{"id":97341,"date":"2025-08-20T17:43:10","date_gmt":"2025-08-20T17:43:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/us\/97341\/"},"modified":"2025-08-20T17:43:10","modified_gmt":"2025-08-20T17:43:10","slug":"monkeys-falling-from-trees-and-baking-barnacles-how-heat-is-driving-animals-to-extinction-global-development","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us\/97341\/","title":{"rendered":"Monkeys falling from trees and baking barnacles: how heat is driving animals to extinction | Global development"},"content":{"rendered":"

The residents of Tecolutilla, Mexico<\/a>, knew the heatwave was bad when they heard the thuds. One by one, the town\u2019s howler monkeys, overcome with dehydration and exhaustion, were falling from the trees like apples, their limp bodies smacking the ground as temperatures sizzled past 43C (110F) in spring last year.<\/p>\n

Those that survived were given ice and intravenous drips<\/a> by rescuers. At least 83 of the primates were found dead in the state of Tabasco, though local veterinarians estimated hundreds throughout the region probably perished.<\/p>\n

Howler monkeys lie dead on the forest floor in Comalcalco, Mexico, after falling from the trees. Photograph: Reuters<\/p>\n

Episodes such as this are unfolding across the world as the climate crisis delivers harsher and more frequent heatwaves. Flying foxes have tumbled<\/a> from trees in Australia; billions of barnacles have baked<\/a> in tide pools in Canada; male beetles have been virtually sterilised<\/a> by soaring temperatures.<\/p>\n

Beyond these local die-offs, ecologists are only just beginning to grasp the full threat that extreme heat poses to the world\u2019s wildlife populations, and how quickly it can drive species towards extinction.<\/p>\n

Maximilian Kotz, a climate scientist at the Potsdam Institute for Climate Impact Research, says: \u201cAs human emissions shift the temperature distribution upwards, this manifests as a strong increase in the number of very hot days \u2013 not just an increase in average temperatures.\u201d<\/p>\n

While the steady drumbeat of climbing average temperatures has long been expected to push species out of their preferred habitats and make food scarce, these episodes of blistering heat constitute a unique threat to wildlife, scientists say.<\/p>\n

Spectacled flying-fox orphans in Tolga bat hospital, after thousands of the threatened animals died from heat stress amid record 42C temperatures in Queensland. Photograph: D Pinson\/Alamy<\/p>\n

Heatwaves are reaping such long-term population crashes in some regions that experts say the climate emergency has become a driver of biodiversity loss on a par with \u2013 or worse than \u2013 deforestation and habitat loss.<\/p>\n

Heatwave frequency has just increased that much more quickly in the tropicsMaximilian Kotz <\/p>\n

Recently, Kotz and his colleagues dug through decades of global monitoring data on more than 3,000 bird populations and daily weather records to tease out whether heatwaves had contributed to observed declines in some parts of the world.<\/p>\n

After controlling for other factors, they found bird populations in temperate, boreal and tundra zones did not seem to suffer much from scorching heat.<\/p>\n

But for those in the tropics, the findings were sobering: extreme heat had slashed tropical bird populations by 25% to 38% over the past 70 years. Tropical songbirds, they found, were hit hardest.<\/p>\n

A toco toucan feeding in Brazil\u2019s Pantanal wetland. A study estimated extreme heat cut tropical bird numbers by 25% to 38% over 70 years. Photograph: Wolfgang Kaehler\/LightRocket\/Getty<\/p>\n

The losses in the tropics have been so profound, in part, because species there are already living near their limit of heat tolerance, Kotz says. At the same time, birds in tropical regions are experiencing dangerously hot days about 10 times more often than they did in the past.<\/p>\n

\u201cHeatwave frequency has just increased that much more quickly in the tropics,\u201d Kotz says.<\/p>\n

A swift is rehydrated at an animal shelter near Paris in France\u2019s heatwave this month. Photograph: S Lecocq\/Reuters<\/p>\n

Exactly how heatwaves drive population declines is not clear from their study,<\/a> published in Nature Ecology & Evolution. But Kotz says it is likely to be a combination of birds dying during heatwaves, heat stress in nests and eggs, and effects on the birds\u2019 food, such as insects, which similarly struggle to survive soaring temperatures.<\/p>\n

Their research suggests that across the tropics changes to the climate have played a greater role in driving bird numbers down than direct human activities, such as logging, mining or farming.<\/p>\n

\u201cFor many of these species that are in protected areas in pristine habitats<\/a>, there can still be really substantial effects from intensifying heat extremes through our greenhouse gas emissions,\u201d Kotz says.<\/p>\n

When a heat dome<\/a> descended on the Pacific north-west in the summer of 2021, unleashing air temperatures above 46C (116F), scientists walking the beaches along the strait of Georgia, off Vancouver Island, were horrified to find tide pools containing thousands of lifeless molluscs and barnacles. Attached to rocks, the creatures were unable to escape to cooler waters.<\/p>\n

Billions of animals dead<\/p>\n

At the time, Prof Christopher Harley, a marine biologist at the University of British Columbia, estimated the heatwave had killed 1 billion animals along the coast.<\/p>\n

