The ‘Fragile Reef’ hypothesis, as I shall call it, holds that the biology of the Reef is so weak and fragile, so precariously balanced between survival and extinction, so pristine and delicate, that it cannot recover from the twin events of physical damage from a Category 4 cyclone (Cyclone Debbie, 2017) and warm water bleaching of shallow corals.
The logical hindcasting implication of the Fragile Reef hypothesis can only be that the Reef has never before recovered from the twin shocks of cyclone damage and shallow water bleaching. Given the length of time the Reef has existed, this just cannot be so. It is also a hindcasting implication of the hypothesis that the Reef has never recovered from tsunami damage.
An underpinning assumption of the Fragile Reef hypothesis is that the biological processes of the Reef are minutely slow, constantly vulnerable to any form of shock, and incapable of the abundant rebound we see so often displayed in other ecological systems.
James Cook University’s James Kerry, a marine biologist, has been quoted by SBS as saying “…. mass bleaching events 12 months apart offer zero prospect of recovery for reefs that were damaged in 2016.” Others in this camp include Professor Terry Hughes, head of the Centre for Excellence for Coral Reef Studies at James Cook University and Dr. Andrew King from the University of Melbourne. Interviews with these dire prognosticators tend to generate headlines along the lines of ‘Damage to Great Barrier Reef irreversible, scientists say’ and ‘Great Barrier Grief: Australia’s treasure is dying’ and ‘The Great Barrier Reef is in its Final Terminal Stage’.
On the other hand, scientists such as Professor Peter Ridd, Ph.D, (Physics) take a different view. Ridd, a marine scientist, is head of the Marine Geophysics Laboratory at James Cook University and has spent more than thirty years working and studying the Reef. Pointing to the robust nature of the Reef, Ridd says, “Come the apocalypse from nuclear war, geological catastrophe or asteroid impact, I don’t fancy the chances of Mankind – but I would bet that rats, cockroaches and especially corals will survive and prosper. They’ve done it before time and again.”
Whose side will time be on?
If the biology of the Reef rebounds – and rebounds abundantly as other natural biological systems rebound after a shock – then the Fragile Reef hypothesis may well be disproven within a timeframe of about a decade. And, as the hypothesis has been advanced so confidently in recent months, its proof or disproof will be quite public.
So, what is the concept of abundant rebound of biological systems? Expressed in these words – “abundant rebound” – it may sound like something new but, to most Australians, it is a concept we already understand. It is the concept of ‘the desert blooming’ – the parched and arid desert turning into carpets of wildflowers after rain. Nature springs to life and performs an abundant rebound. Not only are we, as Australians, aware that this happens, we expect it to happen as the norm.
Driving through kilometres of dry featureless grassland on a huge cattle station in the Northern Territory, I witnessed a dramatic example of abundant rebound after rain in central Australia. I came upon a lake left over from the rains a few months earlier. The lake was as far from the sea as it is possible to be in Australia and, with no further rains, had started drying out. The unexpected sight of the lake, teeming with bird life, was staggering. Thousands of pelicans thronged the waters and patrolled up and down, fishing in teams and tribes. Following the earlier rain, the aquatic food sources the pelicans needed had somehow sprung into life and created a massive population explosion, an incredible feat of abundant rebound. Nature did not just respond in a slow, measured and ponderous way, it responded massively and abundantly.
After drought, parched farmers’ paddocks rebound to abundant growth of waist-high grass. After fire the bush bursts back into life. In our gardens, too, the abundant rebound phenomenon is well known to us where heavily pruned fruit trees return to growth with great vigour.
Abundant rebound happens in many other biological systems, the movement of roaming herbivores in grasslands such as the Serengeti Plains for example. Mass populations of grass eating ruminants arrive on these grasslands on their annual migration. They give the grassland an utter pounding, guzzling and eating as much fresh grass as they can before moving on. The ‘pounded’ grasslands are left trampled and apparently wrecked as ‘pristine’ ecosystems. But the unexpected then happens. The grasslands recover prolifically and abundantly and, in fact, depend on the annual ‘pounding’ for their long term health and survival.
So, does the biological system of the Great Barrier Reef conform with the idea of abundant rebound or not? In examining this question, we should bear in mind one interesting fact – the annual reproductive bloom of the Reef each year is so massive that it can be seen by satellites. The Reef is re-fertilised reproductively on a widespread and random basis every year. Globally, to stretch a metaphor, it is probably Mother Nature’s greatest single orgasm.
