I understand well how devastating these studies must be for researchers. I find it heart ripping reading them, while observing the decimation of birds and their song on my land at Rosebud.
Climate change aggravates bird mortality in pristine tropical forests by Jared D. Wolfe, David A. Luther, Vitek Jirinec, Jeremy Collings, Erik I. Johnson, Robert O. Bierregaard Jr., and Philip C Stouffer , Jan 29, 2025, Science Advances, Vol 11, Issue 5
- Abstract
- INTRODUCTION
- RESULTS
- DISCUSSION
- MATERIALS AND METHODS
- Acknowledgments
- Supplementary Materials
- REFERENCES AND NOTES
Abstract
Stable understory microclimates within undisturbed rainforests are often considered refugia against climate change. However, this assumption contrasts with emerging evidence of Neotropical bird population declines in intact rainforests. We assessed the vulnerability of resident rainforest birds to climatic variability, focusing on dry season severity characterized by hotter temperatures and reduced rainfall. Analyzing 4264 individual bird captures over 27 years, we found that harsher Amazonian dry seasons significantly reduced apparent survival for 24 of 29 species, with longer-lived species being more strongly affected.
Our model predicted that a 1°C increase in average dry season temperature would reduce the mean apparent survival of the understory bird community by 63%.
These findings directly link climate change to declining bird survival in the Amazon, challenging the notion that pristine rainforests can fully protect their biodiversity under increasingly severe climate conditions.
…
Recently, researchers have linked decreased rainfall and higher temperatures during the dry season (Fig. 1, A and B) to incremental decreases in body mass across an entire bird community in the Brazilian Amazon (23). These results underscore hidden biodiversity losses occurring in supposedly intact forests across the Neotropics. …
Population declines stem from reductions in either survival or reproductive success, or both, with populations of longer-lived tropical birds expected to be particularly sensitive to changes in adult survival (24). Identifying how climate change affects these life history parameters is necessary to understand population-level vulnerability to climate change. As such, we hypothesize that declining populations of long-lived birds in seemingly pristine tropical rainforests result from a climatic impact, manifested through a process of understory drying. Our hypothesis is rooted in results from forest fragments (25), where hotter and drier microclimates diminish food resources (19, 26) and impose physiological stress on birds adapted to shaded forest conditions (26, 27). If increasingly severe dry seasons are responsible for the declining abundance of central Amazonian birds within pristine forest, then we should detect a relationship between dry season severity and the apparent survival of understory birds.
…
DISCUSSION
Our results provide the first evidence linking climate change, manifested through increasingly severe dry seasons, with decreased apparent survival estimates from a community of Amazonian birds. Over geologic and macro-evolutionary timescales, Amazonian bird communities have experienced average temperature changes exceeding 1°C. However, such changes likely did not occur as rapidly—over just two decades—as documented in this study, potentially impeding evolutionary adaptation to novel environmental conditions. The impact of climate change on the survival of understory birds likely reflects disruptions in the understory conditions that evolutionarily shaped their ecological niches and life history strategies (11–14,24). Our findings support this perspective, where longer-lived understory birds appear more vulnerable to the worsening conditions of the dry season (Fig. 2). This observation underscores the complex relationship between life history strategy and climate change. Specifically, stable and biodiverse tropical environments fostered the evolution of a latitudinal gradient in life history variation (15). In this gradient, tropical songbirds prioritize adult survival and longer life spans with relatively lower reproductive output, whereas temperate songbirds typically exhibit shorter life spans coupled with higher annual reproductive efforts (29–31). This evolutionary adaptation to regional conditions may have rendered understory tropical birds particularly vulnerable to climatic shifts that adversely affect adult survival. These findings are especially alarming because they reflect demographic patterns of tropical birds within pristine rainforest, a biome thought to be resilient to the adverse effects of climate change (8–10). The acute effects of temperature on avian survival may help clarify previously documented reductions in understory bird populations (19) and associated changes in their behavior observed during intense dry season conditions (26).
