How will sharks respond to climate change? It might depend on where they grew up



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Culum Brown, Macquarie University and Connor Gervais

They may have been around for hundreds of millions of years — long before trees — but today sharks and rays are are among the most threatened animals in the world, largely because of overfishing and habitat loss.

Climate change adds another overarching stressor to the mix. So how will sharks cope as the ocean heats up?

Our new research looked at Port Jackson sharks to find out. We found individual sharks adapt in different ways, depending where they came from.

A Port Jackson shark swimming on the sea bed
Port Jackson sharks in Jervis Bay may be better at responding to climate change than those from The Great Australian Bight.
Connor Gervais, Author provided

Port Jackson sharks from cooler waters in the Great Australian Bight found it harder to cope with rising temperatures than those living in the warmer water from Jervis Bay in New South Wales.

This is important because it goes against the general assumption that species in warmer, tropical waters are at the greatest risk of climate change. It also illustrates that we shouldn’t assume all populations in one species respond to climate change in the same way, as it can lead to over- or underestimating their sensitivity.

But before we explore this further, let’s look at what exactly sharks will be exposed to in the coming years.

An existential threat

In Australia, the grim reality of climate change is already upon us: we’re seeing intense marine heat waves and coral bleaching events, the disappearance of entire kelp forests, mangrove forest dieback and the continent-wide shifting of marine life.

The southeast of Australia is a global change hotspot, with water temperatures rising at three to four times the global average. In addition to rising water temperatures, oceans are becoming more acidic and the amount of oxygen is declining.

Any one of these factors is cause for concern, but all three may also be acting together.

Coral bleaching
Oceans act like a heat sink, absorbing 90% of the heat in the atmosphere. This makes marine environments highly susceptible to climate change.
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One may argue sharks have been around for millions of years and survived multiple climate catastrophes, including several global mass extinctions events.

To that, we say life in the anthropocene is characterised by changes in temperature and levels of carbon dioxide on a scale not seen for more than three million years.




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Rapid climate change represents an existential threat to all life on Earth and sharks can’t evolve fast enough to keep up because they tend to be long-lived with low reproductive output (they don’t have many pups). The time between generations is just too long to respond via natural selection.

Dealing with rising temperatures

When it comes to dealing with rising water temperature, sharks have two options: they can change their physiology to adapt, or move towards the poles to cooler waters.

Moving to cooler waters is one of the more obvious responses to climate change, while subtle impacts on physiology, as we studied, have largely been ignored to date. However, they can have big impacts on individual, and ultimately species, distributions and survival.

Juvenile Port Jackson sharks
Juvenile Port Jackson sharks from our study.
Connor Gervais, Author provided

We collected Port Jackson sharks from cold water around Adelaide and warm water in Jervis Bay. After increasing temperatures by 3℃, we studied their thermal limits (how much heat the sharks could take before losing equilibrium), swimming activity and their resting metabolic rate.

While all populations could adjust their thermal limits, their metabolic rate and swimming activity depended on where the sharks were originally collected from.




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With a rise in water temperature of just 3℃, the energy required to survive is more than twice that of current day temperatures for the Port Jackson sharks in Adelaide.

The massive shift in energy demand we observed in the Adelaide sharks means they have to prioritise survival (coping mechanisms) over other processes, such as growth and reproduction. This is consistent with several other shark species that have slower growth when exposed to warmer waters, including epaulette sharks and bonnethead sharks.

Two brown, spiralled shark eggs: one is about half the size of the other
The smaller egg to the left is from Port Jackson sharks near Adelaide, while the right egg is from sharks in Jervis Bay.
Connor Gervais, Author provided

On the other hand, a 3℃ temperature rise hardly affected the energy demands of the Port Jackson sharks from Jervis Bay at all.

Threatening the whole ecosystem

Discovering what drives responses to heat is important for identifying broader patterns. For example, the decreased sensitivity of the Jervis Bay sharks likely reflects the thermal history of the region.




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Australia’s southeastern coastline is warmed by the East Australian Current, which varies in strength both throughout the year and from year to year. With each generation exposed to these naturally variable conditions, populations along this coastline have likely become more tolerant to heat.

