Australia’s Biggest Reef Is Given A Name & Voice
COASTALWATCH | Environmental Feature
Hiding in Plain Sight: The Great Southern Reef
It’s an accepted fact that the northeastern coastline of Australia is fringed by a gigantic mass of coral known as the Great Barrier Reef. For those with local knowledge, or an inclination to think the idea through, the Great Barrier Reef is of course not a single reef but an interconnected complex of nearly 3,000 separate coral reefs, joined by continuous geography and an interdependence of natural systems.
So too, the Great Dividing Range is a series of peaks and escarpments that dominates the southeastern quarter of the continent. In places, it’s discontinued by wide, flat plains, but we accept its description as a single entity because of all the common features those separate sub-ranges share: watersheds to the Pacific and the Murray Darling, climate, geology and flora and fauna.
Using the same thinking, marine scientists are taking a revolutionary new direction in thinking about our cool temperate reefs. Stretching from Kalbarri in the west, all the way across the southern coast of Australia and around Tassie then up to about the Tweed, a massive swathe of kelp-dominated coolwater reefs are now being grouped together as a single entity – the Great Southern Reef.
Once we think of all these reefs in this way – and it’s likely that future generations of schoolchildren will see this as perfectly obvious – then a series of related questions come crowding forward: did last summer’s El Nino affect the Great Southern Reef (or “GSR”) as badly as it affected the Great Barrier Reef? What about ocean temperature rises, acidification, agricultural runoff and all the other threats we’re now so attuned to up north? How many people are studying this entity, and what are we spending on it? And how much does it actually matter? We put a few of these questions to one of the leading researchers on the GSR, Dr Scott Bennett.
Scott Bennett is s surfer, raised on the granite and quartz sand of northeastern Tassie. He’s a marine ecologist, and his work as taken him everywhere from Townsville to WA, South Africa and more recently to Mallorca, Spain, where he’s turning his gaze to the Mediterranean and the Arctic. He’s there thanks to a European Commission program called the Marie Curie Fellowship, a two-year placement that aims to promote the mobility of scientists throughout Europe (this is what you left behind, England).
According to Scott, the Great Southern Reef concept arose following a public forum a couple of years ago on ABC Radio National’s Big Ideas program. Scott and his colleague Thomas Wernberg invited five leading temperate marine scientists from all over Australia to discuss the importance of temperate reefs and the challenges they face: and discovered they were all focussed on the same things. “The huge biodiversity and important habitat-forming species were the same,” he says. “The important fisheries were the same, and the challenges presented by growing coastal populations, urbanisation and climate change were similar.” And, just like that, came a breakthrough in scientific thinking.
“The difference between the panellists was that they were each talking about their own geographical region of temperate Australia,” says Scott. “We didn’t have a common entity to talk about. Thinking about this afterwards, perhaps this lack of identity was stifling public awareness about temperate reefs. Very few people can name a temperate reef. But similarly, very few can name one of the coral reefs that make up the Great Barrier Reef, despite knowing the entity exists.”
If you’ve snorkelled, say, Esperance or Bicheno on a flat day, or taken a tinny out and fished Port Lincoln or Pambula, you’ll have a feeling for some common elements you wouldn’t find at Mackay. The similarities are not just wishful thinking or instinct, but based in concrete science, according to Scott: “through oceanographic processes like the poleward flow of the East Australian Current down the east coast, and the Leeuwin Current that wraps down the west coast and along the south coast.” These currents are vital in distributing larvae and ‘propagules’ (basically like spores in the wind) throughout the GSR. Thanks to those flows, the GSR has one humble but defining organism: the habitat-forming species of kelp Ecklonia radiata (“common kelp”), which is as abundant at Albany as it is at Wollongong, and all the way round the southern half of the country.
