Drosophila hydei. By Brian Gratwicke - Flickr: Drosophila hydei larger fruitflies for small frogs, CC BY 2.0, link

Study: Fruit Flies Perilously Close to Climate Survival Limits

Guest essay by Eric Worrall

According to Aussie scientists, even mild global warming could push key tropical species over their survival limit. But what they have accidentally demonstrated is the unlikelihood of those limits being breached.


The loss of fertility in males as a result of climate change, particularly in the tropics, may be a better predictor of vulnerability to extinction 

By Dr Belinda van Heerwaarden, University of Melbourne

As temperatures rise across the globe, species will increasingly face environmental conditions beyond their tolerance limits, posing a major risk to biodiversity, food production and health. 

In our recent study, published in Nature Communications, we exposed different species of Drosophila flies to environmental conditions in the laboratory that mimicked climate change.

By following population growth and extinction, we found that tropical species indeed went extinct at temperatures lower than the widespread species. Despite living in the warm tropics, these species were no more heat tolerant than species with distributions extending much further away from the equator.

However, the loss of fertility in males – which occurs at temperatures much lower than lethal temperatures – was a better predictor of individual climate change vulnerability. 

So, how much closer are species to their male fertility limits than their critical thermal limits?

Some of the rainforest species we examined currently experience maximum habitat temperatures around 7 °C below their critical thermal limit or in other words, their warming tolerance is around 7 °C.

In contrast, some species are already experiencing average temperatures during summer months within 1 °C of their male fertility limit. 

So instead of a buffer zone of 7 °C, they may only be able to handle 1°C of warming before populations crash.

Given that many species – particularly tropical species – may be much closer to their thermal limits, the 1.5 to 4 °C of warming currently projected may lead to much more biodiversity loss than most of us probably realise. 

Read more: https://pursuit.unimelb.edu.au/articles/male-fertility-precariously-close-to-climate-change-extinction-limits

The abstract of their study;

Male fertility thermal limits predict vulnerability to climate warming

Belinda van Heerwaarden & Carla M. Sgrò 

Nature Communications volume 12, Article number: 2214 (2021) Cite this article


Forecasting which species/ecosystems are most vulnerable to climate warming is essential to guide conservation strategies to minimize extinction. Tropical/mid-latitude species are predicted to be most at risk as they live close to their upper critical thermal limits (CTLs). However, these assessments assume that upper CTL estimates, such as CTmax, are accurate predictors of vulnerability and ignore the potential for evolution to ameliorate temperature increases. Here, we use experimental evolution to assess extinction risk and adaptation in tropical and widespread Drosophila species. We find tropical species succumb to extinction before widespread species. Male fertility thermal limits, which are much lower than CTmax, are better predictors of species’ current distributions and extinction in the laboratory. We find little evidence of adaptive responses to warming in any species. These results suggest that species are living closer to their upper thermal limits than currently presumed and evolution/plasticity are unlikely to rescue populations from extinction.

Read more: https://www.nature.com/articles/s41467-021-22546-w

Why are tropical species less resistant to warmer temperatures? The answer is obvious – because tropical species never had to evolve persistent genetic resilience to higher temperatures.

Ignoring the possibility of experimental error, either gene plasticity or genetic variation of the entire population is greater than the scientists inferred from cooking a few lab specimens, or the tropics is so resistant to climatic temperature variation, species can comfortably survive within 1C of their survival limit.

The earliest winged insects appeared 480 million years ago. Since then they have changed a lot; I suspect fast breeding short lived species like Drosophila split into a new species every time someone looks at them hard.

The point is, the ancestors of current Drosophila flies likely faced pretty much every level of CO2 and global temperature the Earth could throw at them, likely including levels of CO2 many times greater than today’s geologically low level of ~417ppm CO2.

h/t Tom Nelson, Bill Illis

The obvious inference of the study, that fruit flies can’t exist in the tropics in high CO2 warm periods, is absurd. Even if some tropical species of insects were briefly eradicated by past climate excursions, their range would have been rapidly recolonised by tropical and subtropical species which survived the excursion. Nature abhors an unutilized food source.

