must continue this work by signalling an unwavering commitment to strong climate action.

What are the major parties offering on climate policy?

Worsening climate change – with associated sea-level rise and other harms – is the greatest threat to Pacific island nations.

Pacific leaders have long criticised Australia for its climate policy shortcomings, including its continued reliance on fossil fuels. As Palau’s president Whipps told the ABC this week:

We are urging Australia – and whoever forms the next government – to take the next steps and stop approving new fossil fuel projects and accelerate the phase-out of coal and gas.

The Labor government has not agreed to the phase-out. But it has sought to improve Pacific ties through more ambitious climate action.

In 2022, it introduced a stronger emissions-reduction target – a 43% cut this decade, based on 2005 levels. The same year, Prime Minister Anthony Albanese joined Pacific leaders to declare a climate emergency.

In 2023, Australia signed a climate migration deal with Tuvalu. It also prevents Tuvalu from pursuing a security deal with China.

A Coalition government would review Australia’s 43% cut to emissions. It would also expand gas production, and slow the shift to renewables while building seven nuclear reactors. Dutton is also considering weakening Australia’s signature climate policy, the safeguard mechanism, which aims to reduce industry emissions.

And last month, Dutton suggested the Coalition would ditch the Australia–Pacific bid to host the next United Nations climate summit, known as COP31.

How will this go down in the Pacific?

Australia has dramatically stepped up engagement with Pacific island countries in recent years. This has been guided by the foreign policy goal of integrating Pacific countries into Australia’s economy and security institutions.

But Pacific island leaders also expect Australia – the largest member of the Pacific Islands Forum – to seriously tackle the climate crisis. Should Australia fail on this measure, securing our place in the region during a time of growing strategic competition will become increasingly difficult.

Pacific leaders welcomed Australia’s plans to host the COP31 climate talks and agreed to work with this nation on the joint bid. If Dutton wins power and abandons the COP31 push, he could face a frosty reception when he meets with Pacific island leaders.

Palau, in particular, could embarrass Dutton on the global stage. It will host the Pacific Islands Forum meeting next year, weeks before the COP31 talks. This year, Palau also takes over as chair of the Alliance of Small Island States, an important negotiating bloc in global climate talks.

Countering China’s influence

Australia’s leadership in the Pacific is considered key to our national defence and security. But China’s growing power in the Pacific has weakened Australia’s standing.

In 2022, for example, Solomon Islands signed a security deal with China to allow naval vessels to be based there – effectively allowing a Chinese military base on Australia’s doorstep. As recently as February this year, the Cook Islands signed a series of agreements with China to enhance cooperation.

At the same time, the Trump administration has all but abandoned the United States’ overseas aid program. This leaves Australia with even more work to counter China’s creep into the region.

In last month’s federal budget, Labor redirected aid money to the Pacific to counteract Trump’s cuts. However, Liberal backbenchers reportedly fear Dutton would cut the foreign aid budget and warn a reduction in Pacific aid would strengthen Beijing’s hand.

Climate policy is key to Australia-Pacific goodwill

Australia’s past failures on climate policy have hurt our standing in the Pacific – a point conceded by senior Coalition figure Simon Birmingham.

A Coalition government is likely to continue some diplomatic measures initiated by the Albanese government, such as security agreements with Tuvalu and Nauru, and negotiating a new defence treaty with Papua New Guinea.

But the depth of feeling among Pacific leaders on climate action cannot be overstated. As global geopolitical tensions sharpen, Australia’s next moves on climate policy will be vital to the future of our Pacific relationship.

Wesley Morgan, Research Associate, Institute for Climate Risk and Response, UNSW Sydney

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

Coral reefs are much more than just a pretty place to visit. They are among the world’s richest ecosystems, hosting about a third of all marine species.

These reefs also directly benefit more than a billion people, providing livelihoods and food security, as well as protection from storms and coastal erosion.

Without coral reefs, the world would be a much poorer place. So when corals die or become damaged, many people try to restore them. But the enormity of the task is growing as the climate keeps warming.

In our new research, we examined the full extent of existing coral restoration projects worldwide. We looked at what drives their success or failure, and how much it would actually cost to restore what’s already been lost. Restoring the reefs we’ve already lost around the world could cost up to A$26 trillion.

Global losses

Sadly, coral reefs are suffering all over the world. Global warming and marine heatwaves are the main culprits. But overfishing and pollution make matters worse.

When sea temperatures climb above the seasonal average for sustained periods, corals can become bleached. They lose colour as they expel their symbiotic algae when stressed, revealing the white skeleton underneath. Severe bleaching can kill coral.

Coral bleaching and mass coral deaths are now commonplace. Last month, a massive warm-water plume bleached large areas of Ningaloo Reef on Australia’s northwest coast just as large sections of the northern Great Barrier Reef were bleaching on the northeast coast.

Since early 2023, mass coral bleaching has occurred in throughout the tropics and parts of the Indian Ocean.

Over the past 40 years, the extent of coral reefs has halved. As climate change continues, bleaching events and coral deaths will become more common. More than 90% of coral reefs are at risk of long-term degradation by the end of the century.

Direct intervention

Coral reef restoration can take many forms, including removing coral-eating species such as parrot fish, transferring coral spawn, or even manipulating the local community of microbes to improve coral survival.

But by far the most common type of restoration is “coral gardening”, where coral fragments grown in nurseries are transplanted back to the reef.

The problem is scale. Coral restoration can only be done successfully at a small scale. Most projects only operate over several hundred or a few thousand square metres. Compare that with nearly 12,000 square km of loss and degradation between 2009 and 2018. Restoration projects come nowhere near the scale needed to offset losses from climate change and other threats.

Sky-high costs

Coral restoration is expensive, ranging from around $10,000 to $226 million per hectare. The wide range reflects the variable costs of different techniques used, ease of access, and cost of labour. For example, coral gardening (coral fragments grown in nurseries transplanted back to the reef) is relatively cheap (median cost $558,000 per hectare) compared with seeding coral larvae (median $830,000 per hectare). Building artificial reefs can cost up to $226 million per hectare.

We estimated it would cost more than $1.6 billion to restore just 10% of degraded coral areas globally. This is using the lowest cost per hectare and assuming all restoration projects are successful.

