Adam Smith, James Cook University; Nathan Cook, James Cook University, and Vicki Saylor, Indigenous KnowledgeSnorkellers on the Great Barrier Reef have discovered a huge coral more than 400 years old which is thought to have survived 80 major cyclones, numerous coral bleaching events and centuries of exposure to other threats. We describe the discovery in research published today.
Our team surveyed the hemispherical structure, which comprises small marine animals and calcium carbonate, and found it’s the Great Barrier Reef’s widest coral, and one of the oldest.
It was discovered off the coast of Goolboodi (Orpheus Island), part of Queensland’s Palm Island Group. Traditional custodians of the region, the Manbarra people, have called the structure Muga dhambi, meaning “big coral”.
For now, Muga dhambi is in relatively good health. But climate change, declining water quality and other threats are taking a toll on the Great Barrier Reef. Scientists, Traditional Owners and others must keep a close eye on this remarkable, resilient structure to ensure it is preserved for future generations.
Far older than European settlement
Muga dhambi is located in a relatively remote, rarely visited and highly protected marine area. It was found during citizen science research in March this year, on a reef slope not far from shore.
We conducted a literature review and consulted other scientists to compare the size, age and health of the structure with others in the Great Barrier Reef and internationally.
We measured the structure at 5.3 metres tall and 10.4 metres wide. This makes it 2.4 metres wider than the widest Great Barrier Reef coral previously measured by scientists.
Muga dhambi is of the coral genus Porites and is one of a large group of corals known as “massive Porites”. It’s brown to cream in colour and made of small, stony polyps.
These polyps secrete layers of calcium carbonate beneath their bodies as they grow, forming the foundations upon which reefs are built.
Muga dhambi’s height suggests it is aged between 421 and 438 years old – far pre-dating European exploration and settlement of Australia. We made this calculation based on rock coral growth rates and annual sea surface temperatures.
The Australian Institute of Marine Science has investigated more than 328 colonies of massive Porites corals along the Great Barrier Reef and has aged the oldest at 436 years. The institute has not investigated the age of Muga dhambi, however the structure is probably one of the oldest on the Great Barrier Reef.
Other comparatively large massive Porites have previously been found throughout the Pacific. One exceptionally large colony in American Samoa measured 17m × 12m. Large Porites have also been found near Taiwan and Japan.
Resilient, but under threat
We reviewed environmental events over the past 450 years and found Muga dhambi is unusually resilient. It has survived up to 80 major cyclones, numerous coral bleaching events and centuries of exposure to invasive species, low tides and human activity.
About 70% of Muga dhambi consisted of live coral, but the remaining 30% was dead. This section, at the top of the structure, was covered with green boring sponge, turf algae and green algae.
Coral tissue can die from exposure to sun at low tides or warm water. Dead coral can be quickly colonised by opportunistic, fast growing organisms, as is the case with Muga dhambi.
Green boring sponge invades and excavates corals. The sponge’s advances will likely continue to compromise the structure’s size and health.
We found marine debris at the base of Muga dhambi, comprising rope and three concrete blocks. Such debris is a threat to the marine environment and species such as corals.
We found no evidence of disease or coral bleaching.
‘Old man’ of the sea
A Traditional Owner from outside the region took part in our citizen science training which included surveys of corals, invertebrates and fish. We also consulted the Manbarra Traditional Owners about and an appropriate cultural name for the structure.
Before recommending Muga dhambi, the names the Traditional Owners considered included:
- Muga (big)
- Wanga (home)
- Muugar (coral reef)
- Dhambi (coral)
- Anki/Gurgu (old)
- Gulula (old man)
- Gurgurbu (old person).
Indigenous languages are an integral part of Indigenous culture, spirituality, and connection to country. Traditional Owners suggested calling the structure Muga dhambi would communicate traditional knowledge, language and culture to other Indigenous people, tourists, scientists and students.
A wonder for all generations
No database exists for significant corals in Australia or globally. Cataloguing the location of massive and long-lived corals can be benefits.
For example from a scientific perspective, it can allow analyses which can help understand century-scale changes in ocean events and can be used to verify climate models. Social and economic benefits can include diving tourism and citizen science, as well as engaging with Indigenous culture and stewardship.
However, cataloguing the location of massive corals could lead to them being damaged by anchoring, research and pollution from visiting boats.
Looking to the future, there is real concern for all corals in the Great Barrier Reef due to threats such as climate change, declining water quality, overfishing and coastal development. We recommend monitoring of Muga dhambi in case restoration is needed in future.
