1. The Scientific Literature Supports a Mid-Holocene Highstand and Subsequent Fall

The consensus in the peer-reviewed literature on Quaternary sea-level change for the Great Barrier Reef region is clear: relative sea levels stood higher during the mid-Holocene than they do today.

Multiple independent lines of evidence — including precisely dated fossil coral microatolls, reef cores, and geomorphic features — indicate a highstand of approximately 1 to 2 metres above present levels, with many studies pointing to around 1.5 m as a representative figure for significant portions of the GBR.

This highstand occurred roughly 6,000 years ago, after the main phase of post-glacial sea-level rise. Following the peak, sea levels fell gradually toward present values over the subsequent few thousand years.

While there is evidence of some shorter-term variability or minor oscillations in places, the overall trajectory is one of emergence — the land (or reef flat) effectively rising relative to sea level as waters receded from their Holocene maximum.

This is not contested science!

It is documented across the GBR through careful fieldwork by researchers using the most reliable proxies available, particularly coral microatolls whose flat tops record the upper limit of coral growth constrained by tidal levels.

2. Evidence from Coral Cays — and What You Can See at Lady Elliot

Coral cays like Lady Elliot Island are themselves archives of sea-level change.

These islands form on mature reef flats once sea level has stabilised or begun to fall, allowing sediment (coral rubble, shells, and sand) to accumulate above the waterline through wave and storm action.

At Lady Elliot, the shallow platform reef has existed since at least ~6,500 years before present. Island-building by shingle progradation began shortly before ~3,200 years BP and proceeded at relatively steady rates.

This timing fits neatly with the tail end of the highstand period: the reef flat had reached a state where it could support cay formation as sea levels were near or falling from their maximum.

What makes Lady Elliot particularly valuable for public understanding is how accessible and visible these processes remain today.

3. Field Evidence You Can See (and Photograph) on the Reef Flat

Walk the reef flat at Lady Elliot at low tide and you will encounter classic indicators of a higher past sea level followed by relative fall.

Microatolls:

These are massive coral colonies (often Porites) with living rims around the edges but flat, dead tops. The dead upper surface marks the former limit of coral growth, constrained by exposure at low tide. Living coral is now restricted to the margins and lower parts of the colony. Many of these features sit at elevations consistent with having grown when sea level was higher; their current “stranded” appearance reflects the subsequent fall.

My photographs of these microatolls — especially close-ups showing the sharp contrast between the dead flat top and the living peripheral coral — provide powerful visual confirmation of emergence.

The living section of the microatoll is dark brown, replete with healthy zooxanthellae within the coral polyps.

Reef-flat morphology:

The broad, relatively flat expanse of the reef platform itself, with cemented or emergent sections and limited vertical coral growth in the interior, is characteristic of a reef that reached sea level during or near the highstand and has since experienced relative lowering. You can contrast this with the more actively accreting outer reef slopes.

Associated features:

Stranded or higher-level beachrock and cemented shingle ridges on and around the cay further support periods of higher water influence in the past, followed by stabilisation at lower levels. The concentric shingle ridges of the cay itself record ongoing but orderly accumulation in a regime of relative stability or slight fall.

These visible features at Lady Elliot do not stand alone. They corroborate the more detailed, radiometrically dated microatoll and core records from other GBR sites.

4. How This Challenges Popular Narratives

This geological perspective stands in stark contrast to the dominant public narrative that portrays current sea-level rise as an unprecedented existential threat to the Great Barrier Reef, with little historical context provided.

The alarm often focuses on projections of tens of centimetres of rise while ignoring that, since humans first arrived in Australia some 40,000–65,000 years ago, sea levels have risen by around 120 metres — the vast majority of it naturally and long before the industrial era.

To be clear, sea levels have risen 12,000 centimetres — which is 120 metres — since the last ice age!

The reef we see today largely formed after that massive rise, during and after the Holocene Highstand.

At Lady Elliot and similar sites, the corals and cays have already demonstrated resilience to changes on the order of a metre or more over millennia.

Microatolls and reef flats show clear evidence of adaptation through lateral growth and sediment dynamics once vertical accommodation space diminished.

This does not mean modern changes are irrelevant — rates, additional stressors (temperature, water quality), and human context matter — but it does mean we should view them with proper geological perspective rather than as something entirely novel or catastrophic in isolation.

Time to Think

Spending time on the reef flat at Lady Elliot, camera in hand, observing these microatolls and landforms directly, is one of the best antidotes to the ‘madness’ of decontextualised alarm. The evidence is there for anyone willing to look, and think.

There is also opportunity just to sit and think, as John Abbot did that afternoon of 13th May 2001.

Even read a book, as I did after my photographing.