The main study included some weasel words – “… It is also possible that extreme temperature events may be more effective in driving evolutionary responses in these traits, particularly for CTmax. However, other studies that have directly selected upon CTmax or acute heat knockdown have also failed to show a sustained response …”.

My suggestion; given the geological history of the Earth, the hypothesis that an entire species is likely to show more ability to adapt than a tank full of lab specimens should be the default assumption, not a grudging admission. Fruit flies are a tough agricultural pest, which have repeatedly demonstrated the ability to rapidly evolve to overcome threats to their species, such as evolving resistance to new pesticides. I suspect if you filled laboratory tanks full of fruit flies with a new pesticide, you might also conclude they show very little ability to adapt. But out of the untold trillions of fruit flies in the wild, some always manage to survive attempts to eradicate them.

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May 1, 2021 2:16 am

If there was one thing that we will not miss if it becomes extinct, it would be Fruit Flies.

Reply to  nicholas tesdorf
May 1, 2021 5:30 am

Don’t forget politicians!

Reply to  IanE
May 1, 2021 8:21 am

There’s more chance of global warming being catastrophic than politicians becoming extinct

Reply to  IanE
May 1, 2021 8:37 am

I was hoping climate scientists but I hear they breed like flies … oh wait.

John Tillman
Reply to  nicholas tesdorf
May 2, 2021 2:13 pm

No such luck.

The only mass extinction event to affect insects was the end Permian Great Dying. A degree warmer globally and less than that in the tropics will have no effect on fruit flies. They evolved when crocs inhabited the Arctic.

May 1, 2021 2:28 am

This temperature map showing the temperature difference between winter and summer may help to explain why tropical species are less resistant to temperatures changes?

Tropical species experience a smaller temperature range between winter and summer than species which live outside the tropics. Species which live outside the tropics must cope with bigger temperature changes.

comment image

Reply to  Sheldon Walker
May 1, 2021 2:53 am

If anybody is interested, I have just published a Kindle book called “How big is Global Warming”. It is available on Amazon.

Ron Long
Reply to  Sheldon Walker
May 1, 2021 3:02 am

Shirley your comments don’t also apply to human evolution? Looks like you are not woke enough.

May 1, 2021 2:34 am

“The answer is obvious – because tropical species never had to evolve persistent genetic resilience to higher temperatures.”
Or perhaps, this is one of many ways that a species goes about evolving persistent genetic anything. If P percent of males cannot reproduce, if the species are to survive, the situation will reverse itself with the next generation, or the one following that one. Good thing that insects reproduce so frequently, since the increased food supply available to the succeeding generations (or their niche replacements) probably won’t last for long.
Really, boom and bust, with the unfit dying out to be replaced by the slightly more fit, was how I thought this evolution thing was supposed to work.

Smart Rock
Reply to  Eric Worrall
May 1, 2021 8:46 am

As we have seen to our cost with antibiotic-resistant bacteria.

The development of industrial melanism in insects and spiders in England’s “dark satanic mills” is an instructive illustration of parallel evolution in separate species in response to a changed environment. Even more instructive is how rapidly the melanism disappeared in the post-industrial era, when the old factories got sandblasted and repurposed.

Evolution happens in real time.

Reply to  Smart Rock
May 1, 2021 7:17 pm

Not meaning to nitpick,
but how sure are you about antibiotics and the supposed resistance of bacteria to antibiotics?

As far as I can tell and know, tetracycline still works fine with no any such problems.

Has been there for quite a long while, with no failure.

just saying

L Flawse
Reply to  dk_
May 1, 2021 4:08 pm

Friuit Flys were not chosen for experiments in heritability for no reason. Prolific breeders with an extremely short generation interval makes them great survivors. It doesn’t take many to survive to create a whole new population.

Ron Long
May 1, 2021 2:59 am

Good comments, Eric. Not only does the Darwin idea of “survival of the fittest” agree with your comments, it strikes me as fascinating that tropical fruit flies are smarter than Belinda and Sara and will, if it warms up for them, simply fly to an area less warm. We’re talking about some seriously small brains here (in both cases, fruit flies and Belinda/Sara).

