Climate heat extremes driving tropical bird decline: study
Intensifying temperatures caused a 25% to 38% reduction in tropical bird populations between 1950 and 2020, compared to a scenario without global warming, scientists based in Europe and Australia reported.
"The findings are pretty stark," lead author Maximilian Kotz, a researcher at the National Supercomputing Centre in Barcelona and the Potsdam Institute for Climate Impact Research (PIK), said.
Bird populations in the tropics now face 30 days of heat extremes per year compared to three per year in the mid-20th century, he noted.
"This has major consequences for how we think about biodiversity conservation," Kotz said by email. "Protecting pristine habitats is crucial, but without dealing with climate change it won't be enough for birds."
Nearly half of all bird species are found in biodiversity-rich tropical regions.
These often colorful animals perform essential services for ecosystems, such as dispersing plant seeds.
But birds living in these regions may already be "close to the limits" of their tolerance to high temperatures, which can cause heatstroke (hyperthermia) or dehydration.
The overview study does not provide figures for individual species, but earlier literature is rich with examples of the devastating impact of rising temperatures.
One documented the heat-related decline of birds in Panama, including the king quetzal, the red-crested quetzal, the two-colored kingfisher and the aurora trogon.
Another study published in 2017 showed how some tropical hummingbirds are now forced to seek shade to regulate their temperature in extreme heat, cutting into the amount of time they can spend searching for life-sustaining nectar.
Extreme heat waves, which are becoming more frequent, represent a far greater threat than increases in average temperatures or rainfall, another result of human-induced climate change.
Up to now, it has been assumed that the decline in bird populations worldwide was due mainly to other well-identified factors, especially habitat loss, pesticide use, hunting, and invasive species, especially snakes that snack on bird eggs and mosquitos carrying avian malaria.
But the new findings "challenge the view that direct human pressures have so far been the dominant driver of impacts on bird populations compared to climate change in tropical regions," according to the authors.
To reach this conclusion, they analyzed observational data from more than 3,000 bird populations around the world and used statistical modelling to isolate the effects of extreme weather from other factors.
The findings help complete the picture of tropical bird decline, noted Aimee Van Tatenhove, a post-doctoral fellow at Cornell University's Center for Avian Population Studies who was not involved in the study.
"Deforestation has an obvious impact — trees are cut and habitat is destroyed," she said. "We need long-term datasets like the authors used to understand how extreme temperatures impact avian populations."
"This study is an important reminder that we need to continue examining different causes of population declines and apply those findings to conservation initiatives," she continued.
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Japan Times
5 days ago
- Japan Times
Climate heat extremes driving tropical bird decline: study
Tropical bird populations have plummeted not only due to deforestation but also extreme heat attributable to climate change, according to a study published on Monday in the journal Nature Ecology & Evolution. Intensifying temperatures caused a 25% to 38% reduction in tropical bird populations between 1950 and 2020, compared to a scenario without global warming, scientists based in Europe and Australia reported. "The findings are pretty stark," lead author Maximilian Kotz, a researcher at the National Supercomputing Centre in Barcelona and the Potsdam Institute for Climate Impact Research (PIK), said. Bird populations in the tropics now face 30 days of heat extremes per year compared to three per year in the mid-20th century, he noted. "This has major consequences for how we think about biodiversity conservation," Kotz said by email. "Protecting pristine habitats is crucial, but without dealing with climate change it won't be enough for birds." Nearly half of all bird species are found in biodiversity-rich tropical regions. These often colorful animals perform essential services for ecosystems, such as dispersing plant seeds. But birds living in these regions may already be "close to the limits" of their tolerance to high temperatures, which can cause heatstroke (hyperthermia) or dehydration. The overview study does not provide figures for individual species, but earlier literature is rich with examples of the devastating impact of rising temperatures. One documented the heat-related decline of birds in Panama, including the king quetzal, the red-crested quetzal, the two-colored kingfisher and the aurora trogon. Another study published in 2017 showed how some tropical hummingbirds are now forced to seek shade to regulate their temperature in extreme heat, cutting into the amount of time they can spend searching for life-sustaining nectar. Extreme heat waves, which are becoming more frequent, represent a far greater threat than increases in average temperatures or rainfall, another result of human-induced climate change. Up to now, it has been assumed that the decline in bird populations worldwide was due mainly to other well-identified factors, especially habitat loss, pesticide use, hunting, and invasive species, especially snakes that snack on bird eggs and mosquitos carrying avian malaria. But the new findings "challenge the view that direct human pressures have so far been the dominant driver of impacts on bird populations compared to climate change in tropical regions," according to the authors. To reach this conclusion, they analyzed observational data from more than 3,000 bird populations around the world and used statistical modelling to isolate the effects of extreme weather from other factors. The findings help complete the picture of tropical bird decline, noted Aimee Van Tatenhove, a post-doctoral fellow at Cornell University's Center for Avian Population Studies who was not involved in the study. "Deforestation has an obvious impact — trees are cut and habitat is destroyed," she said. "We need long-term datasets like the authors used to understand how extreme temperatures impact avian populations." "This study is an important reminder that we need to continue examining different causes of population declines and apply those findings to conservation initiatives," she continued.