Even our conservative estimate is four times more than the total investment in coral restoration over the past decade ($410 million).

But it’s reasonable to use the highest cost per hectare, given high failure rates, the need to use several techniques at the same site, and the great expense of working on remote reefs. Restoring 10% of degraded coral areas globally, at $226 million a hectare, would cost more than $26 trillion – almost ten times Australia’s annual GDP.

It is therefore financially impossible to tackle the ongoing loss of coral reefs with restoration, even if local projects can still provide some benefits.

Location, location, location

Our research also looked at what drives the choice of restoration sites. We found it depends mostly on how close a reef is to human settlements.

By itself, this isn’t necessarily a bad thing. But we also found restoration actions were more likely to occur in reefs already degraded by human activity and with fewer coral species.

This means we’re not necessarily targeting sites where restoration is most likely to succeed, or of greatest ecological importance.

Another limitation is coral gardening normally involves only a few coral species – the easiest to rear and transplant. While this can still increase coral cover, it does not restore coral diversity to the extent necessary for healthy, resilient ecosystems.

Measuring ‘success’

Another sad reality is that more than a third of all coral restoration efforts fail. The reasons why can include poor planning, unproven technologies, insufficient monitoring, and subsequent heatwaves.

Unfortunately, there’s no standard way to collect data or report on restoration projects. This makes it difficult – or impossible – to identify conditions leading to success, and reduces the pace of improvement.

Succeed now, fail later

Most coral transplants are monitored for less than 18 months. Even if they survive that period, there’s no guarantee they will last longer. The long-term success rate is unknown.

When we examined the likelihood of extreme heat events immediately following restoration and in coming decades, we found most restored sites had already experienced severe bleaching shortly after restoration. It will be difficult to find locations that will be spared from future global warming.

No substitute for climate action

Coral restoration has the potential to be a valuable tool in certain circumstances: when it promotes community engagement and addresses local needs. But it is not yet – and might never be – feasible to scale up sufficiently to have meaningful long-term positive effects on coral reef ecosystems.

This reality check should stimulate constructive debate about when and where restoration is worthwhile. Without stemming the pace and magnitude of climate change, we have little power to save coral reefs from massive losses over the coming century and beyond.

Other conservation approaches such as establishing, maintaining and enforcing marine protected areas, and improving water quality, could improve the chance a coral restoration project will work. These efforts could also support local human communities with incentives for conservation.

Reinforcing complementary strategies could therefore bolster ecosystem resilience, extending the reach and success of coral restoration projects.

Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Node Leader in the ARC Centre of Excellence for Indigenous and Environmental Histories and Futures, Flinders University; Clelia Mulà, PhD student in Marine Ecology, The University of Western Australia, and Giovanni Strona, Doctoral program supervisor, University of Helsinki

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

The details of a new visa enabling Tuvaluan citizens to permanently migrate to Australia were released this week.

The visa was created as part of a bilateral treaty Australia and Tuvalu signed in late 2023, which aims to protect the two countries’ shared interests in security, prosperity and stability, especially given the “existential threat posed by climate change”.

The Australia–Tuvalu Falepili Union, as it is known, is the world’s first bilateral agreement to create a special visa like this in the context of climate change.

Here’s what we know so far about why this special visa exists and how it will work.

Why is this migration avenue important?

The impacts of climate change are already contributing to displacement and migration around the world.

As a low-lying atoll nation, Tuvalu is particularly exposed to rising sea levels, storm surges and coastal erosion.

As Pacific leaders declared in a world-first regional framework on climate mobility in 2023, rights-based migration can “help people to move safely and on their own terms in the context of climate change.”

And enhanced migration opportunities have clearly made a huge difference to development challenges in the Pacific, allowing people to access education and work and send money back home.

As international development expert Professor Stephen Howes put it,

Countries with greater migration opportunities in the Pacific generally do better.

While Australia has a history of labour mobility schemes for Pacific peoples, this won’t provide opportunities for everyone.

Despite perennial calls for migration or relocation opportunities in the face of climate change, this is the first Australian visa to respond.

How does the new visa work?

The visa will enable up to 280 people from Tuvalu to move to Australia each year.

On arrival in Australia, visa holders will receive, among other things, immediate access to:

• education (at the same subsidisation as Australian citizens)
• Medicare
• the National Disability Insurance Scheme (NDIS)
• family tax benefit
• childcare subsidy
• youth allowance.

They will also have “freedom for unlimited travel” to and from Australia.

This is rare. Normally, unlimited travel is capped at five years.

According to some experts, these arrangements now mean Tuvalu has the “second closest migration relationship with Australia after New Zealand”.

Reading the fine print

The technical name of the visa is Subclass 192 (Pacific Engagement).

The details of the visa, released this week, reveal some curiosities.

First, it has been incorporated into the existing Pacific Engagement Visa category (subclass 192) rather than designed as a standalone visa.

Presumably, this was a pragmatic decision to expedite its creation and overcome the significant costs of establishing a wholly new visa category.

But unlike the Pacific Engagement Visa – a different, earlier visa, which is contingent on applicants having a job offer in Australia – this new visa is not employment-dependent.

Secondly, the new visa does not specifically mention Tuvalu.

This would make it simpler to extend it to other Pacific countries in the future.

Who can apply, and how?

To apply, eligible people must first register their interest for the visa online. Then, they must be selected through a random computer ballot to apply.

The primary applicant must:

• be at least 18 years of age
• hold a Tuvaluan passport, and
• have been born in Tuvalu – or had a parent or a grandparent born there.

People with New Zealand citizenship cannot apply. Nor can anyone whose Tuvaluan citizenship was obtained through investment in the country.

This indicates the underlying humanitarian nature of the visa; people with comparable opportunities in New Zealand or elsewhere are ineligible to apply for it.

Applicants must also satisfy certain health and character requirements.

Strikingly, the visa is open to those “with disabilities, special needs and chronic health conditions”. This is often a bar to acquiring an Australian visa.

And the new visa isn’t contingent on people showing they face risks from the adverse impacts of climate change and disasters, even though climate change formed the backdrop to the scheme’s creation.