Rapid increases in average temperature and decreases in average rainfall can affect birds in numerous ways, but are likely to affect insectivorous species—those most vulnerable to climate change—in two primary aspects. First, understory tropical birds are adapted to relatively cool and stable conditions where elevated temperatures may result in heightened physiological stress, leading these birds to select microclimate refugia, if available, to mitigate the deleterious impacts of understory drying. Recent studies from the Brazilian Amazon support this latter assertion whereby Jirinec et al. (26) observed variations in microclimates across seasons and elevations, with the driest conditions occurring at higher elevations and milder conditions in valleys. They found that Formicarius analis, an understory insectivorous bird, abandoned higher and more open locations and moved to valleys and areas with more cover, putative microclimate refugia, when subjected to hot and dry conditions. More recently, Jirinec (27) used temperature loggers attached to multiple understory insectivorous bird species to measure thermoregulatory behaviors and found that many species relied on bathing and rainfall to lower their internal body temperatures.
Conversely, studies from Panama did not find statistically significant associations between thermal physiological traits and temperature variation across various bird species that occupy dissimilar habitats and forest strata (32). Specifically, none of the four thermal physiological traits measured from wild birds that were captured and brought into a laboratory—lower critical temperature, upper critical temperature, thermal neutral zone breadth, and heat tolerance limit—showed a clear relationship with habitat type or vertical stratum. Unexpectedly, species from open habitats and the forest canopy exhibited narrower thermal safety margins compared to those from forested habitats and the forest understory (32). This contradicted predictions from previous studies that have shown strong links between local-scale temperature variation and thermal physiology and did not support the hypothesis that tropical understory birds are more sensitive to environmental change due to their constrained thermal physiology (33). Contradictory results from field observations in Brazil and laboratory measurements in Panama may reflect that laboratory conditions do not fully capture the stress that increased temperatures pose to birds when they are actively foraging and moving through their environment.
The second way hot and dry conditions can affect insectivorous species is by decreasing arthropod diversity and availability. In the tropics, arthropod assemblages vary as a function of microclimates where humid forests coupled with increased leaf area tend to host more abundant and diverse arthropod communities (34). This pattern reflects the physiological limitations of arthropods, small ectotherms with a high surface area–to–volume ratio, which face inherent risks of desiccation in arid microclimates. The risk of desiccation serves as an environmental filter, resulting in larger-bodied, less diverse, and less abundant arthropod assemblages in warmer and drier microclimates (35). For example, in the cloud forests of the Andes in northern Peru, researchers found that variation in rainfall resulted in a twofold change in arthropod biomass, with differences observed before and after the dry season (36). These results highlight the importance of climate fluctuations in shaping arthropod communities and suggest a link between increasing temperatures, decreased rainfall, and diminished food resources for birds in tropical forests.
Irrespective of whether hot and dry conditions lower apparent survival of birds through physiological stress, decreased food resources, or a mixture of both, climate change appears to affect birds during seasonally dry periods. These processes likely reflect the patterns of understory drying found in forest fragments and locations in pristine forest most susceptible to desiccation: upland (terra firme) forests, which are the focus of this study and represent roughly 82% of the central Amazon (37). Forests near streams or rivers may be more resilient to understory drying and subsequent loss of biodiversity (26). For example, at Cocha Cashu Biological Station in the Peruvian Amazon, a forest located within a mature flood plain, there has been little change in dry season temperature or precipitation (38), and bird community structure showed little change in two samples taken 36 years apart (39). The varied impacts of climate change on tropical bird communities and their habitats highlight distinct characteristics that make certain birds and their forests susceptible to a changing climate, whereas others remain resilient. Understanding the mechanisms through which climate change erodes biodiversity in pristine forests represents a pressing line of inquiry. Identifying the landscape characteristics that confer resilience to tropical forests and formulating policies to safeguard these resilient forests are essential steps toward ensuring the persistence of vulnerable tropical bird communities into the 22nd century.
