Mangroves at risk of collapse if emissions not reduced by 2050, international scientists predict

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Mangroves are amongst the most valuable of natural ecosystems, supporting coastal fisheries and biodiversity. view more  Credit: Dr Nicole Khan

An international research team comprising scientists from the University of Hong Kong, the Nanyang Technological University, Singapore (NTU Singapore), Macquarie University and the University of Wollongong (Australia) as well as Rutgers University (USA) has predicted that mangroves will not be able to survive with rising sea-level rates reached by 2050, if emissions are not reduced. The team’s findings were recently published in one of the world’s top peer-reviewed academic journal Science.

Using sedimentary archives from the Earth’s past, researchers estimated the probability of mangrove survival under rates of sea-level rise corresponding to two climate scenarios – low and high emissions.

When rates of sea-level rise exceeded 6 mm per year, similar to estimates under high emissions scenarios for 2050, the researchers found that mangroves very likely (more than 90% probability) stopped keeping pace. In contrast, mangroves can survive sea-level rise by building vertically when the rise remains under 5 mm per year, which is projected for low emissions scenarios during the 21st century.

The threshold of 6 mm per year is one that can be ‘easily surpassed’ on tropical coastlines – if society does not make concerted efforts to cut carbon emissions, said lead investigator of the study, Professor Neil Saintilan, from the Department of Earth and Environmental Sciences at Macquarie University.

Professor Saintilan said, “We know that sea-level rise is inevitable due to climate change, but not much is known about how different rates of sea-level rise affect the growth of mangroves, which is an important ecosystem for the health of the earth.”

“Most of what we know about the response of mangroves to rising sea level comes from observations over the past several years to decades when rates of rise are slower than projected for later this century. This research offers new insights because we looked deeper into the past when rates of sea-level rise were rapid, reaching those projected under high emissions scenarios,” said Dr Nicole Khan, Assistant Professor of Department of Earth Sciences, The Unviersity of Hong Kong.

Why mangroves matter

With their iconic roots that rise from under the mud, mangrove stands grow in a process called vertical accretion. This feature is crucial to the ecosystem as it helps to soak up greenhouse gas emissions (carbon sequestration) at densities far greater than other forests, and provides a buffer between the land and sea – helping protect people from flooding on land.

The study, which covered 78 locations over the globe, explores how mangroves responded as the rate of sea-level rise slowed down from over 10 mm per year 10,000 years ago to nearly stable conditions 4,000 years later. The drawdown of carbon as mangrove forests expanded over this time period contributed to lower greenhouse gas concentrations.

The study found that mangroves will naturally encroach inland if its ability to vertically accrete is hindered.

“Our results underscore the importance of adopting coastal management and adaptation measures that allow mangroves to naturally expand into low-lying coastal areas to protect these valuable ecosystems,” said Dr Khan.

Professor Benjamin Horton, Chair of the Asian School of the Environment at NTU Singapore, who co-authored the paper, said, “In 30 years, if we continue upon a high-emissions trajectory, essentially all mangroves, including those across southeast Asia, will face a high risk of loss.”

“This research therefore highlights yet another compelling reason why countries must take urgent action to reduce carbon emissions. Mangroves are amongst the most valuable of natural ecosystems, supporting coastal fisheries and biodiversity, while protecting shorelines from wave and storm attack across the tropics,” Professor Horton added.

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Paper titled “Thresholds of mangrove survival under rapid sea-level rise”, published in Science, June 5 2020.

62 thoughts on “Mangroves at risk of collapse if emissions not reduced by 2050, international scientists predict

  1. “The study found that mangroves will naturally encroach inland if its ability to vertically accrete is hindered.”

    Problem solved! Next question?

    Having spent a lot of time around mangroves in the past. They grow and spread like weeds and adapt to changing coastal conditions. Not a good advert for Climate change doom mongering.

    • Mangroves are a bloody nuisance here in northern NZ. The warmer it gets the more invasive they are.

      • What is it with the name “mangrove” in the first place?

        It’s not a very gender neutral term. This name should be changed to something more socially acceptable like “zegrove” or “negrove.”

