Claim: Global Warming Could Stress Tropical Plants

Cassowary Vicki Nunn / CC BY-SA

Guest essay by Eric Worrall

A recent Paleo climate study which demonstrated thriving tropical rainforests in a period when CO2 levels reached 2000ppm (5x today’s level) during the early Eocene has not discouraged UNSW climate scientists from predicting imminent doom.

Climate change threat to tropical plants

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Half of the world’s tropical plant species may struggle to germinate by 2070 because of global warming, a new UNSW study predicts.

Tropical plants closer to the equator are most at risk from climate change because it is expected to become too hot for many species to germinate in the next 50 years, UNSW researchers have found.

Their study analysed almost 10,000 records for more than 1300 species from the Kew Gardens’ global seed germination database. 

The research, published in the journal Global Ecology and Biogeography last month, was the first to look at the big picture impact of climate change on such a large number of plant species worldwide. 

Lead author Alex Sentinella, UNSW PhD researcher, said past research had found that animal species closer to the equator would be more at risk from climate change.

“The thought was that because tropical species come from a stable climate where it’s always warm, they can only cope with a narrow range of temperatures – whereas species from higher latitudes can cope with a larger range of temperatures because they come from places where the weather varies widely,” Mr Sentinella said. 

“However, this idea had never been tested for plants.

“Because climate change is a huge issue globally, we wanted to understand these patterns on a global scale and build upon the many studies on plants at an individual level in their environment.”

Read more:

The abstract of the study;

Tropical plants do not have narrower temperature tolerances, but are more at risk from warming because they are close to their upper thermal limits

Alexander T. Sentinella, David I. Warton, William B. Sherwin, Catherine A. Offord, Angela T. Moles



Tropical species are thought to be more susceptible to climate warming than are higher latitude species. This prediction is largely based on the assumption that tropical species can tolerate a narrower range of temperatures. While this prediction holds for some animal taxa, we do not yet know the latitudinal trends in temperature tolerance for plants. We aim to address this knowledge gap and establish if there is a global trend in plant warming risk.



Time period


Major taxa studied



We used 9,737 records for 1,312 species from the Kew Gardens’ global germination database to quantify global patterns in germination temperature.


We found no evidence for a latitudinal gradient in the breadth of temperatures at which plant species can germinate. However, tropical plants are predicted to face the greatest risk from climate warming, because they experience temperatures closer to their upper germination limits. By 2070, over half (79/142) of tropical plant species are predicted to experience temperatures exceeding their optimum germination temperatures, with some even exceeding their maximum germination temperature (41/190). Conversely, 95% of species at latitudes above 45° are predicted to benefit from warming, with environmental temperatures shifting closer to the species’ optimal germination temperatures.

Main conclusions

The prediction that tropical plant species would be most at risk under future climate warming was supported by our data, but through a different mechanism to that generally assumed.

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University of New South Wales is home to Ship of Fools Professor Chris Turney, leader of an expedition to the Antarctic to study melting ice which got stuck in the irony.

I love this new study because in my opinion it is a perfect example of climate scientists discarding or ignoring observations which do not fit their model.

There is no chance anthropogenic CO2 will lead to 1000ppm CO2, let alone 2000ppm, because there is nowhere near enough recoverable fossil fuel available to achieve early Eocene levels of atmospheric CO2. Since tropical plants handled early Eocene temperatures just fine, and we will never achieve early Eocene CO2 levels, there is no chance anthropogenic CO2 poses any kind of existential threat to tropical plants.

But the most extreme climate models predict lethal tropical temperatures by the end of the century.

A few climate scientists have courageously pointed out this contradiction means worst case climate model predictions about future tropical conditions must be wrong. But the rest just seem to blindly follow the output of their computers, and make alarmist statements which in my opinion bear no relationship to reality.

Note: If you ever see the bird in the picture at the top of this post in the Aussie tropics, don’t bother it, get as far away from it as you can. Like most Aussie wildlife Cassowaries want to kill you, and have a good chance of succeeding.

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July 4, 2020 6:13 pm

Nothing stands between an alarmist climate scientists who is predicting imminent doom and a large Pot of Gold. The fact that the heavy cloud cover in the tropics protects against increased temperatures is carefully forgotten. In addition the plants like the extra CO2 and a bit more warmth at night.
Eric is correct. If you get that close to a Cassowary, watch the feet as well as the beak!

July 4, 2020 6:15 pm

guy in Florida was killed by his pet cassowary not to long ago…

anywho, I thought the tropics were supposed to see the least change in temperature

Reply to  Latitude
July 5, 2020 12:07 am

Yes, oddly we do not see any mention of the actual temperature rises they are assuming will happen in the tropics by 2020.

My guess is that they are taking some upper limit “global warming” like 5 deg C. and erroneously applying to global average to the tropics.

The tropics have seen ZERO “global warming” so far, they are the thermo-regulator of the planet.

Rich Davis
July 4, 2020 6:16 pm

Ok, so quiz time. Where is the daytime Tmax change least pronounced? That’s right, at the equator.