Japan Times
07-08-2025
- Japan Times
Death of a delta: Pakistan's Indus sinks and shrinks
Salt crusts crackle underfoot as Habibullah Khatti walks to his mother's grave to say a final goodbye before he abandons his parched island village on Pakistan's Indus delta. Seawater intrusion into the delta, where the Indus River meets the Arabian Sea in the south of the country, has triggered the collapse of farming and fishing communities. "The saline water has surrounded us from all four sides," Khatti said from Abdullah Mirbahar village in the town of Kharo Chan, around 15 kilometers from where the river empties into the sea. As fish stocks fell, the 54-year-old turned to tailoring until that, too, became impossible with only four of the 150 households remaining. "In the evening, an eerie silence takes over the area," he said, as stray dogs wandered through the deserted wooden and bamboo houses. Kharo Chan once comprised around 40 villages, but most have disappeared under rising seawater. The town's population fell from 26,000 in 1981 to 11,000 in 2023, according to census data. Khatti is preparing to move his family to nearby Karachi, Pakistan's largest city, and one swelling with economic migrants, including from the Indus delta. The Pakistan Fisherfolk Forum, which advocates for fishing communities, estimates that tens of thousands of people have been displaced from the delta's coastal districts. However, more than 1.2 million people have been displaced from the overall Indus delta region in the last two decades, according to a study published in March by the Jinnah Institute, a think tank led by a former climate change minister. Habibullah Khatti, a local resident, walks over the salt crusts deposited in Abdullah Mirbahar village in Kharo Chan town, in the Indus delta, south of Pakistan on June 25. | AFP-JIJI The downstream flow of water into the delta has decreased by 80% since the 1950s as a result of irrigation canals, hydropower dams and the impacts of climate change on glacial and snow melt, according to a 2018 study by the U.S.-Pakistan Center for Advanced Studies in Water. That has led to devastating seawater intrusion. The salinity of the water has risen by around 70% since 1990, making it impossible to grow crops and severely affecting the shrimp and crab populations. "The delta is both sinking and shrinking," said Muhammad Ali Anjum, a local WWF conservationist. 'No other choice' Beginning in Tibet, the Indus River flows through disputed Kashmir before traversing the entire length of Pakistan. The river and its tributaries irrigate about 80% of the country's farmland, supporting millions of livelihoods. The delta, formed by rich sediment deposited by the river as it meets the sea, was once ideal for farming, fishing, mangroves and wildlife. But more than 16% of fertile land has become unproductive due to encroaching seawater, a government water agency study in 2019 found. In the town of Keti Bandar, which spreads inland from the water's edge, a white layer of salt crystals covers the ground. Boats carry in drinkable water from miles away, and villagers cart it home via donkeys. "Who leaves their homeland willingly?" said Haji Karam Jat, whose house was swallowed by the rising water level. He rebuilt farther inland, anticipating more families would join him. "A person only leaves their motherland when they have no other choice," he said. Way of life British colonial rulers were the first to alter the course of the Indus River with canals and dams, followed more recently by dozens of hydropower projects. Earlier this year, several military-led canal projects on the Indus River were halted when farmers in the low-lying riverine areas of Sindh province protested. To combat the degradation of the Indus River Basin, the government and the United Nations launched the "Living Indus Initiative" in 2021. Muhammad Saleem, a local leader, shows newly planted mangroves in Keti Bandar town of the Thatta district near the Indus delta on June 25. | AFP-JIJI One intervention focuses on restoring the delta by addressing soil salinity and protecting local agriculture and ecosystems. The Sindh government is currently running its own mangrove restoration project, aiming to revive forests that serve as a natural barrier against saltwater intrusion. Even as mangroves are restored in some parts of the coastline, land grabbing and residential development projects drive clearing in other areas. Neighboring India, meanwhile, poses a looming threat to the river and its delta, after revoking a 1960 water treaty with Pakistan which divides control over the Indus basin rivers. It has threatened to never reinstate the treaty and build dams upstream, squeezing the flow of water to Pakistan, which has called it "an act of war." Alongside their homes, the communities have lost a way of life tightly bound up in the delta, said climate activist Fatima Majeed, who works with the Pakistan Fisherfolk Forum. Women, in particular, who for generations have stitched nets and packed the day's catches, struggle to find work when they migrate to cities, said Majeed, whose grandfather relocated the family from Kharo Chan to the outskirts of Karachi. "We haven't just lost our land, we've lost our culture."
Japan Times
05-08-2025
- Japan Times
'Silent killer': the science of tracing climate deaths in heat waves
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