Health - the menace of mosquitoes

A warm, wet spring means more mozzies. How to protect yourself from the diseases they spread

Cameron Webb, University of Sydney

Mosquito bites are annoying. They can also have deadly consequences. So what diseases do mosquitoes in Australia carry?

And with warmer weather on its way and rain expected to continue, how can you prepare for the coming mosquito season?

Mosquitoes are deadliest animal

Mosquitoes kill more people than any other animal. Worldwide, more than half a million people die each year from mosquito bites that transmit malaria parasites.

Australia is fortunate to be free of major outbreaks of malaria, though occasional cases do occur.

The most common mosquito-borne disease in Australia is caused by Ross River virus. Around 5,000 cases are reported each year and, while never fatal, the illness can be severely debilitating. Symptoms include fever, rash, joint pain and fatigue.

Mosquito populations fluctuate year by year. A/Prof Cameron Webb (NSW Health Pathology), CC BY-NC-SA

Murray Valley encephalitis virus is responsible for very rare but potentially fatal disease. It’s detected most years in northern Australia.

There has been a resurgence of the virus in southeastern parts of Australia following flooding in recent years. Mosquitoes pick up the virus from waterbirds throughout the Murray Darling Basin before they pass on the pathogen to people. Mosquito and waterbird populations both boom after flooding.

Mosquitoes in some coastal areas of Victoria can also pass on the flesh-eating bacteria that can cause Buruli ulcer.

What about Japanese encephalitis?

Japanese encephalitis virus can cause fever, headaches, vomiting and, in rare cases, death.

Over the summer of 2021-22, there were 45 cases of Japanese encephalitis in southeastern Australia. This virus was never expected to spread so widely. In some parts of Australia, people died due to mosquito bites for the first time in around 50 years.

Scientists and health authorities thought Japanese encephalitis virus would transmit in a similar way to the closely related Murray Valley encephalitis virus, with outbreaks typically occurring after flooding that provided ideal conditions for both mosquitoes and the waterbirds carrying the virus.

But we now know pigs – especially feral pigs – are in the mix too, along with a range of other animals.

With gaps in our understanding of what drives local transmission, predictions of Japanese encephalitis activity are now proving to be less reliable. This makes it hard to work out the threat it may pose this summer.

Last summer, despite the lack of any substantial rainfall, the virus turned up even though mosquito (and waterbird) populations were generally low.

The virus also wasn’t limited to those areas where we’d expect to see it. There is growing evidence it’s made its way to the east coast, with the virus detected in the suburbs of Brisbane.

Ongoing wet weather can provide ideal conditions for mosquitoes. A/Prof Cameron Webb (NSW Health Pathology), CC BY-NC-SA

How will the weather impact mosquitoes this season?

Like all insects, mosquitoes thrive in warmer weather. But they also need water.

It doesn’t really matter if it’s a “wet” or “dry” summer, mosquitoes are always active. But sometimes there are more – lots more.

In most parts of Australia, there is currently no shortage of water. Some regions have had record rainfall this winter, with more on the way.

The Bureau of Meteorology is predicting above-average rainfall through to the end of the year. Once the weather warms up, it could be a “buzzy” start to mosquito season.

This doesn’t mean outbreaks of mosquito-borne disease are inevitable. But we need to be alert to the risks and how best to protect ourselves and family.

Scientists like me trap mosquitoes across Australia each summer to track changes in their abundance, as well as activity of pathogens. A/Prof Cameron Webb (NSW Health Pathology), CC BY-NC-SA

Monitoring mozzies

More rain means a greater risk of mosquito-borne disease. But outbreaks aren’t easy to predict, so surveillance is critical.

Australian state and territory health authorities undertake monitoring of mosquitoes and the pathogens they carry each year. The objective is to provide an early warning of elevated risk of mosquito-borne diseases. This may be due to increased mosquito activity or the detection of mosquito-borne pathogens.

