In the Photic Zone

On an atoll​ in the Indian Ocean, on an April day in 1836 when the water was unusually smooth, Charles Darwin wandered out over a coral reef. He gazed through the water into the ‘gullies and hollows’ below. He admired the scene, though not excessively. The naturalists he had read had described ‘submarine grottos decked with a thousand beauties’. This was, he thought, ‘rather exuberant language’. The marine biologist Juli Berwald was more impressed. She describes her first encounter with a coral reef as ‘love at first sight’. The reef was ‘awash in colour … beyond Baroque … each delicate petal and tendril was a revelation; each filigree and lattice an astonishment.’ She had one thing Darwin didn’t: a snorkel.

Coral reef in the Komodo National Park, Indo­nesia, photographed by Martin Strmiska in 2012.

Before the 20th century, a coral reef was not a place that could be easily visited. Indigenous people who lived on and around reefs could see them underwater, diving with open eyes or using goggles made from polished sea-turtle shell, but most arrivals could only squint from the surface. Beauty, even biology, was not usually the main purpose of their visits. Darwin was interested in the geology of the reef. One of the aims of the Beagle expedition was to investigate theories of coral atoll formation. Hoping to ascertain at what depth coral could survive, the crew tried pulling up specimens from the outer reef. They used anchors, hooks, grappling irons and chains, to no avail. In the end, they resorted to swinging a lead weight smeared with tallow to pick up faint ‘impressions’ of coral, like a brass rubbing made with a wax crayon. Darwin cited these observations as proof that corals could not grow more than thirty fathoms down. In truth, he had already conceived his theory and had little use for these greasy shadows. Coral atolls were ‘a wonder which does not at first strike the eye of the body, but rather after reflection, the eye of reason’.

The snorkel has done for coral reefs what the microscope did for bacteria, but there were hiccups along the way. In 1928, the Royal Society funded a scientific expedition to the Great Barrier Reef. The divers had a sophisticated piece of equipment: a diving helmet. According to Maurice Yonge, a scientist on the trip, it looked like ‘a dustbin’ with ‘plate glass windows’. A tube connected the helmet to a boat on the surface, allowing air to be sent down with a car-tyre pump. It was cutting-edge, but depth perception was poor – the glass in the helmet was badly positioned.

Refraction means that objects appear around a third larger underwater than they do on dry land. And just a few metres from the surface, everything turns blue. In the open ocean, most fish look blue or silver, but in shallow tropical water, well-lit by the sun from above, bright cartoon-like colours flourish. Tropical regions of the sea are nutrient-poor and barren compared to cooler waters: in these blue deserts, reefs are oases of concentrated marine life. They are also dying at unprecedented rates. Local pressures – overfishing, physical damage, pollution, disease – all contribute. But the main cause is simply warming water.

Reef-building corals don’t do it alone. They rely on a symbiotic relationship with algae that live inside their soft bodies and provide them with nutrients through photosynthesis, as well as giving them their bright colours. When the corals get too warm, they lose their algae. The change is microscopic but easily visible. The algae disappear and so do the bright colours, leaving the coral ghostly white – what’s known as coral bleaching. If the corals can’t regain their algae, they starve and die.

A recent assessment of climate tipping points in Science designated low-latitude coral reefs one of the ecosystems most vulnerable to rising temperatures. The IPCC predicts that at 1.5°C of warming, between 70 and 90 per cent of tropical and subtropical coral reefs will be lost. At 2°C, many researchers predict that 99 per cent of them will not survive past 2050. Coral science is now no longer about conservation. As Berwald puts it, scientists are ‘way past’ that. Her book is a study of science in ‘emergency mode’, as biologists and philanthropists pursue ‘crazy ideas’ in the hope that they might preserve some vestige of existing reefs.

Corals were a puzzle to naturalists long before Darwin. Around 300 BCE, Theophrastus (Aristotle’s successor as head of the Lyceum) wrote that ‘coral is similar to a stone, is shaped like a root, and found in the sea.’ They were classified as lithophytes (stony plants) by Linnaeus in the early 18th century. Then, in 1752, the French ‘physician-botanist’ Jean-André Peyssonnel sent a treatise to the Royal Society from Guadeloupe. Peyssonnel showed that corals were not, despite appearances, plants, but colonies of tiny animals. As one reader noted with admiration, Peyssonel’s work was all the more impressive given that ‘tranquillity of mind, which a just observer should always be in possession of, is frequently disturbed in those little slight boats used by the coral-fishers.’ By 1834, corals were firmly positioned in the subphylum Anthozoa (‘flower-animals’).

