Claim: Carbon Removal Using ‘Blue Carbon’ Habitats “Uncertain and Unreliable”

Peer-Reviewed Publication


Restoring coastal vegetation – so called ‘blue carbon’ habitats – may not be the nature-based climate solution it is claimed to be, according to a new study. 

In their analysis researchers from the University of East Anglia (UEA), the French Centre National de la Recherche Scientifique (CNRS) and the OACIS initiative of the Prince Albert II of Monaco Foundation, challenge the widely held view that restoring areas such as mangroves, saltmarsh and seagrass can remove large amounts of carbon dioxide (CO2) from the atmosphere.  

The findings of their review, published today in the journal Frontiers in Climate, identify seven reasons why carbon accounting for coastal ecosystems is not only extremely challenging but risky.  

These include the high variability in carbon burial rates, vulnerability to future climate change, and fluxes of methane and nitrous oxide. The authors, who also looked at information on restoration costs, warn that extra measurements can reduce these risks, but would mean much higher costs. 

However, they stress that blue carbon habitats should still be protected and, where possible, restored, as they have benefits for climate adaptation, coastal protection, food provision and biodiversity conservation. 

Lead author Dr Phil Williamson, honorary reader in UEA’s School of Environmental Sciences, said: “We have looked into the processes involved in carbon removal and there are just too many uncertainties. The expected climate benefits from blue carbon ecosystem restoration may be achieved, yet it seems more likely they will fall seriously short.   

“If you want to have extra carbon removal, you need extra habitat, and the scope for restoration is limited. Many of these sites have been built on, for coastal settlement, tourism and port development. 

“Nevertheless, we believe that every effort should be made to halt, and wherever possible reverse, the worldwide loss of coastal vegetation. That’s because blue carbon habitats are more than carbon stores – they also provide storm protection, support biodiversity and fisheries, and improve water quality.” 

The sediments beneath mangrove forests, tidal saltmarshes and seagrass meadows are rich in organic carbon, accumulated and stored over many hundreds of years.   

Many recent studies and reviews have favourably identified the potential for these coastal blue carbon ecosystems to provide a natural climate solution in two ways: by conservation, reducing the greenhouse gas emissions arising from the loss and degradation of such habitats, and by restoration, to increase carbon dioxide drawdown and its long-term storage. 

This new review focuses on the latter, assessing the feasibility of achieving quantified and secure carbon removal (negative emissions) through the restoration of coastal vegetation. 

Increasingly businesses and states have pledged to offset their emissions by restoring these ecosystems through carbon credits, assuming reliable knowledge on how much CO2 they will remove in future from the atmosphere.   

However, Dr Williamson and co-author Prof Jean-Pierre Gattuso, of CNRS and the OACIS initiative of the Prince Albert II of Monaco Foundation, say the policy problem is more subtle. That is, CO2 removal using coastal blue carbon restoration has questionable cost-effectiveness when considered only as a climate mitigation action, either for carbon-offsetting or for inclusion in countries’ Nationally Determined Contributions, which set out their efforts to reduce emissions and adapt to the impacts of climate change under the Paris Agreement. 

“If we use these ecosystems for carbon offsets in a major way, expecting that they would remove up to, say, 100 gigatonnes of carbon dioxide over the period 2025-2100, but find they only remove 10 or maybe just one gigatonne of CO2, then climate tipping points could be crossed, with really serious consequences,” said Dr Williamson. 

“If, however, such ecosystems are restored to protect biodiversity, and we find that they also remove several gigatonnes of CO2, then that would be a bonus, assuming other means are used for climate mitigation. 

“Restoration should therefore be in addition to, not as a substitute for, near-total emission reductions. Where coastal blue ecosystems restoration projects are carried out primarily for carbon removal, they need to include comprehensive long-term monitoring to verify that the intended climate benefits are being achieved.” 

Prof Gattuso said: “Many important issues relating to the measurement of carbon fluxes and storage have yet to be resolved, affecting certification and resulting in potential over-crediting.  

“The restoration of coastal blue carbon ecosystems is nevertheless highly advantageous for climate adaptation, coastal protection, food provision and biodiversity conservation. Such action can therefore be societally justified in very many circumstances, based on the multiple benefits that such habitats provide at the local level.” 

‘Carbon removal using coastal blue carbon ecosystems is uncertain and unreliable, with questionable climatic cost-effectiveness’, Phillip Williamson and Jean-Pierre Gattuso, is published in Frontiers in Climate on July 28. 