\u201cI was nervous making that estimate publicly because it was a bit back of the envelope,\u201d he says, but now adds that they underestimated the toll. \u201cWe now have better numbers for that: we estimate 10 billion barnacles and 3 billion mussels [died] just in the strait of Georgia.\u201d<\/p>\n

Harley says that while deaths in the billions may sound like an extinction-level event, abundant and fast-reproducing tidal species have proved surprisingly resilient.<\/p>\n

Dead mussels in British Columbia, Canada, during the 2021 heatwave that killed an estimated 10 billion barnacles and 3 billion mussels just in the strait of Georgia. Photograph: Christopher Harley<\/p>\n

\u201cThe barnacles came back really fast. It took a few more years for the mussels to start creeping back in,\u201d he says. \u201cBut if you went out to the shore of Vancouver right now, you wouldn\u2019t immediately think, \u2018There was a disaster here four years ago\u2019.\u201d<\/p>\n

Those animals that managed to survive the heatwave may also be slightly better adapted to extreme temperatures, meaning their offspring could carry that same tolerance.<\/p>\n

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Other coastal species that thrive at the ebb and flow of the ocean, such as starfish, may have crawled into cooler waters when the heatwave took hold, Harley says. But among those that perished, it could take decades to recover the more slow-reproducing species.<\/p>\n

Aphids struggle with the heat. Photograph: SDym Photo\/Alamy<\/p>\n

Harley\u2019s preliminary data also examines the outcomes for insect populations. Honeybees appeared to have fared well, he says, but \u201caphids had a really tough go\u201d.<\/p>\n

It fits with global research that finds temperature extremes can cause a mix of reactions among insect species, from outbreaks to breakdowns.<\/p>\n

In a 2020 research review paper<\/a> in Global Change Biology, scientists noted that many of the world\u2019s insects were unable to regulate their body temperature during heatwaves because they mimicked ambient temperatures. Extreme heat can therefore push species beyond their limits.<\/p>\n

Yet heatwaves can also trigger a temporary outbreak: a dramatic increase in a population that quickly burns through local food sources and ultimately causes a crash. This, the authors noted, could lead to local insect extinctions.<\/p>\n

How heat changes animal bodies<\/p>\n

Epidemiologists have clearly established how heatwaves affect humans, but there has been scant research exploring the physiological consequences for non-human mammals.<\/p>\n

PJ Jacobs, an evolutionary biologist at the University of Pretoria in South Africa, is trying to close that gap. His recent research<\/a> has focused on small mammals, which are especially vulnerable to heatwaves because of their larger surface area to volume ratio, which means they heat up more easily.<\/p>\n

If there\u2019s a massive heatwave, animals are not going to be active when temperatures are so extremePJ Jacobs, biologist<\/p>\n

In a study published last December, Jacobs examined the effects of heatwaves on small African rodents \u2013 the mesic four-striped field mouse and Namaqua rock mouse.<\/p>\n

He simulated a heatwave in a lab to test how the fertility of the male mice would be affected. Both experienced a serious drop in testosterone levels and other fertility measures.<\/p>\n

This, Jacobs says, suggests that intensifying heatwaves could jeopardise the ability of small animals to reproduce, potentially shrinking populations if they cannot access cooler refuges, such as shady spots or grassy shelters. That could have a serious effect further up the food chain.<\/p>\n

A Namaqua rock mouse in South Africa\u2019s Namaqualand region. A study showed how a heatwave caused a serious drop in the animals\u2019 testosterone levels. Photograph: Neil Bowman\/Alamy<\/p>\n

Heatwaves also affect animals at a behavioural level that poses limits to survival.<\/p>\n

\u201cIf there\u2019s a massive heatwave happening, animals are not just going to go out and be active when temperatures are so extreme,\u201d Jacobs says. \u201cThey have to rest in the shade which means they can\u2019t go and do other things related to their fitness \u2013 reproduction and feeding.\u201d<\/p>\n

At the same time, he adds, \u201cIf you hit those severe temperature extremes, you\u2019re going to get those effects at the physiological and molecular level. That\u2019s going to cause disorientation and dehydration. And you just collapse \u2013 you faint.\u201d<\/p>\n

Even when the lab mice sought water to cool down, \u201cthe brain was the one tissue that was still affected\u201d, says Jacobs. \u201cThe brain is obviously the control box of the body. If the brain doesn\u2019t function properly, you\u2019re going to have monkeys falling out of trees.\u201d<\/p>\n

Find more age of extinction coverage here<\/a>, and follow the biodiversity reporters Phoebe Weston<\/a> and Patrick Greenfield<\/a> in the Guardian app for more nature coverage<\/p>\n","protected":false},"excerpt":{"rendered":"The residents of Tecolutilla, Mexico, knew the heatwave was bad when they heard the thuds. One by one,…\n","protected":false},"author":2,"featured_media":97342,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[51],"tags":[79,201],"class_list":{"0":"post-97341","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-wildlife","8":"tag-science","9":"tag-wildlife"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/97341","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=97341"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/97341\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/97342"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=97341"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=97341"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=97341"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}