May 1, 2021 3:14 am

Tell the authors to call me back when they can explain why the most biodiverse place on the planet (the Amazon rainforest) is also among the hottest places on the planet.

Reply to  Jit
May 1, 2021 5:37 am

In fact the Coastal Rainforest in Brazil is/was most diverse than the Amazon. Some regions had 500 different plant species per km2, not to mention the animal species in the area. But still, I agree with your point.

May 1, 2021 3:19 am

You can ask a simple question , given most species on the planet have been around for what is millions of years , how did they manage to survive what in that time scale is various significant changes in climate . ?

Tom Abbott
Reply to  knr
May 1, 2021 4:14 am

Good question.

John Tillman
Reply to  knr
May 1, 2021 5:58 am

Order Diptera evolved in the Early Triassic, about 235 million years ago. Suborder Brachycera existed in the Jurassic Period, but might have arisen in the Late Triassic. Family Drosophilidae could have appeared even before the spread of flowering plants in the Early Cretaceous.

Most fruit flies don’t actually eat vegetation, but the yeast and microbes which break down fruit. Some species have evolved herbivory, but remain in the minority.

But even if they developed in the Late Cretaceous, fruit flies lived for tens of millions of years under conditions much hotter than now, with CO2 four or five times higher. For that matter, same goes for a Paleocene Epoch origin.

John Tillman
Reply to  John Tillman
May 2, 2021 7:35 am

Should read 245 million.

Reply to  knr
May 1, 2021 9:11 am

The claim is that temperature change has never happened this quickly before. Never mind that it happened just as rapidly coming out of the LIA, or that we only have decade level resolution for relatively recent history.

May 1, 2021 3:41 am

A study about life and extinction, published in a scientific journal,
produced by the same kinda of the bright loot,
who even to this day consider the actual timming of life, fauna and flora in Chernobyl, simply non relevant and fictional, totally ignored as with no much of interest for learning.

According to their methods, yes there should only be some weird mutant
flora species and a “paradise” of cockroaches of strange and weird forms and sizes.

Any time now the gigantic worms of Chernobilia just about to introduce their might to the pesky humans.


Reply to  whiten
May 1, 2021 3:50 am

Oh well,
still, unfortunately, or not,
the worms of Chernobilia faceing currently the most severe “speed of light” extinction of species before even established as a proper new species.

Please, try a guess why and how.!

Yes you guessed right!


Reply to  whiten
May 1, 2021 3:54 am

surprised they havent made a chernobyl mutant mushroom/worm etc rampage movie yet

Reply to  ozspeaksup
May 1, 2021 4:24 am

Maybe simply because the Chernobyl event disaster was/is REal…
and not some non realistic, invented nonsense AGW Terminator of life as we know it!

A so non real existential threat, which even threatens with “extinction” the consideration of “nuclear winters” that supposed to be already in the pipeline, according to the predictions by this kinda of loot!

An existential terminator threat to the Terminator(s) too.

Where is Arnold when nedded the most!

Mumbles McGuirck
Reply to  whiten
May 1, 2021 5:17 am

“Where is Arnold when needed the most?”
He became Governor of California and turned into a ‘girlie man’. 😕

Reply to  Mumbles McGuirck
May 1, 2021 6:06 am

You not telling me, in some “weird” way now, that Arnold is now listed under the name;



Mumbles McGuirck
Reply to  ozspeaksup
May 1, 2021 5:19 am
May 1, 2021 3:51 am

fruit flies survice 50c temps and then cold stores and still survive within weeks from harvest to store to table. vinegar flies do the same.
these people need to get into the real world more often

Reply to  ozspeaksup
May 1, 2021 11:04 am

How sagacious my childhood pals now seem when repeatedly reminded me: “time flies like an arrow, but fruit flies like a banana.”

Farmer Ch E retired
Reply to  ozspeaksup
May 1, 2021 8:11 pm

“these people need to get into the real world more often”

My real world experience managing my Dad’s Cherry Orchard in MT for many years is that if multiple sprays throughout the season don’t eliminate the flies, nothing will. Early sprays are long-lasting and some don’t allow reentry into the orchard for a time period. The closer to harvest, the more benign sprays are used that aren’t as long lasting. At harvest, very safe sprays are used that allow workers to pick the fruit immediately. Fruit fly traps are set and if one is caught, you can lose your entire crop or lose the ability to access markets in other states like WA and CA. After processing in WA, some of the fruit from MT was going to retailers like Costco.

