AI has a hidden water cost − here’s how to calculate yours

Source: The Conversation – USA (2) – By Leo S. Lo, Dean of Libraries; Advisor to the Provost for AI Literacy; Professor of Education, University of Virginia

How many AI queries does it take to use up a regular plastic water bottle’s worth of water? kieferpix/iStock/Getty Images Plus

Artificial intelligence systems are thirsty, consuming as much as 500 milliliters of water – a single-serving water bottle – for each short conversation a user has with the GPT-3 version of OpenAI’s ChatGPT system. They use roughly the same amount of water to draft a 100-word email message.

That figure includes the water used to cool the data center’s servers and the water consumed at the power plants generating the electricity to run them.

But the study that calculated those estimates also pointed out that AI systems’ water usage can vary widely, depending on where and when the computer answering the query is running.

To me, as an academic librarian and professor of education, understanding AI is not just about knowing how to write prompts. It also involves understanding the infrastructure, the trade-offs, and the civic choices that surround AI.

Many people assume AI is inherently harmful, especially given headlines calling out its vast energy and water footprint. Those effects are real, but they’re only part of the story.

When people move from seeing AI as simply a resource drain to understanding its actual footprint, where the effects come from, how they vary, and what can be done to reduce them, they are far better equipped to make choices that balance innovation with sustainability.

2 hidden streams

Behind every AI query are two streams of water use.

The first is on-site cooling of servers that generate enormous amounts of heat. This often uses evaporative cooling towers – giant misters that spray water over hot pipes or open basins. The evaporation carries away heat, but that water is removed from the local water supply, such as a river, a reservoir or an aquifer. Other cooling systems may use less water but more electricity.

The second stream is used by the power plants generating the electricity to power the data center. Coal, gas and nuclear plants use large volumes of water for steam cycles and cooling.

Hydropower also uses up significant amounts of water, which evaporates from reservoirs. Concentrated solar plants, which run more like traditional steam power stations, can be water-intensive if they rely on wet cooling.

By contrast, wind turbines and solar panels use almost no water once built, aside from occasional cleaning.

Large concrete towers emit vapor into the atmosphere.
Cooling towers, like these at a power plant in Florida, use water evaporation to lower the temperature of equipment.
Paul Hennessy/SOPA Images/LightRocket via Getty Images

Climate and timing matter

Water use shifts dramatically with location. A data center in cool, humid Ireland can often rely on outside air or chillers and run for months with minimal water use. By contrast, a data center in Arizona in July may depend heavily on evaporative cooling. Hot, dry air makes that method highly effective, but it also consumes large volumes of water, since evaporation is the mechanism that removes heat.

Timing matters too. A University of Massachusetts Amherst study found that a data center might use only half as much water in winter as in summer. And at midday during a heat wave, cooling systems work overtime. At night, demand is lower.

Newer approaches offer promising alternatives. For instance, immersion cooling submerges servers in fluids that don’t conduct electricity, such as synthetic oils, reducing water evaporation almost entirely.

And a new design from Microsoft claims to use zero water for cooling, by circulating a special liquid through sealed pipes directly across computer chips. The liquid absorbs heat and then releases it through a closed-loop system without needing any evaporation. The data centers would still use some potable water for restrooms and other staff facilities, but cooling itself would no longer draw from local water supplies.

These solutions are not yet mainstream, however, mainly because of cost, maintenance complexity and the difficulty of converting existing data centers to new systems. Most operators rely on evaporative systems.

A simple skill you can use

The type of AI model being queried matters, too. That’s because of the different levels of complexity and the hardware and amount of processor power they require. Some models may use far more resources than others. For example, one study found that certain models can consume over 70 times more energy and water than ultra‑efficient ones.

You can estimate AI’s water footprint yourself in just three steps, with no advanced math required.

Step 1 – Look for credible research or official disclosures. Independent analyses estimate that a medium-length GPT-5 response, which is about 150 to 200 words of output, or roughly 200 to 300 tokens, uses about 19.3 watt-hours. A response of similar length from GPT-4o uses about 1.75 watt-hours.

Step 2 – Use a practical estimate for the amount of water per unit of electricity, combining the usage for cooling and for power.

Independent researchers and industry reports suggest that a reasonable range today is about 1.3 to 2.0 milliliters per watt-hour. The lower end reflects efficient facilities that use modern cooling and cleaner grids. The higher end represents more typical sites.

Step 3 – Now it’s time to put the pieces together. Take the energy number you found in Step 1 and multiply it by the water factor from Step 2. That gives you the water footprint of a single AI response.

Here’s the one-line formula you’ll need:

Energy per prompt (watt-hours) × Water factor (milliliters per watt-hour) = Water per prompt (in milliliters)

For a medium-length query to GPT-5, that calculation should use the figures of 19.3 watt-hours and 2 milliliters per watt-hour. 19.3 x 2 = 39 milliliters of water per response.

For a medium-length query to GPT-4o, the calculation is 1.75 watt-hours x 2 milliliters per watt-hour = 3.5 milliliters of water per response.

If you assume the data centers are more efficient, and use 1.3 milliliters per watt-hour, the numbers drop: about 25 milliliters for GPT-5 and 2.3 milliliters for GPT-4o.

A recent Google technical report said a median text prompt to its Gemini system uses just 0.24 watt-hours of electricity and about 0.26 milliliters of water – roughly the volume of five drops. However, the report does not say how long that prompt is, so it can’t be compared directly with GPT water usage.

Those different estimates – ranging from 0.26 milliliters to 39 milliliters – demonstrate how much the effects of efficiency, AI model and power-generation infrastructure all matter.

Comparisons can add context

To truly understand how much water these queries use, it can be helpful to compare them to other familiar water uses.

When multiplied by millions, AI queries’ water use adds up. OpenAI reports about 2.5 billion prompts per day. That figure includes queries to its GPT-4o, GPT-4 Turbo, GPT-3.5 and GPT-5 systems, with no public breakdown of how many queries are issued to each particular model.

Using independent estimates and Google’s official reporting gives a sense of the possible range:

  • All Google Gemini median prompts: about 650,000 liters per day.
  • All GPT 4o medium prompts: about 8.8 million liters per day.
  • All GPT 5 medium prompts: about 97.5 million liters per day.
A small black spigot spews a stream of water over a green grass lawn.
Americans use lots of water to keep gardens and lawns looking fresh.
James Carbone/Newsday RM via Getty Images

For comparison, Americans use about 34 billion liters per day watering residential lawns and gardens. One liter is about one-quarter of a gallon.

Generative AI does use water, but – at least for now – its daily totals are small compared with other common uses such as lawns, showers and laundry.

