Environment - Climate Change - cities are becoming hotter

 

We know how to cool our cities and towns. So why aren’t we doing it?

A/Prof. Elmira Jamei, Victoria University

This week, Victoria recorded its hottest day in nearly six years. On Tuesday, the northwest towns of Walpeup and Hopetoun reached 48.9°C, and the temperature in parts of Melbourne soared over 45°C. Towns in South Australia also broke heat records.

This heatwave is not an outlier. It is a warning shot.

These weather conditions rival the extreme heat seen in the lead-up to the 2019–20 Black Summer, and they point to a future in which days like this are no longer rare, but routine.

What makes this summer so confronting is not just how hot it has been, but this: Australia already knows how to cool cities, yet we are failing to do it. Why?

Urban heat is not inevitable

Cities heat up faster and stay hotter than surrounding areas because of how they are built. Dense development, dark road surfaces, limited shade, and buildings that trap heat and rely heavily on air-conditioning create the “urban heat island” effect.

This means cities absorb vast amounts of heat during the day and release it slowly at night, preventing the city from cooling down even after sunset. During heatwaves, this trapped heat accumulates day after day and pushes temperatures well beyond what people can safely tolerate.

Future urbanisation is expected to amplify projected urban heat, irrespective of background climate conditions. Global climate change is making the urban heat island effect worse, but much of the heat we experience in cities has been built in through decades of planning and design choices.

Hot cities are not only a result of climate change, they are also a failure of urban planning. zpagistock/Getty

Heat is a health and equity crisis

Heatwaves already kill more than 1,100 Australians each year, more than any other natural hazard. Extreme heat increases the risk of heart and respiratory disease, worsens chronic illness, disrupts sleep and overwhelms health services.

Poorly designed and inadequately insulated homes, particularly in rental and social housing can become heat traps. People on low incomes are least able to afford effective cooling, pushing many into energy debt or forcing them to endure dangerously high temperatures. Urban heat deepens existing inequalities. Those who contributed least to the problem often bear the greatest burden.

Australia has expertise, but not ambition

Here is the paradox. Australia is a major contributor to global research on urban heat. Australian researchers are developing national tools to measure and mitigate urban heat, and studies from cities such as Melbourne have quantified urban heat island intensity and investigated how urban design can influence heat stress.

Additionally, Australia already has the technologies to cool cities, from reflective coatings and heat-resilient pavements to advanced shading systems. Yet many of our cities remain dangerously hot. The issue isn’t a lack of solutions, but the failure to roll them out at scale.

Internationally, we are lagging behind countries where large-scale heat mitigation projects are already reducing urban temperatures, cutting energy demand and saving lives.

For example, Paris has adopted a city-wide strategy to create “cool islands”, transforming public spaces and schoolyards into shaded, cooler places that reduce heat stress during heatwaves.

In China, the Sponge City program, now implemented in cities such as Shenzhen and Wuhan, uses green infrastructure and water-sensitive design to cool urban areas and reduce heat stress.

Paris has a city-wide strategy to create cool zones by transforming public spaces into shaded environments. 42 North/Unsplash, CC BY

Symbolic change can’t meet the challenge

Too often, urban heat policy stops at small, symbolic actions, a pocket park here, a tree-planting program there. These measures are important, but they are not sufficient for the scale of the challenge.

Greening cities is essential. Trees cool streets, improve thermal comfort and deliver multiple health and environmental benefits. But greenery has limits. If buildings remain poorly insulated, roads continue to absorb heat and cooling demand keeps rising, trees alone will not protect cities from extreme temperatures in the coming decades.

Urban heat is a complex systems problem. It emerges from how cities are built, and is largely shaped by construction materials, building codes, transport systems and planning decisions locked in over generations. Scientists know a great deal about how to reduce urban heat, but many responses remain piecemeal and intuitive rather than systemic.

Designing an uncomfortable future

Research suggests that even if global warming is limited to below 2°C, heatwaves in major Australian cities could approach 50°C by 2040. At those temperatures, emergency responses alone will not be enough. Beyond certain temperature thresholds, behaviour change, public warnings and cooling centres cannot fully protect people.

The choices we make now about buildings, streets, materials and energy systems will determine whether Australian cities become increasingly unliveable, or remain places where people can safely live, work and age.

The battle against urban heat will be won or lost through design, technology, innovation and political will. Cities need to deploy advanced cool materials across roofs, buildings and roads, in combination with nature-based solutions. This will only work if governments use incentives to reward heat-safe design. Heat must be planned for systematically, not treated as a cosmetic problem.