I was reading Meditations by Marcus Aurelius on the beach when we visited Lady Elliot for the week in May 2021. This philosopher from long ago, when sea levels were higher at the Great Barrier Reef, is know for warning against conformity,

“The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane.”

BMAC is a new Australian environmental charity. This note shows how field observations are consistent with the scientific literature for understanding sea level change within a geological context at the Great Barrier Reef.

John Abbot, featured in the first photograph, is a director of BMAC, with a Bachelor of Science (major chemistry) from Imperial College, London, and a Doctor of Philosophy from McGill University, Quebec (Canada), he also has degrees in law and public administration.

Hovering near a cluster of leather finger corals, a large, mottled shape caught my eye. It was a Flowery Rockcod (Epinephelus fuscoguttatus) — also known in Queensland as the Brown-marbled Grouper. This impressive fish, with its distinctive pattern of dark blotches and pale spots, is listed as Vulnerable to extinction by the IUCN. Seeing one up close, resting calmly against the reef, was a great privilege.

Few divers or snorkelers ever encounter these shy, large predators.

Of course, I had my underwater camera with me, and I got some great photographs. Increasingly, I post these at iNaturalist. You can view the full observation (and photo) here: https://www.inaturalist.org/observations/331150866

There is actually a whole series of photographs with the same fish for that moment in time, that you can click through. Of course, it’s a ‘research grade’ observation.

I document what I see, and these direct observation matters more than models or headlines. My iNaturalist page is full of these encounters — corals, damselfish, sharks, rays, and groupers from Green Island, the Ribbon Reefs, Yongala, and beyond.

Explore them all here: https://www.inaturalist.org/observations/jennifermarohasy

You’ll find the Flowery Cod from Green Island, healthy Porites bommies, curious parrotfish, and much more. These are real moments from real dives, not aggregated statistics or press releases falsely suggesting doom and gloom because that is the official narrative.

Supporting More Underwater Adventures

Thanks to the newly established Bryant Macfie Environmental Charity (BMAC), donations to my research work are now tax-deductible in Australia.

Your support can help fund more dives, fieldwork, photography, and direct observations like this one at Green Island — so we can continue documenting the real state of the Great Barrier Reef and other complex environmental systems.

If you’d like to contribute, you can email me at EnvironmentalCharity@substack.com, or call me/Jennifer on +61 41 887 3222.

Every donation helps get me (and the camera) back into the water.

Bryant followed in his father’s footstep, becoming a doctor, and then training as a radiologist in London. A radiologist is a medical doctor who interprets medical images to diagnose and treat diseases.

After migrating to Australia in the 1970s, Bryant worked hard, invested wisely, and slowly built a very successful medical practice focused not just on Perth, but also serving rural and regional Western Australia.

In 2003, Bryant Macfie decided to become a philanthropist, focused on supporting evidence-based public policy. This included support for Dr Jennifer Marohasy and Dr John Abbot through the B. Macfie Family Foundation including research into new ways of forecasting rainfall using artificial intelligence — work that has resulted in many peer-reviewed publications, collaborations with the Indonesian Bureau of Meteorology, Chinese Academy of Sciences and greater public understanding of natural climate change.

The philanthropy grew out of Bryant’s commitment to open scientific inquiry, initially through environmental research scholarships at the University of Queensland.

Dr Macfie is also acknowledged in volumes of the Climate Change: The Facts book series edited by Jennifer Marohasy.

BMAC will honour this legacy and build on it.

Complex natural systems require open-minded scientific inquiry free from political or funding bias. Our work focuses on:

• Distinguishing natural versus human influences on climate,

• Improving forecasts for rainfall and extreme weather,

• Understanding human impacts, including on the Great Barrier Reef, and

• Sharing this information publicly through freely available research, websites, and publications.

All activities are exclusively charitable.

Our Mission
To objectively examine complex environmental systems. We evaluate all available evidence without assuming the science is settled, and we make our findings accessible to both scientists and the general public.

Our Vision
To undertake independent, evidence-based evaluations of environmental systems and publish results. We aim to provide clear, unbiased information that helps individuals, communities, and decision-makers navigate complex environmental issues.

We plan to build on the legacy of earlier work funded by the B. Macfie Family Foundation.

The photograph taken from an airplane window in 2024, is of the lower reaches of the Pioneer River and shows healthy stands of mangroves between the sugarcane fields and the water. In 2011 John Abbot and Jennifer Marohasy published Has the Herbicide Diuron Caused Mangrove Dieback? A Re-Examination of the Evidence in the journal Human and Ecological Risk Assessment focused on this catchment and concluding that flood-driven burial of mangrove pneumatophores was the far more likely cause of the die-back.