But its water demand is not fixed. Google’s disclosure shows what is possible when systems are optimized, with specialized chips, efficient cooling and smart workload management. Recycling water and locating data centers in cooler, wetter regions can help, too.

Transparency matters, as well: When companies release their data, the public, policymakers and researchers can see what is achievable and compare providers fairly.

The Conversation

Leo S. Lo does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. AI has a hidden water cost − here’s how to calculate yours – https://theconversation.com/ai-has-a-hidden-water-cost-heres-how-to-calculate-yours-263252

Lifetime trends in happiness change as misery peaks among the young – new research

Source: The Conversation – UK – By Alex Bryson, Professor of Quantitative Social Science, UCL

Tero Vesalainen/Shutterstock

For years now, research studies across the world looking at happiness across our lifetimes have found a U-shape: happiness falls from a high point in youth, and then rises again after middle age. This has been mirrored in studies on unhappiness, which show a peak in middle age and a decline thereafter.

Our new research on ill-being, based on data from 44 countries including the US and UK, shows this established pattern has changed. We now see a peak of unhappiness among the young, which then declines with age. The change isn’t due to middle-aged and older people getting happier, but to a deterioration in young people’s mental health.

A closer look at data from the US shows this clearly. We used publicly available health data, which surveys more than 400,000 people each year, to identify the percentage of people in the US in despair between 1993 and 2024. Those we define as being in despair were the people who had answered that their mental health was not good every day in the 30 days preceding the survey.

Across most of the period, among both men and women, levels of despair were highest among the oldest age group (45-70) and higher for the middle-aged (25-44) than the young (18-24). However, the percentage of young people in despair has risen rapidly. It’s more than doubled for men, from 2.5% in 1993 to 6.6% in 2024, and almost trebled for women – from 3.2% to 9.3%.

Despair also rose markedly among the middle-aged, but less rapidly. It’s gone up from 4.2% to 8.5% for women and from 3.1% to 6.9% for men. The percentage of older men and women in despair rose only a little over the period.

As a result, by 2023-24 relative levels of despair across age groups were reversed for women. The youngest age group has the highest levels of despair, and the oldest age group the lowest. For men, the level of despair was similar for the youngest and middle-aged groups, and lowest for the oldest age group.

These trends have resulted in a very different relationship between age and ill-being over time in the US.

Between 2009 and 2018, despair is hump-shaped in age. However, the rapid rise in despair before the age of 45, and especially before the mid-20s, has fundamentally changed the lifecycle profile of despair. This means that the hump-shape is no longer apparent between 2019 and 2024.

Despair rose the most for the youngest group but also rose for those up to age 45; it remained unchanged for those aged over 45.

Our study found similar trends for Britain, based on analyses of despair in the UK Household Longitudinal Survey and anxiety in the Annual Population Survey. It also shows that the percentage in despair declines with age in another 42 countries between 2020 and 2025, based on analyses of data from the Global Minds Project.

Investigating causes

Research into the reasons for these changes is underway but remains inconclusive. The growth in despair predates the COVID pandemic by a number of years, although COVID may have contributed to an increasing rate of deterioration in young people’s mental health.

There is a growing body of evidence that identifies a link between the rise in ill-being of the young and heavy use of the internet and smartphones. Some research suggests that smartphone use is indeed a cause of worsening youth mental health. Research that limited access to smartphones found significant improvements in adults’ self-reported wellbeing.

However, even if screen time is a contributory factor, it is unlikely to be the sole or even the chief reason for the rising despair among the young. Our very recent research, which has not yet been peer-reviewed, points to a reduction in the power of paid work to protect young people from poor mental health. While young people in paid work tend to have better mental health than those who are unemployed or unable to work, the gap has been closing recently as despair among young workers rises.

Although the causes of the changes we describe have yet to be fully understood, it would be prudent for policymakers to place the issue of rising despair among young people at the heart of any wellbeing strategy.

The Conversation

Alex Bryson receives funding from the United Nations Development Program.

David Blanchflower received funding from the UN.

Xiaowei Xu receives funding from UKRI.

ref. Lifetime trends in happiness change as misery peaks among the young – new research – https://theconversation.com/lifetime-trends-in-happiness-change-as-misery-peaks-among-the-young-new-research-263665

Microplastics, pregnancy and the placenta: what we know and what we don’t

Source: The Conversation – UK – By Priya Bhide, Clinical Reader Women’s Health Research Unit, Centre for Public Health and Policy, Queen Mary University of London

alphaspirit.it/Shutterstock

During pregnancy, the placenta is the lifeline between mother and baby. It supplies the foetus with oxygen and nutrients, removes waste products and acts as a partial shield against harmful substances. But it is not an impenetrable barrier.

A 2023 systematic review found evidence that microplastics – tiny plastic particles less than five millimetres in size – may be able to cross from the mother’s bloodstream into the foetus. If confirmed, this could have serious consequences for development during pregnancy and for the long-term health of future generations.

Plastic waste does not simply disappear. Over time, sunlight, environmental conditions and mechanical wear break it down into smaller and smaller fragments: from large pieces known as macroplastics, to mesoplastics, to microplastics and eventually to nanoplastics: particles less than 100 nanometres across, small enough to be measured on the scale of molecules.

These particles come from the breakdown of everyday items: polyethylene from plastic bags and bottles, polypropylene from food containers and straws, polystyrene from takeaway cups and packaging, polyethylene terephthalate (PET) from drinks bottles, and polyvinyl chloride (PVC) from pipes, toys and clothing.

A 2025 review examining research in animals, lab-grown cells and human tissue samples found that both microplastics and nanoplastics can cross the placental barrier. Once inside, they may disrupt the delicate workings of the fetoplacental unit – the combined system of placenta and foetus – in several ways.

Studies suggest microplastics can block or interfere with the normal pathways cells use to communicate, trigger programmed cell death (apoptosis), and cause oxidative stress – a form of cellular damage that occurs when harmful oxygen-containing molecules build up faster than the body can neutralise them. Some plastics may also disrupt the endocrine system, which controls hormone release essential for growth and development.

How to limit your exposure to microplastics | BBC Global.

The ability to cross the placental barrier is especially concerning because this barrier normally acts as a highly selective filter, protecting the developing foetus from many harmful substances while allowing essential nutrients and oxygen through. If plastics bypass these defences, they could interfere with organ formation and long-term health during one of the most vulnerable stages of human development.

Exactly how these particles cross into the placenta is still not fully understood. Factors such as particle size, weight and surface charge – the tiny electrical charge carried by a particle – seem to play a role, as does the biological environment they move through.