Most organisms live, die and are folded straight back into nature: their bodies break down and are subsumed into other beings. Corals are different. While there are many different sorts of Anthozoa, their basic unit is a polyp: an individual soft flower-animal similar to an anemone. While anemones are solitary, in corals these polyps band together to form colonies. As they grow, they build a skeleton of limestone around themselves, drawing calcium and carbon molecules from the seawater. They also draw in carbon dioxide to feed their resident algae. Over time these skeletons accumulate upwards and outwards. Corals build on their predecessors, leaving their own legacy behind them for the next generation. Reefs are, in part, the frozen exuberant bouquets of the past.

As animals that make islands, corals were a source of fascination for 19th-century scientists. In 1836, Darwin wrote that ‘we feel surprised when travellers relate accounts of the vast piles & extent of some ancient ruins; but how insignificant are the greatest of these’ compared to what had been built by ‘rock-making Polypi’. There was a paradox here too. Coral atolls are found in deep waters in the open ocean, yet the corals that compose them are shallow-water organisms. How did they form? Some writers speculated that they were little crowns on top of volcanoes hidden just below the surface. But it seemed implausible that there would be so many submerged volcanoes of exactly the right height.

Darwin proposed an alternative theory. Rather than hypothesising fixed volcanoes, he let them move. Imagine a volcanic island encircled by a ring of coral. Now imagine that the island is slowly sinking. As it sinks, its coral fringe will keep growing and climbing towards the light. (Darwin didn’t know the reason corals can’t grow at depth: their symbiotic relationship with algae, which restrict growth to the photic zone, wasn’t discovered until 1883.) Eventually, the island will be far below the waves, but a column of coral will stretch up from the depths to the surface, creating a shadow of the original island’s shape. The creeping accretion of coral towards the surface is a way of tracking the even slower subsidence of the ocean floor. As David Dobbs observed in Reef Madness (2005), Darwin’s account of atoll formation has similarities with his later theory of natural selection. Tiny creatures can build islands; minute variations can create species. Both theories offer a natural-historical version of integral calculus. Adding infinitesimal amounts of change can get you the answer you need, if you keep your nerve during the calculation. When, in 1952, US military scientists drilled down through Enewetak Atoll in the Marshall Islands, they went through 1400 metres of coral before hitting a basalt base.

While recent threats to reefs may make them seem fragile, they have existed for most of the past 500 million years. There are gaps in the geological record where ocean chemistry and climate didn’t favour reef growth, but isolated corals have always survived, allowing reefs to return. And while reef growth is slow by our timescale, their elision of the biological into the geological is a rapid underwater fossilisation. They weave stone into and out of existence in a geological instant. Most reefs are far more dynamic than Darwin thought, with erratic periods of growth and degradation as sea levels change. Almost all that we see today of the Great Barrier Reef formed within the past eight thousand years. Before water levels changed and the reef bloomed, Aboriginal and Torres Strait Islanders lived on what is now the seafloor. Their oral history retains a memory of the events that led to the formation of thousands of interlinked reefs.

It was on the Great Barrier Reef that scientists first observed bleaching – in the 1920s Yonge recorded seeing ‘whitened skeletons of corals killed by the heat’ – but we still don’t fully understand how the coral-algae symbiosis breaks down or even how it works in the first place. Finding ways to avoid bleaching (ideas include probiotic transplants, new algal partners and genetically modified heat-resistant coral) is a major focus of current research. But some of the more preliminary questions remain unanswered. For instance, which party initiates the break-up – the coral or the algae? Does it even make sense to ask such a question?

Coral science depends on other uneasy alliances. Reefs are places where the super-rich go on holiday and, in recent years, some of their most beloved tropical paradises have been ruined. Berwald describes the disappointment of the Microsoft co-founder Paul Allen on discovering there was nowhere left to dive in the Maldives – coral bleaching had occurred on every reef. He sought out ‘coral experts’ to address the problem and pledged up to $4 million a year to fund a high-resolution satellite map of coral. This intervention is typical of coral philanthropy, which results in (sometimes fairly random) projects but rarely engages with the causes of global warming.

Many coral scientists feel they have little choice but to collaborate. The map Allen funded arose from the ‘Fifty Reefs’ project, a philanthropic initiative led by Richard Vevers, an ex-advertising executive who now runs a ‘creative agency’ for ocean conservation, focusing on coral reefs. Vevers persuaded a group of researchers to use modern portfolio theory – usually applied to stocks and shares – to identify fifty coral reefs that ‘made more sense’ for investment. Allen’s map might aid similar valuation efforts in the future. When Berwald puts it to Lizzie McLeod from the charity Nature Conservancy that this sort of analysis avoids the underlying problem, McLeod tells her that ‘any effort that generates financing [is] a good thing.’