We hope our research will mean current and future generations care for this wonder of nature, and respect the connections of Manbarra Traditional Owners to their Sea Country.
Luke Halpin, Monash University; Rohan Clarke, Monash University, and Rowan Mott, Monash UniversityGiant bird-eating centipedes may sound like something out of a science-fiction film — but they’re not. On tiny Phillip Island, part of the South Pacific’s Norfolk Island group, the Phillip Island centipede (Cormocephalus coynei) population can kill and eat up to 3,700 seabird chicks each year.
And this is entirely natural. This unique creature endemic to Phillip Island has a diet consisting of an unusually large proportion of vertebrate animals including seabird chicks.
We show how large, predatory arthropods can play an important role in the food webs of island ecosystems. And the Phillip Island centipede achieves this through its highly varied diet.
A well-armed predator stirs in the night
This centipede can grow to almost one foot (or 30.5cm) in length. It is armed with a potent venom encased in two pincer-like appendages called “forcipules”, which it uses to immobilise its prey. Its body is protected by shield-like armoured plates that line each of the many segments that make up its length.
On warm and humid nights, these strictly nocturnal arthropods hunt through thick leaf litter, navigating a labyrinth of seabird burrows peppered across the forest floor. A centipede on the prowl will use its two ultra-sensitive antennae to navigate as it seeks prey.
The centipede hunts an unexpectedly varied range of quarry, from crickets to seabird chicks, geckos and skinks. It even hunts fish — dropped by seabirds called black noddies (Anous minuta) that make their nests in the trees above.
A frightful discovery
Soon after we began our research on the ecology of Phillip Island’s burrowing seabirds, we discovered chicks of black-winged petrels (Pterodroma nigripennis) were falling prey to the Phillip Island centipede.
We knew this needed further investigation, so we set out to unravel the mystery of this large arthropod’s dietary habits.
To find out what these centipedes were eating, we studied their feeding activities at night and recorded the prey species they were targeting. We also monitored petrel chicks in their burrow nests every few days, for months at a time.
We eventually began to see consistent injury patterns among chicks that were killed. We even witnessed one centipede attacking and eating a chick.
From the rates of predation we observed, we calculated that the Phillip Island centipede population can kill and eat between 2,109 and 3,724 petrel chicks each year. The black-winged petrels — of which there are up to 19,000 breeding pairs on the island — appear to be resilient to this level of predation.
And the predation of black-winged petrels by Phillip Island centipedes is an entirely natural predator-prey relationship. By preying on vertebrates, the centipedes trap nutrients brought from the ocean by seabirds and distribute them around the island.
In some sense, they’ve taken the place (or ecological niche) of predatory mammals, which are absent from the island.
Restoration and recovery
Up until just a few decades ago the Phillip Island Centipede was very rare. In fact, it was only formally described as a species in 1984.
After an intensive search in 1980, only a few small individuals were found. The species’s rarity back then was most likely due to severely degraded habitats caused by pigs, goats and rabbits introduced by humans to the island.
The removal of these invasive pests enabled black-winged petrels to colonise. Their population has since exploded and they’re now the most abundant of the 13 seabird species that breed on Phillip Island.
They provide a high-quality food source for the Phillip Island centipede and have therefore likely helped centipede population to recover.
Ancient bone deposits in the soil suggest that prior to the black-winged petrel’s arrival, Phillip Island was home to large numbers of other small burrow-nesting seabird species. It’s likely the Phillip Island centipede preyed on these seabirds too.
Now, thanks to the conservation efforts of Norfolk Island National Park, the island’s forest is regenerating alongside endemic species like the centipede, as well as the critically endangered Phillip Island hibiscus (Hibiscus insularis).
As a driver of nutrient transfer, the persistence of the Phillip Island centipede (and its healthy appetite) might just be key to the island’s ecosystem recovery. But we’ll need to do more research to fully understand the intricate links in this bustling food web.
Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this new series, we’ve invited them to share their unique photos from the field.
Tasmania’s native forests are home to some of the tallest, most beautiful trees in the world. They provide a habitat for many species, from black cockatoos and masked owls to the critically endangered swift parrot.
But these old, giant trees are being logged at alarming rates, despite their enormous ecological and heritage value (and untapped tourism potential). Many were also destroyed in Tasmania’s early 2019 fires.
