An uptick in heat extremes, driven by human-caused climate change, has caused tropical bird populations to decline by up to 38% since the 1950s, according to a first-of-its-kind analysis.
The study combines ecological and climate attribution techniques to trace the fingerprint of fossil-fuelled climate change on declining wildlife populations.
It shows that an increase in heat extremes driven by climate change has caused tropical bird populations to decline by 25-38% in the period 1950-2020, when compared to a world without warming.
The findings could help to explain why tropical bird numbers have declined even in pristine rainforests, a phenomenon that previously mystified biologists, the scientists say.
‘Chance encounter’
Over the past few decades, an emerging field of science known as “climate attribution” has used a standardised set of techniques to trace the fingerprint of human-caused warming on different elements of the climate system, ranging from worsening extreme weather events to episodes of glacier melt.
The new research, published in Nature Ecology and Evolution, is the first to use climate attribution techniques to detect the fingerprint of climate change on declining wildlife populations.
The study came about following a “chance encounter” between lead author Dr Maximilian Kotz, a climate scientist at the Barcelona Supercomputing Center in Spain, and his co-authors, who are biodiversity experts at the University of Queensland in Australia, while Kotz was completing a research stay in Australia.
Kotz says to Carbon Brief:
“As far as we are aware, this is the first animal climate attribution study.”
The researchers decided to focus on birds, rather than other animal species, as they have the “best available data, covering a good range of different species and geographies”, he adds.
Heat extremes
The authors examine how an intensification of heat extremes could have impacted bird populations, while controlling for other factors known to affect wildlife, including average temperature increase and human pressures, such as land-use change.
Episodes of extreme heat are known to have an immediate and long-lasting impact on birds, Kotz says:
“High temperature extremes can induce direct mortality in bird populations due to hyperthermia and dehydration. Even when they don’t [kill birds immediately], there’s evidence that this can then affect body condition which, in turn, affects breeding behaviour and success.”
Using statistical techniques, the scientists first analyse historical records to identify how bird populations have responded to fluctuations in climate, including heat extremes, over 1950-2020.
The team sourced global data on bird populations from the database that underlies the Living Planet Index, put together by the environmental charity WWF. They note it is the most comprehensive database available, but still has “clear geographic biases”, with global north regions better represented than those in the global south.
They use an attribution framework to estimate the extent to which human-caused warming influenced the changes in heat extremes observed in that time period, then calculate the impact of these climate-change-driven heat extremes on bird population changes from 1950-2020.
(The authors defined “heat extremes” as temperatures within the top 1% of daily temperatures over 1940-70, with data taken from ERA5, a global reanalysis dataset, which combines data from weather stations, satellites and model output.)
To understand how this would compare to a world without climate change, the researchers subtract this impact from the historical records.
Comparing their results to the counterfactual world without climate change allowed them to quantify how bird populations have changed as a result of human-driven increases in heat extremes.
Mapped
The research finds that human-driven heat extremes have had “strong negative impacts” on bird population numbers, with those residing at lower latitudes being the most affected.
The map below shows the percentage change in bird population abundance attributed to heat extremes over 1950-2018, when compared to a world without climate change.
On the map, dark red shows large decreases in population abundance, while light blue indicates small increases. (Abundance refers to the number of individual animals in a given population.)
The research finds that birds in the tropics have experienced the largest declines attributable to heat extremes.
It concludes that an uptick in heat extremes has caused tropical bird abundance levels to decline by 25-38% in the period 1950-2020, when compared to a world without warming.
The range in the size of that impact reflects the results of different models, which each use slightly different techniques to simulate changes to bird populations, Kotz says.
Tropical turmoil
In their paper, the authors note that their finding that tropical birds have experienced the most substantial declines are “consistent” with other studies indicating that “birds in these regions may be closer to the thermal limits at which impacts start to occur”.
They add that the findings are “particularly pertinent, given recent documentation of declining tropical bird populations, even in undisturbed habitats”.
One previous study found that in a “relatively undisturbed” part of the Amazon rainforest, bird abundance declined by more than 50% from 2003 to 2022. Similar results were found in a forest in Panama.