Populations in the Great Australian Bight, in contrast, don’t experience such variability, which may make them more susceptible to climate change.

So why is this important? When sharks change their behaviour it affects the whole ecosystem.

The implications range from shifts in fish stocks to conservation management, such as where marine reserves are assigned.

Sharks and rays generally rank at the top or in the middle of the food chain, and
have critical ecosystem functions.

Port Jackson sharks, for example, are predators of urchins, and urchins feed on kelp forests — a rich habitat for hundreds of marine species. If the number of sharks decline in a region and the number of urchins increase, then it could lead to the loss of kelp forests.

The top of a swimming Port Jackson shark
Port Jackson sharks feed on feed on urchins in kelp forests.
Connor Gervais, Author provided

What’s next?

There’s little research dedicated to understanding how individuals from different populations within species respond to climate change.

We need more of this kind of research, because it can help identify hidden resilience within species, and also highlight populations at greatest risk. We have seen this in action in coral bleaching events in different parts of Australia, for example.

We also need a better handle on how a wide range of species will respond to a changing climate. This will help us understand how communities and ecosystems might fragment, as each ecosystem component responds to warming in different ways and at different speeds.

Steps need to be taken to address these holes in our knowledge base if we’re to prepare for what follows.




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One-fifth of ecosystems in danger of collapse – here’s what that might look like


The Conversation


Culum Brown, Professor, Macquarie University and Connor Gervais, Connor Gervais

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

Not just hot air: turning Sydney’s wastewater into green gas could be a climate boon



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Bernadette McCabe, University of Southern Queensland

Biomethane technology is no longer on the backburner in Australia after an announcement this week that gas from Sydney’s Malabar wastewater plant will be used to power up to 24,000 homes.

Biomethane, also known as renewable natural gas, is produced when bacteria break down organic material such as human waste.

The demonstration project is the first of its kind in Australia. But many may soon follow: New South Wales’ gas pipelines are reportedly close to more than 30,000 terajoules (TJs) of potential biogas, enough to supply 1.4 million homes.

Critics say the project will do little to dent Australia’s greenhouse emissions. But if deployed at scale, gas captured from wastewater can help decarbonise our gas grid and bolster energy supplies. The trial represents the chance to demonstrate an internationally proven technology on Australian soil.

pipeline at beach
The project would turn Sydney’s sewage into a renewable gas.
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What’s the project all about?

Biomethane is a clean form of biogas. Biogas is about 60% methane and 40% carbon dioxide (CO₂) and other contaminants. Turning biogas into biomethane requires technology that scrubs out the contaminants – a process called upgrading.

The resulting biomethane is 98% methane. While methane produces CO₂ when burned at the point of use, biomethane is considered “zero emissions” – it does not add to greenhouse gas emissions. This is because:

  • it captures methane produced from anaerobic digestion, in which microorganisms break down organic material. This methane would otherwise have been released to the atmosphere

  • it is used in place of fossil fuels, displacing those CO₂ emissions.

Biomethane can also produce negative emissions if the CO₂ produced from upgrading it is used in other processes, such as industry and manufacturing.

Biomethane is indistinguishable from natural gas, so can be used in existing gas infrastructure.




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The Malabar project, in southeast Sydney, is a joint venture between gas infrastructure giant Jemena and utility company Sydney Water. The A$13.8 million trial is partly funded by the federal government’s Australian Renewable Energy Agency (ARENA).

Sydney Water, which runs the Malabar wastewater plant, will install gas-purifying equipment at the site. Biogas produced from sewage sludge will be cleaned and upgraded – removing contaminants such as CO₂ – then injected into Jemena’s gas pipelines.

Sydney Water will initially supply 95TJ of biomethane a year from early 2022, equivalent to the gas demand of about 13,300 homes. Production is expected to scale up to 200TJ a year.

Two women look over the Malabar plant
The project involves cleaning and upgrading biogas from the Malabar Wastewater Treatment Plant.
Sydney Water

Biomethane: the benefits and challenges for Australia

A report by the International Energy Agency earlier this year said biogas and biomethane could cover 20% of global natural gas demand while reducing greenhouse emissions.