Settlement support is crucial

With the first visa holders expected to arrive later this year, questions remain about how well supported they will be.

The Explanatory Memorandum to the treaty says:

Australia would provide support for applicants to find work and to the growing Tuvaluan diaspora in Australia to maintain connection to culture and improve settlement outcomes.

That’s promising, but it’s not yet clear how this will be done.

A heavy burden often falls on diaspora communities to assist newcomers.

For this scheme to work, there must be government investment over the immediate and longer-term to give people the best prospects of thriving.

Drawing on experiences from refugee settlement, and from comparative experiences in New Zealand with respect to Pacific communities, will be instructive.

Extensive and ongoing community consultation is also needed with Tuvalu and with the Tuvalu diaspora in Australia. This includes involving these communities in reviewing the scheme over time.

Jane McAdam, Scientia Professor and ARC Laureate Fellow, Kaldor Centre for International Refugee Law, UNSW Sydney

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

Over the weekend, Labor promised to subsidise home batteries by 30%. This would save about A$4,000 per household up front for an average battery. The scheme has a goal of one million batteries by 2030, costing an estimated $2.3 billion.

The promise was received broadly favourably as a measure to help with cost of living pressures and encourage the broader shift to clean energy. Labor’s policy has some similarity to an earlier Greens pledge. Last month, the Coalition hinted it was working on its own home battery plan. Opposition leader Peter Dutton has attacked Labor’s plan, claiming the subsidies would benefit the rich.

Dutton makes a good point. Upfront subsidies have to be well targeted. If they’re not, they could easily go to wealthier households and leave poorer ones behind.

To fix it, Labor should start with lower subsidies – and means test them.

What’s the fuss about home batteries?

Homes with batteries can use stored solar energy instead of grid energy, or charge from the grid when power is cheap and use it when grid power is expensive. They can reduce power bills by around $1,000 a year.

Over 300,000 Australian households already have a home battery. Uptake was already accelerating in Australia and overseas, as battery prices fall and power prices climb.

If this policy leads to 1 million batteries by 2030 as Labor hopes, they would boost grid stability, reduce demand for expensive peak power from gas generators and even avoid the need to build some new transmission lines. These would be positive – if the benefits can be spread fairly.

Subsidies must be properly targeted

Caution is necessary, because we have seen very similar issues with previous schemes.

When solar panels were expensive in the 2000s, many state governments offered subsidies to encourage more households to put them on their roofs. On one level, this worked well – one third of all Australian households now have solar. But on another, it failed – richer households took up solar subsidies much more than poorer, as my research has shown. As solar prices have fallen, this imbalance has partly been corrected.

Home batteries are now in a similar situation. Installing an average sized home battery of between 5 and 10 kilowatt hours can cost less than $10,000, without the proposed federal subsidy. But this upfront cost means it’s currently largely wealthy households doing it, as I have shown in other research.

If Labor’s policy isn’t properly targeted, wealthier households are more likely to take it up. This is because they can more easily afford to spend the remaining cost. Studies on electric and other vehicle subsidies in the United States show at least half of the subsidies went to people who would have bought the vehicle regardless. That’s good for wealthy households, but unfair to others.

Targeting has advantages for governments, too. Proper targeting would reduce the cost to the public purse.

So who should be eligible?

Wealthier households are likely to be able to afford home batteries without the subsidy – especially as costs fall.

The cost of living crisis has hit less wealthy households hardest. A home battery policy should focus heavily on giving these households a way to reduce their power bills.

How can governments do this? Largely by means-testing. To qualify for the subsidy, households should have to detail their financial assets.

To begin with, a policy like this should only be eligible for households outside the top 25% for wealth.

What about the 31% of Australians who rent their homes? This diverse group requires careful thought.

Governments may have to offer extra incentives to encourage landlords to install home batteries. The solar roll-out shows landlords do benefit, as they can charge slightly higher rent for properties with solar.

How much should subsidies be?

Labor’s election offering of a 30% subsidy is too generous.

While home batteries can cost more than $10,000, cheaper battery options are now available and state incentive schemes are also emerging. Western Australia, for instance, will have its own generous battery subsidy scheme running before July 1.

Some households might be able to get subsidies at both state and national levels, which would cover most of the cost of a smaller battery.

When governments offer high subsidies at the start of a new scheme, there’s a real risk of a cost blowout.

To avoid this, governments should begin with the lowest subsidy which still encourages household investment. If low subsidies lead to low uptake, the government could then raise subsidies after an annual review.

Another option is to vary how much the subsidy is based on household wealth. Lower wealth households get higher subsidies (say $2,500) while higher wealth households get a much lower subsidy (say $500).

Governments could even consider equitable reverse auctions, where households with similar wealth compete for subsidies. Governments can then choose lower bids in the interest of cost-effectiveness.

At present, Labor’s policy would give higher subsidies for larger batteries. This isn’t ideal. On solar, there’s a lack of evidence higher subsidies lead to larger solar systems, while households with more wealth tend to get larger solar systems.

Good start, improvement needed

Labor’s home battery policy has been welcomed by many in the energy sector. But as it stands, we cannot be sure it will fairly share the benefits of home batteries.

If Labor or the Coalition does offer a well-targeted home battery policy, it would be world leading. Over time, it would directly help with the rising cost of living and ensure less wealthy households benefit.

Rohan Best, Senior Lecturer, Department of Economics, Macquarie University

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

As climate change wreaks havoc with the world’s oceans, future production of fish, crustaceans and other aquatic organisms is under threat.

Our new research shows how this disturbance will play out for Australia’s prawn industry, which is concentrated in Queensland. We found by 2100, sea level rise threatens to flood 98% of the state’s approved prawn areas.

The problem is not confined to prawns – Queensland barramundi farming is also at risk from sea-level rise. Climate change also poses challenges for other major seafood industries in Australia, including salmon in Tasmania.

Australian seafood is vital to our culture and diets, and the national economy. We must take steps now to ensure the aquaculture industry thrives in a warmer world.

Spotlight on Queensland prawns

Aquaculture refers to breeding, rearing and harvesting fish, crustaceans, algae and other organisms in water. Australia’s aquaculture industry is expected to be worth A$2.2 billion by 2028–29.