Experiments using human placental models found that larger polystyrene particles (50–500 nanometres) did not damage placental cells and, in some cases, even seemed to improve their survival. By contrast, much smaller particles (20–40 nanometres) caused some cells to die and slowed the growth of others.

Animal studies show mixed results. In some experiments, most nanoplastics stayed in the placenta, with only a small amount reaching the foetus. In studies using human placentas in the lab, larger particles were usually trapped, while smaller ones could pass through in limited amounts.

Other research has found that nanoplastics can travel into foetal organs, including the brain, lungs, liver, kidneys and heart. Even when these organs looked normal under the microscope, researchers sometimes found smaller placentas and lower birth weights – changes that can affect a baby’s health.

Overall, this suggests that not all nanoplastics are dangerous, but certain sizes and types may pose real risks during pregnancy.

Critical window for microplastic harm

Foetal development is a finely tuned process, with cell growth, movement and death all tightly regulated. This makes it particularly vulnerable to environmental “insults” during critical windows of development. According to Barker’s foetal reprogramming theory, also known as the “developmental origins of health and disease” hypothesis, the conditions in the womb can “programme” how a baby’s organs, tissues and metabolism develop.

Harmful exposures during pregnancy, such as poor nutrition, toxins, stress, or pollutants like microplastics, can permanently alter the way organs form and function. These changes might not cause illness immediately, but they can increase the risk of chronic conditions such as diabetes, high blood pressure and heart disease later in life.

For example, if the placenta is damaged or nutrient supply is restricted, the foetus may adapt by prioritising blood flow to the brain at the expense of other organs. While this can help survival in the short term, it may result in smaller kidneys, altered metabolism or changes in blood vessel structure, all of which carry long-term health consequences.

Mothers are unknowingly passing on microplastics to unborn babies, doctors warn | 7NEWS.

Microplastics consumed through food or water may also disrupt the gut’s delicate balance of microbes, damage the intestinal lining, interfere with nutrient absorption and change how fats and proteins are processed.

Laboratory experiments show that polystyrene nanoparticles can enter embryos, accumulate in multiple organs and cause effects such as a slowed heart rate and reduced activity, even at very low doses. When inhaled by the mother, these particles can travel to the placenta and on to the foetal brain and heart.

There is also concern about potential effects on the developing brain. Some studies indicate that microplastics can build up in regions vital for learning, memory and behaviour, including the cerebellum, hippocampus and prefrontal cortex. Once there, they can cause oxidative damage, change the levels of neurotransmitters (the brain’s chemical messengers) and switch off certain genes needed for healthy brain development.




Read more:
Microplastics are in our brains. How worried should I be?


In animals, prenatal exposure to microplastics has been linked to anxiety-like behaviour, impaired learning, abnormal patterns of nerve cell growth, thinner brain tissue and disrupted connections between neurons.

Gaps in knowledge

Despite these worrying signs, there is still much we do not know. Research in this area is hampered by the fact that most studies are done in animals or in controlled laboratory settings, with little direct evidence from pregnant women.

We still do not fully understand how microplastics travel through the body, how much can accumulate in the placenta and foetus, or how easily they can be cleared.

What is clear is that further research is urgently needed. Understanding whether microplastics pose a genuine threat to reproductive health and foetal development could help shape policies on plastic production, consumption and disposal — and inform the advice given to women during pregnancy.

The Conversation

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

ref. Microplastics, pregnancy and the placenta: what we know and what we don’t – https://theconversation.com/microplastics-pregnancy-and-the-placenta-what-we-know-and-what-we-dont-262820

Yaba’s grip: how cheap methamphetamine is fuelling Thailand’s addiction crisis

Source: The Conversation – UK – By Joseph Janes, Senior Lecturer in Criminology, Swansea University

Yaba, a cheap and potent methamphetamine-caffeine pill often dubbed “crazy medicine”, has become one of Thailand’s most pressing public health crises. Easy to produce and widely available, yaba is used by everyone from factory workers seeking stamina to partygoers chasing a high.

With its low price, intense effects and highly addictive nature, yaba is one of the most commonly abused stimulants in southeast Asia – and its spread shows no sign of slowing. Yaba’s rapid rise over the past 30 years as a street drug marks a troubling evolution.

Originally introduced to east Asia during the second world war to enhance soldiers’ endurance, methamphetamine has become known as “nazi speed” in some circles. And what began as a wartime stimulant is now at the heart of a regional addiction crisis.

A typical yaba pill contains around 30% methamphetamine. When mixed with caffeine it acts as a powerful central nervous system stimulant. The drug delivers a quick and intense burst of energy, euphoria and heightened alertness, often accompanied by reduced appetite.

Users often crush and smoke the pills, though some swallow them whole. The high lasts for hours, followed by a comedown marked by exhaustion, insomnia and paranoia.

Despite its dangers, yaba is alarmingly accessible. In some areas, a single pill costs as little as 10p, making it available to the region’s poorest and most vulnerable. Yaba is now the most widely abused form of methamphetamine in Thailand and its neighbouring countries, including Laos, Cambodia and Vietnam. Its use is particularly prevalent among young people, and its popularity is rapidly growing.

A Sky News report on yaba, August 2025.

The golden triangle and the yaba boom

The golden triangle, where Myanmar, Thailand and Laos meet, has long been notorious for its role in the global opium trade. But today, it’s at the heart of Asia’s methamphetamine crisis.

According to the UN, the production and trafficking of synthetic drugs in the region have grown exponentially, with methamphetamine seizures in 2024 hitting a record 236 tonnes, a 24% increase.

Much of this production is centred in Myanmar’s Shan State, where ongoing conflict has created the ideal conditions for industrial-scale drug operations. Armed groups, often relying on drug profits to fund their military activities, operate in regions beyond government control. These lawless areas, combined with relative stability in others, have allowed for the large-scale manufacturing of yaba and other methamphetamines.

Thailand continues to serve as both a primary transit route and an end market for yaba. In 2024, Thai authorities seized over 139 million yaba pills. But despite record-breaking seizures, the actual volume of yaba reaching the streets is believed to be far higher, highlighting the limitations of enforcement efforts alone.




Read more:
Synthetic drugs are having devastating effects around the world, from Sierra Leone to the UK


While Thailand leads the region in drug seizures, efforts are outpaced by the scale of the trade. Smugglers, often armed, transport hundreds of thousands of pills at a time, exploiting porous borders – particularly between Thailand and Myanmar. Thai authorities find themselves in a constant game of whack-a-mole. When they shut down one trafficking route another quickly emerges.

Meanwhile, trafficking routes are diversifying. New land corridors now link Myanmar with Cambodia through Laos, while maritime networks are expanding across Malaysia, Indonesia and the Philippines. These changes have turned a local problem into a transnational crisis.