Frontiers in Climate


Systematic review


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Carbon removal using coastal blue carbon ecosystems is uncertain and unreliable, with questionable climatic cost-effectiveness



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July 28, 2022 11:01 pm

Have we noticed any other anti CO2 actions that have
“questionable cost-effectiveness “?

I think they mean they don’t see any way for the insiders to profit from this kind of project.

July 29, 2022 12:26 am

“there are just too many uncertainties”.

What a giveaway. Should have said the science is settled

Reply to  fretslider
July 29, 2022 1:48 am

Yeah don’t question the science when it’s settled-
Concerns raised over hidden drug data (

Rod Evans
July 29, 2022 12:52 am

From what we actually know and can see after 30 years (the minimum period of comparison for climate measurements) the only real impact from increasing CO2 is a much greener world. More green plants in better condition than was the case 30 years back. That extra green growth, has enabled record harvests and better fed people and better condition wildlife.
More whales, more Polar Bears, more seals in general a better world environment.
The other impact being indicated though still open to some debate is the minimum night time temperature in the colder parts of the world has increased by a fraction of a degree.
Can anyone explain why that good fortune is a situation we must do all in our power to stop?

Peta of Newark
July 29, 2022 1:11 am

Climate is not the problem and CO2 has perfectly nothing to do with anything.

This story illustrates nicely what The Problem in this world now is..

i.e. That no matter what anybody says or writes, no matter what they do or what they propose to do..
That Thing Is Wrong

That a self-important agenda-driven little nobody will jump out of a tree or out from under a rock (iow Modern Government/Bureaucracy/University) and slag you off

It is total utter complete paranoia, a deep seated mistrust of everybody by everybody else.
It can not end happily.

And here it is in full flow in the UK this morning = the Met Office Mouths are biting the hands that feed them…
On BBC News frontpage, a headline with the last word missing – try guess what it might be before you click the link..

BBC Headline:UK heatwave: Weather forecasters report unprecedented ¿____¿

edit: Damn you spellchecker.
I trust everyone saw how it changed ‘ivory tower‘ into ‘tree
my bad. sorry.

Michael ElliottMichael Elliott
Reply to  Peta of Newark
July 29, 2022 1:29 am

It looks like the usual””Give us more money”.

Anyway note the name ” East Anglia”.

Michael VK5ELL

Reply to  Michael ElliottMichael Elliott
July 29, 2022 1:47 pm

yeah. considering their past fabrications in regards to ‘climate gate’ I would
advise everyone to take whatever they say with a huge helping of salt.

Geoff Sherrington
July 29, 2022 1:33 am

The coast of my homeland,Australia,is rather long and supports mangroves and others of the types described. We see no need to live in fear of their widespread loss.
OTOH, the university of East Anglia sits near a short sore on the English Channel, whose geography helps sting coastal erosion.
The author seems a trifle insular. Might even think his Ashes team is superior to our, from modelling.
Geoff S

Reply to  Geoff Sherrington
July 29, 2022 1:49 am

Nit pick:-
Norwich is near the North Sea, not the Enlish Channel.

Richard Page
Reply to  Geoff Sherrington
July 29, 2022 2:12 am

I have said it before and I’ll say it again; the aussies complain that us brits whinge about the weather while they whinge about cricket and rugby scores! Whinging Aussies!

Rolf H Carlsson
July 29, 2022 1:33 am

It is very strange and unforgiveable that self-alleged researcher do not know about General Sysems Theory as originally outlined by the German biologist Bertalanffy.

July 29, 2022 3:42 am

What a load of cobblers!

Paul Stevens
July 29, 2022 3:51 am

Where is the proof that “climate tipping points” exist? Terminology enters the conversation due to repetition and the next thing you know it’s an accepted fact. The climate alarmist lexicon is full of this type of terminology. None of it has been proven or demonstrated through evidence of pat occurences.

Dr. Bob
Reply to  Paul Stevens
July 29, 2022 5:24 am

Tipping Points are in the mind of the beholder. Or the mind of ManBearPig. But no where else. If they did exist, they would have been reached many times in the past. But the past to a Climate Scientist is yesterday, and no further back.

Clyde Spencer
Reply to  Paul Stevens
July 29, 2022 1:37 pm

The alarmists have a good track record of inventing or appropriating vocabulary to advance their scare program.

David Dibbell
July 29, 2022 4:01 am

“Carbon Removal Using Coastal Blue Carbon Ecosystems Is Uncertain and Unreliable, With Questionable Climatic Cost-Effectiveness”
So now we’re realizing that uncertainty can produce an unreliable outcome? Who knew? Paging Pat Frank!