Aquaculture can involve a variety of methods, from ponds and sea cages to indoor tank systems and even giant ships.

Aquaculture is one of Queensland’s fastest-growing primary industries – partly due to burgeoning production in prawn farming.

Queensland is also expected to experience a 0.8m sea-level rise by 2100, under a high-emissions scenario. Our research investigated how this could affect the state’s aquaculture industry.

We did this by examining existing data on coastal inundation and erosion from sea-level rise, combined with data on current and future aquaculture production areas.

We found 43% of sites where aquaculture production is currently occurring are at risk from sea-level rise. Prawn farming is the most vulnerable.

About 98% of areas approved for prawn farming in Queensland are expected to be inundated by seawater by 2100. The risk includes 88% of areas currently producing prawns. Prawns are grown in large ponds on land near the coast with access to saltwater, which makes them particularly vulnerable to inundation. Annual prawn production losses due to sea-level rise could reach up to A$127.6 million by century’s end.

Inundation and coastal erosion can cause breaches in pond walls compromising their structural integrity. These risks may be amplified when sea-level rise coincides with coastal flooding. Rising seas can also increase salinity in surrounding soils and groundwater, further affecting ponds. Other aquaculture infrastructure, such as hatcheries, buildings, and roads, may also be disrupted.

The Gold Coast region – a prawn production hub – is particularly vulnerable. Damage caused by ex-Tropical Cyclone Alfred highlights the vulnerability of coastal infrastructure to extreme weather. This will only worsen as the planet warms.

Queensland barramundi farms also face a serious threat. Some 44% of areas producing barramundi are likely to be exposed to inundation, causing up to A$22.6 million in annual production losses. Meanwhile, two of Queensland’s designated “Aquaculture Development Areas” – regions earmarked by the state government for industry expansion – may be unsuitable due to future sea levels. Both are located in the Hinchinbrook Shire Council area.

Beyond rising seas

Globally and in Australia, climate change is posing myriad challenges to seafood farmers.

Rising water temperatures stress animals such as salmon, lowering oxygen levels which slows growth rates and increases their risk of disease. Such depletion is a particular concern in already low-oxygen environments, such as Tasmania’s Macquarie Harbour.

Ocean heatwaves can cause mass fish deaths and devastate production. In Tasmania in February, more than 5,500 tonnes of dead fish were dumped at southern Tasmanian waste facilities – a problem linked to warmer water temperatures.

Dead and decomposing fish can further alter oxygen levels in water, spread disease to wild populations and attract scavengers. In the Tasmanian case, fish remains washed up on public beaches, angering the public and leading to calls for greater industry regulation.

Extreme weather further complicates aquaculture operations. Storms, flooding and abnormal rain patterns can affect water salinity which impacts species growth and survival. They can also damage vital infrastructure, which may allow animals to escape.

This occurred in 2022, when repeated flooding and disease outbreaks on oyster farms in New South Wales led to complete stock losses, prolonged farm closures and workers being laid off.

Surviving a warmer future

Not all aquaculture operations will suffer under climate change. Warming waters can lead to longer growing seasons in temperate regions. It can also expand suitable habitat for tropical species such as tilapia, mussels and oysters. Regions previously inhospitable to aquaculture may become viable production zones.

For the countries and producers that are expected to suffer, those that plan for and adapt to climate shifts can minimise losses.

Key steps industry and government can take include:

• planning farms in lower-risk areas and relocating vulnerable sites

• implementing climate-resilient infrastructure and restoring coastal ecosystems near farms to buffer against climate impacts

• expanding to include diverse species and selectively breeding stock that can tolerate the changing conditions

• strategic government policies and planning, financial incentives, and investment in resilient infrastructure to help the industry stay ahead of climate risks.

With the right strategies, Australia’s aquaculture industry can adapt to a changing climate and continue to contribute to food security and community wellbeing.

Caitie Kuempel, Lecturer, School of Environment and Science, Griffith University and Marina Christofidis, PhD HDR Student & Water Infrastructure Analyst, Griffith University

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

Visitors to Australia are often shocked at having to declare an apple or wooden item under our biosecurity policies. Biosecurity policies are used to keep out pest species and diseases. But they’re expensive to uphold and people can question their worth.

The good news is, they work – and Antarctica’s strict biosecurity policies prove it.

Under the web of agreements governing Antarctica, cargo must be checked for any sign of plants, seeds, insects and rodents. Visitors must ensure the items they bring are clean.

In our new research, we analysed a century of data on how many species have been introduced to the icy continent and surrounding sub-Antarctic islands.

Though there’s little human presence here, many species have been introduced and several have established – including rodents, aphids, and weedy plants – in a surprisingly short time. But across most sub-Antarctic islands, we found the rate of introduced species has remained steady, or slowed, after biosecurity policies were introduced, even as more humans arrived.

The exception was the Antarctic continent itself, where species introductions are increasing. This is likely due to surging visitor numbers and inconsistent biosecurity efforts between different nations and tourist operators.

Our work shows biosecurity policies work – if they’re followed.

Biosecurity in the cold

Antartica and sub-Antarctic islands such as Heard and McDonald Islands have an exceptional richness of species. Wandering albatrosses and emperor penguins live nowhere else. Some islands are home to meadows of megaherbs.

Unfortunately, introduced species have had dramatic effects. Mice eat albatrosses alive. Midges entirely change the functioning of terrestrial systems. Weedy plants outcompete and displace unusual plants on several islands.

Antarctic environments are particularly susceptible to introduced species. New species tend to have faster life cycles and are more tolerant of disturbance. Most indigenous species evolved without predators or competitors.

As the climate heats up, introduced species get a boost. Warmer conditions make it easier for them to get their first foothold, and they do better with warmer climates than do the indigenous species.

These vulnerabilities are why nations responsible for sub-Antarctic islands and those who jointly govern Antarctica through the Antarctic Treaty put strict biosecurity protocols in place from the 1990s onwards.

These policies ban the deliberate introduction of new species and specify the measures visitors and cargo have to undergo to reduce the chance of new species being introduced accidentally.