A Vice documentary, The Meth Warlords of the Golden Triangle.

Thailand’s response to the yaba crisis has been a mix of hardline enforcement and hesitant reform, with mixed results. A controversial policy has allowed possession of up to five yaba tablets, distinguishing users from traffickers.

A government-backed proposal to cut this to one tablet has been approved in principle and is awaiting enactment. So, the five-pill rule is still in force. Though a step toward decriminalisation, it’s a policy which has failed to offer a coherent strategy for treating addiction.

Indeed, investment in drug treatment and harm reduction has been sluggish. Formal rehabilitation services remain scarce and unevenly distributed. Without accessible, evidence-based support, many users end up cycling between incarceration and relapse.

In the absence of government-led solutions, some communities have turned to grassroots alternatives. Across Thailand, Buddhist monasteries have become unlikely centres of detox, blending ritual with rudimentary treatments.

These detox programmes often involve communal steam baths followed by the ingestion of a secret herbal concoction that is said to purge toxins through vomiting. Though lacking clinical oversight, they offer discipline and belonging for those with nowhere else to turn.

Lessons

Yaba’s rapid spread is not just Thailand’s problem but a symptom of a broader, global failure. Conflict-driven economies, porous borders and the worldwide demand for cheap synthetic drugs have created the perfect conditions for yaba to thrive. When chemicals are easily sourced, production is decentralised and law enforcement is overwhelmed, illicit drug markets grow faster than they can be contained.

Thailand’s experience highlights the shortcomings of the decades-long “war on drugs”. Despite record seizures and intensified enforcement efforts, the yaba trade continues to expand. It’s cheaper, faster and more deadly than before. Criminal networks adapt faster than authorities can act, while users are often criminalised rather than supported.

What’s needed now is not more punishment, but a serious, coordinated effort that includes public health infrastructure and evidence-based harm reduction strategies.

Buddhist monasteries should not have to serve as a stand-in for state-funded addiction treatment. The resurgence of the golden triangle as a global synthetic drug hub is a warning that the world cannot afford to ignore.

The Conversation

Joseph Janes does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. Yaba’s grip: how cheap methamphetamine is fuelling Thailand’s addiction crisis – https://theconversation.com/yabas-grip-how-cheap-methamphetamine-is-fuelling-thailands-addiction-crisis-262765

Democrats dig in with a new type of campaign against Trump

Source: The Conversation – UK – By Dafydd Townley, Teaching Fellow in US politics and international security, University of Portsmouth

Over the past few months, the governor of California, Gavin Newsom, has increasingly become a focal point for the Democratic party’s resistance to the US president, Donald Trump.

And a poll taken in August 2025 gave Newsom a bump in support from Democrats and Democratic-leaning independents, going from 11% in June to 19% in August. He was the only potential 2028 Democratic presidential candidate who saw gains in the survey.

Touted by many as a potential replacement for the ailing Joe Biden as the 2024 Democrat presidential nominee, Newsom didn’t have a chance to stand as Biden passed the mantle directly to Kamala Harris.

But in the past few months the charismatic former mayor of San Francisco has been increasingly outspoken in his criticism of the Trump administration. On August 27 he said Americans needed to “wake up” to threats he said were posed by the current administration.

Part of Newsom’s approach has recently been to adopt the same mass communication methods as Trump has. This is not the highbrow intellectual route that Democrats have taken in the past. This is AI slop – the low-quality, mass-produced online content generated by artificial intelligence, designed to manipulate social media platform’s algorithms for greater exposure.

New social media style

Over the past few weeks, Newsom’s team has released numerous social media messages mimicking and mocking Donald Trump.

For instance, this month, Newsom’s staff posted a message on X featuring an AI-generated image of the governor wearing a crown on the cover of Time magazine, accompanied by the caption: “Long Live the King.” The following day, the same account reposted an AI-generated image of a muscular Newsom holding the American flag with the caption: “In Gavin We Trust.”

The approach seems to be popular. Newsom’s team also released parody-Trump merchandise with reports suggested that it raised US$100,000 (£73,900) online on its first day of release. And Newsom’s use of this AI-produced content may well be redefining how Democrats attack Republicans in the future.

Newsom made no excuses for taking such a route. When questioned by Fox LA about this new approach recently he said: “I’ve changed, the facts have changed; we (the Democrats) need to change.”

The California governor is not the only Democrat to stand up to Trump. While Democrats in Congress are hamstrung by the Republican majority in both the House and Senate, elected Democrat officials in state governments are working hard to limit Trump’s influence.

When Trump federalised the California National Guard to end public protests against the activities of the Immigration and Customs Enforcement agency (Ice), Newsom and California’s attorney-general, Rob Bonta, sued Trump, defense secretary Pete Hegseth, and the Department of Defense.

Newsom and Bonta argued that the president had exceeded his constitutional authority, as such action had been taken without the governor’s consent. Newsom defiantly declared that: “The president is not a king and is not above the law.”

An appeals court allowed Trump to retain control of the National Guard while the lawsuit continued. The federal trial opened in San Francisco on August 11, and a judgment had not been released as this article went live.

California governor Gavin Newsom has been testing out a new style of social media, and it’s getting noticed.

In Chicago

As well as ordering the Department of Defense to create specialist National Guard units to deal with civil unrest, Trump has also threatened to use troops in other Democrat-controlled cities such as Baltimore and New York, where he also claims that state governments are failing to deal with crime waves.

On August 26, in an eloquent but defiant speech, Illinois governor JB Pritzker warned Trump not to send troops to Chicago: “Mr President, do not come to Chicago. You are neither wanted here nor needed here,” Pritzker said.

Mirroring Newsom’s claims of executive overreach, Pritzker said that Trump’s determination to use troops to reduce crime figures in Democrat-controlled cities around the country was to “lay the groundwork to circumvent our democracy, militarise our cities and end elections”.

“If this were happening in any other country, we would have no trouble calling it what it is, a dangerous power grab,” Pritzker said.

Trump has used the National Guard as a law enforcement tool in Washington DC, another Democrat-controlled city, since the middle of August. The US president sent troops, complete with armoured vehicles, to the nation’s capital, where he claimed violent crime was out of control. While the troops were initially unarmed, in the past week officials have said that guard members have been authorised to carry either their M17 pistols or M4 rifles.

According to figures released by the Washington Metropolitan Police Department, violent offences were at their lowest level in 2024 in 30 years. The pattern appears to be continuing in 2025, with violent crime down 26% compared to this time last year and robberies falling by 28%. The Democrat mayor of Washington DC, Muriel Bowser, called Trump’s deployment of troops an “authoritarian push”.