May 1, 2021 3:58 am

Abject bullshit is abject bullshit. Fruitflies mate under trees on things that have evaporative cooling.

Farmer Ch E retired
Reply to  Prjindigo
May 1, 2021 8:24 pm

Irrigation during the growing season definitely adds to the evaporative cooling.

Reply to  Farmer Ch E retired
May 2, 2021 9:01 am


You guys missing the point.

These other guys had already compensated for things, like one you mention.

For example, one compensation had to do with circumcision of the mails, all of them, prior to the experiment.



May 1, 2021 4:04 am

This just means there’s a selective pressure and therefore species will adapt through evolution.

Tom Abbott
May 1, 2021 4:10 am

From the article: “Given that many species – particularly tropical species – may be much closer to their thermal limits, the 1.5 to 4 °C of warming currently projected may lead to much more biodiversity loss than most of us probably realise.”

Things are looking up for the insects! The current global temperatures have cooled by 0.7C since 2016. Hitting the 1.5C threshold above the average for the period from 1850 to the present is a long way off.

The “hottest year evah!”, 2016 was 1.02C above the average. The temperatures would have to climb by 0.5C from there to reach the minimum threshold of 1.5C, that strikes fear in the hearts of these scientists. But instead of the temperatures continuing to climb higher after 2016, the temperatures have cooled since then and we are now 0.7C below the 2016 highpoint.

I hope this comment helps to calm these scientists down. They are worrying themselves over something that may not happen at all.

The year 1934 in the U.S. was warmer than the year 2016 by about 0.5C, according to James Hansen and friends, which would put 1934 right at the 1.5C above the average, minimum threshold for supposed climate disaster, but the insects survived that period in history, so that’s even more cause for the scientists to stop their handwringing.

May 1, 2021 4:20 am

I’m certain the Brewing industry would not miss fruit flies or their larvae

Best not to get their hopes up with junk science like this

May 1, 2021 4:51 am

Drosophila in general and melanogaster in particular are known for a wide genetic variability, so I see no problem to adapt to a not measured but calculated higher temperature difference ?

May 1, 2021 4:59 am

Drosophila flies survive an awful lot of adverse lab conditions, including being knocked out long enough to be counted. I am sure a few can survive slight average temperature increases, unfortunately.

May 1, 2021 6:06 am

I didn’t read too much of it, but it occurred to me… Are the temps in au tropics really that stable? I’d guess not… what if those fruit flies ARE sensitive to temps and become more fragile at stable temps including loss of fertility?

Reply to  Rick
May 1, 2021 6:10 am

Stable temps… Ie. The temperature in a laboratory.

May 1, 2021 6:37 am

“The earliest winged insects appeared 480 million years ago. Since then they have changed a lot; I suspect fast breeding short lived species like Drosophila split into a new species every time someone looks at them hard.”

Interesting conjecture. Is there any evidence to support that? What are, and where are, the new “species” descended from the fruit fly?

Since they must be the most studied species in man’s exploration of evolution/genetics, with millions (?) of generations observed and manipulated, it would be great to see the evidence of new “species” that evolved.

Or is the fruit fly species of 480 million years ago essentially the fruit fly species of today?

Pat from kerbob
Reply to  Kent Clizbe
May 1, 2021 8:42 am

They reproduce only a little slower than bacteria and viruses, all evolve and change rapidly, else we wouldn’t have dozens of covid variants
You have to do genetic testing to detect differences

Reply to  Pat from kerbob
May 1, 2021 12:19 pm

“They reproduce only a little slower than bacteria and viruses, all evolve and change rapidly, else we wouldn’t have dozens of covid variants
You have to do genetic testing to detect differences”

Back to the question, then: Where are the “species”?

A chihuahua is a member of the dog species, so is a great dane. You can do genetic testing to detect the difference, you can also see the difference. They are NOT “evolved” species, though.