Former Greens leader Bob Brown recently launched a legal challenge to Tasmania’s native forest logging. And this year, Forestry Watch, a small group of citizen scientists, found five giant trees measuring more than five metres in diameter inside logging coupes. “Coupes” are areas of forest chopped down in one logging operation.
These trees are too important to be destroyed in the name of the forestry industry. This is why my husband Steve Pearce and I climb, explore and photograph these trees: to raise awareness and foster appreciation for the forests and their magnificent giants.
What makes these trees so special?
Eualypytus regnans, known more commonly as Mountain Ash or Swamp Gum, can grow to 100 metres tall and live for more than 500 years. For a long time this species held the record as the tallest flowering tree. But last year, a 100.8 m tall Yellow Meranti (Shorea faguetiana) in Borneo, claimed the title — surpassing our tallest Eucalypt, named Centrioun, by a mere 30 centimetres.
Centrioun still holds the record as the tallest tree in the southern hemisphere. But five species of Eucalypt also grow above 85 m tall, with many ranking among some of the tallest trees in the world.
It’s not only their height that make these trees special, they’re also the most carbon dense forests in the world, with a single hectare storing more than 1,867 tonnes of carbon.
Our giant trees and old growth forests provide a myriad of ecological services such as water supply, climate abatement and habitat for threatened species. A 2017 study from the Central Highlands forests in Victoria has shown they’re worth A$310 million for water supply, A$260 million for tourism and A$49 million for carbon storage.
This significantly dwarfs the A$12 million comparison for native forest timber production in the region.
Tasmania’s Big Tree Register
Logging organisation Sustainable Timber Tasmania’s giant tree policy recognises the national and international significance of giant trees. To qualify for protection, trees must be at least 85 m tall or at least an estimated 280 cubic metres in stem volume.
While it’s a good place to start, this policy fails to consider the next generation of big, or truly exceptional trees that don’t quite reach these lofty heights.
That’s why we’ve created Tasmania’s Big Tree Register, an open-source public record of the location and measurements of more than 200 trees to help adventurers and tree-admirers locate and experience these giants for themselves. And, we hope, to protect them.
Logging is a very poor economic use for our forests. Native forest logging in Tasmania has struggled to make a profit due to declining demand for non-Forest Stewardship Council certified timber, which Sustainable Timber Tasmania recently failed. In fact, Sustainable Timber Tasmania sustained an eye watering cash loss of A$454 million over 20 years from 1997 to 2017.
The following photos can help show why these trees, as one of the great wonders of the world, should be embraced as an important part of our environmental heritage, not turned to wood chips.
It’s not often you get to see the entirety of a tree in a single photo. This tree above is named Gandalf’s Staff and is a Eucalyptus regnans, measuring 84 m tall.
While Mountain Ash is the tallest species, others in Tasmania’s forests are also breathtakingly huge, such as the Tasmanian blue gum (Eucalyptus globulus) at 92 m, Manna gum (Eucalyptus viminalis) at 91 m, Alpine ash (Eucalyptus delegatensis) at 88 m and the Messmate Stringybark (Eucalyptus obliqua) at 86 m.
This giant tree, pictured above, was a Messmate Stringybark that was felled in coupe, but was left behind for unknown reasons. Its diameter is 4.4 metres. Other giant trees like this were cut down in this coupe, many of which provided excellent nesting habitat for the critically endangered swift parrot.
Old-growth forests dominated by giant trees are excellent at storing large amounts of carbon. Large trees continue to grow over their lifetime and absorb more carbon than younger trees.
The tree in the photo above is called Obolus, from Greek mythology, with a diameter of 5.1 m. Names are generally given to trees by the person who first records them, and usually reflect the characteristics of the tree or tie in with certain themes.
For example, several trees in a valley are all named after Lord of the Rings characters, such as Gandalf’s Staff (pictured above), Fangorn and Morannon.
Giant trees are typically associated with Californian Redwoods or the Giant Sequoias in the US, where tall tree tourism is huge industry. The estimated revenue in 2012 from just four Coastal Redwood reserves is A$58 million dollars per year, providing more than 500 jobs to the local communities.
Few Australians are aware of our own impressive trees. We could easily boost tourism to regional communities in Tasmania if the money was invested into tall tree infrastructure.
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When I first came across the kauri pine (Agathis robusta), I certainly wasn’t impressed by their growth. Mixed among other species in a young rainforest plantation, they seemed destined to be left behind by the faster-growing trees (I did think they looked nice, though).