        • Positive discrimination is clearly in order to balance the white male patriarchal naming system.

          They will now be referred to as famgroves. Anyone refusing to comply will be “cancelled” and lose their job.

          Don’t forget that everything in nature is fragile and in a delicate balance. The slightest change in any environmental variable will cause imminent collapse of the whole ecosystem.

    • Those fragile, tender mangroves must need to be hand tended, then. It’s a marvel they made it through all the ups and downs of the previous natural wild climate swings. If they should fade away now, because of mankind’s slight three degrees it would be so ironic! Oh, the tragedy! Oh the comedy!

    • University of Hong Kong, the Nanyang Technological University, Singapore (NTU Singapore), Macquarie University and the University of Wollongong (Australia) as well as Rutgers University (USA)

      So now you know where not to send your kids.

    • Yes there’s a nice negative feedback mechanism: warmer temperatures in subtropics => mangrove zone extends farther from tropics => mangroves trap sediment, help stabilize and grow coastlines vertically and laterally => less sea level rise relative to land.

  2. Strange how mangroves coped at the end of the last ice age, when sea levels rose far faster than today.

    • I think mangroves evolved Late Cretaceous through the Early Tertiary and there are over 100 species. I’m confident of their survival.

    • Surely you know all creatures great and small evolved in the last 11,000 years so are ill-equipped to deal with a bit of warming

      (do i really need a sarc tag?)

  3. Mangroves build land in tropical and subtropical regions, similar to the way compass grass, goldenrod and bayberries build land along the temperate coastline in New England where I live. Mangroves in particular tend to trap sediments from nearby rivers, and build soil underneath from deposition of their own leaf litter mixed with the sediments.

    It is NOT TRUE, as doomsayers insist, that beaches only erode, that coastlines only deteriorate. On arm-shaped Cape Cod where I live, two barrier beaches, Monomoy Island at the elbow and Sandy Neck at the bicep, have both grown significantly just in my lifetime.

    The main threat to mangroves is physical removal by humans. Left to their own devices they will expand coastlines into the sea.

  4. This is all “smoke and mirrors” stuff and we keep on letting them get away with it.

    There is no direct correlation between CO2 emissions and rising sea levels or the ability of mangroves to cope with changes in sea levels up or down. The only indirect connection is based on an entirely unproven series of assumptions that raised CO2 levels will cause a rise in global temperatures, that this rise will be of sufficient magnitude to cause a measurable increase in the rate of sea level rise and that that increase will be rapid enough to overwhelm the ability of mangroves (and, elsewhere, corals) to evolve to cope.

    None of these hypotheses — even to call them that is being generous — has any established basis in scientific fact.

    “ We know that sea-level rise is inevitable due to climate change …” No, we don’t.
    “ This feature [vertical accretion] is crucial to the ecosystem as it helps to soak up greenhouse gas emissions (carbon sequestration) at densities far greater than other forests…” Which immediately begs the question by making the assumption that carbon sequestration is “crucial” without any explanation as to why.

    We are in grave danger here of circular reasoning. Until somebody provides irrefutable evidence of the increased CO2>dangerous global warming>dangerous sea level rise correlation, which observations are not supporting, theoretical research supported only by models, guesswork and wishful thinking is a meaningless and dangerous waste of time.

    • Newminster,
      Exactly!
      It’s all founded on unreal modelled projections of some improbable outcome, and that’s their entire argument.
      Yet more hyped GIGO from University of Wollongong (Australia) as well as Rutgers University (USA).

    • Well stated Newminister! Until the peer reviewers question these assumptions the waste will continue. The waste begets believers who , having heard that 97% of peer reviewed papers accept CAGW and the believers promote expensive, harmful and useless policy. Most venues won’t even let this view point be heard so it is more than difficult for those of us with this understanding to have a say.

  5. I enjoy starting the morning with the first cup of coffee and reading WATTS, because the WATTS readers (minus a few trolls) quickly tear apart the false reports by deranged (but focused!) “researchers”. Stay sane and safe.

    • Well said, Mr. Long. I feel the same way. WATTS provides a preventative, and an antidote to the mind-numbing, relentless drumbeat of doomsday scenarios elsewhere on media of all kinds.