It turns out the use of troops in Washington DC has not gone down that well with Americans. According to a Reuters/Ipsos poll during the last week in August, only 38% of Americans supported Trump’s actions, with 46% opposed.

After what had seemed to be a good start to the year for Trump, his job approval rating is fragile. With the midterms just over a year away, the Republicans need to keep one eye on the polls if they wish to retain their majorities in the House and Senate.

Whether Newsom’s pushback against the administration is the start of his campaign for 2028 is unclear, but it would do him no harm to establish himself as a national political figure, a portrayal with which he can build a campaign for 2028.

The Conversation

Dafydd Townley does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. Democrats dig in with a new type of campaign against Trump – https://theconversation.com/democrats-dig-in-with-a-new-type-of-campaign-against-trump-263869

Research shows children’s wellbeing drops when they start secondary school – here’s why

Source: The Conversation – UK – By Paty Paliokosta, Associate Professor of Special and Inclusive Education, Kingston University

Rawpixel.com/Shutterstock

For many pupils, the move to secondary school is a moment of anticipation – new friends, new subjects, and a growing sense of independence. But research in England shows this transition often comes with a hidden cost: a sharp and lasting decline in wellbeing.

Data from a 2024-2025 survey carried out by education support and research company ImpactEd Group with over 80,000 pupils shows a drop in children’s wellbeing between year six – the last year of primary school – and year eight.

This report found that enjoyment of school plummets, feelings of safety decline, and belief that their efforts will lead to success (known as self-efficacy) drops significantly. Children receiving free school meals were also less likely to say they enjoyed school, with this gap continuing to widen into secondary school.

This isn’t just adolescent growing pains. Secondary school pupils in the UK are more miserable than their European peers. Data from the Pisa programme, which assesses student achievement and wellbeing internationally, shows that in 2022 the UK’s 15-year-olds had the lowest average life satisfaction in Europe.

It’s a systemic problem – but one that can be changed.

Difficult transitions

Moving to secondary school involves much more than a change of location. Pupils must adapt to new teachers, routines, academic demands and social dynamics. And this takes place while they are going through puberty, one of the most intense periods of emotional and neurological development.

Research on school transitions stresses that success depends not only on a child’s “readiness,” but also on the school system’s capacity to support them.

Unfortunately, many schools prioritise performance metrics over relationships. This may leave many pupils – particularly those who are neurodivergent, have special educational needs, or who come from minoritised backgrounds – feeling disconnected and unsupported. This can deeply affect their wellbeing.

One major barrier to belonging is the use of zero-tolerance behaviour policies. These strict approaches to discipline – silent corridors, isolation booths, high-stakes punishments such as suspensions – are becoming more common in large secondaries and academies. Advocates have claimed these policies create firm boundaries in schools. But for many pupils, especially those with ADHD, autism, or a history of trauma, they may instead create anxiety, alienation and disengagement from school.

Children with special educational needs are excluded from school at some of the highest rates in the country. According to the Children and Young People’s Mental Health Coalition, a collaborative network of over 300 organisations including mental health organisations and youth support services, many of these children are not “misbehaving,” but expressing unmet emotional and mental health needs. Punitive responses frequently worsen their difficulties.

Pupils on stairs at school
The environment of secondary school can be very different to that of primary education.
Rawpixel.com/Shutterstock

Schools that adopt behaviour policies that focus on emotional literacy and building trust have reported success in building a caring environment.

A hidden curriculum

While these challenges affect many students, working-class pupils often face a more acute and entrenched form of educational alienation. A deeper look into the structure of secondary education in England reveals systemic inequalities that shape how different children experience school.

According to Professor Diane Reay, a leading expert on education and social class, the British school system continues to fail working-class children. Her research suggests that schools in disadvantaged areas are more likely to feature rigid discipline, “teaching to the test,” and a narrow, fact-heavy curriculum. In such spaces, there is little room for creativity, critical thinking, or personal expression.

Instead of feeling seen and valued, many working-class students may experience school as a place of constant control and low expectations. They are more likely to encounter deficit narratives: being told what they lack, rather than having their strengths recognised or nurtured.

This dynamic plays out most starkly during the transition to secondary school. Pupils from working-class backgrounds often enter year seven already disadvantaged – socially, economically, and in terms of cultural capital. This means that in unfamiliar settings where middle-class norms dominate, they may not speak the “right” way, dress the “right” way, or know the unspoken rules. These students frequently find themselves on the outside looking in.

Beyond class, issues of race and cultural background also play a key role in how pupils experience school. Students from minority backgrounds often also encounter what researchers refer to as the “hidden curriculum”.

This is a set of unspoken norms that reflect white, middle-class values, and which they may be unfamiliar with. This affects everything from which stories are told in the curriculum to how the behaviour of students is interpreted by teachers.

The year-seven dip is not inevitable. But reversing it requires more than tweaks to transition plans or behaviour policies. It demands a fundamental shift in how we understand inclusion, belonging and educational success. Schools need to put policies in place that help students feel safe, connected and empowered to manage conflict. And they should recognise that working-class and marginalised pupils face systemic barriers, and commit to dismantling them.

The Conversation

Dr Paty Paliokosta is an Associate Professor in Inclusive Education and leads the Inclusion and Social Justice SIG at Kingston University, London. She co-leads the National SENCO Advocacy Network.

ref. Research shows children’s wellbeing drops when they start secondary school – here’s why – https://theconversation.com/research-shows-childrens-wellbeing-drops-when-they-start-secondary-school-heres-why-260737

The First King of England: Æthelstan and the Birth of a Kingdom – a deep and nuanced analysis of a complex monarch

Source: The Conversation – UK – By Clare Downham, Professor, University of Liverpool

Æthelstan ( 894 to 939) in an illustration in a manuscript of Bede’s Life of Saint Cuthbert. Wikimedia

The reign of Æthelstan (924 to 939) has excited a significant amount of study in recent years. In 2004 there was The Age of Athelstan, by Paul Hill. In 2011, Sarah Foot published Æthelstan: The First King of England, and in 2018, Tom Holland released Athelstan: The Making of England. A key theme in these books is the role of Æthelstan as unifier of the kingdom of England.

Æthelstan’s most famous battle, Brunanburh (937) was fought against a coalition of vikings and Celtic-speaking peoples. Brunanburh was seen, perhaps erroneously, to secure the future of a unified England. As a historian of this period, I have argued that the “kings and battles” story of the past often cloaks the longer-term engines of political change.

