Alert readers of the Guardian website may remember a rather sensational article posted there as long ago as 11th July 2016, under the heading “Massive mangrove die-off on Gulf of Carpentaria worst in the world, says expert”. It was said that an El Niño event played a part, but climate change also got the blame:
Climate change and El Niño have caused the worst mangrove die-off in recorded history, stretching along 700km of Australia’s Gulf of Carpentaria, an expert says.
Needless to say, the opportunity was also taken to say that all this destruction, the result of climate change, coincided, with “the world’s worst global coral bleaching event, as well as the worst bleaching event on the Great Barrier Reef”, which was also attributed to “unusually warm water”.
Without any sense of irony:
Norm Duke, an expert in mangrove ecology from James Cook University, flew in a helicopter over 700km of coastline, where there had been reports of widespread mangrove die-offs.
He was “shocked” by what he saw. He calculated dead mangroves now covered a combined area of 7,000 hectares…
Furthermore:
The clear culprit in this case was climate change, which was warming waters and making rainfall more erratic, Duke said. That put the mangrove forests at their tolerance limit, and when a strong El Niño hit the world this year – warming waters in northern Australia and drawing rainfall away – they were pushed past their tolerance thresholds.
In the wake of the scare stories about the Great Barrier Reef turning out to be overdone, there is now a similar development regarding the mangrove swamps. Not, sadly, in this case, that they have recovered in a way that surprises experts and confounds the climate change hysteria. Rather, that experts have now decided that the “clear culprit” in this case is not, after all, climate change. Today the Guardian has an article with a rather different heading: “‘Wobbly’ moon probable cause of mass tree deaths in Australia, scientists say”.
Well then, what’s the story now?
A wobble in the moon’s orbit around Earth affects mangrove cover across Australia and likely contributed to mass tree deaths in the Gulf of Carpentaria, new research suggests.
A study published in the journal Science Advances has found that an 18.61-year cycle known as the lunar nodal cycle shapes the condition of tidal wetlands…
…Along the Arnhem coast in the Northern Territory and the Carnarvon coast in Western Australia, the researchers found that peaks in closed canopy cover – where thickened mangrove canopy covered more than 80% of ground area – coincided with the peak tidal phases of the moon’s wobble.
They believe the lunar wobble likely contributed to mass mangrove dieback in the Gulf of Carpentaria in 2015-16, an event in which an estimated 40m trees died. At the time, a “low tidal range” phase of the lunar wobble coincided with a severe El Niño.
“They had a combination of a 40cm drop in the mean sea level associated with the El Niño and, on top of that, a 40cm drop in tide range [due to the lunar wobble],” Saintilan said. “There were mangroves in creeks [previously] being inundated every day that might have been inundated just a handful of times in the whole of the dry season.”
A quirk of the lunar wobble is that it has the opposite tidal effects along coastlines which have one high tide daily compared to those that have two high tides daily.
In a region with only one daily high tide, a phase of the lunar cycle may result in a lower tidal range and less frequent water inundations. The same phase will have the inverse effect along coastlines with two daily high tides, resulting in more mangrove inundation.
The Gulf of Carpentaria is one of few Australian coastlines that has one high tide daily. Mangroves in adjacent regions that survived the 2015-16 El Niño were in a “high tidal range” phase of the lunar cycle. The El Niño was previously thought to be the cause of the mass dieback [and climate change – don’t forget climate change!], but “the nodal cycle also seems like a necessary condition for mangrove mortality”, Saintilan said…
What? Not climate change? Er, no…:
“So far, global warming has been good for mangroves. With higher sea levels they’ve been expanding into areas that they could not survive before,” he said.
Far from being the “clear culprit”, we are now told that climate change (or its nominal predecessor, global warming) has been good for mangroves. Whatever next?
Climate Scepticism 
Mark, thanks for highlighting this. It’s a reminder for me that ecology is perhaps not what it used to be: once a science, now it is a feeling.