July 4, 2020 6:16 pm

crap…said the magic word again…try again

guy in Florida was k177ed by his pet cassowary not to long ago…

anywho, I thought the tropics were supposed to see the least change in temperature

Reply to  Latitude
July 5, 2020 12:09 am

Oh no , not the k-word, you should know better. ki11ed reads better but k177ed is a nice way of pointing out this stupid filter issue still needs fixing.

Pretty please !

July 4, 2020 6:27 pm

”Claim: Global Warming Could Stress Tropical Plants”

Please someone make it stop.
I work with plants all day. Temperate and tropical. The authors obviously have no experience whatsoever as to the adaptability of these things.

”Time period

Present–2070.” Oh do tell how you study something in 2070 without a time machine.

Tiger Bee Fly
Reply to  Mike
July 4, 2020 7:23 pm

IIRC, Dr. Michael Crichton had a character in State Of Fear say that facts do not exist in the future.

I liked that, and still do.

John M. Ware
July 4, 2020 6:34 pm

So that picture at the head of the article is a cassowary! At first glance I thought it was a fish. I do know of the cassowary’s IQ (irritability quotient) and have no plans to get near one, let alone mount and try to ride it. (Yes, my vision is not wholly trustworthy, and I would apologize for it; but I thought my mistake was funny and someone might enjoy it. And please, don’t irritate the cassowary!)

Neil Stuart
Reply to  John M. Ware
July 5, 2020 12:49 am

I thought it was a fish also at first -then I saw the eyelashes.

Reply to  John M. Ware
July 5, 2020 12:53 am

I thought it was from Jurassic Park, it looks like a (supposed) dinosaur head. There is definitely an air of menace about it.

Reply to  John
July 5, 2020 10:39 am

Cassowary seem to be near dinos, as birds usual are, it is a special one 😀

July 4, 2020 6:54 pm

All these plants made it through the Holocene Optimum, which was probably 3-4ºC warmer than now.

These “climate scientistsᴸᴼᴸ” epitomise the standard ignorance of all alarmist pseudo-scientists..

July 4, 2020 7:00 pm

The flora like CO2, the fauna like O2, and everyone has a deeply-seated prejudice for a sunny and warm existence, in a partnership made on Earth.

4 Eyes
July 4, 2020 7:20 pm

Without imminent climate change these people are on the unemployment queue. And they know it.

July 4, 2020 7:24 pm

The more humid it is, the less effect CO2 has. Even the IPCC acknowledges that fact.

July 4, 2020 7:25 pm

Don’t worry about the tropics, if a miracle happens and it gets very very hot, plant life will adapt and spread to higher latitudes making new jungles.
Of course, with hotter temperatures, you get more cloud cover which will turn deserts into usable land with more rain for crops. A win-win.
This warmer weather is a good scenario, much more preferable than a coming Ice Age. Have you ever noticed how much plant life and animals live north of the Arctic Circle? Life gets more abundant the closer you get to the Tropics which tells you all you need to know about which is better.

As a side note, UV radiation doubles every 200 miles between the north pole and the equator. (The actual numbers for your area is available on any solar panel sales website) increased UV radiation must therefore also be good for plant and animal life.

Rich Davis
Reply to  Max
July 5, 2020 6:44 am

Correlation but not causation. UV is net harmful. Just not enough to overcome the benefits of warmth and moisture going from pole to equator. In small doses it has some benefits to be sure, such as to stimulate vitamin D production, but on balance it’s harmful at tropical strength.

By your same logic, since air pollution is greatest in densely populated cities, air pollution must be good for people. See the fallacy?

Clyde Spencer
July 4, 2020 7:48 pm

“Tropical plants closer to the equator are most at risk from climate change because it is expected to become too hot for many species to germinate in the next 50 years, …”

First, most of the rise in global and regional temperatures (contributing to a rising average) is the minimum, not the maximum. Second, the tropics are warming the least of all climate zones. Third, it is unreasonable to assume that all tropical plants are equally close to their thermal maximum. Fourth, the unstated assumption is that should the alarm over rising temperatures be true, tropical plants would be unable to adapt trough genetic mutation. Lastly, many plants will be able to migrate up the side of mountains and survive until the next cooling cycle. The quality of peer-reviewed research has declined to abominable levels!

Rich Davis
Reply to  Clyde Spencer
July 5, 2020 6:59 am

The purpose is not to advance knowledge. The purpose is to proselytize for the green faith.

You can’t use real science to prove a false religion, and you don’t get published if you write heresy. Shoddy work that supports the dogma is rewarded. Rigor that calls doctrine slightly into question is punished.

Kids to feed, mortgage to be paid, which way would you go?

Clyde Spencer
Reply to  Rich Davis
July 9, 2020 3:40 pm

When I was in high school I thought that I might want to become a lawyer. I decided that it would be better to get an honest job.

July 4, 2020 7:52 pm

Wonder why I have to use a heating pad to germinate for my garden. The only thing that germinates at ambient in the spring in BC Canada is weeds.