      • “mind-numbing, relentless drumbeat of doomsday scenarios”

        Great way to put it and absolutely true. Some kind of mass mental disorder.

    • Unfortunately, the powers that be, don’t read WUWT

      I’m not even sure they read anything other than their scripts

  6. Going by observations as opposed to ” research results” by “scientists” which ” predict” what “might” happen “if” CO2 continues to rise, I am happy to know that mangroves are sbsolutely safe.

  7. And yet mangroves easily cope with floods and daily tides that are far greater than any sea level rise.

    • Yes but that is the real world on the models they all die … All Models Matter .. take a knee in solidarity.

    • Yep. You stole my comment. LOL Only the brain dead would think something that copes with daily tidal swings could not adapt to rising sea levels. Unless the sea will rise so high so fast they are completely covered by the sea without a chance to reestablish themselves further towards the new shore line. If this is the case, mangroves will be the least of our worries. FYI – I am not one whose worried about this.

  8. ” under high emissions scenarios for 2050,”….> China……not one word about China

  9. Since the sea level rise rate is about 1.5 mm/yr base on direct measurements by tide gauges and has been for at least the past 150 years, there does not seem to be a problem here.

  10. One more thought on Mangroves. Maybe they can plant new mangroves on higher ground. Most od the mangrove you see on our coast on the gulf of thailand are planted. I know all of the mangrove on the phetburi coast were planted by volunteers after shrimp farmers had torn them down.

    https://youtu.be/FYxiZrJwmpo

    • The mangroves grow inland by themselves as water levels rise – the article itself states this. And that assumes the sea level rise is real and significant.

  11. biggest threats are green yuppies wanting to be on the coast in a nice marina or biz in china etc ripping em out for harbours and factory builds and land reclamation outwards ie china and singapore etc
    nasty stinky mozzie ridden places but we need em for migrating birds as well as crabs n other life
    fence em off from people n let em be
    best laugh was a 1mm water depth making a difference?
    roflmao glad i didnt have the coffee in hand

  12. It does make me wonder how well mangroves would do if the sea level fell! Somehow they survived a fall in Sea Levels of many metres during the Ice ages.
    Perhaps Global warming causes Sea Level to change horizontally……..who knew?!!!

    • I note that all the dire climate predictions are to take place at some time AFTER the “scientists” making said predictions will be retired.

      Is there a pattern here?
      Maybe an observation that warrants a scientific study, and an hypothesis?

  13. Did these people even take a coastal ecology course? Like EVER?

    What a bunch of crap this “study’ is….debunked by Ecology 101.

  14. When rates of sea-level rise exceeded 6 mm per year, similar to estimates under high emissions scenarios for 2050

    Since today’s rates are about 2 mm/yr for the last 30 years, that’s an increase of 4mm/yr or an acceleration of 0.13 mm/yr². by 2050. Even the highly manipulated data from Colorado University’s Sea Level Research Group only predicts 0.084 mm/yr². The international research team from Hong Kong, Singapore), Australia, and the United States are pulling numbers out of their ass.

    • No the numbers are not coming out of their ass their lower part is so plugged up with shit its very obvious its leaking into their brain and the hole there is huge. The only good thing that so called scientific paper is good for is wiping you know where.

      • I should have said out of thin air, or maybe just making it up. Bullshit is a good term for it as well.

    • RCP 8.5 strikes again! When funding is on the line, we get unrealistic scenarios combined with absurd modeling assumptions to create the scariest results.

  15. I asked **THE LEADING EXPERT(S) ON EARTH** about this a couple years ago.

    They replied; “They don’t grow that slowly.” “You know they’re already IN the water, right?”

    • But Ocean Acidification may dissolve their roots. pH 7.5 is highly corrosive don’t ya know.
      /s

  16. This study has about as much merit as the one a few months ago that claimed “climate change” is making horses fatter. Is there a competition between universities to see who can get the most ridiculous study funded?

  17. They. “predict” !!!
    I always heard models aren’t able to predict what ever, they produce scenarios, not more, not less.