In this process, every coral polyp releases eggs or sperm on one or two nights related to the moon phase in late October or early November. This is usually referred to as ‘Mass Coral Spawning’ and, although it has been occurring for perhaps millions of years, humankind only become aware of it just over three decades ago — 1981, to be precise. It was unknown to science before that. This prompts the question; ‘If a tree falls in the forest, and nobody hears it, did it make a noise?’ If mass coral spawning took place before 1981, and we didn’t know about it, did it really happen?
Ocean currents, eddies and wave action, carry the bloom to distant parts of the Reef. The currents mix the reproductive bloom north and south as well as east and west and also vertically in the water column. In this way, deeper corals, not affectted by surface warming, can help reproductively fertilise the surface corals that have been affected by sea surface temperature rises. The rejuvenation happens over an area of thousands of square kilometres.
The annual reproductive bloom acts as an abundant rebound mechanism for damaged sections of the Reef. Past damage from cyclones has been greater than the 2017 event, Cyclone Debbie which was a Category 4. The rating system of cyclones is a logarithmic scale where a category 5 is not just 20 per cent more powerful than a Category 4. It is a multiple of a Category 4 – the next mathematical plateau higher in energy release. Over a long period of time, the random probability of multiple Category 5 strikes at any point north of Townsville is a certainty.
How does the extremely short time span of our knowledge of Mass Coral Spawning relate to another phenomenon of which we have only recent knowledge – coral bleaching. Playing with the earlier question a little, ‘If a tree falls in the forest, and the CSIRO doesn’t hear it, did it really fall and did it make a noise?’ It may sound like a game-playing question, but it can bring out an intriguing difference in attitudes to two different phenomena we have only recently discovered. Our knowledge of the reproductive bloom of the Reef only extends back about 36 years and yet marine biologists assume, quite rightly, that this process has been happening forever. If the bloom is the tree in the forest, then the immediate assumption of these biologists is that, yes, it must have made a noise.
Now let us transfer this sequence of thinking to the phenomenon of coral bleaching. The reaction of many marine biologists on the question of bleaching is, for some reason, the reverse. They assume that it could not have happened, and not have happened on a widespread and repeated fashion, before we discovered it. This is actually a different answer to the ‘If a tree falls …’ question.
The knowledge of bleaching as a part of Reef ecology actually pre-dates our knowledge of Mass Coral Spawning (back to at least 1931, in fact). So, why the rush to conclude that widespread bleaching is completely new? Why the rush to promote it as such? Why the self-assured attitude of certainty about this narrative?
The recent bleaching has been associated with warm surface water in the Western Pacific, not widespread warmer temperatures of the world generally. The worldwide system of over 3000 Argo buoys has not detected temperature rise in the top 2000 metres of the world’s oceans. The rise in sea surface temperature needed to bleach the Reef had to be, therefore, a local event, and the recent phase of the El Nino cycle must be the prime suspect. There is nothing unusual or bizarre about this because the El Nino cycle has been repeating over and over for thousands of years.
When looking at the Fragile Reef hypothesis, we must bear in mind that the Reef is close to, and faces squarely, the subduction zone created by the boundary of the Australian and Pacific tectonic plates. The Tsunami waves given off by the intersection of the two tectonic plates have created far greater challenges to the biology of the Reef than cyclone damage or shallow water bleaching.
There is evidence on the Queensland coast that significant tsunamis have impacted the coast in the past. Any such tsunamis impacting the Queensland coast had to ‘come over’ the Reef itself prior to reaching the coast. Think now of those images from Japan of the 2015 tsunami impacting the coast and rolling remorselessly for kilometres inland, washing away fishing boats, harbour installations, cars, trucks, villages, farm houses, and other infrastructure. To horrify yourself about the power of a tsunami, watch the YouTube clip below.
The kinetic energy delivered to a shallow ocean reef by a big tsunami is many multiples of the energy delivered by a Hiroshima-sized atomic bomb. It is a feature of the discourse of some believers in the Fragile Reef hypothesis that the Reef in its current format is somehow everlasting, timelessly, pristine and never changing and, further, that it has has been that way since the dawn of time. This is a wrong belief. The Reef as we see it today was not complete until about 7000 years ago, finally being formed not long before the Pharaohs started building their pyramids. But people have been in Australia for 50,000 years at least and this is approximately seven times the lifespan of the Reef in its current format.
To put this in context with other Australian terrain features, Uluru was tilted to its current position about forty million years ago. The biggest impact crater in Australia, Gosse Bluff, south west from Alice Springs, came into being when a 600 metre diameter rock fell from space. This happened around 140 million years ago. The Reef is recent.