The GSR is a nursery and a shelter and a gigantic living museum of biodiversity, hosting marine plants, sponges, crustaceans, chordates, bryozoans, echinoderms and molluscs. And it’s likely that that tens of thousands of species within the system are yet to be identified. “Endemism” is the measure of geographic uniqueness of a creature, and it’s a prominent feature of the GSR, because of the profound evolutionary isolation of our continent over the last 23 million years. A simple example: an estimated 77% of the 565 species of red seaweed found on the GSR are not found anywhere else on Earth. We get a sense of that abundance as the bottom passes under our feet in the lineup, but we never seem to think it through.
A comparison of the GBR and the GSR shows up some interesting parallels. Whereas the Great Barrier Reef is made up of thousands of individual reefs dominated by corals, interspersed with sand, seagrass and mangroves, spread along approximately 2000 km of coastline and connected by one primary boundary current, the Great Southern Reef is similarly composed of thousands of individual reefs, dominated instead by kelps, interspersed with sand and seagrass, along approximately 8000 km of coastline and connected by two primary boundary currents.
But here’s the major difference, and the reason it’s remarkable that we haven’t thought about all this before. Around 67% of Australians (or 16.2 million people) live within 50km of the GSR, and that number will double by 2060. And almost every one of Australia’s 2.7 million surfers paddle out over it. Jake’s, The Box, The Right, Shipsterns, Bells, Ours, Shark Island and Lennox – all of them are united by a miracle of geography we hadn’t yet considered.
Scientific awareness of the notion of a giant southern reef is yet to attract decent funding.
It’s hard to estimate the economic worth of the GSR overall – obviously you could slice it a dozen different ways. But Scott and his colleagues have arrived at a “conservative estimate” of $10 billion per annum, based solely on the value of commercial fisheries, recreational fishing and regional tourism – areas where the researchers could find reliable economic reporting. “To put this value into context,” says Scott, “using the same methods…the Great Barrier Reef has been valued at approximately $6 billion annually.”
It’s worth noting here that the commercial fishery component of the $10 billion figure is based only on rock lobster (A$375 million) and and abalone (A$135 million), and doesn’t even count many valuable reef fish like the WA Dhufish. And that the WA rock lobster fishery, at AU$185 million per annum, is the most valuable single-species fishery in Australia. Compare that against the combined gross value of everything taken by commercial fishers on the Great Barrier Reef, at AU$120 million annually. To put that another way, rock lobster and abalone fishing on the GSR is more than seven times more valuable than all commercial fishing on the GBR combined.
SEE ALSO: Requiem For The Reef
Nor does our GSR figure even look at indirect GDP contributors like carbon sequestration. Or, looking much wider, if you factor in the “nutrient cycle” (the process of turning critters into food), you add another $187 billion. That’s why Scott’s estimate of $10 billion is conservative. The GSR is worth a fortune.
Over the five years between 2010 and 2014, coral reef research received AU$55.3 million in research funding from the Australian Research Council. In the same period, only AU$4 million went to temperate reef research. And remember, that’s despite the GSR spanning 8000 kms of coastline, five states and 38 federal electorates, despite 16 million Australians living near it, and despite the $10 billion it generates annually in our economy.
The comparison between the two natural systems has also been measured by studying media coverage: temperate reefs receive 1-3 % of the local and national media coverage about reefs: a whopping 97-99% of reef-related news coverage is about coral reefs. Prior to this story, the GSR has received little coverage in our local surf media (a story last year in The Conversation was republished on Swellnet, and there have been excellent pieces published in The Atlantic and The Inertia overseas).
To be clear, the coral dollars are well spent: we’re world leaders. But we now know the importance of kelp forests in Australia warrants a similar commitment to temperate reefs, and the use of the term ‘Great Southern Reef’ might help to focus economic thinking.
It makes strong instinctive sense – though there’s been no specific research into it yet – that indigenous thinking might have turned to the notion of a continuous reef system across southern Australia. Indigenous author Bruce Pascoe talks of a whale songline that stretches from Hervey Bay to Albany. The depth and abundance of culture along these coasts is extraordinary – Scott estimates there are “at least 42 language groups from the Southwest, Spencer, Riverine, Southeast and Tasmanian indigenous regions of Australia that border onto the Great Southern Reef.” And these are peoples who have relied heavily on the reefs for their nutrition and cultural practices, “as evidenced by things like the shell middens we still see along our coasts today and the beautiful Maireener kelp shell (Phasianotrochus irisodontes) jewellery produced by Tasmanian Aboriginal people, for example.”