In the most untouched, pristine parts of the Amazon, birds are dying. Scientists may finally know why, Populations have been falling for decades, even in tracts of forest undamaged by humans. Experts have spent two decades trying to understand what is going on by Tess McClure, 30 Jan 2025, The Guardian
Something was happening to the birds at Tiputini. The biodiversity research centre, buried deep in the Ecuadorian Amazon, has always been special. It is astonishingly remote: a tiny scattering of research cabins in 1.7m hectares (4.2m acres) of virgin forest. For scientists, it comes about as close as you can to observing rainforest wildlife in a world untouched by human industry.
Almost every year since his arrival in 2000, ecologist John G Blake had been there to count the birds. Rising before the sun, he would record the density and variety of the dawn chorus. Slowly walking the perimeter of the plots, he noted every species he saw. And for one day every year, he and other researchers would cast huge “mist” nets that caught flying birds in their weave, where they would be counted, untangled and freed.
For years, these counts captured birds’ annual fluctuations; they had good and bad years, seasons in which nests were disrupted by storms and others when they boomed. But by about 2012, Blake and his collaborators could see something was shifting. The birds were dying: not in masses at once, struck down by a plague, but generation by generation. The yearly fluctuations he had spent a decade recording slowly stopped their upward leaps, the trend line transforming into an unyielding downward slope. By 2022, their numbers had almost halved. Blake did not need the graph to tell him something was wrong; when he rose to listen to the dawn chorus, he could hear that it was muted. Songs were missing. Some species simply vanished.
I’ve been devastated observing the same happen at Rosebud. I used to spend my early mornings in June working with windows wide open to listen to the astounding choruses of bird song. Meadow lark, American gold finch, cat bird, Baltimore orioles, yellow-headed and red-winged black bird, brown thrasher song was plentiful as well as songs sung by many other species. After Encana’s frac invasion and wildfires and spring/summer temperatures started escalating with no rains, Junes became quieter and quieter. The last few years now, Junes are mostly silent. Later, when the great horned owls taught their young to hunt, I loved listening with windows wide open in the dark to the screeching instructions. This too, has gone mostly silent. On extremely hot smokey days, I used to see birds on the ground gaping, unable to fly or to seek food/water (pollution from wildfires in Alberta includes toxic crap from oil, gas, frac and bitumen facilities/wells, chemical storage and toxic radioactive waste burning up with the forests). Now on smokey days, birds are nowhere to be seen.
“A number of them I have not heard for quite a few years now,” he says, over a broken video connection from the research centre; far from the outside world, it has intermittent power and relies on a satellite connection. “There are definitely some species that, for whatever reason, do not seem to be here any more.”
In North America and Europe, scientists have long warned bird numbers are falling, but mostly that has been explained by their contact with humans. As cities and farms expand, forests around them become fragments, animal habitats shrink, pollution contaminates rivers, pesticides and fertilisers kill off insects. Even pets are a factor – in the US, domestic cats are killing up to an estimated 4 billion birds a year. Tiputini, however, is one of the few patches of the planet not directly feeling those pressures: no nearby farms, no polluting factories, no encroaching loggers, no roads in. Yet, their birds were dying.
At other remote sites around the world, scientists had been starting to observe similar trends. In Brazil, the Biological Dynamics of Forest Fragments Project (BDFFP) is an ecological study located deep in primary Amazon forest, unreachable by road. These regions hold some of the oldest living forests on the planet – they evaded the ice age events that remade forests in the US and Europe with the growth and retreat of glaciers. “In the Amazon, we’ve had pockets of stable forests over millions of years,” says ecologist Jared Wolfe, one of the project’s research scientists. “The site is truly amazing.”