With leadership and a handful of well-designed, large-scale projects, Australia could shift from laggard to leader. We have the science. We have the industry. We have the solutions. The heat is here. The only real question is whether we act, or keep absorbing it.

A/Prof. Elmira Jamei, Associate professor, Victoria University

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

Health - Fish oil and Omega 3 benefits and limitations

 

Should I take a fish oil supplement for my heart, joints or mood?

Mary Bushell, University of Canberra

Fish oil, also known as omega-3, is one of the most popular dietary supplements. It’s often promoted to protect the heart, boost mood, reduce inflammation and support overall health.

But how much of this is backed by science, and when might fish oil supplements actually be worth taking?

A long history

People have been taking oils from fish for centuries.

Modern interest surged in the 1970s when scientists studying Inuit diets discovered omega-3 fatty acids and their heart-protective effects.

By the 1980s, fish oil capsules were being marketed as an easy way to get these healthy fats.

What’s in fish oil?

Fish oil comes from oily fish such as salmon, sardines, tuna, herring and mackerel. It’s rich in a special type of fat called omega-3 polyunsaturated fatty acids (PUFAs), mainly EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).

These omega-3s play an important role in how our cells function. Every cell in the body is surrounded by a thin, flexible layer called a cell membrane. This membrane works like a protective skin: it keeps the cell’s contents safe, controls what moves in and out, and helps cells communicate with one another.

Omega-3s don’t build the membrane itself, but they slot into it, becoming part of its structure. This helps the membrane stay fluid and flexible, allowing it to work more efficiently, especially in tissue that relies on fast, precise signalling, such as in the brain and eyes.

Because we can’t make enough omega-3s on our own, we need to get them from food or, sometimes, supplements.

How are fish oil supplements made?

After fish are caught, their tissues are cooked and pressed to release oil. This crude oil is purified and refined to remove impurities including heavy metals such as copper, iron and mercury.

During processing, the oil may be concentrated to boost its EPA and DHA content.

The purified oil is then encapsulated in soft gels or bottled as liquid oil.

Some supplements are further treated to reduce odour or the familiar “fishy” aftertaste.

Fish oil and heart health

Omega-3 fatty acids are best known for their role in heart health, particularly for lowering triglycerides, a type of fat in the blood that, when elevated, can increase the risk of heart disease.

A 2023 paper pooled 90 clinical trials with more than 72,000 participants and found a near linear relationship between dose and effect. That doesn’t mean “more is always better”, but higher doses tended to produce bigger improvements in heart-related risk factors.

It found you need more than 2 grams per day of EPA and DHA combined to meaningfully lower triglycerides (by 15 to 30%). This is most relevant for people with existing heart disease, high triglycerides, or obesity.

But it’s important to read the label. A “1,000 mg” fish oil capsule usually refers to the total oil weight of the oil, not the active omega-3 content. Most standard capsules contain only about 300 mg of combined EPA and DHA the rest is other fats.

At lower doses, changes in blood fats were modest. The same analysis suggested low-dose fish oil may even nudge LDL or “bad” cholesterol up slightly, while having only a small effect on triglycerides.

At lower doses, any changes to heart health are modest. Pixabay/Pixels

A 2018 trial tested a high-strength purified EPA product (4 grams per day) in people already taking statins to lower their cholesterol. Over five years, it prevented one major heart event (heart attack, stroke or urgent procedure) for every 21 people treated. However this was a prescription-only pharmaceutical-grade EPA, not a standard fish-oil capsule.

In Australia, fish oils are sold in pharmacies, health food stores and supermarkets. Some concentrated products are available as “practitioner-only” supplements via health professionals.

The same purified EPA used in the 2018 trial is now available in Australia as Vazkepa, a prescription-only medicine. It was added to the Pharmaceutical Benefits Scheme (PBS) in October 2024, making it more accessible for high-risk patients.

For otherwise healthy people, the evidence that standard fish oil supplements prevent heart attacks or strokes is much less convincing.

What about arthritis and joint pain?

Fish oil has mild anti-inflammatory effects.

In people with inflammatory arthritis (such as rheumatoid arthritis), omega-3s can reduce joint tenderness and morning stiffness.

These benefits, however, require higher consistent doses, usually around 2.7g of EPA and DHA per day. This is the equivalent of around nine standard 1,000mg fish oil capsules (containing 300 mg of EPA and DHA) daily for at least eight to 12 weeks.

Can fish oil improve mood?

Some studies suggest omega-3s, particularly those higher in EPA, can modestly reduce symptoms of clinical depression when taken alongside antidepressants.