One of the hope for increased funding in this area is that more effort can be devoted to unearthing indigenous understandings of reef ecology, both for their cultural importance and for the learnings they might impart.
The Great Southern Reef isn’t in bad shape overall, if you compare it to reefs elsewhere. But like many marine ecosystems, it’s feeling the stress from human pressures: pollution, development and climate change. Some specific parts of the reef are in terrible shape: in the west and southeast, reef water temperatures are rising two to four times faster than global averages.
Scott Bennett calls kelp forests the GSR’s “biological engine” - they support a unique collection of temperate marine species. But his research shows that on those western reefs, the kelp forests are dying in the north and growing in the south. You’re not imagining it when you feel that winters aren’t as cold as they used to be – isotherms (lines of temperature) are shifting poleward at a rate of 20 to 50 km per decade. Because of the east-to-west alignment of Australia’s southern coast, there will come a point when continued warming means “there is no more southerly habitat to which (the kelps) can retreat.” In the words of the researchers, “This would devastate lucrative fishing and tourism industries worth more than $10 billion per year and have catastrophic consequences for the thousands of endemic species supported by the kelp forests of Australia’s Great Southern Reef.”
1. Loss of giant kelp in the east
As warm, nutrient-poor water drives southward from the East Australian Current into eastern Tasmania, we’re seeing dramatic losses of giant kelp (Macrocystis pyrifera) forests. If ever you’ve had the chance to dive among these beautiful structures, you’ll know that their destruction fundamentally alters a local environment. They’re habitat and hiding place for everything from fur seals to lobster and whelks. As a consequence, in August 2012 the Australian giant kelp forests became the first marine community to be listed as endangered under the Environment Protection and Biodiversity Conservation Act
2. The Rise of the Urchins
Observed changes include expansion of a dark purple subtidal sea urchin, a range of intertidal invertebrates, zooplankton and coastal fishes. In the case of the Longspine or “Black” sea urchin (Centrostephanus rodgersii) in the south-eastern GSR, range extension and population expansion has led to overgrazing of kelp forests, resulting in bare patches called “urchin barrens”, and reduced fisheries productivity. They’re native to NSW, but temperature changes have enabled them to get a foothold in Tassie. At up to 30cm in diameter, and with an appetite to match, they’re a serious threat to Tassie’s kelp forests. And once they've destroyed the larger marine plants they'll scrape micro algae off the rocks and live quite happily in their own barrens. Tasmanian ecologists Craig Johnson and Scott Ling have shown that large crayfish predate on the urchins, and help maintain healthy kelp forests. Trouble is, southern rock lobsters are themselves under significant pressure from overfishing.
3. The 2011 event in the west
In 2011, a once in 200 year “marine heatwave” blasted across southwestern Australia for over ten weeks, driven by unusually strong La Niña conditions which turbocharged the Leeuwin Current, pushing tropical water polewards. Simultaneously, the exchange of heat between air and sea was unusually high, and both processes were superimposed onto a decades-long warming trend.
The result was extensive damage to the GSR. Particularly at Kalbarri, scientists watched kelp forests contract virtually overnight. South of the township, Scott and his colleague Thomas Wernberg saw “100 % loss of kelp across 385 square km of reef.”
“We thought we were in the wrong spot,” Scott told The Atlantic recently. “It was like someone had bulldozed the reef. It was like a moonscape underwater—scungy, brown, and empty.”
Kalbarri is something of a hinging point between coral and kelp. Just 60km offshore, the Houtman Abrolhos islands have always had healthy coral reefs, even though they’re directly in the path of the Leeuwin Current. Until now, however, cooler coastal waters have enabled kelp forests to dominate the reefs nearer shore.