Given the uncertainty around Japanese encephalitis, it’s also important to monitor locations where the virus has not yet been detected.

How to stay safe this spring and summer

There’s a lot you can do to protect yourself and family from mosquito bites and mosquito-borne disease.

A vaccine is available for those at risk of Japanese encephalitis. See your local health professional for advice on accessing the vaccine.

But there aren’t vaccines for the other local mosquito-borne diseases. Nor are there any specific treatments for these diseases. So preventing mosquito bites is the best way to protect yourself.

If you’re outdoors when mosquitoes are active, cover up with long pants, a long-sleeved shirt and covered shoes. Apply an insect repellent containing diethyltoluamide, picaridin, or oil of lemon eucalyptus to all exposed skin.

Skip the stickers, patches and wristbands, as the evidence shows they aren’t a reliable way to prevent bites.

Keep your property free of mosquito breeding grounds, too. Mosquitoes can lay eggs in any container that fills with water: a plant saucer, a bird bath, discarded plastic buckets, bottles or tins. Tip them out each week, cover them up or throw them away.

Cameron Webb, Clinical Associate Professor, School of Medical Science & Sydney Infectious Diseases Institute; Principal Hospital Scientist, University of Sydney

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

Health and exercise - weightlifting and bone density

Does weightlifting improve bone density?

Inti St Clair/Getty

Hunter Bennett, University of South Australia

You may have heard high-impact activity – exercise such as running, jumping, football and basketball – is good at building bone density and strength. But what about when you’re standing still, lifting weights at the gym?

The good news is weight training is great for bone health. But some exercises are more effective than others. Here’s what the science says.

What is bone density?

Bone density, also known as bone mineral density, is essentially a measure of how many minerals (such as calcium and phosphorus) are packed into your bones.

It gives you an indication of how solid your bones are, which is important because denser bones are generally less likely to break.

However, bone density is not quite the same as bone strength.

Bones also rely on a range of other compounds (such as collagen) to provide support and structure. So, even dense bones can become brittle if they are lacking these key structural components.

However, bone mineral density (measured with a bone scan) is still considered one of the best indicators of bone health because it is strongly linked to fracture risk.

While there is likely a genetic component to bone health, your daily choices can have a big impact.

What affects your bone health?

Research shows a few factors can influence how strong and dense your bones are:

Getting older: As we age, our bone mineral density tends to decrease. This decline is generally greater in women after menopause, but it occurs in everyone.

Nutrition: Eating calcium-rich foods – dairy in particular, but also many vegetables, nuts, legumes, eggs and meat – has been shown to have a small impact on bone density (although the extent to which this reduces fracture risk is unclear).

Exposure to sun: Sunlight helps your body make vitamin D, which helps you absorb calcium, and has been linked to better bone density.

Exercise: It is well established that people who do high-impact and high-load exercise (such as sprinting and weight training) tend to have denser and stronger bones than those who don’t.

Smoking: Older people who smoke tend to have lower bone density than those who don’t smoke.

Why does movement improve bone density?

In the same way that your muscles get stronger when you expose them to stress, your bones get stronger when they’re asked to handle more load. This is why exercise is so important for bone health – because it tells your bones to adapt and become stronger.

Many of us know that people at risk for bone loss – post-menopausal women and older adults – should be focused on exercising for bone health.

However, everyone can benefit from targeted exercise, and it’s arguably just as important to prevent declines in bone health.

In fact, whether you are male or female, the younger you start, the more likely you are to have denser bones into your older life. This is crucial for long-term bone health.

Do weights improve bone density?

Yes. One of the most effective exercises for bone health is lifting weights.

When you lift weights, your muscles pull on your bones, sending signals that encourage new bone formation. There is a large body of evidence showing weight training can improve bone density in adults, including in post-menopausal women.