A 2019 review of 26 trials (involving more than 2,000 people) found a small overall benefit, mainly for EPA-rich formulations at doses up to about 1 gram per day. DHA-only products didn’t show clear effects.

That doesn’t mean fish oil is a mood booster for everyone. For people without diagnosed depression, omega-3 supplements haven’t been shown to reliably lift mood or prevent depression.

How much can you take?

For most people, fish oil is safe.

Common side effects include a fishy aftertaste, mild nausea and diarrhoea. Taking capsules with food or choosing odourless or “de-fishified” products can help.

Prescription strength products such as Vazkepa (high-dose EPA) are also well tolerated, but they can slightly increase the risk of irregular heartbeat (atrial fibrillation) and bleeding.

Up to 3 grams per day of combined EPA and DHA from supplements is generally considered safe for most adults.

Higher doses for specific medical conditions should be taken under medical supervision.

So, should you take it?

The Heart Foundation recommends Australians eat two to three serves of oily fish a week. This would provide 250–500 mg of EPA and DHA per day.

If you don’t eat fish, a fish oil supplement (or algal oil if you’re vegetarian or vegan) can help you meet your omega-3 needs.

If you have heart disease (with high triglycerides) or inflammatory arthritis, fish oil may offer extra benefits. But dose and product type matter, so speak with a health professional.

For most people, though, two or three serves of oily fish each week remain the simplest, safest and most nutritious way to get omega-3s.

Mary Bushell, Clinical Associate Professor in Pharmacy, University of Canberra

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

Environment - microplastics - documentary: 'Plastic People'

Environment - shark attacks in Australia

Figure 1 Source: The Conversation (c) 2025 and NSW Government Sharksmart

Shark attacks against humans in the ocean are not regular incidents in Australia despite the number of people swimming/diving/surfing in the sea and the proximity of numerous species of shark. The recent 4 attacks in 48 hours in the coastline of NSW is unusual and has given rise to discussion as to the reasons why this activitry is occuring. Figure 1 (above) shows the most common species of shark responsible for attacks over the past thirty years. Some of the shark species are known for being ocean hunters (Great White, Tiger shark) while others are well known as species found in harbours, river estuaries and inlets (Bull shark). Figure 2 below provides the statistical data of shark incidents showing that the Great White shark is by far the greatest source of attacks.

The recent spate of attacks and a more broad trend of shark activity is conisdered by several marine scientists as being linked to land activities and the impact on the ocean. The washing offshore of runoff of pesticides, waste, organic nutrients and other waste together with murky water from storms creates a perfect hunting environment for predatory sharks as bait fish become more plentiful. When humans enter that environment, they are at susbstantial risk. Shark behaviour is also not well understood and continues to be the subject of research by marine biologists. 

Figure 2: Source: The Conversation 2025

Figure 3 below provides a map of the location of the shark incidents around the Australian continent. The northern part of the continent around the coastline of northern Western Australia and the Northern Territory has far fewer attacks. This region has a sparse population and the geography is a harsh wilderness or national parks such as Kakadu National Park. The dominant species and apex predator in Northern Australia is the saltwater crocodile not the shark.

Figure 3: Source: The Conversation (c) 2025

Environment - the scourge of microplastics

                                            
Source: AI generated images. 

      

Environment - Bushfires can create weather

When bushfires make their own weather

Jason Sharples, UNSW Sydney; Andrew Dowdy, The University of Melbourne; Luke Burgess, The University of Melbourne, and Todd Lane, The University of Melbourne

Bushfires are strongly driven by weather: hot, dry and windy conditions can combine to create the perfect environment for flames to spread across the landscape.

But sometimes the relationship flips: fires can generate their own weather systems, which can then dramatically alter the spread and intensity of the blaze.

One of the most striking examples of this phenomenon is the formation of pyrocumulonimbus clouds — towering storm clouds born from fire.

How can a fire make winds and clouds?

Large bushfires release enormous amounts of energy – sometimes comparable to that emitted from a nuclear bomb. This heats the air in the vicinity of the fire, causing it to rise rapidly in a powerful, buoyant, fire-driven updraft.

Surrounding air rushes in at ground level to replace the rising hot air, feeding the fire with oxygen like a bellows and sometimes accelerating its spread. In extreme cases, the fire and its induced winds can become a self-sustaining system, feeding and growing from the weather it creates.

If the plume rises high enough it can cool to a temperature where the water vapour in the plume will begin to condense into clouds. This is essentially the same process that leads to the formation of ordinary cumulus clouds, except it occurs within a fire’s plume and is called pyrocumulus.