This latest book to add to this history is The First King of England: Æthelstan and the Birth of a Kingdom by David Woodman, which addresses both themes of English unification and viking politics. It also seeks to provide deeper insights into the personality of King Æthelstan. The result is a highly engaging and informative biography.

The writing is well pitched for a general reader. The terminology used in tenth-century political history is explained in a clear and concise way without seeming patronising to the reader. This is particularly useful in the introduction where the different sources for Æthelstan’s reign are discussed, inviting the reader to consider how historical narratives are constructed from the evidence that survives.

Woodman draws on a range of contemporary sources. He also makes extensive use of the 12th-century text, Gesta regum Anglorum (Deeds of the kings of England), by historian William of Malmesbury, which is a
key source for the life of Æthelstan. Given that legends surrounding this tenth-century king were already evolving and developing a life of their own in William’s time, a deeper dive into that particular text to evaluate its reliability, would have been welcome.

There is intriguing discussion in Woodman’s book around the challenges that Æthelstan faced at the start of his reign. Tensions had arisen between Æthelstan and his father Edward the Elder, as the king appears to have favoured Æthelstan’s half and younger brother Ælfweard of Wessex as his successor. Such family rivalries provide relatable drama to usher in the reign of the new king.

Æthelstan’s support was based in Mercia (a powerful kingdom which was in the Midlands) while his brother’s was in Wessex (a major kingdom in what is now south west England). When Edward the Elder died in 924, Æthelstan was accepted as King of Mercia but reluctantly in Wessex, even though Ælfweard died shortly after his father.

These rivalries and family dramas could suggest that the rebellion at the Mercian stronghold of Chester, which just preceded the death of Edward the Elder in 924, had been instigated by Æthelstan himself (although this point is not made by Woodman). The intrigue continues as some years later, Æthelstan was implicated in the death of Ælfweard’s full brother Edwin.

The circumstances in which Æthelstan later extended his power over Northumbria and how he held together a unitary “kingdom of England” are explored in thoughtful detail. One of the greatest strengths of the book is the discussion of categories of contemporary sources: diplomas (written grants of lands and privileges), laws and coinage.

Æthelstan’s diplomas were issued at his court, recording time and place and witness lists. Their records are skilfully deployed by Woodman to trace Æthelstan’s travels, the changing membership and hierarchy of his assemblies, his claims to power, and the literary skills and possible identity of their authors.

Far from being a dry and dusty subject, Woodman writes vividly about Æthelstan’s laws. Legal punishments reveal harsh insights.

For example, according to one code, if an enslaved man is found guilty of theft of goods over a certain value, he was to be stoned to death by fellow slaves. Æthelstan took a harsher line than his predecessors on theft, and comparison with earlier codes may have merited more overarching consideration to understand his reign.

This uptick in state violence may correlate with growing imbalances of power and concerns over obedience as government became more powerful. Centralisation of authority and obedience are themes in Woodman’s discussion of coin iconography, the locations of mints and how the recorded names of those who minted the coins demonstrate cultural diversity in Æthelstan’s England.

Woodman provides a well-rounded analysis of Æthelstan’s government, dealing with ecclesiastical politics and piety. Æthelstan offered conspicuous gifts to churches whose favour he sought to win at home and abroad.

There are also insightful discussions around Æthelstan’s scholarly interests and his collection and donation of relics and manuscripts. These provide compelling glimpses into the king’s personality.

The desire to dominate neighbouring peoples also appears as a less savoury personality trait. Æthelstan sought to make his bombastic claims to be king of all Britain, or “Rex totius Britanniae,” which became a reality through negotiation and threats of violence. The 934 campaign, which the king led to North Britain (Scotland and England did not exist in 926 but this would have been modern-day Scotland), gives rise to extended discussion and helps readers understand the events leading to the famous Battle of Brunanburh, three years later.

Another significant bonus in this book is the analysis of Æthelstan’s continental links. As accounts of his reign tend to be focus on the “making of England” (and even a “making of Britain”) narrative, this dimension of his reign and his legacy has not always received the attention it deserves. Woodman brings together the significant articles on this topic composed by Sarah Foot, Simon MacLean and others, and combines them with perceptive analysis of primary sources.

Overall, Woodman presents Æthelstan as a European king, a scholar, with ruthless ambitions and a strong streak of piety. It would be easy to caricature Æthelstan within certain narratives that aligns with views of English nationhood as it is today, but this book provides a deeper and more nuanced analysis of this fascinating king.


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This article features references to books that have been included for editorial reasons, and may contain links to bookshop.org. If you click on one of the links and go on to buy something from bookshop.org The Conversation UK may earn a commission.

The Conversation

Clare Downham does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. The First King of England: Æthelstan and the Birth of a Kingdom – a deep and nuanced analysis of a complex monarch – https://theconversation.com/the-first-king-of-england-aethelstan-and-the-birth-of-a-kingdom-a-deep-and-nuanced-analysis-of-a-complex-monarch-264145

Sri Lanka moved to end elite impunity with arrest of former president

Source: The Conversation – UK – By Thiruni Kelegama, Lecturer in Modern South Asian Studies, Oxford School of Global and Area Studies., University of Oxford

Sri Lanka’s former president and six-time prime minister, Ranil Wickremesinghe, was arrested on August 22 for allegedly misusing state resources while in office. He is accused of using public funds to attend his wife’s graduation ceremony in London after an official visit to the US in 2023. Wickremesinghe has since been granted bail on a 5m rupee (£12,300) bond.

His arrest represents one of the most consequential moments in the Sri Lanka’s postcolonial history. It marks the first time a former head of state has ever been detained in Sri Lanka, shattering the longstanding assumption that those at the top of the country’s politics remain forever beyond the reach of the law.

The assumption of elite impunity was built on decades of precedent. This reached its apex under the Rajapaksa family, who dominated Sri Lankan politics between 2005 and 2022, as corruption was woven into the very fabric of governance.

The Rajapaksas captured state institutions, placing family members and loyalists in key positions across the bureaucracy, military and judiciary. Public wealth was also diverted for private gain. The certainty that those in power would remain beyond legal reach, regardless of the scale of abuse, became embedded in Sri Lanka’s political DNA.

That certainty cracked in 2022 when mass protests, commonly known as Aragalaya, swept the Rajapaksas from office. The following year, the Sri Lanka’s supreme court held the family responsible for bankrupting the state by mishandling the economy.

This was a landmark ruling, but one that had little material effect. The Rajapaksas were only condemned and not punished. Wickremesinghe’s arrest is different. It shows that accountability has moved beyond a single dynasty and now threatens the entire Sri Lankan political class.