But not all exercises are created equal. For example, some evidence suggests large compound exercises that place more load on the skeleton – such as squats and deadlifts – are particularly effective at increasing density in the spine and hips, two areas prone to fractures.

What type of weight training is best?

Lifting heavier weights is thought to produce better results than lifting lighter ones. This means doing sets of three to eight repetitions using heavy weights is likely to have a greater impact on your bones than doing many repetitions with lighter ones.

Similarly, it takes a long time for your bones to adapt and become denser – usually six months or more. This means for healthy bones, it’s better to integrate weight training into your weekly routine rather than do it in bursts for a few weeks at a time.

Exercises that use body weight, such as yoga and pilates, have many health benefits. However they are unlikely to have a significant impact on bone density, as they tend to put only light stress on your bones.

If you are new to weight training, you might need to start a bit lighter and get used to the movements before adding weight. And if you need help, finding an exercise professional in your local area might be a great first step.

Exercising for bone health is not complex. Just a couple of (heavy) weight training sessions per week can make a big difference.

If you’re concerned you have low bone density, speak to your doctor. They can assess whether you need to go for a scan.

Hunter Bennett, Lecturer in Exercise Science, University of South Australia

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

Environment - Climate Change - Extreme weather and declining tropical birdlife

70 years of data show extreme heat is already wiping out tropical bird populations

DeAgostini/Getty Images

James Watson, The University of Queensland; Maximilian Kotz, Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS), and Tatsuya Amano, The University of Queensland

Human-driven climate change threatens many species, including birds. Most studies on this topic focus on long-term climate trends, such as gradual rises in average temperatures or shifts in rainfall patterns. But extreme weather events are becoming more common and intense, so they warrant further attention.

Our new research shows extreme heat is having a particularly severe effect on tropical birds. We found increased exposure to extreme heat has reduced bird populations in tropical regions by 25–38% since 1950.

This is not just a temporary dip – it’s a long-term, cumulative effect that continues to build as the planet warms.

Our research helps explain why bird numbers are falling even in wild places relatively untouched by humans, such as some very remote protected tropical forests. It underscores the urgent need to reduce greenhouse gas emissions, to conserve the remaining biodiversity.

Digging into huge global datasets

We analysed data from long-term monitoring of more than 3,000 bird populations worldwide between 1950 and 2020. This dataset captures more than 90,000 scientific observations.

Although there are some gaps, the dataset offers an unmatched view of how bird populations have changed over time. Some parts of the world such as western Europe and North America were better represented than others, but all continents were covered.

We matched this bird data with detailed daily weather records from a global climate database that stretches back to 1940. This allowed us to track how bird populations responded to specific changes in daily temperatures and rainfall, including extreme heat.

We also looked at average yearly temperatures, total annual rainfall, and episodes of unusually heavy rainfall.

Using another dataset that reflects human industrial activity over time, we accounted for human pressures such as land development and human population density.

By combining all these sources of data, we created computer models to evaluate how climate factors and human impacts influence bird population growth.

Our research confirmed the work of other climate scientists showing extreme heat events have increased dramatically over the past 70 years, especially near the equator.

Birds in tropical regions are now experiencing dangerously hot days about ten times more often than they did in the past.

Tropical birds have experienced a 10-fold increase in exposure to extreme heat over the past 60 years. Kotz, M. et al. (2025) Nature Ecology & Evolution

What we found: extreme heat is the biggest climate threat to birds

While changes in average temperature and rainfall do affect birds, we found the increasing number of dangerously hot days had the greatest effect – especially in tropical regions.

This is a major concern because tropical birds often have small home ranges and are highly specialised in terms of the habitats and climates they persist in. In many cases tropical birds exist within a small range of heat tolerance.

At temperatures beyond a bird’s limit of endurance, they go into hyperthermia, where their body temperature rises uncontrollably. In this state, birds may adopt a drooped-wing posture to expose more skin for heat loss, hold their beaks open and pant rapidly, spread their feathers, and become lethargic or disoriented. In severe cases, they lose coordination, fall from perches, or even collapse unconscious.