How much, then, is the Great Barrier Reef worth? According to a 2017 report by Deloitte Access Economics, written the year after the reef’s largest recorded bleaching event, ‘the world’s largest living organism’ is ‘priceless’. It has enormous spiritual and cultural significance, particularly to the Aboriginal and Torres Strait Islanders who are recognised as its Traditional Owners. But, with that throat-clearing out the way, the Deloitte report goes on to employ its Brand Asset Valuator methodology – used by ad agencies since 1992 to assess ‘momentum, future potential and resonance’ – to quantify the reef’s ‘total asset value’ to Australia. The figure they came up with was US$42 billion. As the Deloitte authors put it, ‘with great brand value comes great responsibility.’ In their framing, the reef is equivalent to twelve Sydney Opera Houses.

The Great Barrier Reef is unusual in that it lies within the territory of a rich nation. Coral reefs make up less than 1 per cent of the ocean’s total area and are concentrated in a belt around the tropics. Nearly all come under the remit of poor countries. This leads to wildly different stakes in their survival. Western philanthropists want to save the reefs because they find them beautiful; those who live near reefs depend on them for food. One of the biggest local threats to coral is blast fishing, where dynamite is thrown overboard to kill fish. The practice accelerated in Indonesia after the Second World War, when the Dutch colonists sold leftover dynamite to local fishermen. When the dynamite ran out, the fishermen switched to homemade bombs made from fertiliser and kerosene. The practice is ruinous to reefs, but it is efficient: on average, each $1 bomb leads to $2 of fish. As with burning fossil fuels, the short-term economic calculus is inescapable.

Berwald is good at scrutinising the science, but when it comes to the money behind it she admits that the jargon has ‘all the allure of saltine crackers’. This means that she doesn’t apply the same scepticism when writing about the ‘new financial tools and business ideas’ proposed to save corals. At one point, she describes the way international debt is leveraged for marine conservation. A rich country will discount some of the debt of a poor country and allow a conservation agency to buy up that debt – with a guarantee that the poor country spends the value of the original debt on conservation efforts. Berwald describes such arrangements as ‘win-win-win’. But it’s not that straightforward. Rich countries are forcing poor countries to assume responsibility for ‘conserving’ ecosystems whose destruction the rich countries are bringing about. The voices of people who live on and around coral reefs are seldom heard in the world of international finance. Berwald mentions their ‘extensive experience and knowledge of the marine world’, but it would be more helpful to consider what could be gained from using it.

Some philanthropists have gone beyond conservation of existing reefs and become obsessed with building new ones. Reefs can be seeded by attaching fragments of living coral to a network of small steel bars. Here the world of coral philanthropy is its own vibrant and bizarre ecosystem. Berwald deadpans lines such as: ‘In 2021, Mars, through its cat food brand Sheba, built a reef in the thirty-year-old rubble field near Bontasua.’ She travels to Florida, Sulawesi, Bali and the Dominican Republic, goes to scientific conferences and talks to people with such bold new notions as cooling the ocean around the Great Barrier Reef by spraying salt into clouds. Altogether it’s an incoherent mess of schemes, most of which, in the words of the reef scientist Terry Hughes, are ‘pretty laughable’.

Berwald returns to Vevers, the ex-adman, whenever she needs a ‘dose of optimism’. He’s full of bright ideas. After learning that, before they bleach, corals sometimes turn a range of startling fluorescent colours, he launches a campaign called Glowing Glowing Gone, as part of which he presents a coral-inspired colour palette to ‘thousands of screaming creatives’ in LA, alongside ‘the vice president of Pantone’. But even Vevers acknowledges that there are serious risks in letting the whims of philanthropists dictate the ebb and flow of coral research. At the start of Life on the Rocks, the XPRIZE Foundation – a group of entrepreneurs who believe ‘the world’s biggest problems are the world’s biggest business opportunities’ – is devising a prize to stimulate technological development to save coral reefs. The venture capital model is explicit. One XPRIZE official tells Berwald that other possible projects – such as ‘feeding a billion people’ or ‘extracting carbon from the atmosphere’ – have already had money ‘thrown at them’ without success. Berwald wonders how ‘wealthy, smart, inspired people’ who know nothing about coral reefs will cope when their ideas hit the real world. She’s right to wonder: the much hyped prize falls dormant after the sovereign wealth fund of Abu Dhabi pulls out of backing it. The optimism and tenacity of people still working to protect coral reefs is inspiring. But philanthropists like a good news story. By the end of the book, Vevers admits that companies have decided coral seems like a lost cause.