These protocols include cleaning equipment, clothing and cargo. In many cases, these policies also require eradication of any potentially damaging species if found.

Is it worth it?

All this takes time and money. To do it properly requires many hours of inspections and specific facilities, among other things. Ongoing research is also needed, to ensure the policies keep working.

But eradication of species once established is often even more expensive. Costs are rising globally. Invasive species have cost Australia at least A$390 billion since the 1960s. Eradicating introduced rabbits, rats and mice from Australia’s Macquarie Island cost about A$25 million.

So, are our biosecurity efforts worth the cost?

Assessing the effectiveness of biosecurity policies is rare because it is difficult. To properly gauge effectiveness, you need data from before and after the policy came in. It’s also hard to pinpoint when a species made the jump to the cold; it’s harder to spot one new plant than a thriving population years after the first seeds took root.

We believe our work solves these problems. We collected data on species arrivals across the Antarctic region and corrected for biases using new mathematical approaches that account for differences in survey effort over time.

Most species introductions now happen by accident. Because introductions are closely tied to the numbers of visitors, we expected more species would arrive as visitor numbers grew. But on most sub-Antarctic islands, that didn’t happen. Species arrived at the same rate or more slowly than expected, even as more visitors came.

In other words, the policies are working.

Why is Antarctica the exception?

Since 1998, biosecurity policies for the Antarctic continent haven’t managed to slow the rates of introductions.

Newly introduced species are largely being found on the Antarctic Peninsula, where most tourists and scientists go. The peninsula has the mildest climate of the whole continent and is where Antarctica’s native flowering plants are found, as well as mosses, lichens and fungi.

The new arrivals include annual bluegrass which displaces native plants. Also arriving are invertebrates, such as midges and springtails which can alter how nutrients are cycled in soil and shift other ecosystem functions.

It’s not fully clear why biosecurity policies aren’t working as well on the continent as for the islands. Likely causes include inconsistencies in how biosecurity is policed by different nations, a rapidly warming climate and very rapidly growing numbers of people to the peninsula.

What does this mean for the world?

Introduced species are one of the largest environmental and economic challenges we face, according to an authoritative recent assessment.

This may seem surprising. But the unchecked impact of species such as red fire ants, varroa mite and feral pigs cost Australian farmers billions each year. Prevention is usually better – and cheaper – than the cure.

What our research shows is that biosecurity policies actually work to protect the environment and are likely to be cheaper than the cost of control or eradication. Introduced species now cost the global economy an estimated $423 billion annually.

Society and decision-makers can see environmental regulations as a cost without a benefit. Being able to show the real advantages of these regulations is vital.

Rachel Leihy, Ecologist, Arthur Rylah Institute for Environmental Research; Melodie McGeoch, Professor of Ecology, Monash University, and Steven Chown, Director, Securing Antarctica's Environmental Future and Professor of Biological Sciences, Monash University

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

One of the biggest challenges in predicting Antarctica’s deeply uncertain future is understanding exactly what’s driving its ice loss.

A vast network of lakes and streams lies beneath the thick ice sheet. This water can lubricate the ice, allowing it to slide more rapidly toward the ocean.

Our new research shows “subglacial water” plays a far larger role in Antarctic ice loss than previously thought. If it’s not properly accounted for, future sea-level rise may be vastly underestimated.

Including the effects of evolving subglacial water in ice sheet models can triple the amount of ice flowing to the ocean. This adds more than two metres to global sea levels by 2300, with potentially enormous consequences for coastal communities worldwide.

Understanding the role of subglacial water

Subglacial water forms when the base of the ice sheet melts. This occurs either due to friction from the movement of the ice, or geothermal heat from the bedrock below.

The presence of subglacial water enables ice to slide over the bedrock more easily. It can also cause further melting under ice shelves, leading to even faster ice loss.

So it’s crucial to understand how much subglacial water is generated and where it goes, as well as its effect on ice flow and further melting.

But subglacial water is largely invisible. Being hidden underneath an ice sheet more than two kilometres deep makes it incredibly difficult to observe.

Scientists can drill boreholes through hundreds to thousands of metres of ice to get to it. But that’s an expensive and logistically challenging process.

Alternatively, they can use ice-penetrating radar to “see” through the ice. Another technique called laser altimetry examines changes in the height of the ice at the surface. Bulges might appear when lakes under the ice sheet fill, or disappear when they empty.

More than 140 active subglacial lakes have been identified beneath Antarctica over the past two decades. These discoveries provide valuable insights. But vast regions — especially in East Antarctica — remain unexplored. Little is known about the connections between these lakes.

What we did and what we found

We used computer simulations to predict the influence of subglacial water on ice sheet behaviour.

We used two computer models:

• an advanced ice sheet model that simulates how the ice sheet flows and responds to climate.
• a specialised hydrology model that predicts subglacial water production and flow.

Then we explored how different assumptions about subglacial water pressure affect ice sheet dynamics. Specifically, we compared scenarios where water pressure was allowed to change over time against scenarios where it remained constant.

When the effects of changing subglacial water pressure were included in the model, the amount of ice flowing into the ocean under future climate nearly tripled.

These findings suggest many existing sea-level rise projections may be too low, because they do not fully account for the dynamic influence of subglacial water.

Our research highlights the urgent need to incorporate subglacial water dynamics into these models. Otherwise we risk significantly underestimating the rate and magnitude of future sea-level rise.

In the video below, the moving dark lines show where grounded ice begins to float. The left panel is a scenario where subglacial water is not included in the ice sheet model and the right panel is a scenario that includes the effects of evolving subglacial water.

A looming threat

Failing to account for subglacial water means global sea-level rise projections are underestimated by up to two metres by 2300.

A two-metre rise would put many coastal cities in extreme danger and potentially displace millions of people. The economic damage could reach trillions of dollars, damaging vital infrastructure and reshaping coastlines worldwide.

It also means the timing of future tipping points are underestimated too. This is the point at which the ice sheet mass loss becomes much more rapid and likely irreversible. In our study, most regions cross this threshold much earlier, some as soon as 2050. This is deeply concerning.

The way forward

Understanding Antarctica’s hidden water system is challenging. The potential for rapid, catastrophic and irreversible ice loss remains.