The classic types of cloud. Pyrocumulus and pyrocumulonimbus are much like their ordinary namesakes, but generated by fire. Valentin de Bruyn/Wikimedia, CC BY-NC-ND

Fire-generated thunderstorms

If the fire is large and intense enough, the plume can keep rising. As the cloud rises above altitudes of around 3–5 kilometres, temperatures can drop well below freezing. Water droplets freeze into ice crystals, releasing another burst of latent heat that further energises the rising plume.

The rapidly rising plume now contains ice and supercooled water — a mixture that is key to thunderstorm-like processes. It is through this process that a fire-generated thunderstorm is born, a pyrocumulonimbus cloud.

Pyrocumulonimbus clouds can reach altitudes of 10–15 kilometres, penetrating the stratosphere.

A pyrocumulus grows over the Mount Lawson fire. Satchandcogallery/Facebook

Inside them, strong vertical motions generate turbulence, with ice and water droplets colliding and causing the separation of electrical charges. This can result in lightning, often striking far from the original fire front and in some cases igniting new fires.

These clouds can rise so high that they leave a clear signature visible by satellite, including a long shadow cast over the rest of the cloud and smoke. The first pyrocumulonimbus for this summer may have happened yesterday near the border of NSW and Victoria.

Lightning was detected nearby but this was among lightning occurring in many places across the Southeast states, so it may have just been pyrocumulus clouds, which can still present a significant threat. For example, the deadly 2019 Jingellic fire, which produced tornadic winds, developed a towering pyrocumulus but not a pyrocumulonimbus.

The strong updrafts created by pyrocumulonimbus can cause gusty conditions accelerating fire spread and making it less predictable. The storm can produce a strong updraft bringing fresh air in underneath to the fire, while flinging burning embers over 40km potentially creating new fires. At the same time, strong downdrafts created by the storm can flatten trees and create dangerous conditions for firefighters.

When does this happen?

Not every bushfire spawns its own weather. Pyrocumulonimbus formation requires a delicate balance between the size and intensity of the fire and the stability of the atmosphere.

Firstly, the fire must be large and intense enough to release massive amounts of heat. Secondly, the surrounding atmosphere needs to be suitably conducive to vertical motion. Both of these together allow for the plume to rise.

Smoke plumes from bushfires in Victoria, January 2025. NASA

Third, moisture in the mid-levels of the atmosphere can enhance the chances of pyrocumulonimbus formation. Moist mid-level air can get caught up in the rising plume and then add to latent heat release when it condenses and freezes, which keeps the plume rising.

The future of fire and thunder

Fire-generated thunderstorms were practically unheard of a few decades ago, but they appear to be becoming more common.

One notable example is the unprecedented number that occurred during the Black Summer of 2019–2020. Other outbreaks include around Melbourne in the Black Saturday fires of 2009 and the Canberra fires in 2003.

In all of those cases, the thunderstorms were so intense they injected smoke into stratosphere, where it circled the Earth and affected global climate patterns. Other examples of extreme weather they can cause include fire-generated tornadoes, as well as black hail in the Canberra fires.

Human-caused climate change has already caused more dangerous weather conditions for bushfires for many regions of Australia, including more dangerous conditions for fire-generated thunderstorms.

Observations show more dangerous conditions are now occurring during summer and also with an earlier start to the fire season, particularly in parts of southern and eastern Australia. These trends are very likely to increase into the future, with climate models showing more dangerous weather conditions for bushfires and fire-generated thunderstorms due to increasing greenhouse gas emissions.

Why understanding this matters

Understanding how bushfires can create their own weather is crucial for forecasting and emergency response. Traditional fire behaviour models often assume that weather drives fire, but when fires start driving weather, those models can fail.

Incorporating prediction of fire-generated clouds into fire management systems helps authorities anticipate sudden changes in fire intensity and spread. Targeted research incorporating satellite monitoring and advanced atmospheric modelling is now being used to better understand and detect conditions favourable for pyrocumulonimbus formation.

This knowledge allows for better warnings, resource allocation, and strategies to protect lives and property.

Bushfires are no longer just a local hazard — they can become atmospheric engines with global reach.

Jason Sharples, Professor of Bushfire Dynamics, School of Science, UNSW Canberra, UNSW Sydney; Andrew Dowdy, Principal Research Scientist in Extreme Weather, The University of Melbourne; Luke Burgess, PhD Candidate, Weather and Fire Extremes, The University of Melbourne, and Todd Lane, Professor, School of Geography, Earth and Atmospheric Sciences; ARC Centre of Excellence for the Weather of the 21st Century, The University of Melbourne

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