Pat from kerbob
Reply to  Fran
July 4, 2020 8:07 pm

Yes, in calgary I use several of those pads to encourage germination.
Warmer and wetter future equals 😀😀😀

July 4, 2020 8:26 pm

More of the same …. as I described in a recent post, “know-nothings down south”, which can be extended:
” … who come up here to teach grand[person] to suck eggs.” We are paying these people to be stupid and they continue to fulfill this role.
Advice on meeting a cassowary: stop. Walk backwards very slowly. Raise your arms as high as they will go. This does not represent some kind of surrender; cassowaries rarely attack things that are taller than they are.
Note the term “rarely”. The coordinates of the picture place the camera in Gladstone, which is well south of cassowary natural habitat. So, if real, the image is probably recorded through a chain-link fence. Can’t see how the photographer would have survived otherwise. Coolpix 90 camera has telephoto zoom, but it’s not that good.

July 4, 2020 9:08 pm

“Climate change threat to tropical plants”

And the climate science threat to tropical people.

July 4, 2020 10:13 pm

The one thing life is not it delicate. Plants will and do, exploit the most minuscule habitat. From pine trees growing from cracks in stone on a cliff, to moss exploiting a patch of mortar in a wall.

I once went down an Ochre mine, along the passage were lights, every 10 yards. Round each light was a little oasis of green. Hundreds of meters underground. Seeds had wafted in, found light, damp, and nutrients and set up home.

Plants are tough, really tough.

Mike Dubrasich
July 4, 2020 11:02 pm

Gotta love this quote:

Conversely, 95% of species at latitudes above 45° are predicted to benefit from warming …

Granted the authors are spewing foolishness, but even a blind pig finds an acorn once in awhile.

Warmth will BENEFIT 95% of the species! Told you so …

Gold star goes to UNSW! About time they earned one.

Jeff Alberts
Reply to  Mike Dubrasich
July 5, 2020 8:42 am

No, warmth will benefit “95% of species at latitudes above 45°”.

Not the same as what you said.

July 4, 2020 11:04 pm

Vines (“lianas”) will do best in higher tropical temperatures & plants with larger leaf area will do better than those sparsely leaved. A nice excursion of actual plant science is the free full text available online of (2016) ” The effect of rising temperature on the ecophysiology of tropical forest trees.”

Climate believer
July 4, 2020 11:31 pm

“We aim to address this knowledge gap”

I suggest you aim a little higher.

Alasdair Fairbairn
July 5, 2020 12:39 am

Oh dear! Yet another of these articles. This nasty habit of Editors/Scientists extrapolating detailed research up to global levels by pontificating on unsubstantiated conjectures about the climate is deplorable, totally unprofessional and only serves to damage the reputation of science.
To me this gives gives strong indication of the political corruption of the scientific process.

July 5, 2020 3:55 am

“Claim: Global Warming Could Stress Tropical Plants”

Or not.

July 5, 2020 5:26 am

Looks like somebody is after hundreds of thousands of dollars/pounds to study something which is of no worry…

Universities get hundreds of millions every year, yet we still need tax money for useless time wasters who scare us for personal gain.

July 5, 2020 8:59 am

Archaeologist and researcher describes sea level rise and fall in the Gulf of Maine at the time of the Maritime Archaic Native tribes circa 7000 years ago.

Also touches on the gulf stream. This is really eye opening. Go to the 16:13 mark.

Tiger Bee Fly
July 5, 2020 11:39 am

That’s very interesting! I think Dr. Crichton meant it perfectly prosaically, but I still really enjoyed reading the article and following up on the criticisms as well. Thanks!

July 5, 2020 5:41 pm

But I thought that Global Warming was going to affect the poles most, and have very little effect on the tropics.

(Replace “affect” and “effect” with “impact” if you really must.)

July 5, 2020 5:44 pm

Remember that, while most Aussie wildlife wants to kill you, not all of it can. The honey possum would love to rip you to shreds, but it is about the size of your thumb and has no venom.

Cassowaries are a bit larger.

Geoff Sherrington
July 5, 2020 11:03 pm

Some warm clmate plants require high temperatures to germinate. The heat of a bush fire exceeds that of a summer day. In some past research, we even used concentrated sulphuric acid on seeds to get them to germinate.
Just because there is a change in air temperature, that does not mean a similar change in soil temperature for seeds that germinate in the soil horizon. There is commonly a temperature gradient in the soil as you go deeper. If it gets too hot for seeds buried shallow, it could well be OK for seeds buried deeper.
The whole conjecture of this article is on false premises.
A better experiment would take seeds from one mapped climate zone to another to see what grows, but that experiment has often been done without alarm because temperature is not usually the main cause if poorer germination. Try rainfall, frost, humidity, annual daylight hours, season lengths, pests, diseases before even getting to acts if man like costs if production, yields, profits, fertilizers, soil preparation in general.
Rather a bad fail, the concepts in this paper. Geoff S

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