Thousands of Sri Lankans waving flags at a protest.
Thousands of Sri Lankans attend a protest demanding the resignation of former president Gotabaya Rajapaksa in 2022.
Ajit Wick / Shutterstock

The timing of the arrest deepens its significance. Sri Lanka is currently under an International Monetary Fund (IMF) bailout programme to help stabilise its economy. It was negotiated by Wickremesinghe in the wake of bankruptcy and is now being carried forward by the National People’s Power (NPP) government.

The bailout loan comes with punitive terms. Higher taxes, subsidy cuts and shrinking public services are all being shouldered by ordinary citizens. They pay daily for a crisis born of elite misrule. In this context, elite accountability is not just symbolic, it is the bare minimum of justice.

Moment of truth

This moment is defining for the NPP government. Anura Kumara Dissanayake was elected in 2024 having pledged to prosecute corruption and abolish the executive presidency – the constitutional embodiment of unaccountable power since 1978. His government faces both opportunity and test in Wickremesinghe’s arrest.

Few individuals embodied establishment politics more fully than Wickremesinghe did. The immediate response to his arrest was telling. Three former presidents, Chandrika Kumaratunga, Mahinda Rajapaksa and Maithripala Sirisena, along with opposition leader Sajith Premadasa rushed to show solidarity with the detained ex-president. This suggests the old guard’s instinct for self-preservation remains strong.

If prosecutions prove selective, the NPP also risks echoing the very cynicism it sought to displace – wielding justice as a political weapon rather than institutionalising it as a principle. While the government has already launched investigations into a broad swathe of former officials – from a member of the Rajapaksa dynasty to more than 20 ex-ministers – these early moves could be symbolic.

The real test lies with the Rajapaksas. Their rule was virtually synonymous with impunity. If they too are truly held to account, it would mark a genuine transformation from dynastic protection to the beginning of rule of law.

Such moves carry risks. Prosecutions may be dismissed as political vendetta, further polarising Sri Lanka’s already fragmented society. The protests that erupted in Colombo following Wickremesinghe’s arrest offer early evidence of this dynamic.

But the danger of inaction is greater. To do nothing, after an economic collapse born of corruption and elite mismanagement, would reinforce public cynicism and effectively license future impunity. It would tell citizens already enduring austerity that, once again, those at the top remain beyond reach.

Wickremesighe’s arrest also sends a signal beyond Sri Lanka’s borders. For years, the country’s reputation was defined by scandals and violations that went unpunished.

In 2015, for example, Sri Lanka’s central bank issued ten times the advertised amount of 30-year bonds at inflated interest rates. This cost the state an estimated 1.6 billion rupees (roughly £3.9 million) in excess losses. Then, several years later, no criminal proceedings were brought against senior officials for failing to act on intelligence warnings ahead of the 2019 Easter Sunday bombings that killed 269 people.

This pattern of impunity extended beyond domestic scandals. The UN Human Rights Council had passed multiple resolutions on Sri Lanka over alleged war crimes and enforced disappearances. Yet here too the state’s response remained the same. It made promises of accountability that never materialised.

The arrest of Wickremesinghe suggests this may be changing. It is a signal that Sri Lanka is finally serious about the rule of law – not just as a slogan, but as practice.

Sri Lanka’s myth of elite untouchability has cracked, but whether it shatters completely depends on what follows. While Wickremesinghe’s arrest is historic, lasting transformation requires institutions capable of sustained accountability.

The choice before the NPP is clear: accountability as a spectacle or as a system. Having paid the price of impunity, Sri Lankans may finally be positioned to demand its opposite.

The Conversation

Thiruni Kelegama receives funding from the Rights to the Discipline Grant by the Antipode Foundation (2024). She is a Director of the Institute of Political Economy, Sri Lanka.

ref. Sri Lanka moved to end elite impunity with arrest of former president – https://theconversation.com/sri-lanka-moved-to-end-elite-impunity-with-arrest-of-former-president-263945

Warming temperatures affect glaciers’ ability to store meltwater, contributing to rising sea levels

Source: The Conversation – Canada – By Danielle Halle, PhD Candidate, Glaciology, University of Waterloo

In higher elevations, firn, frozen water that is something between snow and ice, covers the top of glaciers. Firn plays a critical role in regulating glacial meltwater and sea level rise.

It does this by absorbing meltwater, the water released by melting glaciers. The ability of the firn layer to absorb meltwater — its “sponginess” — can be determined by the amount of pore space available, which is impacted by several variables such as temperature, firn grain size and presence of ice layers within the firn layer. A more spongy firn layer allows for more meltwater to be stored as it trickles down and refreezes when it reaches colder temperatures at depth.

Layers of firn can exist between refrozen ice layers. The greater the number of refrozen ice layers there are embedded within the firn layer, the more intense a melt period has been. These layers can act as a barrier against meltwater being stored within the spongy firn layer, forcing the meltwater to flow to lower elevations, eventually exiting the glacier as runoff into the ocean.

Glacial loss

The Devon Ice Cap is located within Inuit Nunangat, the homelands of the Inuit. It is one of the largest ice caps in the Canadian Arctic at approximately 14,000 square kilometres in area and with a maximum thickness of approximately 880 metres.

The Devon Ice Cap is one of many ice masses that play a vital role in the Arctic ecosystem, including in the nearshore marine ecosystem.

a map showing the location of the Devon ice cap
A 1969 map of the Devon Ice Cap, Nvt.
(Glacier Atlas of Canada/Government of Canada)

Our research team found that the Devon Ice Cap in Nunavut experienced a decrease in the amount of refrozen glacial meltwater in its firn layer. This was caused by the cooler-than-average summer air temperatures the region experienced in 2021.

Air temperature and glacier melt are closely related, and our research shows how the firn layer is affected by climate changes. It also highlights the fact that climate change does not happen in a linear fashion. Rather, temperatures fluctuate while trending globally towards glacial loss.

Comparing data

We observed how much ice was in the firn layer by extracting six shallow firn cores from different elevations in 2022 and comparing them to cores extracted in 2012.

We found that at the lowest elevation sites on the ice cap (1,400 metres above sea level), where air temperatures are expected to be warmer than at higher elevations, the amount of refrozen meltwater content decreased by nearly 30 per cent. Conversely, at the highest elevation site (1,800 metres above sea level, where temperatures are colder), the decrease was about 11 per cent. These changes occurred despite higher average summer temperatures between 2012 and 2022.

a researcher site on ice
Documenting the different layers of the firn cores collected fromt the Devon Ice Cap in 2022.
(B. Danielson), CC BY

Greenland Ice Sheet

A similar pattern was also observed on the Greenland Ice Sheet in 2019. Researchers there found less glacial meltwater had refrozen within the firn layer along several points.