More observations are needed to improve our models, particularly from remote regions such as East Antarctica. Continuing to gather information from boreholes, ice-penetrating radar and satellites will help us better understand how the underside of the ice sheet behaves. These techniques can then be combined with computer simulations to enable more accurate projections of future ice loss and sea-level rise.

Our new research shows integrating subglacial water dynamics into ice sheet models is a top priority. Understanding this hidden threat is crucial as the world grapples with the consequences of global warming especially rising seas.

Chen Zhao, ARC DECRA Senior Research Fellow, Institute for Marine and Antarctic Studies, University of Tasmania and Ben Galton-Fenzi, Principal Scientist, Australian Antarctic Division

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

Rising seas are already affecting coastal communities in Aotearoa New Zealand. On a global average, the sea level is now 18 centimetres higher than it was in 1900, and the annual rate of increase has been accelerating to currently 4.4 millimetres per year.

This may not seem much, but it is already amplifying the impact of storm and tidal surges. Over the coming decades and centuries, this will pose increasingly serious problems for all coastal communities.

But this is not the end of our troubles. Some parts of New Zealand’s coastline are also sinking. In many New Zealand cities, shorelines are steadily subsiding, with growing impacts on coastal infrastructure.

Our new research reveals where and how fast this is happening. We found the coastlines near all major cities in New Zealand are sinking a few millimetres each year, with some of the fastest rates in coastal suburbs of Christchurch, where the land is still adjusting to the impact of the 2011 earthquake.

Relative increase in sea level

Sea-level rise is happening globally because the ocean is expanding as it continues to warm and glaciers and polar ice sheets are melting.

Meanwhile, land subsidence operates on regional or local scales, but it can potentially double or triple the effects of sea-level rise in certain places. This dual effect of rising seas and sinking land is know as relative sea-level rise and it gives coastal communities a more accurate projection of what they need to prepare for.

To understand which parts of the coast are most at risk requires detailed and precise measurements of land subsidence. The key to this is to observe Earth from space.

We have used a technique known as interferometric synthetic aperture radar (InSAR). This involves the repeat acquisition of satellite radar images of the Earth’s surface, tied to very accurate global navigation satellite system measurements of ground stations.

This builds on earlier work by the NZSeaRise project, which measured vertical land movement for every two kilometres of New Zealand’s coastline. Our study uses a significantly higher resolution (every ten metres in most places) and more recent datasets, highlighting previously missed parts of urban coastlines.

Urban hotspots

For instance, in Christchurch the previous NZSeaRise dataset showed very little subsidence at Southshore and New Brighton. The big differences in the new data are not due to the increase in spatial resolution, but because the rate of vertical land movement is very different from the time prior to the 2011 earthquake.

Localised subsidence in these Christchurch suburbs is up to 8mm per year, among the fastest rates of urban subsidence we observed. These areas sit upon natural coastal sand dunes above the source area of the earthquake and the Earth’s crust is still responding to that sudden change in stress.

We have tracked vertical movement of the land with millimetre-scale precision for five major cities in New Zealand. The InSAR technique works particularly well in urban areas because the smooth surface of pavements, roads and buildings better reflects the satellite radar beam back into space where it is picked up by the orbiting satellite.

This means the estimates of relative sea-level rise for these cities are close to or above 7mm per year. If sustained, this amounts to around 70cm of sea-level rise per century – enough to seriously threaten most sea defences.

Our new satellite measurements provide a detailed picture of urban subsidence, even within single suburbs. It can vary by as much as 10mm per year between parts of a city, as this map of Dunedin and the Otago Harbour shows.

We found hotspots of very rapidly sinking regions. They tend to match areas of land that have been modified, particularly along the waterfront. During the 20th century, many acres of land were reclaimed from the ocean, and this new land is still compacting, creating an unstable base for the overlying infrastructure.

One example of this is in Porirua Harbour, where a section of reclaimed land near the mouth of Porirua Stream is sinking at 3–5mm per year. This is more than double the average rate for Porirua’s coast.

Paradoxically, perhaps, it is only by looking back on our planet from outer space that we can begin to see with sufficient detail what is happening to the land in our own backyard.

The good news is that we can use the results to identify coastlines that are particularly vulnerable to sea-level rise and plan accordingly for any future development. Our new measurements are just the first step in what must become a major effort to watch the ups and downs of our coastlines and urban areas.

Jesse Kearse, Postdoctoral Researcher, Geophysics, Kyoto University

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Nearly three fourths of Earth is covered by oceans, making the planet look like a pale blue dot from space. But Japanese researchers have made a compelling case that Earth’s oceans were once green, in a study published in Nature.

The reason Earth’s oceans may have looked different in the ancient past is to do with their chemistry and the evolution of photosynthesis. As a geology undergraduate student, I was taught about the importance of a type of rock deposit known as the banded iron formation in recording the planet’s history.

Banded iron formations were deposited in the Archean and Paleoproterozoic eons, roughly between 3.8 and 1.8 billion years ago. Life back then was confined to one cell organisms in the oceans. The continents were a barren landscape of grey, brown and black rocks and sediments.

Rain falling on continental rocks dissolved iron which was then carried to the oceans by rivers. Other sources of iron were volcanoes on the ocean floor. This iron will become important later.

The Archaean eon was a time when Earth’s atmosphere and ocean were devoid of gaseous oxygen, but also when the first organisms to generate energy from sunlight evolved. These organisms used anaerobic photosynthesis, meaning they can do photosynthesis in the absence of oxygen.

It triggered important changes as a byproduct of anaerobic photosynthesis is oxygen gas. Oxygen gas bound to iron in seawater. Oxygen only existed as a gas in the atmosphere once the seawater iron could neutralise no more oxygen.

Eventually, early photosynthesis led to the “great oxidation event”, a major ecological turning point that made complex life on Earth possible. It marked the transition from a largely oxygen free Earth to one with large amounts of oxygen in the ocean and atmosphere.

The “bands” of different colours in banded iron formations record this shift with an alternation between deposits of iron deposited in the absence of oxygen and red oxidised iron.