The idea was that if you have huge expanses of forest, that’s going to protect everything … it does protect a lot of things. But apparently not everything
John G Blake, ecologist
But in 2020, when researchers there compared bird numbers with the 1980s, they found a number of species in deep decline. At another site in Panama, scientists working in a 22,000-hectare (54,000-acre) stretch of intact forest had been gathering bird data since the mid-1970s. By 2020, their numbers had gone off a cliff: 70% of species had declined, most of them severely; 88% had lost more than half their population. At some sites, scientists are beginning to observe “almost complete community collapse”, says Wolfe. “This is occurring in pristine environments, which is really unsettling.”
For decades scientists have been trying to understand what is going on. Blake and collaborator ornithologist Bette A Loiselle published their first paper documenting the declines in 2015, but could not definitively say what was causing them. They tested birds for disease and parasites, and found no clear links. They considered the possibility that an unknown toxin or pollutant had seeped in – but there was no evidence of that. “I suspect whatever is causing these declines is something much more widespread,” Blake says. “It would not be something specific to the Tiputini area.”
The most likely answer, they concluded, was the climate crisis. “There’s very little else – at least that I know of – that has such large scale worldwide impacts,” says Blake.
A decade later, their instincts are proving correct. This week, Wolfe and collaborators published new work directly linking rising temperatures to bird declines. Their research, published in Science Advances, tracked birds living in the forest understory at the BDFFP against detailed climate data. They found that harsher dry seasons significantly reduced the survival of 83% of species. A 1C increase in dry season temperature would reduce the average survival of birds by 63%.
Exactly how the heat is causing bird numbers to decline is tricky to pinpoint, Wolfe says, but “these birds are intrinsically linked to small, small changes in temperature and precipitation”. One of the most immediate ways a heating planet hurts wildlife is by putting them out of step with their food sources: when fewer insects survive dry seasons, or leaves bloom and fruit ripens at different times, birds find themselves unable to forage and feed their young. Their nests begin to fail. Within a few generations, their numbers fall.
The losses documented in these remote stations have implications far beyond birds. “The idea has always been that if you have huge expanses of forest, then that’s going to protect everything,” Blake says. “And, well, it does protect a lot of things. But apparently not everything.”
Most western conservation works by sectioning off wilderness, as national parks or reserves. These places are like arks: reservoirs of wildlife that we hope will be saved, even as people transform the land around them. But what the researchers were seeing with birds suggested that these arks are far more fragile than first thought.
Wolfe likens the problem to pollution in a large body of water. When scientists measure water quality, they think about pollution in two ways. “Point source” pollution might be a gushing oil pipe: it’s doing huge damage, but by shutting it off you fix the problem.
“Nonpoint source” would be the small dribbles of oil coming from every car in the area, washed down off the roads and into the waterways: each contribution might be tiny, but the cumulative effect can be huge – and hard to shut off. “It’s very difficult to combat,” Wolfe says. What is happening to the birds “feels like a nonpoint source; a wicked complex problem where you have breakdowns in biological interactions that are causing these declines.”
Above 2012 photo is of Encana/Ovintiv’s sloppy excessive illegal dumped waste near my home and the Hamlet of Rosebud. Companies lie to farmers telling them it’s free fertilizer to con them into accepting this bad industry practice. Dumping of waste is common throughout oil and gas sacrifice zones, including in official wildlife areas, as illegally as at Rosebud. This waste is toxic, and can be radioactive. It does not stay put. Much of it will wash into streams, creeks, sloughs, lakes and rivers and seasonal drainages as snow melts (especially as with climate chaos, springs are happening faster and hotter, without freezing at night to slow down the runoff and erosion) and thunderstorms and or heavy dumps of rain which are occurring more frequently with more extreme dumps in short periods of time. What are the cumulative harms to life from hundreds of companies dumping hundreds of tonnes of toxic waste, shoddily everywhere repeatedly year after year violating the rules, dumped by hundreds of waste dumping trucks racing throughout sacrifice zones, notably in frac fields. Humans are supposed to be stewards of the land and water which sustains us and all other life, instead, we are incessant destroyers, polluters and rapists. I find it unbearable to watch. And worse, as human greed escalates along with travel and wasting fossil fuels for fun and escaping the horrors of humanity, and billionaires use frac’d gas to power insanely stupid and completely unnecessary water and energy sucking rockets, AI and data centres, frac’s are getting more monstrous, removing more and more water from the vital hydrogeological cycle, and producing more and more radioactive deadly waste.
