Beneficial effects of rising CO2 for plants disappear under flooding, 33-year field experiment reveals
SMITHSONIAN
Wetlands across the globe are in danger of drowning from rising seas. But for decades, scientists held out hope that another aspect of climate change—rising carbon dioxide (CO2)—could trigger extra plant growth, enabling coastal wetlands to grow fast enough to outpace sea-level rise. That helpful side effect is disappearing, they discovered in a new study published May 18.
“Too much water is a stress, an environmental stress, for plant response to high CO2,” said Chunwu Zhu, lead author of the report in Science Advances. Zhu, a biologist with the Chinese Academy of Sciences, conducted the study while on a fellowship with the Smithsonian Environmental Research Center (SERC).
Conserving wetlands is critical both to fight climate change and adapt to it. Besides providing habitat, wetlands sequester massive amounts of carbon and protect people from some of climate change’s more extreme effects, such as hurricanes and typhoons.
“Although they occupy just a fraction of the Earth’s surface, they provide outsized ecosystem services, which are basically benefits to people,” said corresponding author Pat Megonigal, a biogeochemist with SERC. “And we value them partly because, by protecting a relatively small part of the Earth, we can have big positive impacts on the environment.”
Carbon Dioxide’s Diminishing Returns
The study took place at SERC’s Global Change Research Wetland, a research site Megonigal runs on the western shore of Maryland. The wetland is home to several futuristic experiments, where scientists simulate the climate of 2100. For this study, the researchers relied on an experiment that started in 1987—currently the world’s longest-running field experiment on how rising CO2 impacts plants. Inside 15 open-top chambers, scientists have been raising CO2 concentrations by an additional 340 parts per million, roughly doubling atmospheric CO2 levels of 1987. Another 15 chambers serve as controls, with no added CO2. The team focused on the 10 chambers with “C3” plants—a group of plants known to respond vigorously to high CO2 that includes roughly 85% of plant species on Earth.
For about the first two decades of the experiment, plant growth in the higher CO2 chambers flourished. Above ground, plants in the high-CO2 chambers grew on average 25% more than plants in the untreated chambers. The effect was even more powerful underground: High CO2 triggered about 35% more root growth. Root growth is especially critical for wetland survival, as roots help wetlands build soil and keep the foundations growing upward even as seas continue to rise.
“Even though elevated CO2 contributes to sea-level rise, it also enhanced the marsh’s ability to accrete vertically during the early years of the experiment,” said Don Cahoon, a coauthor and research ecologist, emeritus, with the U.S. Geological Survey.
But after 2005, the effect declined and vanished. For the last 14 years of data in the study, there was no average difference in plant growth between the high-CO2 and normal chambers.
“The CO2 effect has always been one of the silver linings of climate change,” said coauthor Adam Langley, an ecologist with Villanova University. “Well, at least plants are going to grow more. But we see here that they didn’t. So the silver lining to me just got a little cloudier.”
The team examined several possible explanations for the drop-off: precipitation, temperature, the saltiness of the water during growing season or the presence of critical soil nutrients, like nitrogen. Only sea-level rise showed any link to plant growth. Once sea levels at the wetland rose 15 centimeters above where they began in 1987, the benefits of higher CO2 disappeared.
“In some ways, this is a race,” said Lewis Ziska, a coauthor and plant physiologist at the Columbia University Mailman School of Public Health. “A race between what CO2 can do and what sea level can do.”
Escaping the Flood
Sea-level rise can shut down extra growth for a very simple reason. As waters rise, wetlands flood more frequently. Plants need oxygen as well as CO2—and wetland plants evolved to get most of their oxygen from air rather than water.
“Plants are aerobic, oxygen-breathing organisms,” Megonigal said. “And that includes their roots. And so they’re fundamentally faced with this problem of having their root system in an environment that doesn’t have any oxygen in it.”
Some wetlands may yet be able to escape drowning. If wetlands cannot rise higher by building soil, migrating inland is another possibility. However, that can only happen if they have enough space. For many communities, allowing room for wetlands to move in would require a shift in how they use and value the land.