The key thing that ecologists once knew about intertidal habitats is that they occupy a strip that is “just right” for them. The plants on the seaward edge of the land are typically stress-resistant specialists, which cannot survive in competition with entirely terrestrial plants. Higher plants have roots, and require soft sediment. (Intertidal algae, which do not have roots, are able to colonise rocks.) Plants may increase sedimentation, which raises (and drains) the land. This eventually becomes suitable for terrestrial plants, which can out-compete the specialists.
If you knock out a band of mangroves, the habitat will be recolonised. This is a normal and natural phenomenon – or it was, until ecology stopped being science and became a feeling.
How is climate change supposed to affect mangroves, which thrive in the hottest climates where suitable sediment is available? The only rational possibility is by rising sea level, if that could exceed the deposition rate of the trapped sediment. But this misunderstands coastal dynamics, which are hardly ever due to sea levels rising or falling, but due to sediment being picked up in one place and dropped in another. That is, the band of habitat may move, but it won’t shrink.
Now let’s talk about the actual threats to mangroves, and the connection with climate change. Here’s a Google Earth snip of mangroves at Cap-Haitien, 2004:
Now let’s see how it looks today:
This is what the houses look like:
Photo by Rémi Kaupp from: wiki at https://en.wikipedia.org/wiki/Mangrove_tree_distribution
What happens when a storm washes all this away?
It will be blamed on climate change.
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The above comment was slightly edited because I mangled the tag (which I later removed so the photo could be seen as embedded.) The original caption at wiki says
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Jit,
Thanks for that – very interesting indeed.
I have given the Guardian credit for running the story suggesting that climate change isn’t the culprit. However, I give them no points in respect of their failure to refer back to their earlier article and issue a correction, and their failure to alert their readers to the fact that increasingly alarmist claims about climate change are being debunked. To read the latest article, you would think nobody ever said “The clear culprit in this case was climate change, which was warming waters and making rainfall more erratic…”.
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“Burning mangrove trees for a living: ‘I’d quit tomorrow if I could'”
https://www.bbc.co.uk/news/world-asia-66393515
As so often, human activities are causing a problem for nature, but not in the form of human-induced climate change.
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Perhaps not the most appropriate place to put this, but given the reference in the article to mangroves being removed, why not here?
“‘First line of defence’: mangroves – and mitigation – lost in Fiji’s tourism development
Mangroves, vital in protecting villages from environmental disasters, have been destroyed to build luxury hotels”
https://www.theguardian.com/world/2023/dec/13/fiji-magrove-destruction-why-tourism-restoration-plan-importance-the-price-of-paradise
Note all the references to international tourism (no doubt with associated long-distance flights and GHG emissions). It makes a bit of a mockery of Fiji’s non-stop talk of its climate change problems (with the ever-willing BBC pushing this:
https://www.bbc.co.uk/news/world-asia-61774473
https://www.bbc.co.uk/news/av/world-asia-54138677
https://www.bbc.co.uk/news/world-asia-43625608
And note this:
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“Despair as the sea slowly swallows a Kenyan beauty spot“
The beauty spot is being taken by climate change. The sea has encroached 100 m in twenty years. Nevertheless, there are hints that some people at least think there might be more local explanations:
I don’t know who the “climate experts” are.
I had to chuckle at this bit:
My diagnosis – knowing nothing about the location – is erosion. I’m sure someone with time on their hands and a couple of decades of satellite photography could make a case for it.
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There are a few paragraphs of interest in the middle of that article:
...The depletion of mangrove forests along the shoreline – the coast’s main line of defence against erosion – is to blame.
Mangrove forests are full of salt-tolerant trees and shrubs that prevent sea water from advancing into farmlands by stabilising soil that otherwise could be washed away.
The cause of their disappearance appears to be a combination of deforestation by locals wanting coveted hard wood – and rising sea water as a result of climate change, which scientists feel is the major factor....