If you or I had gone to an island in today’s iteration of the reef – say, Green Island – just over ten thousand years ago, we would have looked out over what is now the sea and seen a landscape consisting of some mildly undulating country and a few rounded hills here and there. We might even come in contact with groups of Aboriginal people roaming on what is now the sea bed.
At the time of our imagined travel, the shore line of the Pacific Ocean would have still been about 30 kilometres to the east.
At the time of our time warp, the size and shape the Australian ‘continent’ was vastly different to what it is today. Australia was joined to New Guinea; there was a land bridge to what is now Tasmania; over in the West, the Swan River flowed quietly past what is now Rottnest Island and far out to sea; to the south, the Murray River flowed some hundreds of kilometres further to reach the ocean.
All these things began to be inundated by the sea around 18,000 years ago, at the onset of the interglacial period in which we now live. This interglacial period – the Holocene – is just one of a recurrent series of interglacial periods that have taken place within a long an persistent ice age – The Pleistocene. All this inundation or ‘drowning’ of landscapes has included the landscape that now forms the Great Barrier Reef.
In the area where the Great Barrier Reef now exists, the ocean level rise was around 120 metres to 140 metres and so rapid the Aboriginal population would have watched it happen. In those times, the rate of advance of the sea was much speedier than anything we have seen today. It was eroding into the landscape at a rate of around 50 metres per year. The human occupants had to migrate westward with reasonable haste to get away from it. This rise happened between about 18,000 years and 6,000 years ago. To put it in context, the rise in sea levels was approximatelyas high as a 30-storey office tower. In the past, corals have coped with extremely rapid, and sustained, sea level rise.
If we accept the above as a summation of how the Reef came into being, then we must accept that the robustness of the Reef has been tested many, many times. Coral sands and rocks are features which further place the Fragile Reef hypothesis in doubt. They are an indication that the reef has recovered from many instances of damage and destruction. Coral sands on the beaches of islands on the Reef are not generally the same as sand on beaches on the mainland. The sands on mainland beaches like Bondi are silicone based sands and are tiny particles of weathered rock eroded from the landscape and carried to the ocean by the action of rivers. These tiny particles are washed about by the ocean and gather on beaches.
The ‘sands’ on coral islands in the Great Barrier Reef are different. They are the broken-apart remnants of dead corals. They are essentially the calcium carbonate bits and pieces left over from damaged and dead corals in the sea. Peter Ridd says, ‘The corals grow on the smashed bodies of their ancestors.’ Large deposits of coral sands could not form without coral damage and coral death.
A further indicator that corals are not fragile biological systems comes in the ability of corals to grow in the same location to keep up with sea bed subduction. It was in 1836 that Charles Darwin on his famous voyage on HMS Beagle first observed and recorded this feature when he was in the tropical western Pacific. By drilling on an island, he discovered that the depth of coral rock (dead coral) was far greater than the depth at which corals could thrive underwater. He could not drill deep enough to find evidence of bedrock. Darwin postulated that these islands were ‘growing’ in response to sea level rise.
The important thing about Darwin’s observation of vertical growth of coral islands was that he recognised dynamic biological processes at work. It was a sequence of corals dying, the dead skeletons becoming beds of calcium carbonate rock, and new corals growing on that enabled the reefs to keep pace with the apparent sea level rise.
And it wasn’t just the 140 metres of sea level rise of the current warm period in which we live that the corals have coped with. It was a far greater sea level ‘rise’ created by the subduction of the sea floor where the islands originally stood. The sea bed was ‘sinking’ as the Pacific tectonic plate slid under the Australian plate. It continues to slide today.
It was not until the atomic tests in the Pacific by the Americans in 1952 that the enormous magnitude of this ability for coral islands to grow upwards was discovered. This was at Eniwetok atoll. The Americans drilled until they found bedrock and the depth was a staggering 1267 metres (4158 feet). This is a city office tower to a height of around the 250th level. No such office tower exists in the world. No such office tower comes near this height. Again, go out into the street of a big city, look up at the highest building you can find, extend that height a few more times into the sky, and then ask yourself whether you believe that the biology of coral reefs is fragile or robust.
In mentioning Eniwetok, it is also worth noting that the corals at the atom bomb test site are now fully recovered. Tsunami or atom bomb, take your pick — corals can revive after the most severe physical stress.
The history of the Reef coming into being, and its adaption to its current location, must surely argue persuasively against the Fragile Reef hypothesis.
David Mason-Jones writs on environmental issues. More of his thoughts can be found here