In the meantime, Earth’s climate accountants will need to rethink the planet’s carbon budget. Now that scientists know extra CO2 does not always stimulate wetland growth as much as they thought, how much carbon wetlands can absorb in the coming decades remains even more uncertain.
The study will be available on the journal’s website after publication. For photos, an advance copy of the article or to speak with the authors, contact Kristen Goodhue at goodhuek@si.edu.
JOURNAL
Science Advances
DOI
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Accelerated sea-level rise is suppressing CO2 stimulation of tidal marsh productivity: A 33-year study
ARTICLE PUBLICATION DATE
18-May-2022
“…where scientists simulate the climate of 2100.”
Or rather where scientists try to imagine what the climate of 2100 might be like as per the narrative.
“Earth’s climate accountants”
The high priests of the Church of AGW and latter day alarmists
Yeah. More sci-fi passing as actual “science”. The word “simulate” is very close to “models”.
These AGW clowns will do anything to keep the money flowing and them from having to find useful productive employment of some sort. Like, flipping burgers or washing cars.
Hmm, 15cm would be the sea level rise in 2100 so the plants will be fine – and I am sure that the plants will have no problem migrating up from the shore to wherever is optimum for them, especially with the extra help from the CO2.
It’s sad when the scientists are so indoctrinated by the Church of AGW, even when they aren’t climate scientists but real scientists like botanists, and still twist their positive results into a climate Watchtower rag call for the end of days.
That is the part these studies never take into consideration: Sea level 7,000 years ago was much higher than current (and much higher than even their RCP8.5 fantasy “projects”,) yet there are wetlands in existence all around the world. How is that possible if sea level rise killed all the wetlands off in the past?
What Sea level Rise? 1.6mm per annum! What nonsense some of these “researchers” produce!
At some places sea level raises much more rapidly than average. This article does not say if the 15 centimeters in so 37 years is just what that area does or if the rise was artificial, but 15 centimeters is well within the rate of increase some places experience, totally without any CO2 effect on sea level. Wetlands are frequently low lying areas near the oceans.
True, but as sea level rises, there are always low lying areas adjacent to the new level. Contrary to popular opinion, plants migrate faster than sea level rises.
Usual garbage from u reek a lot.
Quote:”But after 2005, the effect declined and vanished. For the last 14 years of data in the study, there was no average difference in plant growth between the high-CO2 and normal chambers.
Well done people, you’ve discovered Soil Erosion.
Now that that out to any local or distant farm you want and consider Nitrogen Fertiliser instead of Carbon Dioxide Fertiliser
Maybe throw in some Glyphosate and also, keep digging up and burying everything that ever grows there
Then and only then, tell us about roots
Could a simple explanation be that temperatures stopped rising after 2005? “Correktions” hide this?
This was focused on sea shore wetlands – like mangroves. So fertilizer is not applicable.
Now of course they chose to totally pound the Doomsday drum even though the plants responded well to extra CO2 – 15cm would be the sea level rise over the next 50 years at least and probably around a 100 according to the current average.
And of course they chose to ignore that the healthy, happy, vigorously growing plants would easily be able to colonize their way up the shoreline as sea levels rose, and they forgot (chose to forget…) to mention the vast majority of plants growing far away from shore that are loving all that extra CO2 that they are starving for, and hopefully the extra warming that we’ve been promised, that never seems to materialize, will lead to move ocean evaporation and hence more rain, that those starving plants will also love.
Actually I think the key quote from the abstract (mysteriously missing from the Smithsonian article) is
So another effect stopped the benefit in this very specific circumstance of being right on the coast but somehow they ignore that minor fact with their statement
Maybe he should have qualified how small a difference it made to his view of the “silver lining”
The geologic history of sea level and atmospheric carbon dioxide variance is very large, and yet wetlands have been with us for hundreds of millions of years, now, somehow, 33 years of investigation, under doubtful scientific control, suggests a risk for continuation of wetlands? Remember when National Geographic was a reliable source of information?
My father loved NG so much that he bought his six children subscriptions, every year.