A black-collared barbet (Lybius torquatus) from Botswana. Sergey Dereliev

If they survive the experience, they can suffer long-term damage such as heat-induced organ failure and reduced reproductive capacity. Heat exposure reduces breeding success by lowering adult body condition and reducing time spent foraging – because the birds must rest or seek shade during the hottest hours.

It also causes heat stress in eggs and nestlings. In extreme events, nestlings may die from hyperthermia, or parents may abandon nests to save themselves.

Heat also increases a bird’s demand for water — not because they sweat (birds lack sweat glands) but because they lose water rapidly through evaporative cooling. This happens mainly via panting (respiratory evaporation) and, in some species, gular fluttering (rapid vibration of throat skin to increase airflow), as well as evaporation through the skin. As temperatures climb, these processes accelerate, causing significant dehydration unless birds can drink more frequently or access moister food.

Our study found that across tropical areas, the impact of climate change on birds is perhaps even greater now than the impact of direct human activities such as logging, mining or farming. This is not to say habitat destruction due to these activities is not a serious issue – it clearly is a major concern to tropical biodiversity. But our study highlights the challenges climate change is already bringing to birds in tropical regions.

Extreme heat is bad for birds in more than one way. James Watson, Maximilian Kotz and Tatsuya Amano with icons from Flaticon, design by Canva.

A clear warning

Our research highlights the importance of focusing not just on average climate trends, but also on extreme events. Heatwaves are no longer rare, isolated incidents – they are becoming a regular part of life in many parts of the world.

If climate change continues unchecked, tropical birds – and likely many other animals and plants – will face increasing threats to their survival. Change may be too fast and too extreme for many species to adapt.

And as tropical regions host a huge share of the world’s biodiversity, including nearly half of all bird species, the ripple effects could be far-reaching.

Conservation strategies must take this into account. Protecting habitats from human industrial development remains important, but it’s no longer enough on its own. Proactive action to help species adapt to climate change needs to be part of wildlife protection plans – especially in the tropics.

Ultimately if we are to preserve global biodiversity, slowing down and eventually reversing climate change is essential. That means cutting greenhouse gas emissions, investing in ways to draw down existing carbon dioxide levels, and supporting policies that reduce our impact on the planet. The fate of tropical birds – and countless other species – depends on it.

Tropical bird population declined by one-third since 1980 due to climate change, featuring the study’s lead author Maximilian Kotz (Potsdam Institute for Climate Impact Research)

James Watson, Professor in Conservation Science, School of the Environment, The University of Queensland; Maximilian Kotz, Marie Curie Postdoctoral Research Fellow, Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS), and Tatsuya Amano, Associate Professor, School of the Environment, The University of Queensland

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

Climate change - city heatwaves increase when polluting aerosols are reduced

   aerosol cover in cities                    Shutterstock

In one of the more perverse impacts of environmental monitoring and pollution control, researchers have found that heatwaves increase as harmful aerosol pollution is reduced for the purpose of obtaining cleaner air. The warming has been found to be greater in populated locations where, commensurately, there tends to be more air pollution.

Aerosols cause lower temperatures as they reflect sunlight away from the planet either through altering the cloud composition or as a direct effect. Cleaning up the air and removing aerosols for better human health has resulted ironically in increasing heatwaves and generally warming the climate. Researchers have found that for most of last century, heatwave frequency was slowed despite rising greenhouse gas emissions. This changed from 2005 as declines in polluting aerosols became more apparent. A related issue is that aerosol pollution may have masked up to half the warming effect of greenhouse gas emissions up till now. The net impact has been that aerosol reduction has added heatwaves across the planet by approximately two days per decade.