The entire mindset of atmospheric “carbon” dysphoria to begin with has been driven by uncertain and unreliable modeling. So there’s that.

Gerry, England
July 29, 2022 6:12 am

If you believe in the CO2 scam you might be concerned. If you don’t it is just a shrug of the shoulders.

July 29, 2022 6:32 am

We don’t need to remove CO2 from the atmosphere — we do need to restore shorelines that have been foolishly damaged by silly human development. Sea Grass beds = Good. Magrove forests = Good. Dunes and dune grasses = Good.

An error in shoreline environments is the refusal of conservationists to admit that shorelines themselves are ephemeral, shifting, ever changing — all part of the natural system.

Reply to  Kip Hansen
July 29, 2022 7:06 am

Having just returned from the Caribbean islands, I can agree with some of the foolishly over developed coasts, but I don’t see restoration of coastal swamps and mosquito farms fitting in with the islander’s main source of income, tourism.
If the coast were extended I suspect it would be quickly drained for beach front condos.

Reply to  Rocketscientist
July 29, 2022 3:06 pm

Rocketscientist ==> Restoration of natural shorelines is vital for Caribbean islands. Mangroves forests don’t grow on beaches….but are needed to protect some types of shorelines from storm damage and provide nurseries for the reef fish that feed the local populations. (Besides, large mangrove forests, like Jobos Bay on the south of Puerto Rico, provide safe hurricane refuge for sailboats.)

Andy Pattullo
July 29, 2022 8:06 am

Once again the University of Evasive Answers has stated: “there are no solutions to this catastrophic climate problem we invented literally out to thin air, but please send more money.”

H. D. Hoese
July 29, 2022 8:22 am

This explains what the priorities are, from the paper. Improving “water quality” too often means making them pretty again. “Nature based solutions involving marine processes, such as CBCE [Coastal Blue Carbon Ecosystems] restoration, are attractive not only for climate mitigation but also in the context of their other benefits, that include improved food security, reduced coastal erosion, and rebuilding marine biodiversity.”

Fisheries and other estuarine and marine ecological models are receiving heavy criticism for their lack of consideration for open water area fauna from anchovies to birds. Many eclipses ago a geologist got in trouble calling marshes “speed bumps,” varying in their effect. Many early restorations, even some number now, failed in their nebulous goals. Blue carbon areas are often mud, black a common color where productivity is the highest. Look at a coastline map and compare the relative areas. Healy, T, Y. et al.2002. Muddy Coasts of the World: Processes, Deposits and Functions. Elsevier

As for “marine diversity” the relatively overstudied Chesapeake Bay has a high open water/grassbed-marsh ratio. Overall fisheries there according to this paper found discrimination against demersal animals but overall probably not much change. Kemp, W. M. and 17 other authors. 2005. Eutrophication of Chesapeake Bay: Historical trends and ecological interactions. Marine Ecology Progress Series. 303:1-29. doi:10.3354/meps303001 Open Access

July 29, 2022 9:36 am

” … then climate tipping points could be crossed” … this is where I stopped reading.
As a French engineer I am deeply shocked that the CNRS was able to spend even a penny on this bogus study on equally absurd claims about the CO2 sequestration fantasy.

jeffery P
July 29, 2022 11:05 am

We keep focusing on carbon. This is a red herring. Carbon is the scapegoat.

The goal is to tear down western civilization and replace our culture of freedom, individual rights and free markets with global governance, group rights based on demographic characteristics (race, gender, sex, etc) and fascist economics.


Clyde Spencer
July 29, 2022 1:33 pm

Approximately two-thirds of atmospheric methane is natural. THE major source of methane is from wetlands. To the extent that preempted coastal ecosystems are remediated to their original state, then the restorations increase methane emissions while the alarmists are clamoring for reductions.

Spencer’s Third Law: For every social action there is an equal and opposite reaction, known as unintended consequences.

Pat from kerbob
July 30, 2022 12:52 am

I read this and the comments below
Everyone misses the point I think.

Their point is it’s not possible to store enough carbon
So back to destroying our energy infrastructure, they can’t allow hope to continue

July 30, 2022 7:30 am

The quest to sequester CO2 is the result of high level indoctrination. There is no proof that the human contribution of CO2 to the environment has any measurable effect. This was clearly proven by the recent global shutdown induced by the human reaction to the fears of Covid19.

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