By the late 1970s, NG’s overt “humans are evil” mantra caused me to start canceling subscriptions immediately after they sent notice.
I refused to allow the subscriptions to “continue” and Insisted they credit my father for the remainder.
This caused some friction with my father, until I started handing my father NG issues with the simple request that he find “science” or “verified data”.
NG’s issue after issue were all emotional pictures with false labels and humans are causing all the damage.
My father’s sole response was the pictures are good… He agreed to never sign me up to NG crap again.
National Geographic hasn’t been a reliable source of information since the early 1970s. Nothing they printed could be accepted without verification.
I went through the same thing with my son! I got the little 10 year old genius a subscription because I remembered my fondness for it in 70s or 80s, and though I can tune out the climate disaster nonsense and enjoy the pictures and the data and even a different POV – he has no patience for it all – I taught him too well!
Only for a tiny, recent fraction of that tie period have humans been getting in the way of what marshy areas will do as the land and climate change. The rapid and massive engineering in favor of cities, industries, and agriculture can’t be equated to normal geological changes over long periods.
Sea level rise has not accelerated over the past century or two so wetlands have been facing inundation over a long period and seem to have survived if they have room to move. Those plots will be submerged eventually so the experiment was doomed to fail unless the vertical growth exceeded the sea level rise. Maybe they needed more CO2
Yep, by “tubing” the plants , they have essentially drowned them. Pretty dumb really.
Remember when they were tagging penguins, but the tagged birds kept dying?
And failing to breed because tags or transmitters were viewed negatively by mates.
They put cameras on them and they couldn’t catch fish! Biobozos probably didn’t realize that the drag from even small paraphernalia interferes with the bird’s precise muscular movents for lining up with the moving fish for the grab.
Maybe they need less forced drainage and infilling.
Wow, who would have thought floods are bad for land based plants.
The good news is that sea level rise doesn’t seem to bother kelp. That’s one less thing to be alarmed about.
It never occurred to these pea brains that a rising sea level & more flooding could create wetlands
on higher ground where new plants could grow in sympathy for their long lost bretheren below! 😮
So, they trapped the plants in tubes, and didn’t let them grow properly with the very slight sea level rise. Ok. !
FAIL !!
“Even though elevated CO2 contributes to sea-level rise”
LOL.. just make it up, guys. ! Don’t worry about any evidence.
It’s a tenet of the their religion. No evidence required.
Gwad ! This is even worse than the coral reefs are going the way of the dodo bird bullshit
Yes the Great Barrier Reef is bleaching again! The research plane filming the Reef must be flying even higher than before!
Whatever the situation, you know it’s bad and worse than we expected.
Looking at the design of the chambers, they might well have been able to introduce extra CO2, but they also diminish the amount of sunlight reaching the plants. Also doesn’t appear to be a large enough sample to prove anything.
“But after 2005, the effect declined and vanished. For the last 14 years of data in the study, there was no average difference in plant growth between the high-CO2 and normal chambers. ”
No, thats not true. C3 plants dont adapt into C4 plants in 15 years. Thats ridiculous.
So we have all been fooled by the use of high CO2 levels in greenhouses? It really doesn’t work? Someone should tell the farmers who do this.
Silver linings, like photos of fun in the Sun, are a dangerous distraction from climate breakdown- h/t The Guardian
Here’s the key phrase that demonstrates the lack of self awareness by these warmunists:
So what they’re alleging is that evolution only worked in the past not the present. Plants can and should no longer evolve, but must stay exactly as they are today, in exactly the same places, with exactly the same characteristics now, because 2022 is the Goldie Locks of natural history, and can only be devolved to something worse.
WTF?
These plants evolved to fit their environment over thousands if not milions of years, and will always do so. The climate often changes faster than plants are able to evolve, hence some plants gain, while other plants lose, during any abrupt changes. Ditto for the animals who eat those plants, and the animals who eat the animals who eat those plants. Lengthy changes in the environment of course allow for a less radical change in biotic hierarchy and success.
The bottom line, with sea level rising at only 8-9 inches per century, wetland plants will simple relocate themselves to higher ground gradually over time. Just as they have for the many dozens of times that sea level rose, then fell, then rose again in the past.