  18. “This research therefore highlights yet another compelling reason why countries must take urgent action to reduce carbon emissions. Mangroves are amongst the most valuable of natural ecosystems, supporting coastal fisheries and biodiversity, while protecting shorelines from wave and storm attack across the tropics,” Professor Horton added.

    Mangroves are plants and as such will benefit from increased levels of CO2 – perhaps we need studies into how beneficial elevated levels of CO2 are to mangrove growth

  19. I notice that Rutgers is involved here, why do they have a special affinity for garbage ocean science?

    Also, i really hate the left-speak of using “we know that…” when trying to pass off some conjecture as established fact.
    Example
    One leftist climactically insane writes a “paper” on the canadian oilsands stating that 80% of it must be left in the ground or the world ends, then all the other climactically insane start quoting how “we know that 80% of the oilsands must be left in the ground” even though we don’t know that, its just conjecture that came out of the imagination of one mental pipsqueak.

  20. The guys “gots da money” and it’s multi-national coinage!

    What do we gots? We got knowledge

    Good luck with that, when you want to by some good IPA and Pilsner for the 4th holiday.

  21. “Mangroves at risk of collapse if emissions not reduced by 2050″ international scientists predict.

    ……”bet they don’t” someone said.

  22. ” … mangroves will naturally encroach inland … ” No they don’t. Not around here (Coral Sea) anyway. Although it might look like it to the uninformed. They can be part of the mechanism that results in coastal accretion. If they cause a substantial enough accretion the ones that are sufficiently inshore die off as they no longer have access to tidal flows. They also move. It may be that the sand bar they are on moves and they move with it, but I have being looking at the local mangrove forests for 30 years and I’m sure there have been individual trees that have actually changed position. As for their effect on carbon sequestration, that’s laughable. Yes they absorb CO2 blah blah but due to their effect in providing nurseries for juvenile fish, habitat for all sorts of other critters, and they trap floating vegetation and debris, they are also producing it from decay. How come these researchers failed to notice the stink? Did they actually go visit any mangroves?

    • I’m sure there have been individual trees that have actually changed position.

      You mean like the Ents?

    • “Did they actually go visit any mangroves?”

      Probably not. It would be a prime case where fieldwork is rather nasty. Mangroves are an interesting habitat, but it is smelly, hot, difficult to move in and full of mosquitos.

      Mangroves as a matter of fact is the only tropical habitat I know that is anywhere near as bad for mosquitos as taiga or muskeg.

  23. If only there were some sort of selection among organisms, such that those whose genes let them cope better with a change in the environment like rising sea-levels did better than those that didn’t.
    Then there wouldn’t be a problem.

  24. “This research therefore highlights yet another compelling reason why countries must take urgent action to sustain my grants and secure my tenure.”

    FIFY.

  25. 12,000 years ago sea-level was 120 metres below the present. That amounts to 10 millimetres per annum ON AVERAGE. But if the sea-level became stable at near-present levels in just 4000 years, as the authors state,the rate of change would be 25 millimetres per annum. Obviously all the mangroves died. Once more, what happened to peer review?

  26. Last time I looked at an authority, a few minutes ago, I found this “…in subtropical and tropical regions of the world.” Mitsch and Gosselink, Wetlands, Van Nostrand Reinhold. What is the correlation of ocean productivity with the presence of mangroves, thought it was around upwelling areas in cooler climates, river deltas? A little homework would be nice. Bay de Mongles (Mangrove Bay) is 8 miles inland from the Louisiana coast, killed back by freezes, coast once had 10′ tall mangroves killed by freezes and hurricanes. When Louisiana was settled in the early18th century mangroves were so common as to hinder access.

    Montz, G. N. 1977. A vegetational study of the Timbalier and Isles Dernieres barrier islands, Louisiana. Proceedings Louisiana Academy Science. 40:59-69.
    Du Pratz, M. Le Page. 1774. The History of Louisiana. T. Beckett, London, 1972 Reprint, English translation. Claitors, Baton Rogue, LA.