As well as creating zero-emissions energy from wastewater, biomethane can be produced from waste created by agriculture and food production, and from methane released at landfill sites.

The industry is a potential economic opportunity for regional areas, and would generate skilled jobs in planning, engineering, operating and maintenance of biogas and biomethane plants.

Methane emitted from organic waste at facilities such as Malabar is 28 times more potent than CO₂. So using it to replace fossil-fuel natural gas is a win for the environment.




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It’s also a win for Jemena, and all energy users. Many of Jemena’s gas customers, such as the City of Sydney, want to decarbonise their existing energy supplies. Some say they will stop using gas if renewable alternatives are not found. Jemena calculates losing these customers would lose it A$2.1 million each year by 2050, and ultimately, lead to higher costs for remaining customers.

The challenge for Australia will be the large scale roll out of biomethane. Historically, this phase has been a costly exercise for renewable technologies entering the market.

A woman cooking with gas
Biomethane will be injected into the existing gas network and delivered to homes.
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The global picture

Worldwide, the top biomethane-producers include Germany, the United Kingdom, Sweden, France and the United States.

The international market for biomethane is growing. Global clean energy policies, such as the European Green Deal, will help create extra demand for biomethane. The largest opportunities lie in the Asia-Pacific region, where natural gas consumption and imports have grown rapidly in recent years.

Australia is lagging behind the rest of the world on biomethane use. But more broadly, it does have a biogas sector, comprising than 240 plants associated with landfill gas power units and wastewater treatment.

In Australia, biogas is already used to produce electricity and heat. The step to grid injection is sensible, given the logistics of injecting biomethane into existing gas infrastructure works well overseas. But the industry needs government support.

Last year, a landmark report into biogas opportunities for Australia put potential production at 103 terawatt hours. This is equivalent to almost 9% of Australia’s total energy consumption, and comparable to current biogas production in Germany.

The distribution of reported operational biogas upgrading units in the IEA Bioenergy Task 37-member countries.

Current use of biogas in Australia.

A clean way to a gas-led recovery

While the scale of the Malabar project will only reduce emissions in a small way initially, the trial will bring renewable gas into the Australia’s renewable energy family. Industry group Bioenergy Australia is now working to ensure gas standards and specifications are understood, to safeguard its smooth and safe introduction into the energy mix.

The Morrison government has been spruiking a gas-led recovery from the COVID-19 recession, which it says would make energy more affordable for families and businesses and support jobs. Using greenhouse gases produced by wastewater in Australia’s biggest city is an important – and green – first step.




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The Conversation


Bernadette McCabe, Professor and Principal Scientist, University of Southern Queensland

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

Drones, detection dogs, poo spotting: what’s the best way to conduct Australia’s Great Koala Count



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Romane H. Cristescu, University of the Sunshine Coast; Celine Frere, University of the Sunshine Coast, and Desley Whisson, Deakin University

Federal environment minister Sussan Ley this week announced A$2 million for a national audit of Australia’s koalas, as part of an A$18 million package to protect the vulnerable species.

The funding might seem like a lot – and, truth be told, it is more than most threatened species receive. But the national distribution of koalas is vast, so the funding equates to about A$1.40 to survey a square kilometre. That means the way koalas are counted in the audit must be carefully considered.

Koalas are notoriously difficult to detect, and counts so far have been fairly unreliable. That can make it hard to get an accurate picture of how koalas are faring, and to know where intensive conservation effort is needed – especially after devastating events such as last summer’s bushfires.

Methods for counting koalas range from the traditional – people at ground level looking up into the trees – to the high-tech, such as heat-seeking drones. So let’s look at each method, and how we can best get a handle on Australia’s koala numbers.

Environment Minister Sussan Ley holding a koala
Environment Minister Sussan Ley has pledged $2 million for a national koala count.
Glenn Hunt/AAP

Why we need to know koala numbers

Gathering data about species distribution and population size is crucial, because governments use it to assess a species’ status and decide what protection it needs.