Today is not the Goldie Locks age . Today is just a point in time on an everchanging planet.
Warmunists and their “static analysis” are the most ignorant and unscientific of people today, with no sense of the biosphere and how it always adjusts to climatic change.
But, but but… where do you expect the poor souls to get their future research grants from if they report that there’s nothing to be concerned about?
Duane, we know what the response to that will be.
That it’s different now, temps have never changed this fast before, etc etc
Bullshit on top of bullshit ad infinitum
Great points, very well stated. BTW, I could only find the porridge that was either too
hot or too cold- Oh noes, I’ll starve to death!
wait ??? they are admitting that CO2 is beneficial to plants ? even plants that aren’t in danger of flooding ? (i.e. 99% of all plants) they better be careful … thats dangerously close to denier territory …
When you’re a left-wing climate scold you’re always going to look for the dark lining in the slivery cloud.
If you don’t invest in a flood defense your field gets flooded even if CO2 remains the same.
Problem solved. No extra cost.
I’m confused (“A subset of the experimental plots in the study is dominated by the North American C3 sedge Schoenoplectus americanus (formerly Scirpus olneyi”). I worked some with competent marsh botanists in this community. One of the most complicated set of plant communities are in the Chenier Plain extending from Vermilion Bay, Louisiana to Galveston Bay, Texas.There was even an “Intermediate Marsh” recognized between fresh and brackish marsh. Much of it is high brackish marsh where olneyi was a favored muskrat food, close relative americanus in freshwater, part of a complex of bulrushes. Small pieces of this marsh extend both south, east and up the east coast. The classic work is O’Neil, T. 1949. The Muskrat in the Louisiana Coastal Marshes. Louisiana. Department of Wild Life and Fisheries. New Orleans, 152p. Department once had Wildlife as a fitting separated word when main office was in New Orleans.
There is a great deal of new taxonomic change going on based specifically on genetics not cited in their paper so they may have sorted it out better or the increased and acknowledged inundation by itself has operated. Important facts from the paper were that the site was “more frequently inundated” and “ in a region of rapid deep subsidence.” In the Gulf much of the area is coastal prairie which might increase the marsh with sea level rise. One of the authors (Cahoon, don’t recall meeting) did a great deal of good marsh work in Louisiana, much on storm effects, apparently moved to the Chesapeake. Has a cited review–Cahoon, D. R., et al., How Plants Influence Resilience of Salt Marsh and Mangrove Wetlands to Sea-Level Rise. Estuaries and Coasts 44, 883–898 (2021). https://doi.org/10.1007/s12237-020-00834-w
There is a new symposium (“Concepts and Controversies in Tidal Marsh Ecology Revisited”) in 2021 Estuaries and Coasts, volume 44(6). Marsh restoration is currently a big industry, too much seems to be failing and not followed up properly.
Well they’ve had to stop talking about Pacific and Indian Ocean islands disappearing due to SLR. Coral growth and sand deposition keeps up with 2mm -3mm/yr rise.
Unfortunately there are other manmade forces at work beyond any alleged CO2 related SLR, mainly subsidence for wetlands and floodplains. The subsidence is many cases caused by fresh water-ground water extraction, and/or the piling of multistory buildings on compresible clays. Also in the case of the Mississippi Delta are also the extensive flood control/flood mitagation levees, dams and diversions that are preventing silt deposition of lowlands to occur during occasional flood events.
So it’s complicated. But SLR is just one component of disappearing wetlands. 100 years ago draining swamps was considered good.
Idiots, on a loud silly parade!
Sheer nonsense.
When wetlands flood, new wetlands come into being as water fills previously drier lands.
An oversight that proclaims these researchers have not investigated wetlands survival during hundreds of feet of sea level rise since the last glacial.
Besides the fact that wetlands survived sea level dropping hundreds of feet going into a glacial period.
Plants grew more lushly with greater root mass for two decades. Then that lush growth stopped.
That suggests something else changed. Respiration or photosynthesis is prevented or water/nutrient pathways are blocked.