The case for green oceans

The recent paper’s case for green oceans in the Archaean eon starts with an observation: waters around the Japanese volcanic island of Iwo Jima have a greenish hue linked to a form of oxidised iron - Fe(III). Blue-green algae thrive in the green waters surrounding the island.

Despite their name, blue-green algae are primitive bacteria and not true algae. In the Archaean eon, the ancestors of modern blue-green algae evolved alongside other bacteria that use ferrous iron instead of water as the source of electrons for photosynthesis. This points to high levels of iron in the ocean.

Photosynthetic organisms use pigments (mostly chlorophyll) in their cells to transform CO₂ into sugars using the energy of the sun. Chlorophyll gives plants their green colour. Blue-green algae are peculiar because they carry the common chlorophyll pigment, but also a second pigment called phycoerythrobilin (PEB).

In their paper, the researchers found that genetically engineered modern blue-green algae with PEB grow better in green waters. Although chlorophyll is great for photosynthesis in the spectra of light visible to us, PEB seems to be superior in green-light conditions.

Before the rise of photosynthesis and oxygen, Earth’s oceans contained dissolved reduced iron (iron deposited in the absence of oxygen). Oxygen released by the rise of photosynthesis in the Archean eon then led to oxidised iron in seawater. The paper’s computer simulations also found oxygen released by early photosynthesis led to a high enough concentration of oxidised iron particles to turn the surface water green.

Once all iron in the ocean was oxidised, free oxygen (0₂) existed in Earth’s oceans and atmosphere. So a major implication of the study is that pale-green dot worlds viewed from space are good candidates planets to harbour early photosynthetic life.

The changes in ocean chemistry were gradual. The Archaean period lasted 1.5 billion years. This is more than half of Earth’s history. By comparison, the entire history of the rise and evolution of complex life represents about an eighth of Earth’s history.

Almost certainly, the colour of the oceans changed gradually during this period and potentially oscillated. This could explain why blue-green algae evolved both forms of photosynthetic pigments. Chlorophyll is best for white light which is the type of sunlight we have today. Taking advantage of green and white light would have been an evolutionary advantage.

Could oceans change colour again?

The lesson from the recent Japanese paper is that the colour of our oceans are linked to water chemistry and the influence of life. We can imagine different ocean colours without borrowing too much from science fiction.

Purple oceans would be possible on Earth if the levels of sulphur were high. This could be linked to intense volcanic activity and low oxygen content in the atmosphere, which would lead to the dominance of purple sulphur bacteria.

Red oceans are also theoretically possible under intense tropical climates when red oxidised iron forms from the decay of rocks on the land and is carried to the oceans by rivers or winds. Or if a type of algae linked to “red tides” came to dominate the surface oceans.

These red algae are common in areas with intense concentration of fertiliser such as nitrogen. In the modern oceans, this tends to happen in coastline close to sewers.

As our sun ages, it will first become brighter leading to increased surface evaporation and intense UV light. This may favour purple sulphur bacteria living in deep waters without oxygen.

It will lead to more purple, brown, or green hues in coastal or stratified areas, with less deep blue colour in water as phytoplankton decline. Eventually, oceans will evaporate completely as the sun expands to encompass the orbit of Earth.

At geological timescales nothing is permanent and changes in the colour of our oceans are therefore inevitable.

Cédric M. John, Professor and Head of Data Science for the Environment and Sustainability, Queen Mary University of London

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“Out of sight, out of mind” is how we often treat what is flushed down our toilets. But the drugs we take, from anxiety medications to antibiotics, don’t simply vanish after leaving our bodies. Many are not fully removed by wastewater treatment systems and end up in rivers, lakes and streams, where they can linger and affect wildlife in unexpected ways.

In our new study, we investigated how a sedative called clobazam, commonly prescribed for sleep and anxiety disorders, influences the migration of juvenile Atlantic salmon (Salmo salar) from the River Dal in central Sweden to the Baltic Sea.

Our findings suggest that even tiny traces of drugs in the environment can alter animal behaviour in ways that may shape their survival and success in the wild.

A recent global survey of the world’s rivers found drugs were contaminating waterways on every continent – even Antarctica. These substances enter aquatic ecosystems not only through our everyday use, as active compounds pass through our bodies and into sewage systems, but also due to improper disposal and industrial effluents.

To date, almost 1,000 different active pharmaceutical substances have been detected in environments worldwide.

Particularly worrying is the fact that the biological targets of many of these drugs, such as receptors in the human brain, are also present in a wide variety of other species. That means animals in the wild can also be affected.

In fact, research over the last several decades has demonstrated that pharmaceutical pollutants can disrupt a wide range of traits in animals, including their physiology, development and reproduction.

Pharmaceutical pollution in the wild

The behavioural effects of pharmaceutical pollutants have received relatively less attention, but laboratory studies show that a variety of these contaminants can change brain function and behaviour in fish and other animals. This is a major cause for concern, given that actions critical to survival, including avoiding predators, foraging for food and social interaction, can all be disrupted.

Lab-based research has provided useful insights, but experimental conditions rarely reflect the complexity of nature. Environments are dynamic and difficult to predict, and animals often behave differently than they do in controlled settings. That’s why we set out to test the effects of pharmaceutical exposure in the wild.

As part of a large field study in central Sweden, we attached implants that slowly released clobazam (a common pharmaceutical pollutant) and also miniature tracking transmitters to juvenile Atlantic salmon on their seaward migration through the Dal.

We found that clobazam increased the success of this river-to-sea migration, as more clobazam-treated salmon reached the Baltic Sea compared with untreated fish. These clobazam-exposed salmon also took less time to pass through two major hydropower dams that often delay or block salmon migration.

To better understand these changes, we followed up with a laboratory experiment which revealed that clobazam also altered how fish group and move together – what scientists call shoaling behaviour – when faced with a predator.

This suggests that the migration changes observed in the wild may stem from drug-induced shifts in social dynamics and risk-taking behaviour.

What does this mean for wildlife?

Our study is among the first to show that pharmaceutical pollution can affect not just behaviour in the lab, but outcomes for animals in their natural environment.

While an increase in migration success might initially sound like a positive effect, any disruption to natural behaviour can have ripple effects across ecosystems.