In 480 million years, where are the “evolved” fruit fly species?

May 1, 2021 6:47 am

Which few climate scare extrapolation studies will make the cut when popular writers of the future mock the global warming era with limited examples. It’s going to be difficult to pick among the millions in the dustbin of history at that point.

Reply to  ResourceGuy
May 1, 2021 9:06 am

I would like to see a metric applied to CAGW “science” articles. This metric would count the number of weasel words like “may,” “could,” etc. — all within context of course, to make sure that they are being used as weasel words.

Then those popular writers of the future could mock a CAGW writer of today by saying, “…and this article has a CYA rating of 97%…” — or however the metric is set up to read.

Gordon A. Dressler
May 1, 2021 7:38 am

One simple question: Why is the above article newsworthy?

I take it for granted (since about 10 years ago) that the AGW/CAGW alarmists will be informing us, quite frequently, that XXX (insert here the name of any arbitrarily-chosen plant or animal) is “perilously close to climate survival limits” . . . that is, extinction caused by climate change.


Jim Gorman
May 1, 2021 7:54 am

Sounds like the same shinola to me. Temps are going to rise the same amount, everywhere, at the same time. That’s why GAT and GCM’s are useless. They have displayed no ability whatsoever to forecast regional differences in temperature, rainfall, or climate in general.

Other scientists take the media propaganda at face value and in return propagate invalid conclusions. Science gone mad, mad I tell you!

Carlo, Monte
Reply to  Jim Gorman
May 1, 2021 8:20 am

Frankenflies! Run away!

May 1, 2021 8:06 am

YAY! Fruit flies are bad for vegans and vegans are good for the earth. Win win.

May 1, 2021 8:16 am

The facts are that 99.9% of all species that ever lived on earth are already extinct. It had nothing to do with humans. So one must then logically accept that extinction is a natural and normal process for all life on earth.

Reply to  Doonman
May 1, 2021 8:45 am


Great point. As Carlin said in his famous Earth Day skit,

“we didn’t kill them all!”

Gums sends…

Reply to  Doonman
May 1, 2021 8:54 am

“Extinction begets Diversity.”

Smart Rock
May 1, 2021 8:16 am

These researchers all seem to make the tacit assumption that if there is 1.5° of warming globally, that every point on the planet warms by 1.5°.

Whereas, even in their cherished models, almost all the surface warming is concentrated in higher latitudes. Tropical rain forests seem to have a natural temperature limit, probably because increased insolation leads to increased evapotranspiration, which leads to more clouds, which leads to more tropical rainstorms, which leads to more cooling. As we have seen in tropical oceans (thanks for your many posts on this, Willis).

In any other branch of science, this sort of erroneous underlying assumption would lead to ridicule from their colleagues, published retraction of conclusions, loss of prestige, loss of research funding, possibly even loss of their jobs. In practice, in any other branch of science, peer reviewers would normally pick up on the error and the paper would have to be rewritten.

But not in “Climate Science – Where Conclusions Come First” ™

Climate science is many things, but science is not one of them.

Abolition Man
Reply to  Smart Rock
May 1, 2021 5:55 pm

Smart Rock,
Very like the Communists of old who said; “Show me the man, and we’ll find the crime,” today’s practioners of scientism start with their conclusions then search for corroborating data!
Kind of like the current DOJ and FBI, now that I think about it!

Pat from kerbob
May 1, 2021 8:50 am

Canada’s very own fruit fly David Suzuki made his name studying fruit flies.
Oh, and proclaiming the end of everything due to human overpopulation (he has 5 kids) and overconsumption (of course he has multiple residences).

Just another hypocrite

Steve Reddish
May 1, 2021 8:55 am

Polar bears have survived predictions of demise due to “polar amplification”, so those who make predictions of demise are now concentrating on the opposite end of the climate zone spectrum?
This is yet another example of the failure of one type of predicted disaster to materialize resulting in the prediction of an opposite type of disaster.
Doomsters just gotta predict doom!

May 1, 2021 9:06 am

Humans are also perilously close to their survival limits. As Willis recently demonstrated in his peer review request, maximum average temperatures are limited to about 27.5 C.

