High CO2 levels cause plants to thicken their leaves, could worsen climate change effects
Plant scientists have observed that when levels of carbon dioxide in the atmosphere rise, most plants do something unusual: They thicken their leaves.
And since human activity is raising atmospheric carbon dioxide levels, thick-leafed plants appear to be in our future.
But the consequences of this physiological response go far beyond heftier leaves on many plants. Two University of Washington scientists have discovered that plants with thicker leaves may exacerbate the effects of climate change because they would be less efficient in sequestering atmospheric carbon, a fact that climate change models to date have not taken into account.
In a paper published Oct. 1 in the journal Global Biogeochemical Cycles, the researchers report that, when they incorporated this information into global climate models under the high atmospheric carbon dioxide levels expected later this century, the global “carbon sink” contributed by plants was less productive — leaving about 5.8 extra petagrams, or 6.39 million tons, of carbon in the atmosphere per year. Those levels are similar to the amount of carbon released into the atmosphere each year due to human-generated fossil fuel emissions — 8 petagrams, or 8.8 million tons.
“Plants are flexible and respond to different environmental conditions,” said senior author Abigail Swann, a UW assistant professor of atmospheric sciences and biology. “But until now, no one had tried to quantify how this type of response to climate change will alter the impact that plants have on our planet.”
In addition to a weakening plant carbon sink, the simulations run by Swann and Marlies Kovenock, a UW doctoral student in biology, indicated that global temperatures could rise an extra 0.3 to 1.4 degrees Celsius beyond what has already been projected to occur by scientists studying climate change.
“If this single trait — leaf thickness — in high carbon dioxide levels has such a significant impact on the course of future climate change, we believe that global climate models should take other aspects of plant physiology and plant behavior into account when trying to forecast what the climate will look like later this century,” said Kovenock, who is lead author on the paper.
Scientists don’t know why plants thicken their leaves when carbon dioxide levels rise in the atmosphere. But the response has been documented across many different types of plant species, such as woody trees; staple crops like wheat, rice and potatoes; and other plants that undergo C3 carbon fixation, the form of photosynthesis that accounts for about 95 percent of photosynthetic activity on Earth.
Leaves can thicken by as much as a third, which changes the ratio of surface area to mass in the leaf and alters plant activities like photosynthesis, gas exchange, evaporative cooling and sugar storage. Plants are crucial modulators of their environment — without them, Earth’s atmosphere wouldn’t contain the oxygen that we breathe — and Kovenock and Swann believed that this critical and predictable leaf-thickening response was an ideal starting point to try to understand how widespread changes to plant physiology will affect Earth’s climate.
“Plant biologists have gathered large amounts of data about the leaf-thickening response to high carbon dioxide levels, including atmospheric carbon dioxide levels that we will see later this century,” said Kovenock. “We decided to incorporate the known physiological effects of leaf thickening into climate models to find out what effect, if any, this would have on a global scale.”
A 2009 paper by researchers in Europe and Australia collected and catalogued data from years of experiments on how plant leaves change in response to different environmental conditions. Kovenock and Swann incorporated the collated data on carbon dioxide responses into Earth-system models that are widely used in modeling the effect of diverse factors on global climate patterns.
The concentration of carbon dioxide in the atmosphere today hovers around 410 parts per million. Within a century, it may rise as high as 900 ppm. The carbon dioxide level that Kovenock and Swann simulated with thickened leaves was just 710 ppm. They also discovered the effects were worse in specific global regions. Parts of Eurasia and the Amazon basin, for example, showed a higher minimum increase in temperature. In these regions, thicker leaves may hamper evaporative cooling by plants or cloud formation, said Kovenock.
Swann and Kovenock hope that this study shows that it is necessary to consider plant responses to climate change in projections of future climate. There are many other changes in plant physiology and behavior under climate change that researchers could model next.
“We now know that even seemingly small alterations in plants such as this can have a global impact on climate, but we need more data on plant responses to simulate how plants will change with high accuracy,” said Swann. “People are not the only organisms that can influence climate.”
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From the UNIVERSITY OF WASHINGTON. The research was funded by the National Science Foundation and the UW.
Somehow, I just can’t let this disastrous news worry me, and did they consider that leaves that are 33% thicker store more carbon in the leaf?
Yummier lettuce?
Sorry, this comment may appear assinine but it is at the level of the “oh golly-gosh who would have thought it” discovery. Let’s see: CO2 makes plants grow? Hmmm. And this is a bad thing?
Rather like the Canadian Federal government’s desire to make Canada colder. by reducing CO2. MCCA! Hardly has the right ring, does it? But a colder Canada certainly would be a bad thing.