The authors of the new study say:
“The source of such declines have been noted as unknown, yet they are of a similar order of magnitude to our estimates of the impacts of intensified heat extremes.”
Their results suggest that “in tropical realms, climate change impacts on bird populations may already be comparable to land pressures that lead to habitat destruction and degradation”, the authors say.
This has “potential ramifications” for commonly proposed conservation strategies, such as increasing the amount of land in the the tropics that is protected for nature, they continue:
“While we do not disagree that these strategies are necessary for abating tropical habitat loss…our research shows there is now an additional urgent need to investigate strategies that can allow for the persistence of tropical species that are vulnerable to heat extremes.”
In some parts of the world, scientists and conservationists are looking into how to protect wildlife from more intense and frequent climate extremes, Kotz tells Carbon Brief.
He references one project in Australia which is working to protect threatened wildlife following periods of extreme heat, drought and bushfires.
Informing forecasts
As well as shedding light on what could be behind the rapid decline of birds in the tropics, the findings also underscore the importance of examining changes in climate extremes, rather than just annual global temperature rise, says Prof Alex Pigot, a biodiversity scientist at University College London (UCL), who was not involved in the research. He tells Carbon Brief:
“Most of the models that have been used to make projections of risk to biodiversity under future climate change use long-term climate averages and so the results of this study suggest that our existing risk assessments could be missing these critical impacts of climate change.
“We urgently need to address this and develop early warning systems to be able to anticipate in advance where and when extreme heatwaves and droughts are likely to impact populations – and also rapidly scale up our monitoring of species and ecosystems so that we can reliably detect these effects and feed this information back into our models to refine our future projections for biodiversity.”
Dr Peter Soroye, a biodiversity scientist at the Wildlife Conservation Society Canada, who was also not involved in the research, agrees:
“It’s not just that the climate is getting gradually warmer every year with climate change, it’s that climate change is also driving increasingly frequent and severe extreme temperature events that are putting wildlife at risk.
“As we more fully understand the importance of extremes, it seems increasingly important to consider them when we model or project changes in biodiversity over time.”
The post Fossil-fuelled heat has caused tropical birds to decline by ‘up to 38%’ since 1950s appeared first on Carbon Brief.
Fossil-fuelled heat has caused tropical birds to decline by ‘up to 38%’ since 1950s
Climate Change
DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Blazing heat hits Europe
FANNING THE FLAMES: Wildfires “fanned by a heatwave and strong winds” caused havoc across southern Europe, Reuters reported. It added: “Fire has affected nearly 440,000 hectares (1,700 square miles) in the eurozone so far in 2025, double the average for the same period of the year since 2006.” Extreme heat is “breaking temperature records across Europe”, the Guardian said, with several countries reporting readings of around 40C.
HUMAN TOLL: At least three people have died in the wildfires erupting across Spain, Turkey and Albania, France24 said, adding that the fires have “displaced thousands in Greece and Albania”. Le Monde reported that a child in Italy “died of heatstroke”, while thousands were evacuated from Spain and firefighters “battled three large wildfires” in Portugal.
UK WILDFIRE RISK: The UK saw temperatures as high as 33.4C this week as England “entered its fourth heatwave”, BBC News said. The high heat is causing “nationally significant” water shortfalls, it added, “hitting farms, damaging wildlife and increasing wildfires”. The Daily Mirror noted that these conditions “could last until mid-autumn”. Scientists warn the UK faces possible “firewaves” due to climate change, BBC News also reported.
Around the world
- GRID PRESSURES: Iraq suffered a “near nationwide blackout” as elevated power demand – due to extreme temperatures of around 50C – triggered a transmission line failure, Bloomberg reported.
- ‘DIRE’ DOWN UNDER: The Australian government is keeping a climate risk assessment that contains “dire” implications for the continent “under wraps”, the Australian Financial Review said.
- EXTREME RAINFALL: Mexico City is “seeing one of its heaviest rainy seasons in years”, the Washington Post said. Downpours in the Japanese island of Kyushu “caused flooding and mudslides”, according to Politico. In Kashmir, flash floods killed 56 and left “scores missing”, the Associated Press said.