    • Louisiana must be marginal for mangroves. The nothernmost I know of in Eurasia is at Sharm-el-Sheikh, Egypt about 28 deg N and the southernmost is at Wilsons Prom. Vic. 38 deg S.

  27. What utter hogwash. Being a birdwatcher I’ve visited quite a few mangroves in my days. They are hell for mosquitos but hold a lot of interesting birds some of which are only found in mangroves.

    Mangroves are quite remarkably immune to sea level changes. Some of the best and biggest mangroves I’ve seen were near Derby in West Australia. Derby is famous for its yuge tides – about 37 feet at maximum springs. The tidal range also varies from about 37 feet at springs to about half that at neap.

    So those mangroves not only have to survive 30 feet sea level changes twice every 12 hours. They also must survive that the maximum and minimum sea levels change up and down about 10 feet every two weeks:

    https://www.tide-forecast.com/locations/Derby-Australia/tides/latest

    And of course there is also longer term variations, tides vary over longer periods too, due to the varying interactions of solar and lunar tides and the Earth’s elliptic orbit, annually and over longer periods (up to 18,000 years). Not very much of course but a lot more than 6 mm over a year. I couldn’t find a longer-term curve for Derby, but here is one for Seattle:

    https://faculty.washington.edu/pmacc/LO/Figs_tide_background/Seattle%20SSH%202016.png

    None of this seems to inconvenience the mangroves.

    Also mangroves have a remarkable system for seeding. The seeds sprout while still on the mother tree, and are dropped as seedlings with both roots and leaves (vivipary), these seedlings drift vertical in the water with roots down until they “touch bottom” and settle. If sea-level goes up 6 mm per year I expect that the seedling may have to drift a foot or even two further before taking root. I think this is survivable.

    And after all mangroves survived MWP-1A (Meltwater Pulse 1A) about 14,000 years ago when sea-level rose about 20 meters in 500 years.

    And they not only survived. Remember the birds I mentioned earier, that only live in mangroves. They didn’t evolve in the last 14,000 years, so apparently mangroves managed managed to stay intact enough, and large enough for the birds and other mangrove endemics (there are quite a few) to survive too.

  28. When rates of sea-level rise exceeded 6 mm per year, similar to estimates under high emissions scenarios for 2050, the researchers found that mangroves very likely (more than 90% probability) stopped keeping pace

    At the end of the last glacial period, sea level rose by 120 metres in approximately 7,000 years. According to my pocket calculator, that’s an average of 17 mm/year. And during meltwater pulse 1A, it rose by ±30 metres in ±1,000 years or ± 30 mm/year. Possibly as much as 12 metres in 130 years (but the data are a bit too sparse to be certain of this) which equates to 92 mm/year.

    One of the great unanswered questions of the last 100 years was “Where have all the mangroves gone?” At last, we have an answer!

    Joking aside, this study not only ignores knowledge that can be acquired in less than a minute on the internet, but it’s also common knowledge among anyone who has the slightest knowledge of earth history. Five (or possibly six) of the eight authors are in Earth Science departments of their respective universities in Australia, Hong Kong, USA and Singapore. Wouldn’t that mean that they’ve taken a couple of geology courses? Read a geology textbook? Talked to a colleague who has taken courses and read a geology textbook? Apparently not, because they don’t know what happened in the Holocene! Or is it possible that they do know, don’t care, and published this monstrosity anyway?

    We’ve become so used to junk science in the climate field that we’re almost anaesthetized to it, but this is exceptional. If I hadn’t seen it in print*, I wouldn’t have believed that such lack of knowledge was even possible in what we used to call institutions of higher learning. I nominate this paper for the Golden Trashcan Award. It achieves a truly superhuman level of ignorance and deserves to be memorialized as such. If we don’t preserve this work for posterity, future generations will never believe that we could collectively have been so dumb.

    * the paper is paywalled so I just read the abstract.

  29. I am not going to bother to look this up, but I think the rate of rise of the mean sea level during the early Holocene, when the glaciers covering the northern hemisphere melted was much more than 6 mm/yr. and yet the mangroves still exist.

  30. “…University of Wollongong (Australia)…”

    With this addition their credibility has just been lost.

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