The research Article can be accessed at this link: Anthropogenic aerosol changes disproportionately impact the evolution of global heatwave hazard and exposure

Climate Change and Australia's Great Barrier Reef

World’s biggest coral survey confirms sharp decline in Great Barrier Reef after heatwave

Daniela Ceccarelli, Australian Institute of Marine Science; David Wachenfeld, Australian Institute of Marine Science, and Mike Emslie, Australian Institute of Marine Science

Official analysis of 124 reefs on the Great Barrier Reef shows coral cover has dropped sharply after a record-breaking marine heatwave in 2024, prompting grave fears over the trajectory of the natural wonder.

Over the past few years, fast-growing corals had pushed the Great Barrier Reef’s coral cover to record highs. But those corals were known to be extremely vulnerable and one bad summer away from losing those gains.

Our new report by the Australian Institute of Marine Science (AIMS) shows these fears have been realised. The percentage of living hard coral covering the Great Barrier Reef’s surface dropped in each region we surveyed.

The recent extreme highs and lows in coral cover are a troubling phenomenon. It raises the prospect that the Great Barrier Reef may reach a point from which it cannot recover.

Another global marine heatwave

In healthy corals, tiny algae produce both the coral’s main food source and its vibrant colours. When the water gets too warm, the algae are expelled and the coral’s tissue becomes transparent – revealing the white limestone skeleton beneath. This is called coral bleaching.

Coral can recover if temperatures are reduced and the relationship with the algae is restored, but it’s a stressful and difficult process. And if recovery takes too long, the coral will die.

In June 2023, a marine heatwave bleached coral reefs from the Caribbean to the Indian and Pacific Oceans.

It reached Australia’s east coast in February 2024, causing extensive coral bleaching. Aerial surveys showed three quarters of 1,080 reefs assessed had some bleaching. On 40% of these reefs, more than half the corals were white.

In the aftermath, in-water surveys measured how much coral died in the northern, central and southern Great Barrier Reef. The worst damage lined up with the highest levels of heat stress.

Sharp declines in coral cover

AIMS has surveyed reefs of the Great Barrier Reef each year since 1986, in a project known as the Long-Term Monitoring Program. It is the most extensive record of coral status on any reef ecosystem in the world.

One component of the surveys involves towing an expert observer behind a boat around the full perimeter of each reef. The observer records the amount of live, bleached and dead coral. These observations are then averaged for each location, and for each of the three regions of the Great Barrier Reef.

After each monitoring season we report on the percentage of living hard coral covering the Great Barrier Reef’s surface. It’s a coarse but robust, reliable indicator of the state of the Great Barrier Reef.

Coral losses this year were not uniform across the Great Barrier Reef. On the northern Great Barrier Reef, from Cape York to Cooktown, average coral cover dropped by about a quarter between 2024 and 2025 (from 39.8% to 30%). The largest declines on individual reefs (up to 70% loss) occurred near Lizard Island.

Reefs with stable or increasing coral cover were mostly found in the central region, from Cooktown to Proserpine. However, there was still a region-wide decline of 14% (from 33.2% to 28.6%), and reefs near Cairns lost between 17-60% of their 2024 coral cover.

In the southern reef (Proserpine to Gladstone) coral cover declined by almost a third. In the summer of 2024, southern reefs experienced the highest levels of heat stress ever recorded, resulting in substantial coral loss (from 38.9% to 26.9%).

The declines in the north and south were the largest in a single year since monitoring began 39 years ago.

Despite these losses, the Great Barrier Reef still has more coral than many other reefs worldwide, and remains a major tourist attraction. It’s possible to find areas that still look good in an ecosystem this huge, but that doesn’t mean the large-scale average hasn’t dropped.

More frequent bleaching events

Mass coral bleaching is becoming more frequent as the world warms.

Before the 1990s, mass bleaching was extremely rare. That changed in 1998 with the first major event, followed by another in 2002.