The critical line seems to be 29° south, about halfway between Gerro and Dongara. The kelp deaths were less severe going south of there, but nevertheless amounted to more than 960 square km (96,000 hectares) of destruction between Kalbarri and Margs. What does this look like? “We have several sites, literally out the back of Jakes,” Scott explains. “Up until 2011 they were covered in dense, super-productive beautiful kelp forests. If you dive there today it’s pretty grim. There’s not a kelp to be seen: the reefs are covered by scungy turfs and little tropical seaweeds.”
When that happens, everything suffers: marine plants, invertebrates and fish. And the mix changes. “Before the heatwave, fish and seaweed communities in Kalbarri, were not really distinguishable from those found around Perth or Margs and very different to those found up at Ningaloo,” says Scott. “Now that’s completely changed. While some temperate species remain, on the whole fish and seaweed communities in Kalbarri don’t resemble GSR reefs anymore – and instead look a lot more like the fishes and seaweeds you find on the tropical reefs from Gnaraloo up to Exmouth.” Scientists call this process “regime shift”, and it leads to “novel ecosystems where tropical and temperate species interact, with unknown implications.” In the cautious language that scientists tend to use, they say that this can “alter the balance between consumers and resources.” Consumers are you and me. Resources is where our next meal is coming from. It’s that simple.
The other noteworthy observation is that these reefs haven’t recovered in the ensuing five years. The natural north-to-south flow of the Leeuwin current encourages tropical critter migration down the coast and inhibits cool water species travelling northward from healthier reefs. And plant-eating fish like parrotfish and rabbitfish have come to dominate because of the new abundance of turf algae. The divers found a 400% increase in the biomass of scraping and grazing fishes, a characteristic of coral reefs, not kelp forests. And their extraordinary grazing rates are preventing the recovery of kelp. “We tried to transplant some kelp back onto these reefs to see what would happen and if these tropical fish would actually eat it. They smashed around 40 kg of kelp within 48 hours.”
4. The 2015/16 El Niño
Happily it seems that last summer’s El Niño conditions didn’t hit the southern temperate reefs as hard as they hit the Great Barrier Reef. Scott Bennett’s assessment is that the eastern GSR did experience strong heatwave conditions for several months on end, causing unprecedented “poleward” (southerly) species movements. But it seems the phenomenon didn’t cause massive kelp loss on the scale observed on the west coast in 2011.
But the good news is short-term. The bad news is of longer duration.
5. Climate Change
Kelps and other canopy-forming seaweeds in Australia are sensitive to warming, in a way that’s similar to corals. “Temperate Australia has had a remarkably stable marine climate over the past 20 million years,” says Scott. “That has enabled the GSR to evolve the most diverse and unique seaweed communities in the world. However this stable evolutionary history has also meant that many of these species have adapted to stable environmental conditions. Short term anomalies of only 2-3 degrees are enough to wipe out local populations” - and they‘re becoming more frequent.
Depending where you live, climate change might materialise as a blessing or a curse. Take abalone: they’re sensitive to warming in various ways. During the 2011 heatwave in WA, they were one of the species worst affected by the high temperatures themselves. But in the south-eastern GSR, the abs are highly dependent on the canopy to provide the right habitat, so whatever affects the kelp forest will affect them. In Tassie, anglers are now catching pink snapper, King George whiting and yellowtail kingfish – species that never previously ventured that far south. In the northern reaches of the GSR, where the currents are providing tropical species pressure, there are losses. The luderick (Girella tricuspidata) from northern NSW is one example Scott uses.
Dramatic evidence of long-term warming has already been found along the eastern GSR. Giant kelp has been vanishing from the east coast of Tasmania over the past forty years as a result of warming, overgrazing by species from the north and low nutrient conditions – all driven by a poleward of extension of the EAC. Similar symptoms are appearing along the east coast of mainland Australia.