The decrease in frozen meltwater seen in the Greenland Ice Sheet’s firn layer had also occurred during a time of less surface melt. Less surface melt in one year can help to increase meltwater storage in the firn layer in following years.

Overall, it was found that in the long term, the Greenland Ice Sheet is more sensitive to warming than cooling. In other words, one extreme year of summer heat had a greater impact on the amount of meltwater compared to other cooler years when meltwater was temporarily stored.

Eventually, the Greenland Ice Sheet and other ice masses across the globe will reach a peak refreezing point, where meltwater can no longer be stored within the firn layer because so much has already accumulated, creating an impermeable layer of ice. Instead of this water being stored in the firn layer, it will run through and off the glacier.

Future measurements

Our findings show how the firn layer responds to one summer of below-average air temperatures. A reduction in the amount of refrozen glacial meltwater stored means an increase in the glacier’s capacity to store meltwater for the next season. This demonstrates the firn layer’s ability to potentially reduce meltwater runoff during a given year.

The future of the glaciers and ice caps in the Canadian Arctic will depend on changes in global temperatures and how glacial physical processes respond. The Canadian Arctic consists of 14 per cent of the world’s glaciers and ice caps by volume, and melting glaciers in the region are projected to be one of the greatest contributors to sea-level rise in the next century.

A better understanding of firn processes and changes in porosity will help researchers quantify how much and when sea level rises are expected from the Canadian Arctic glaciers.

The Conversation

Danielle Halle receives funding from POLAR knowledge Canada, Northern Scientific Training Program, Ontario Graduate Scholarship and the University of Waterloo.

Wesley Van Wychen does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. Warming temperatures affect glaciers’ ability to store meltwater, contributing to rising sea levels – https://theconversation.com/warming-temperatures-affect-glaciers-ability-to-store-meltwater-contributing-to-rising-sea-levels-240628

New study shows how Amazon trees use recent rainfall in the dry season and support the production of their own rain

Source: The Conversation – Canada – By Magali Nehemy, Assistant Professor, Department of Earth & Environmental Science, University of British Columbia

The Amazon is the world’s largest tropical forest, home to unmatched biodiversity and one of the planet’s longest rivers. Besides the Amazon River, the Amazon rainforest also features “flying rivers:” invisible streams of vapour that travel through the atmosphere, fuelling rainfall both within the forest and far beyond its boundaries.

The forests play a central role in this system. Much of the moisture that rises into the atmosphere comes from transpiration. Trees pull water from the soil through their roots, transport it to the leaves and release it as vapour. That vapour becomes rainfall — sometimes locally, sometimes hundreds of kilometres away.

In the dry season when rain is scarce, up to 70 per cent of rainfall in the Amazon comes from this moisture-recycling generated by the forest itself. This raises a key question: where do the trees find the water to keep the cycle going during the driest months?

Our study in the Tapajós National Forest

In our recent study, colleagues and I set out to answer this question. In 2021 during the peak of the dry-season, we conducted fieldwork in the Tapajós National Forest, in Pará state, Brazil on the traditional territory of the Mundurukú people.

We worked across two contrasting sites: a hilltop forest with a deep water table (about 40 metres), and a valley forest near a stream where groundwater is much shallower.

The results were surprising. Most water used for transpiration in the dry season did not come from deep reserves, but from shallow soil. In a year without extreme drought or floods, 69 per cent of transpiration on the hill and 46 per cent in the valley came from the top 50 centimetres of soil.

Our research also found that water stored in the shallow soil had fallen on land recently, specifically during the dry season. In other words, the forest rapidly recycles the rain: it falls, infiltrates shallow soil, is absorbed by roots and is released back into the atmosphere, fuelling new rainfall — right when the forest needs water most.

The role of tree diversity

Not all trees contribute to this cycle equally. The Amazon’s diversity means species use different strategies to access water stored in the soil. Our study showed that a key factor is “embolism resistance,” a measure of how well a tree can keep water moving through its tissues during drought.

Trees that are more resistant in preventing air blockages in their water transport system are able to keep drawing water from soil and releasing moisture into the atmosphere, even in the driest months.

Drawing water from dry soil is like a tug-of-war, where water is the rope: the soil holds onto the water while the roots try to pull it free. The drier the soil, the stronger the pull required.

Species with high embolism resistance can keep transpiring as soils dry, therefore they can rely on recently fallen rain in shallow soil. Less resistant species are more drought-sensitive and will rely more on deeper roots to reach stable reserves, or other strategies.

Our study shows that the higher the resistance to embolism, the higher the proportion of shallow water a tree uses, and therefore the more recent rainfall from the dry season is returned to the atmosphere. This is the first evidence that rapid recycling of dry-season rainfall through transpiration is strongly supported by embolism resistance.

The challenge ahead

Rainforests are facing significant threats of human encroachment and deforestation. Recent policy changes in Brazil risk accelerating deforestation in sensitive areas such as the Amazon, the Cerrado savannah and Atlantic Forest — all vital for the water cycle.

A disrupted water cycle with less rain threatens biodiversity and natural habitats, as well as water security food supplies.

Local and Indigenous communities are the most directly affected, but the impacts extend far beyond. The flying rivers also carry Amazonian moisture to southern and central parts of Brazil, supporting agriculture in major grain-producing regions. Less forest means less rain, threatening crops, food security and the economy.

This delicate balance is threatened by deforestation. When forests are cut down, fewer trees release moisture into the air through transpiration, reducing the formation of local and nearby rainfall during the dry season.

Forest loss weakens the very system that sustains rainfall — the recycling of water through transpiration. Our study shows that embolism-resistant trees play a central role by quickly returning dry-season rainfall to the atmosphere, where it fuels new rainfall.

The message is clear: without the forest, there is no rain, and without rain, no forest. The quick recycling of dry-season rain keeps the Amazon alive through its driest months. It also plays a crucial role in triggering the return of the wet season. If the forest loses its ability to recycle this water, the entire hydrological cycle risks collapse.

Brazil will host the 2025 United Nations Climate Change Conference, COP30, in November. As policymakers gather, preserving rainforests like the Amazon must be among the issues at the top of the agenda.

The world’s forests are complex and biodiverse places with delicate natural systems that sustain them. The Amazon truly functions as a rain-making engine that helps sustain life, inside and beyond the forest.

The Conversation

Magali Nehemy does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

ref. New study shows how Amazon trees use recent rainfall in the dry season and support the production of their own rain – https://theconversation.com/new-study-shows-how-amazon-trees-use-recent-rainfall-in-the-dry-season-and-support-the-production-of-their-own-rain-263525