Back-to-back bleaching events occurred for the first time in 2016 and 2017. Since then, bleaching has struck the Great Barrier Reef in 2020, 2022, 2024, and again this year. The impacts of this year’s bleaching event will be revealed following the next round of surveys.

The time between these events is shrinking, giving corals less time to recover. Cyclones and crown-of-thorns starfish are also continuing to cause widespread coral loss.

You’ll see in the following charts how the percentage of coral cover has changed over time. The vertical yellow lines show the mass coral bleaching events increasing in frequency.

Confronting questions

The coral reefs of the future are unlikely to look like those of the past. The loss of biodiversity seems inevitable.

But will the reefs of the future still sustain the half a billion people that depend on them for food and income? Will they continue to protect coastlines from increasing storm activity and rising sea levels? These are confronting questions.

Effective management and research into reef adaptation and recovery interventions may bridge the gap until meaningful climate action is achieved. But above all, the key to securing a future for coral reefs is reducing greenhouse gas emissions.

Daniela Ceccarelli, Reef Fish Ecologist, Australian Institute of Marine Science; David Wachenfeld, Research Program Director – Reef Ecology and Monitoring, Australian Institute of Marine Science, and Mike Emslie, Senior Research Scientist in Reef Ecology, Australian Institute of Marine Science

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

The next UN Climate Change Conference - COP30 in Brazil

 
The 30th Conference of the Parties (COP) for the United Nations Framework Convention on Climate Change will be hosted by Brazil from 10th to 21st November 2025 in Belem, the capital of the state of Para. The city is located close to the Amazon, a crucial location given the climate change impacts on that crucial ecosystem and life resource.  There has been disquiet in the UN about the venue for COP30 as Belem is regarded as economically poor with limited capacity for dealing with an international conference of the size and scale of the COPs. For example, additional transport routes have had to be constructed for COP30 straining resources in Belem and including road construction in the Amazon itself.

Brazil holds the presidency for COP30 and has called for a course-correction as efforts to address climate change and meet agreed commitments are falling well behind stating: "the world must exponentially scale and speed up efforts to meet the commitments we have made".

The second global stocktake will take place  at COP30 measuring countries progress towards meeting the goals of the Paris Agreement. The first stocktake occured at COP28 and the results were far from reassuring. 

Brazil has proposed an action agenda for COP30 comprising six themes with a total of 30 objectives. The six themes are:

1. Transitioning Energy, Industry and Transport
2. Stewarding Forests, Oceans and Biodiversity
3. Transforming Agriculture and Food Systems
4. Building Resiliance for Cities, Infrastructure and Water
5. Fostering Human and Social Development
6. Cross-cutting issues - Unleashing Enablers and Accelerators, including on Finance, Technology and Capacity Building 

The sheer number of objectives and the wide scale of the themes appear far too ambitious and complex to achieve meaningful results and complete international agreement. Tangible results and concrete international cooperation are now essential given the increasingly dire situation.

The COP30 website can be accessed: COP30 Website 

Environmental contamination on the Earth - PFAS chemicals and a new acid rain

                                                          Nature (c) 

Science journal Nature has published further evidence of the pervasive impact of PFAS chemicals in the environment with the detection of trifluoroacetic acid (TFA) across the world in lakes, rivers, bottled water, beer, cereal crops, animal livers, human blood, urine and so on. It's been found in leaves and needles from trees in Germany, Canadian Arctic ice cores and ground water in Denmark. The concentration levels of TFA are rising with concerning increases being five to ten-fold in plants in some countries as one consequence. The graph above from Nature illustrates the increase. 

TFA is being distributed around the world through rain and snow. Wherever it rains, TFA comes with the water. 

TFA is a defined as a 'forever chemical'  as natural processes cannot break the strong carbon-fluorine bonds, a charcteristics of many of the PFAS substances. What is not clear is the health and environment impact on living things on the planet from the long term exposure to this chemical. Other PFAS chemicals have already been found to be carcinogenic. Continuing surveillence is warranted.