Even seemingly beneficial changes to animal behaviour, like faster passage through barriers, can come at a cost. Changes to the timing of migrations, for instance, might lead fish to arrive at the sea when conditions are not ideal, or expose them to new predators and risks. Over time, these subtle shifts could influence the dynamics of entire populations and threaten the balance of ecosystems.

Pharmaceuticals are vital for keeping people and animals healthy. But the accumulation of these drugs in rivers and lakes demands smarter approaches to keeping waterways clean.

One part of the solution is upgrading wastewater treatment plants. Some advanced methods such as ozonation, which involves bubbling ozone gas through wastewater to break down pollutants, can be effective at removing pharmaceuticals. But such advanced treatment systems are often prohibitively expensive to install and out of reach for many regions.

Another promising avenue is green chemistry: designing drugs that break down more easily in the environment or become less toxic after use. Our team has recently highlighted this as a key step toward reducing pharmaceutical pollution in the environment.

Stronger regulations and better drug disposal practices can also help to prevent medications from ending up in waterways in the first place.

There’s no single fix, but by advancing and integrating science, technology and policy, we can help to protect wildlife from the unintended effects of pharmaceutical pollution.

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Jack Brand, Researcher in Behavioural and Movement Ecology, Swedish University of Agricultural Sciences and Michael Bertram, Assistant Professor in Ecology and Ecotoxicology, Swedish University of Agricultural Sciences and Guest Researcher, Stockholm University

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Ocean waves have long been seen as having huge potential as a source of renewable energy. Waves produce an estimated 50 trillion to 80 trillion watts of power worldwide – nearly two to three times the world’s current annual energy consumption.

Many devices have been designed to capture and convert waves’ great power into electricity, but today’s technologies face challenges in efficiency, particularly in deeper waters. As a result, wave energy hasn’t yet taken off as a renewable source in the same way as wind and solar.

One way around this problem lies in the interaction between two types of waves: those on the ocean’s surface, and those that reside underwater. My research group has just published a paper demonstrating how underwater sound waves can be used to make surface waves more powerful, potentially making them a more viable source of energy.

The same insights could also eventually be used to reduce the risks of tsunamis by making them smaller. In addition, in a second new paper we show how underwater waves can be used to improve today’s tsunami early-warning system.

The waves on the surface of the ocean are often created by a combination of wind raising up water and gravity pulling it back down – hence they’re sometimes referred to as surface-gravity waves. On the other hand, their underwater counterparts are sound waves produced by phenomena like earthquakes or volcanic eruptions, sometimes thousands of metres below the surface.

These acoustic waves travel by compressing and expanding the water, similar to how sound moves through the air. They travel across transoceanic distances at the speed of sound in the water (around 1,500 metres per second) before eventually dissipatin. Surface waves travel at much lower speeds, in the order of tens of metres per second.

In classical water wave theory, these two types of waves are considered separate entities, each living in its own world at its own rhythm. The possibility of them interacting only arose on the back of a 2013 research paper that I co-authored, which prompted my colleagues and I to research a phenomenon known as triad resonance.

This is where two acoustic waves transfer energy to a surface wave by matching its frequency, which in turn causes the surface wave to get larger and more powerful (by increasing its amplitude). This opens up the possibility of using an acoustic wave generator to generate sound waves tuned to a particular size and frequency that would enhance (or equally suppress) surface waves.

Enhanced waves would enable today’s wave turbines and oscillating water columns (which use wave power to force air through a turbine) to produce more electricity, effectively overcoming their efficiency problem.

The main requirement would be an acoustic wave generator that could be finely tuned at the required scale. Acoustic wave generators already exist for laboratory purposes, so it’s a question of scaling up an existing technology.

Our research findings show that triad resonance can increase surface wave heights by more than 30%. Of course, the generator would require energy, though the hope is that this too could be powered by waves to minimise carbon emissions. One additional challenge is to ensure that methods are developed to use the acoustic energy efficiently to ensure that the least possible energy is wasted.

Our next step is to produce some more numerical simulations and to conduct a series of small-scale laboratory experiments looking at how triad resonance works in practice. These will help refine our theories and assess their feasibility, hopefully with a view to turning this into a commercial reality.

Tsunami mitigation

I originally suggested the possibility of reducing the height of tsunami waves by manipulating underwater acoustic waves back in 2017. In the new paper, we look at this in more detail.

We found that the resonance mechanism certainly took place at an oceanic scale during the 2022 Tonga earthquake and tsunami. This shows that it’s theoretically possible to manipulate the size of a tsunami using our technique.

The challenge lies in generating and directing the acoustic waves at the required scale and configuration in real-world conditions. This would be more challenging than using acoustic waves to help harness wave energy, not least because of the scale of tsunamis, which would necessitate a much more powerful acoustic-wave generator.

Other issues to overcome would be knowing the exact properties of the tsunami in real time, and the risk that using the wrong configurations could actually make the wave bigger instead of smaller.

While it could take some time to make this feasible, acoustic waves can also potentially help to mitigate tsunamis in a different way. Our second paper demonstrates that monitoring and analysing these waves in real time could complement the existing and emerging technologies for predicting tsunamis, including ocean buoys and seismometers.

There are currently thousands of seismometers deployed around the world, but they only monitor earthquakes, whereas tsunamis can also be caused by landslides, explosions and volcanic eruptions. Even with earthquakes, large seismic readings don’t always entail large tsunamis. This can lead to false alarms, such as in Alaska in 2018.

Meanwhile ocean buoys, which measure sea levels and water pressure, are often faulty because of their operating conditions, and also relatively slow at giving warnings when tsunamis (according to my calculations) can move at speeds of up to 200m per second in the deep ocean.

A complementary system is to measure acoustic waves using an underwater microphone known as a hydrophone. These capture the acoustic waves created by all of the phenomena that cause tsunamis, and the speed at which these waves travel means that just 30 hydrophone stations could cover the entire world’s tsunami high risk areas.

This could be particularly life-saving for coastal communities near the source of a tsunami. It would also support global goals for more resilient coastal cities, such as Unesco’s aim to make all such places “tsunami ready” by 2030.

Usama Kadri, Reader of Applied Mathematics, Cardiff University

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