And coincidentally, unprotected human beings die of exposure when temperatures drop below 27.5 C. We cannot generate enough body heat to overcome radiative heat losses.

Pretty much the only places on earth where temperatures are 27.5 C or above year round are the tropical jungles. Without fire, clothing and shelter, humans could not survive anywhere else. And without technology most of us could not survive in the tropical jungles either.

Abolition Man
Reply to  Ferdberple
May 1, 2021 5:57 pm

One word for survival in the tropics; siesta! Well, two words; margaritas, followed by siesta!

May 1, 2021 9:16 am

Don’t they believe in evolution?
There’s always a distribution in characteristics which is a factor in species adaption.

May 1, 2021 9:37 am

Quantitative genetic analyses have revealed genetic variation for thermoresistance under laboratory conditions, but variation under natural conditions has rarely been identified. In a few cases selection responses within laboratory populations have been linked to specific candidate genes and physiological mechanisms.
Population comparisons have provided evidence for clinal variation in thermoresistance traits, although many studies lack power because only a few populations have been considered. Clinal patterns in candidate genes have also been demonstrated. However evidence for direct selection for thermoresistance and for the involvement of specific genes under natural conditions is mostly lacking. Clinal responses to cold extremes can involve changes in diapause strategies and altered patterns of reproduction. Inbreeding influences thermoresistance and acclimation responses, but inbreeding effects may be environment-specific.
Species differences in heat or in cold resistance commonly match the geographical (climatic) distributions of species. Interspecific differences for heat resistance are usually smaller than for cold resistance. Drosophila species from the same location can differ markedly for stress resistance, and this may allow species to occupy different niches.

Adaptation of Drosophila to temperature extremes: bringing together quantitative and molecular approaches

Reply to  Krishna Gans
May 1, 2021 12:57 pm

What I would like to say, after a little google research, there are so many papers about Drosophilae, biological, genetic, biochemic about temperature and reproduction, none mentioned climate change, so it’s easy to say the paper discussed here seems to be edited by courtesy for climate alarmists.
In one of the latest threads these papers had a special name I unfortunately forgot.

May 1, 2021 9:58 am

I remember “experts” spraying a LOT of Malathion from helicopters in Los Angeles in the ’70’s. Ruined a lot of paint jobs on cars. Was not very successful at eradicating fruit flies. People protested, but they were the “experts” so they told the people they knew better.

Same kind of thing with the Covid BS going on right now. We are essentially livestock in the eyes of the elites.

May 1, 2021 12:59 pm

Time flies like an arrow, fruit flies like a banana.

And never forget Franklin’s Ephemera.

May 1, 2021 3:11 pm

Thank God! About time we wiped those f**kers out.

Robert of Ottawa
May 1, 2021 3:47 pm

Dr. Suzuki will be in mournng.

May 1, 2021 4:22 pm

Another research group that never ran a long term fruit fly population study.

Like mosquitos, rapid breeding cycles cause many of these insect species an amazing ability to adapt, quickly.

Likely, confirmation biased researchers bred fruit flies in cool dry conditions then immediately cranked up the heat in a poorly aerated without proper humidity.

Watched a show about attempting to breed and raise tuna.

The researchers were ecstatic that they kept the tuna larvae alive for eight days in their aquarium…
These were naturally spawned and fertilized tuna larvae.

Unlike most of the climate doomists, the tuna researchers are proceeding properly in building their aquarium tanks; i.e. ensure their fish tanks can keep tuna larvae through maturity stages, alive.
They’ll work on breeding next. That should be entertaining.

Abolition Man
Reply to  ATheoK
May 1, 2021 6:08 pm

The Japanese have been farm raising bluefin tuna since 2002! Also, I’m not sure that larvae is quite correct when speaking of fish. The parents would prefer you call them young tuna!

May 1, 2021 9:11 pm

As an Aussie, would these idiotic scientists stop trying to save these pests. My peaches were devastated by the blighters last year. if they go, i doubt any fruitgrowers would miss them.

Reply to  Quilter52
May 5, 2021 1:46 am

These flies are not the pest species they eat decomposing fruit, otherwise known as vinegar fly or bar flies 😂

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