As John R would say, which is the predominant factor is of critical importance in getting to the nub of that story, yet the BBC makes no attempt to do so. My intuition (which may well be wrong) is that if locals are chopping down the mangrove forest, that is likely to be causing more damage to it than rising sea water, yet the BBC just goes with the line that scientists “feel” rising sea water is the major factor. Dreadfully thin gruel, and very poor journalism. But it supports the cause, so it’s inevitable, sadly.
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Mark, in the accompanying photo of washed-up dead trees, it can clearly be seen that the one in front was cut down by a chainsaw. However, none of its wood was used. The implication is that the tree was cleared for some other (developmental) purpose.
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“The vanishing mangroves of El Salvador: ‘All our efforts may only slow the destruction’”
https://www.theguardian.com/global-development/article/2024/sep/05/mangroves-el-salvador-forests
Here’s the usual genuflection to climate change:
...More than a biodiversity haven, Barra de Santiago serves as a crucial carbon sink in a region battling deforestation, and a natural shield for a country exposed to climate crisis-induced tropical storms and escalating sea levels. It is also home to thousands of people, whose lives are intricately tied to the resources provided by land and sea.
However, this critical natural asset in Central America is in danger due to the effects of the climate crisis, rapid urbanisation, cattle grazing, extensive deforestation from the sugarcane industry, and increasing demand for timber in the country.
Since 1950, El Salvador has lost more than 60% of its mangrove forest. In 1982, an earthquake and tropical storm that hit the coastal region partially destroyed the Barra de Santiago mangrove, accelerating the environmental devastation.
The climate crisis remains a threat to the mangrove forest, as stronger storms are causing trees to fall, and the increase in temperatures is putting this marine life sanctuary at risk.…
The second of those four paragraphs is crucial, because although humankind may be devastating the mangroves, it seems that climate change is, in fact, the least of the issues. This seems to be:
...New urban developments have also been threatening the saltwater forest. Despite allegations of human rights abuses, the ongoing state of emergency in El Salvador – an iron-fist policy launched as a war on gangs by the hardline Nayib Bukele administration in March 2022 – has given a sense of security to those seeking to invest in real estate, leading to a boom in the housing market.
One such example is Oasis, a $5m (£3.8m) housing complex being built by the LAR Development Group. Signs advertising the luxury properties have already appeared at the Barra de Santiago entrance.
The Barra de Santiago is bordered on one side by mangroves with the ocean on the other; the project will be the first to build houses on the mangrove side. The enclave is less than a kilometre wide, and even water and waste management from existing houses on the ocean side can become a critical problem, according to experts.
“It would be necessary to deforest to carry out a project like this. In addition, greywaters and swimming pools don’t usually have good treatment systems and end up in or near the mangroves, affecting the quality of the water and the species that live there,” says Díaz….
…As well as authorising new real estate developments in the area, the government is pushing ahead with phase two of its Surf City project, which will build roads and tourist infrastructure around the east beaches of El Salvador where another large portion of its mangroves are located.
“As long as development goes hand in hand with the destruction, through the construction of hotels and housing complexes, the future will be discouraging,” says Díaz. “Just the Pacific Airport [one of Bukele’s key campaign promises from his first time running for office] will mean a big loss in the country’s remaining mangrove.”...
…Local people, however, hold out little hope of recovering degraded mangrove forests in El Salvador. “The new real estate developments, the use of pesticides and especially the sugarcane industry makes it hard to think that we could return to a healthy forest,” says Díaz. “All of our efforts will probably only slow down the destruction.”
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“Tigers and crocs make mangrove preservation tough work”
https://www.bbc.co.uk/news/articles/crrldyvqe4xo
...Globally, more than half of all mangrove ecosystems are at risk of collapse by 2050, according to a recent report, external from the International Union for Conservation of Nature (IUCN).
“Mangroves are threatened by deforestation, development, pollution, and dam construction, but the risk to these ecosystems is increasing due to sea-level rise and the increased frequency of severe storms associated with climate change,” the report said….
No attempt is made to differentiate the impacts of the different factors.
…The mangroves of South India, Sri Lanka and Maldives are “critically endangered,” according to the IUCN report, external.