A change that happened in 2005… A period when alarmism increasingly became more rabid.
Suggesting that some research team members are not neutral observers.
What if your home is on those drier lands? Do you welcome the flood with open arms?
Its highly likely that a particular clump of grass only has a decade or so lifetime anyway.
Wetland grass is constantly being renewed….
Unless trapped inside a tube.
Rising seas don’t swamp wetlands, they just move them inland by a few feet.
It’s almost as if the global warming warriors have never set foot outside their big city offices.
Regardless of the region where they claim sea level rise, which is debatable in many areas. wetlands are like coral reefs and can adapt (rise) to sea level changes. Duh. They have been doing so for many years. If one considers the 300-400 m sea level rise from the last glacial period, yes, wet lands are in danger. But, our pitiful current changes are well in hand.
“Wetlands across the globe are in danger of drowning from rising seas.”
Or are they in danger of drying up from drought? Or is it cataclysmic artificial growth chamber acidification? Experiments like this create a investigator-specified unnatural environment that has nothing to do with the real world and then create findings consistent with the investigators preconceptions. This is a useless article in terms of showing how real wetlands will evolve, change and thrive however the natural conditions drive them. Some will disappear and new ones form. Nature won’t be bothered by some idiotic closed system in Maryland.
To understand what is terminally wrong with climateering thought from top to bottom, one must look at the foundational model upon which all their other models depend. This is a linear ‘ceteris paribus’ (= ‘with all other things or factors remaining the same’) type of analysis.
Economists use ceteris paribus to isolate one factor, say demand for a product, to see how it reacts to a change in one other factor, say, price. Even in economics, this is totally divorced from reality. All the factors do change if one factor does. If price goes up, people buy less (demand falls), however, the price rise attracts new production and competition, pushing prices down again to where demand absorbs the product at some price, lower than the initial raised price. (Nobel laureate Econ Paul Samuelson, who had a degree in physics, recognized such dynamics in economics as an example of the action of Le Châtelier’s Principle discovered in behavior of physico-chemical systems subjected to a change in one of its components).
In the case of wetlands being flooded and the benefits of CO2 rise therefore being attenuated, this is a perfect example of childlike ceteris paribus thinking. Leaving aside the much larger effects of expanded forests and burgeoning crop yield benefits, common sense (and Le Châtelier!) Informs us that with the gradual encroachment of sea water, the marshlands simply move further landward and are at a slightly higher elevation! The childlike “CO2 Control Knob for earth temperatures” similarly falls victim to the Le Châtelier Principle, and nature’s very muted response to rapidly rising CO2 over the past 50years or so is therefore unsurprising.
Something’s not adding up. They started the experiment in 1987, and say that the extra growth stopped in 2005, which is 18 years later. They also say that the extra growth stopped after a sea level rise of 15 cm.
So that is a rate of 150/18 = 8.3 mm/year. But the SLR rates in the Chesapeake are about 3 mm/year. So they are over by a factor of 2-3x.
Even if the SLR rate locally is 8+ mm/year, that would be due to a local effect such as overpumping of groundwater, and the results could not be generalized to locations with typical SLR rates of 2-3 mm/year.
Well that’s part for the course in climate fear mongering – multiply the rate of change 2 -3 times, blame it all on rising CO2 levels, blame THAT on human activity, and declare a “crisis.”
“Hypothetical Bullshit cubed,” like most so – called ‘climate science.”
The only time these clowns allow themselves to mention the benefits of CO2 is at the same time as claiming that something is cancelling them out.
It’s clear that all this verbiage is as tightly choreographed as a military parade in Pyong Yang on the birthday of the dear leader.
I don’t believe this guy, I think he is full of fertilizer.
It all seems so plausible and sciency on the first read through to a layman but when I started thinking and asking myself some questions about it, well it started not looking so good. Artificially raising CO2, water levels and other factors even if they tried to compensate for them does make drawing any worthwhile conclusions difficult at best.
It gets a B with a must try harder from me.
James Bull
At some point people are going to realise the CO2 is good for the planet on the whole, and any negative impacts are a small but manageable price to pay.