It’s a ‘bad thing’ because plant leaves will stop growing in size at some point, so eventually they must become less efficient per CO2 concentration. This is not really news at all. They just went in extremis and built a fairy model paper of it.
My skepticism arose quickly as I read the article. My first question (which I haven’t yet seen in the comments above) is this: What happened in past ages when CO2 was higher than now? Are there fossils of thick-leaved plants in these times? What happened to growth speeds, atmospheric temperature, and other factors? My impression is that these authors did not study for these factors nor try to answer my questions.
Are there not animals that would love to eat thicker juicier leaves? Say the Koala Bear. Think of all the Koalas that are now starving over wimpy light weight leaves that would enjoy a good thick beefy Eucalyptus leaf.
“In the model, vegetation responds to climate by changing carbon assimilation, stomatal conductance, biomass, and leaf area. ”
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GB005883
You actually have to read these studies to find out how fraudulent they really are. Reading just the abstract isnt enough.
The above quote from the 4th page of the study spills the beans. BTW the study is about C3 plants. This study is the classical case of circular reasoning. Their reasoning went like this 1) CO2 levels are rising 2) Global warming is caused by increased CO2
3) Increased CO2 also causes increased leaf mass in C3 plants.
4) Increased leaf mass in C3 plants causes less carbon to be used by the plants in photosynthesis. Why ? Because the climate model says so.
5) Therefore because less carbon is sequestered by C3 plants, the more net CO2 in atmosphere.
6) The more CO2 in atmosphere and we are back to step number 1.
If hard scientists presented a paper like this in the hard sciences, they would be laughed out of their faculty.
FRAUDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD!!!!!!!!!!!!!!!!!!!!!!
‘Dude’, it’s not a fraud when establishment scientist publishes it. It may be bollocks, but it is bollocks above my paygrade. /sarc
Papers which go after a 900 ppm scenario without explaining how feasible that is, are not quite realistic and may suffer from creepage of alarmism. To put it mildly.
“4) Increased leaf mass in C3 plants causes less carbon to be used by the plants in photosynthesis. Why ? Because the climate model says so.”
No – the the model does not “say so”.
Their model was running the global effects within vegetation of increased CO2 to KNOWN leaf traits.
Yet another stupid study by a bunch of stupid people leading to a stupid conclusion to feed to more stupid people. Stupid!
Leave it to activist warmist “scientists” (used very loosely) to frame a net benefit of higher CO2 (enhanced biosphere) as somehow a negative.
No, they are not stupid. For some 40 odd years many such “Stupid”people have been enjoying a comfortable life style at the taxpayers expense .
MJE
This article is focused on terrestrial plants According to a California Department of Education resource book for high-school science teachers, published in 1967, marine and fresh water plants accounted for about 90% of worldwide photosynthesis, with terrestrial plants the remaining 10%. I did some cursory searching just now but didn’t find anything more current–or anything discussing that particular comparison.
Very good point. How do the marine plants, algae react?
I would imagine pretty much the same as in 1967 with perhaps a slight increase in concentrations. It’s an interesting ratio though, land plants vs marine plants. If the idea is to keep people perpetually worried about CO2 then threats to land plants are just the ticket.
If it was known that marine plants perform the bulk of worldwide photosynthesis then the panic factor would lessen. “Well, good. I’ll still have oxygen to breathe and green salads to eat.”
Some current biogeochemical carbon cycle references estimate about the same amount of photosynthesis and biological mass on dry land and in the oceans. About 50/50.
Other estimates show more land photosynthesis than ocean. Quite a large amount of the pelagic oceans are biological deserts. Fishing boats stay near the continental shelves. Whales know where to find the krill.
There is a lot of land biomass in the tropics. The OCO2 mission shows that.
True, the ocean is lots of miles of very little, except where it isn’t like where they chased whales in the
middle of the Pacific. Moby Dick?
So only approx. 4% mankind’s (taking assumption that we’re not natural 🤣) additional CO2 will cause this, what about nature’s 96%; doesn’t it get any blame?
If I am reading the article correctly, they assume that plant mass will remain constant, so thicker leaves means less leaf area. Obviously the assumption is wrong, so all this proves is stupid assumptions give daft results.
Oh jayzus croist, not ticker leafs.
As Sir Robert Geldoff was quoted
What.
1. A petagram is a billion tonnes – why create more confusion with American ‘short’ tons?
2. They say that A Carbon Sink is sucking up ~6 billion tonnes of carbon annually = (roughly) 15 gigatonnes CO2
This don’t stack up. I thought us naughty humans wre pumping/spewing/belching over 30 gigatonnes
3. No matter #2, where *is* this carbon sink. I work it to be what 3 billion acres of Douglas Fir would soak up = about one-third of all the land area on this Earth that is NOT either desert of ice.