6. Development and Industry
When coastlines are intensely developed, you have the obvious pressures on adjacent reef ecosystems like overfishing and pollution. But subtler processes also begin to work away at the reef: kelp forests in the eastern and central GSR have suffered where they share space with intense coastal development. Mostly the damage is done by nitrogen enrichment from sewage and storm-water outfalls like the notorious Gunnamatta pipe on Victoria’s Mornington Peninsula. These habitat losses will only increase alongside the desirability of coastal living. To make matters worse, local nitrogen enrichment “synergises” with global ocean acidification, giving opportunistic seaweed turfs a competitive advantage over perennial kelps – the end result being tough turf-dominated habitats, and a boom in invasive plant-munching fish.
Runoff of eutrophic water onto our coastal reefs is slowly turning into a good news story. South Australian scientist Sean Connell identified it as the cause of extensive kelp loss throughout metropolitan areas. Similarly around Sydney, waste water runoff until the 1980s resulted in the loss of the important canopy species Crayweed (Phylospora comosa) from urban areas. But better environmental regulation has stopped the dumping, and rehab work by groups like The Crayweed Project is proving effective at restoring underwater forests. One South Australian study found that householders who lived adjacent to areas of marine habitat loss were willing to pay up to AU$67.1 million for improvements to waste-water management to reduce impacts.
So What Do We Do?
Scientific response to the concept appears to be positive so far: Scott listened to several talks at a recent conference in Italy where the GSR concept arose as an example of the importance of temperate reefs.
Despite that, there remains a troubling disconnect between the low public awareness of, and investment in, Australia’s temperate reefs, and their significance to our shared future across five states. We need consistent governance across state borders, but it must be flexible enough to manage the reef across southern Australia. For example, if one fish species ranges across several states, it’d be logical to co-ordinate licensing, closed seasons and catch limits.
Localised strategies like controlling sewage run-offs, (which weaken kelps and thereby exacerbate climate change effects), are good, but they’re really only band-aids. “You could try assisted translocation, taking kelp from other areas and planting them up north,” Thomas Wernberg told The Atlantic. “But with all the herbivores, anything you put up there would need to be caged.”
The only big-picture solution is the one that’s been eluding the world for decades now: we all have to massively reduce our carbon dioxide emissions.
The serious damage to WA’s kelp forests tells us a bit about what the future might hold for Australia’s temperate marine environment. For the Kalbarri coast, the change is probably irreversible. “The probability of prolonged cool conditions that could …facilitate the recovery of kelp forests is becoming increasingly unlikely,” says Scott, “while the risk of more heatwaves…is increasing.”
Movements of species similar to the ones described above are happening all over the temperate oceans of the world, as species migrate to try to stay within their preferred temperature bands. It’s been described by the University of Tasmania’s Gretta Pecl as “the largest climate-driven redistribution of species since the last (Ice Age).”
If almost every surfer in the nation calls some part of the GSR home, then there’s a nagging question of self-interest to address: if all of these interrelated ecosystems collapse, so what? We’re left with bare rocks – they’re still good to surf over, aren’t they? When CW put the question to Scott Bennett, it was clear he’d considered it already. “To me this is like saying to a scuba diver ‘so what if the reef dies, the depth will be the same and you can still breathe underwater’. To the scuba diver, it won’t be the same because one of the pleasures of diving comes from immersing yourself into another world, surrounding yourself with the beauty of all the different species found living on the reef.
“Similarly for the surfer – there’s an intrinsic value in surfing a clean and healthy ecosystem, where you can sit out the back and feel part of nature. Of course riding waves is the ultimate pleasure – but at the same time getting barrelled in clean blue water, with the reef rushing underneath is a whole lot better than getting barrelled in pea soup.”
We’ve got a long way to go but we probably have no choice: we have to engage with the issues confronting the Great Southern Reef. Our current levels of scientific involvement and public discussion aren’t good enough to avoid the perils that lie ahead. One of the continent’s greatest ecosystems has been living – and could die – hidden in plain sight.
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