- SOUTH-SOUTH COOPERATION: China and Brazil agreed to “ensure the success” of COP30 in a recent phone call, Chinese state news agency Xinhua reported.
- PLASTIC ‘DEADLOCK’: Talks on a plastic pollution treaty have failed again at a summit in Geneva, according to the Guardian, with countries “deadlocked” on whether it should include “curbs on production and toxic chemicals”.
15
The number of times by which the most ethnically-diverse areas in England are more likely to experience extreme heat than its “least diverse” areas, according to new analysis by Carbon Brief.
Latest climate research
- As many as 13 minerals critical for low-carbon energy may face shortages under 2C pathways | Nature Climate Change
- A “scoping review” examined the impact of climate change on poor sexual and reproductive health and rights in sub-Saharan Africa | PLOS One
- A UK university cut the carbon footprint of its weekly canteen menu by 31% “without students noticing” | Nature Food
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
Factchecking Trump’s climate report
A report commissioned by the US government to justify rolling back climate regulations contains “at least 100 false or misleading statements”, according to a Carbon Brief factcheck involving dozens of leading climate scientists. The report, compiled in two months by five hand-picked researchers, inaccurately claims that “CO2-induced warming might be less damaging economically than commonly believed” and misleadingly states that “excessively aggressive [emissions] mitigation policies could prove more detrimental than beneficial”80
Spotlight
Does Xi Jinping care about climate change?
This week, Carbon Brief unpacks new research on Chinese president Xi Jinping’s policy priorities.
On this day in 2005, Xi Jinping, a local official in eastern China, made an unplanned speech when touring a small village – a rare occurrence in China’s highly-choreographed political culture.
In it, he observed that “lucid waters and lush mountains are mountains of silver and gold” – that is, the environment cannot be sacrificed for the sake of growth.
(The full text of the speech is not available, although Xi discussed the concept in a brief newspaper column – see below – a few days later.)
In a time where most government officials were laser-focused on delivering economic growth, this message was highly unusual.
Forward-thinking on environment
As a local official in the early 2000s, Xi endorsed the concept of “green GDP”, which integrates the value of natural resources and the environment into GDP calculations.
He also penned a regular newspaper column, 22 of which discussed environmental protection – although “climate change” was never mentioned.
This focus carried over to China’s national agenda when Xi became president.
New research from the Asia Society Policy Institute tracked policies in which Xi is reported by state media to have “personally” taken action.
It found that environmental protection is one of six topics in which he is often said to have directly steered policymaking.
Such policies include guidelines to build a “Beautiful China”, the creation of an environmental protection inspection team and the “three-north shelterbelt” afforestation programme.
“It’s important to know what Xi’s priorities are because the top leader wields outsized influence in the Chinese political system,” Neil Thomas, Asia Society Policy Institute fellow and report co-author, told Carbon Brief.
Local policymakers are “more likely” to invest resources in addressing policies they know have Xi’s attention, to increase their chances for promotion, he added.
What about climate and energy?
However, the research noted, climate and energy policies have not been publicised as bearing Xi’s personal touch.
“I think Xi prioritises environmental protection more than climate change because reducing pollution is an issue of social stability,” Thomas said, noting that “smoggy skies and polluted rivers” were more visible and more likely to trigger civil society pushback than gradual temperature increases.
The paper also said topics might not be linked to Xi personally when they are “too technical” or “politically sensitive”.
For example, Xi’s landmark decision for China to achieve carbon neutrality by 2060 is widely reported as having only been made after climate modelling – facilitated by former climate envoy Xie Zhenhua – showed that this goal was achievable.
Prior to this, Xi had never spoken publicly about carbon neutrality.
Prof Alex Wang, a University of California, Los Angeles professor of law not involved in the research, noted that emphasising Xi’s personal attention may signal “top” political priorities, but not necessarily Xi’s “personal interests”.
By not emphasising climate, he said, Xi may be trying to avoid “pushing the system to overprioritise climate to the exclusion of the other priorities”.