Other Indian mangroves are not on that “red list”.
The Sundarbans are one of those mangroves not considered endangered by the (IUCN).…
…”We are seeing a loss in dense mangrove cover in Sundarbans. Additionally, patches on the western coast are extremely fragmented and eroded due to shrimp farming and development,” he says….
To my (admittedly simplistic) way of thinking, the only proved damage to mangroves comes from human activities and developments. The link to climate is speculative at best. Otherwise, how come the endangered mangroves are where humans are doing their worst? If it was climate change, one might have thought that all Indian mangrove swamps would be equally (or close to equally) endangered.
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“‘I couldn’t watch the forests vanish’: the man restoring Solomon Islands’ vital mangroves”
https://www.theguardian.com/world/2025/jul/15/climate-change-mangroves-solomon-islands
As usual, the Guardian inserts climate change into the equation, while making no attempt at all to establish the extent (significant or insignificant) to which it is a factor:
…Yet in Solomon Islands and across the Pacific, mangroves are increasingly threatened by a combination of human activity and natural forces. Clearing for building materials and small-scale development has led to widespread degradation. These pressures are compounded by rising sea levels, cyclones and storm surges, all of which further erode these critical coastal ecosystems.…
Yet, once we reach some detailed information, it might suggest that climate change is the least of the problems faced by mangrove swamps:
…As populations have grown in Oibola, in Malaita province, demand for firewood and construction materials have increased, and the loss of mangroves has accelerated. Over the past 30 years, at least a third of the surrounding mangrove forest near Oibola has been cleared.
Waleilia says that when he was young, his father cleared many mangrove trees to build a bigger home for his nine children.
“I don’t think he realised the impact it would have. Years later, when I inherited the land, there were fewer fish, and the sea was creeping in.”…
…Waleilia has planted more than 16,000 mangrove seedlings over the past eight years, restoring approximately 40,000 square metres of degraded coastal habitat around Oibola.…
…In Malaita, community-led mangrove restoration efforts helped regenerate more than 1,000 hectares (kha) of tree cover between 2000 and 2020, according to Global Forest Watch. This accounts for more than a fifth of all tree cover across Solomon Islands during that time.…
If climate change was a significant factor, then presumably these efforts wouldn’t work, or at least wouldn’t work very well. Meanwhile….:
…Back on his small waterfront property, Waleilia proudly shows his latest planting site. But he notes not everyone in his community shares his views – some still cut mangroves for firewood out of necessity.…
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“The heart-shaped mangrove formation fading due to rising seas
The Heart of Voh is a symbol of New Caledonia’s pristine environment but its outline is changing due to the climate crisis”
https://www.theguardian.com/environment/2025/aug/15/the-heart-shaped-mangrove-formation-fading-due-to-rising-seas
…In the late 1990s the pale, barren surface of the heart contrasted sharply with the green mangrove forest around it, creating its iconic silhouette when viewed from above. Sitting slightly above the surrounding mudflats, the heart’s soil was dry and salty – too extreme for vegetation to grow.
It was just a yellowish salt flat,” says Dr Cyril Marchand, a mangrove expert at the University of New Caledonia. “No mangroves could survive there.”Over the past 20 years, the conditions in the water began to change.
A species of salt-tolerant mangrove called Avicennia started to grow there and has now fully colonised the heart.
The change is linked to rising sea levels: data shows waters along New Caledonia’s west coast have risen about 2mm a year for several decades. As tidal waters flow into the heart more frequently, the salty soil becomes diluted – the ideal conditions for Avicennia to grow. As the species spreads, the heart’s distinctive shape is changing.
Marchand says if sea levels continue to rise, the salinity will reduce further. That will again change the conditions to allow another species of mangrove – Rhizophora – to spread across the heart...
…While increased mangrove cover seems positive…Protecting the heart is a priority for the local community and tourism operators.
For over 15 years Günter Gerant, a pilot at tourism flight company Haut Vol, has shown tourists the Heart of Voh by air. He says it is one of the most famous things to see in New Caledonia.…
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