In announcing the funding, Ley said the new audit aims to fill data gaps, identify where koala habitat can be expanded, and establish an annual monitoring program.




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So far, population estimates for koalas at the state and national level are rare and highly uncertain. For example, the last national koala count in 2012 estimated 33,000-153,000 in Queensland, 14,000–73,000 in NSW and 96,000-378,000 in the southern states.

This uncertainty can make it hard to detect changes in population trends quickly enough to do something about the threat, such as by limiting development or logging. However, the new audit can use methods not available in 2012, which should help with accuracy.

Three koalas in trees
To date, estimates of koala numbers have been highly uncertain.
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So how do you actually count koalas?

Finding a koala can be difficult. There may be few individuals spread over large areas. And koalas are well camouflaged and quiet, unless bellowing. Finally, they can sit high in the tree canopy.

In numerous research and management programs, we have observed that even the most experienced koala spotter may only see 20–80% of koalas present at a site, especially if the vegetation is thick or the terrain difficult to move through.

Romane Cristescu with detection dog
Romane Cristescu with detection dog USC x IFAW detection dog Bear. Detection dogs have been trained to locate koala and their scats.
Detection Dogs for Conservation

Making the job even harder, existing koala habitat maps can be highly inaccurate and miss unexpected hotspots. However, computer modelling using the latest methods, if carefully validated on the ground, can produce more accurate maps.

Traditional surveys involve multiple people independently searching the same area, and correcting counts based on the number of koalas each observer sees. This helps account for the difficulties in koala counting, but it’s hard, slow and costly work.

Searching for koala scat (poo) also is a common method of determining koala habitat – wherever koalas spend time, they will leave scats. However, the small brown pellets are easily missed, and large surveys for scats are time consuming.

Detection dogs have been trained to locate koala scats: in one study, dogs were shown to be 150% more accurate and 20 times quicker than humans.

And because male koalas bellow during the breeding season, koalas can also be detected with acoustic surveys. Audio recorders are left at a survey sites and the recordings scanned for bellows to determine whether koalas are present.

Recently, heat-seeking drones have also been used to detect koalas. This method can be accurate and effective, especially in difficult terrain. We used them extensively to find surviving koalas after the 2019-20 bushfires.

Citizen scientists can also collect important data about koalas. Smartphone apps allow the community to report sightings around Australia, helping to build a picture of where koalas have been seen. However, these sightings are often limited to areas commonly traversed by people, such as in suburbia, near walking tracks and on private property.

Adult and juvenile koala
Everyday citizens can help with koala counting.
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Getting the koala count right

All these methods involve a complex mix of strengths and weaknesses, which means the audit will need input from koala ecologists if it’s to be successful. Survey methods and sites must be chosen strategically to maximise the benefits of the funding.

Robust research data exists, but is patchy across the koala’s entire range. The first step could include collating all current data, including community sightings, to determine where additional surveys are needed. This will allow for funding to be prioritised to fill data gaps.

It is promising that the announcement includes monitoring over the long term. This will help identify population trends and better understand the response of koalas to ongoing threats. It will also reveal whether actions to address koala threats are working.

Finally, while threats to koalas are generally well understood, they can vary between populations. So the audit should allow for “threat mapping” – identifying threats and looking for ways to mitigate them.

Saving an iconic species

Last summer’s bushfires highlighted how koalas, and other native species, are vulnerable to climate change. And the clearing of koala habitat continues, at times illegally.

Government inquiries and reviews have shown state and federal environment laws are not preventing the decline of koalas and other wildlife. The federal laws are still under review.

However, the new funding underpins an important step – accurate mapping of koalas and their habitat for protection and restoration. This is a crucial task in protecting the future of this iconic Australian species.

Koala sleeping in a tree
The koala count is critical to protecting the species.
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Stopping koala extinction is agonisingly simple. But here’s why I’m not optimistic


The Conversation


Romane H. Cristescu, Posdoc in Ecology, University of the Sunshine Coast; Celine Frere, Senior lecturer, University of the Sunshine Coast, and Desley Whisson, Senior Lecturer in Wildlife and Conservation Biology, School of Life and Environmental Sciences, Deakin University

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