Show me pictures or it didn’t happen
4. If you want to say #3 is done via ‘CO2 fertilashion’ – explain *this* picture first:
5. Not least, since when did ‘scientists’ become astrologers, sooth sayers and fortune tellers. If anyone wants to venture into Wild Speculation, let them go do it, BUT, a true & honest teacher will not go there.
In my book, scientists are teachers. They do not invent things. They discover things and explain them to the rest of us.
To suggest these folks have overstepped their mark is …… is what?
Its an understatement to say its an understatement
6. At least they did admit, more than once, that plants have ‘something to do with climate’
If only, IF ONLY, they’d indulge some Blue-Sky-Brainstorming that did *not* involve CO2 as a climate moderator/controller.
sigh
What is all that CO2 doing hanging over the very place that *should* be soaking it up?
Fat fingers innit..
last line should be under the ‘nasa’ link
The members of the cAGW bandwagon admit flaws in global climate models? Good start. Looks like step 3 in Kübler-Ross model.
However, “climate scientists” have already been given chances to model the climate and, more importantly, to correct their projections. Yet, their models still cannot handle the past, be verified, be corrected and project the future. Their climate models are FUBAR.
They messed it up themselves and have only themselves to blame for it. Too bad. I wish them quick journey to step 5 of Kübler-Ross model.
From I remember from school à long time ago leaves have a variety of cells, viens and an outer layer. I can’t see any mention of which bit gets thicker.
Mesophyll.
“Somehow, I just can’t let this disastrous news worry me, and did they consider that leaves that are 33% thicker store more carbon in the leaf?”
Suddenly Anthony’s a plant physiologist! A man of many talents.
Leaves are made of carbon, if they are thicker there is more carbon. Anyone who breathes should be able to deduce that, no credentials needed.
As always, Kristi ridicules rather than addresses.
Of course Anthony’s point makes perfect sense. Which is why Kristi had to result to ridicule, since even she knew she couldn’t refute it.
And to think, she keeps telling us how educated she is.
“Fossil Fuels”. Can someone please explain why prehistoric plant life is called fossil fuel? BTW- oil comes dripping up from the ocean floor. How did it get *there*?
Because it is fuel from (micro)fossils. The organisms that the oil comes from died and sank to the ocean floor and were buried. Usually anything edible in the ocean gets eaten pretty fast, so oil is mostly produced by organics-rich shales that were deposited at times when the deep ocean was dysoxic and nothing could live there.
Shales are “source rocks” but mostly oil can only be extracted when the oil has moved to more porous “reservoi rocks” which only happans rather rarely. This is the secret behind “hydraulic fraccing”. It is now possible to extract a (rather small) proportion of the vastly larger oil/gas reserves that remain in the source rocks.
And as you say, most oil will ultimately leak up to the surface and be oxidized back to CO2 and H2O.
Coal on the other hand does come from plant remains, more or less similar to modern peat, that was buried and compacted. Coal is vastly more stable than oil and tends to last more or less for ever in the ground.
https://www.google.at/search?client=ms-android-samsung&biw=360&bih=288&ei=2ZWzW5LUDYmIgAbb_a-IBg&ins=false&q=sci+fi+movie+the+triffids&oq=sci+fi+movie+the+triff&gs_l=mobile-gws-wiz-serp.
Ok, I am far from a biological expert. So forgive any mistakes. It seems to me that if plant leaves get thicker, there are two options to explain it, the cells get bigger or the cells increase their numbers.
For cells to grow in size, energy is needed. Where does the energy come from? As I understand it, the energy comes from photosynthesis which uses CO2.
For cells to increase their numbers, new cells must be created and energy is needed. Where does the energy come from? As I understand it, the energy comes from photosynthesis which uses CO2.
So for leaves to thicken, more CO2 is required than today, not less. Am I wrong in my analysis?
A wild guess about why leaves become thicker (and mostly in C3 plants) with higher CO2.
Plants take up CO2 through stomata, mostly on the underside of leaves, which then diffuses throughout the leaf and is used by the leaf cells to photosyntesize. With more CO2 it can probably diffuse further before it becomes too scarce for photosynthesis, so leaves can be made thicker, thereby absorbing more sunlight and photosynthesizing more. C3 plants are most sensitive to CO2 shortage, so any increase would be expected to be greater for them than for C4 plants.
CO2 rise makes fishes and whales go extinct.
Researchers found that many fishes and almost all whales will be extinct within a short period of time. Rising CO2 levels will cause a severe increase in the size of phytoplankton which leads to fish obesity and whale obstipation.
From Cod Grayling‘s Journal of Modern Fishmongering.