There are other ways to know where climate ranks on the policy agenda, Thomas noted:
“Climate watchers should look at what Xi says, what Xi does and what policies Xi authorises in the name of the ‘central committee’. Is Xi talking more about climate? Is Xi establishing institutions and convening meetings that focus on climate? Is climate becoming a more prominent theme in top-level documents?”
Watch, read, listen
TRUMP EFFECT: The Columbia Energy Exchange podcast examined how pressure from US tariffs could affect India’s clean energy transition.
NAMIBIAN ‘DESTRUCTION’: The National Observer investigated the failure to address “human rights abuses and environmental destruction” claims against a Canadian oil company in Namibia.
‘RED AI’: The Network for the Digital Economy and the Environment studied the state of current research on “Red AI”, or the “negative environmental implications of AI”.
Coming up
- 17 August: Bolivian general elections
- 18-29 August: Preparatory talks on the entry into force of the “High Seas Treaty”, New York
- 18-22 August: Y20 Summit, Johannesburg
- 21 August: Advancing the “Africa clean air programme” through Africa-Asia collaboration, Yokohama
Pick of the jobs
- Lancaster Environment Centre, senior research associate: JUST Centre | Salary: £39,355-£45,413. Location: Lancaster, UK
- Environmental Justice Foundation, communications and media officer, Francophone Africa | Salary: XOF600,000-XOF800,000. Location: Dakar, Senegal
- Politico, energy & climate editor | Salary: Unknown. Location: Brussels, Belgium
- EnviroCatalysts, meteorologist | Salary: Unknown. Location: New Delhi, India
DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.
This is an online version of Carbon Brief’s weekly DeBriefed email newsletter. Subscribe for free here.
The post DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report appeared first on Carbon Brief.
DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report
Climate Change
New York Already Denied Permits to These Gas Pipelines. Under Trump, They Could Get Greenlit
The specter of a “gas-for-wind” compromise between the governor and the White House is drawing the ire of residents as a deadline looms.
Hundreds of New Yorkers rallied against new natural gas pipelines in their state as a deadline loomed for the public to comment on a revived proposal to expand the gas pipeline that supplies downstate New York.
New York Already Denied Permits to These Gas Pipelines. Under Trump, They Could Get Greenlit
A “critical assessment” report commissioned by the Trump administration to justify a rollback of US climate regulations contains at least 100 false or misleading statements, according to a Carbon Brief factcheck involving dozens of leading climate scientists.
The report – “A critical review of impacts of greenhouse gas emissions on the US climate” – was published by the US Department of Energy (DoE) on 23 July, just days before the government laid out plans to revoke a scientific finding used as the legal basis for emissions regulation.
The executive summary of the controversial report inaccurately claims that “CO2-induced warming might be less damaging economically than commonly believed”.
It also states misleadingly that “excessively aggressive [emissions] mitigation policies could prove more detrimental than beneficial”.
Compiled in just two months by five “independent” researchers hand-selected by the climate-sceptic US secretary of energy Chris Wright, the document has sparked fierce criticism from climate scientists, who have pointed to factual errors, misrepresentation of research, messy citations and the cherry-picking of data.
Experts have also noted the authors’ track record of promoting views at odds with the mainstream understanding of climate science.
Wright’s department claims the report – which is currently open to public comment as part of a 30-day review – underwent an “internal peer-review period amongst [the] DoE’s scientific research community”.
The report is designed to provide a scientific underpinning to one flank of the Trump administration’s plans to rescind a finding that serves as the legal prerequisite for federal emissions regulation. (The second flank is about legal authority to regulate emissions.)
The “endangerment finding” – enacted by the Obama administration in 2009 – states that six greenhouse gases are contributing to the net-negative impacts of climate change and, thus, put the public in danger.
In a press release on 29 July, the US Environmental Protection Agency said “updated studies and information” set out in the new report would “challenge the assumptions” of the 2009 finding.
Carbon Brief asked a wide range of climate scientists, including those cited in the “critical review” itself, to factcheck the report’s various claims and statements.
The post Factcheck: Trump’s climate report includes more than 100 false or misleading claims appeared first on Carbon Brief.
https://www.carbonbrief.org/factcheck-trumps-climate-report-includes-more-than-100-false-or-misleading-claims/
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