But realising what is happening is necessary to developing solutions, Wolfe says. “One thing I am becoming particularly tired of as a professional researcher, is writing these obituaries for birds,” he says. The research on pristine regions can also reveal potential solutions: early data suggests some forests are bucking the declines. Identifying why – and protecting them – is crucial.
For the scientists who are seeing birds disappear, there is grief in watching some of the most beautiful, ecologically rich places in the world fall into decline. “It is depressing,” Blake says. “When we first got here and started looking, we were just totally amazed at how many birds there were, and their diversity. We keep doing the work – but it’s harder to get excited about doing it because there’s so little.”
Find more age of extinction coverage here, and follow the biodiversity reporters Phoebe Weston and Patrick Greenfield in the Guardian app for more nature coverage.
Refer also to:
Andrew @thewholeshebang.bsky.social:
100% mortality rate for most lifeforms by 2100.
Few if any humans alive by 2045.
Some bacteria may survive in remote locations… Maybe.
David Stone @david-stone.bsky.social:
I’m sure of that.
I wonder when “absolute misery” will set in for everyone (2030?). Parts of the world have already landed there.The suffering by wild beings much much worse.
Andrew @thewholeshebang.bsky.social:
It’s a reasonable punt at 2030.
Food production will be the beginning of the end.
A customer of ours deals in sugar and bulk foodstuffs (6th generation).
They’ve seen 40 – 60% rises in things like sugar, coffee, sultanas etc.
All related to climate change.While con politicos and their billionaire agents blame Trudeau.
Monster Fracs, getting bigger and thirstier, threatening America’s drinking water aquifers
New study: Songbirds’ reproductive success reduced by natural gas compressor noise.
Fracking tied to reduced songbird nesting success
Encana/Ovintiv’s frac invasion at Rosebud started out experimental in about 2000. Company management told us it took them two years of brute force frac’s on many gas wells to finally figure out how to force the tightly adsorbed gas to let go from formation (yet after illegally frac’ing our drinking water aquifers contaminating them with those very gases, the company and regulators blamed nature for our contaminated water wells).
Frac’ing comes with endless water, land and air pollution, and abusive levels of corporate and gov’t lies and trickery, and health-harming noise and 24/7 industrial lighting from an army of ugly pieces of shit compressors. As frac’ing and associated facilities and noise multiplied like mould in bread left out on a hot day, birds and their song decreased, as did chorus frogs. After the frac war eased, the birds and frogs did not return as they were, I think the cumulative harms from frac’ing, cats and human pollution caused heat and drought extremes are too severe to recover from.
A previously frequent view of gold finches singing out my kitchen window at Rosebud. Fifty to sixty nesting pairs of them and many other song birds used to make my 50 acres home spring and summer. Now, I sometimes see the odd solitary finch and rarely hear them. Meadow Larks were plentiful and their song like a choir filled the land and my home morning and evening, now they are few and their song is thin.
The meandering old Rosebud River that runs through my land was wonderful habitat for birds, but sucking up water for frac’ing with most of it lost permanently, extreme drought and heat has turned it dry. Last year, there were only a few puddles of water in the part of the river in the photo above. Blue heron perched on the corrals around my barn hunting Richardson Ground Squirrel instead of fishing in the river.
Loosing the Yellow Monster: Fracking and Radioactivity
Fracking for gas not only uses toxic chemicals that can contaminate drinking and groundwater—it also releases substantial quantities of radioactive poison from the ground that will remain hot and deadly for thousands of years. …
“Radioactivity in the environment, especially the presence of the known carcinogen radium, poses a potentially significant threat to human health,”….