But today I know I judged the kauri unfairly. They can survive for millennia, so they don’t bother doing all their growing in their first couple of decades. But come back 20 years later, and that unassuming tree will be well on its way to being one of the giants of the forest.
Impressive by any measure
By any yardstick, kauri pines are truly unique and impressive. If time is our measure, then the kauri family, Agathis, has endured over epochs, with fossils found in Australia from the early to mid-Jurassic period. Having withstood the rise and fall of the dinosaurs and the evolution and diversification of our flora, 17 species of living fossil trees in the Agathis family remain.
Agathis is an iconic genus of large, ecologically important, and economically valuable conifers that now range over lowland to upper montane rainforests from New Zealand to Sumatra. So, if we judge a plant’s success in terms of its geographical spread or its ability to adapt to a range of conditions, the Kauri family is once again outstanding.
If we measure a plant by appearances, then the tall, robust and handsome Queensland kauri pine remains an impressive – albeit little-known – plant. Reaching up to 50 metres, it emerges above rainforest margins in tropical and subtropical eastern Australia. Its straight, round trunk can grow to 3m in diameter and a combination of smooth mottled bark, coppery new growth and dark green canopy make this tree a world-class ornamental. In parks and gardens across Australia, Kauri pine cuts a fine figure, growing to enormous sizes, even in southern regions.
Our Australian kauri pine, once common in the dry rainforests of Queensland, has become a victim of its own success. A heavy reliance on the highly regarded wood during the earliest stages of the colonial timber industry has left only a few old trees standing, mostly in remote areas or forest reserves. In my role as a research scientist, I have tracked down the kauri’s cousins in the Pacific regions, where the giant pines can now only be found on tops of mountains on remote islands. In New Zealand, the giant kauri that once covered large areas are in danger from the soil-based fungus Phytophora.
Germaine Greer, in her 2014 book White Beech, describes visiting a massive kauri tree on the North Island over 50m tall and 13.5m in girth that is in danger of succumbing to the fungus after a life measured in millennia.
A useful tree
According to the Gymnosperm Database, Queensland kauri was first reported by Europeans in 1842 by Andrew Petrie, who found it growing in the Mary River country, and reported that the native peoples made their nets from its inner bark. A fine, even texture set this timber apart from the more common Hoop pine.
In the South Pacific, the cousins of the Australian kauri have a strong cultural significance and features in the Maori creation myth. The wood from the Southern Kauri (Agathis australis) was used for water craft, and the gum used in traditional tattoos (moko).
Enthusiastic attempts by the Queensland Forest Service to grow the kauri in plantations were devastated by large stick insects. As a result, kauris are now only grown at a very small scale in mixed species rainforest timber plantations, which is where I stumbled upon them.
In about 2002, during my PhD study of young (8-15 years old) rainforest plantations, I first measured kauri as a small tree amongst the well-regarded cabinet timber species of mahoganies and white beech. At first glance, the appeal for me of this Jurassic fossil was merely aesthetic. They were not very impressive in terms of early growth in the plantations; so I focused my attention on the rapid, early growing species.
However, having ignored the kauri for about 10 years, I was astonished (upon return to my old study sites) at how rapidly the kauris had progressed. Not only is this species one of the best performers in terms of diameter growth, but it also has excellent form. It produces straight stems free of large branches that indicates excellent quality logs, for those growers who value wood quality.
My regard for the kauri is now much more than aesthetic; or even as quirky relics from deep time. These trees are showing themselves to be extremely resilient and competitive, under challenging climatic conditions, across a very wide range of sites. They have the capacity to withstand severe storms as well as longer term stresses, such as drought.
I now know that, given the kauri pine can live for many centuries, it is not advisable to measure their value according to the first decade or so of growth, but rather their productivity and resilience across their whole lifespan.
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This article was updated on Tuesday March 12 to correct an error. It previously stated a tree encountered by Germaine Greer was 13.5m in diameter; in fact the tree was 13.5m in girth.
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Pandanus forsteri, a species of screw pine endemic to Lord Howe Island, grows tall like no other tree on Earth. To reach the canopy, these trees have evolved a rainwater harvesting system that enables them to water themselves.
Originally from Micronesia, the palm-like P. forsteri belongs to a group of trees that have populated almost every coastal habitat of the Pacific. In fact, pandans are used by Oceanic cultures for everything from fishing and cooking to medicine and religious ceremonies.
Our research shows that pandans differ in several fundamental ways from more familiar trees, including how they capture water and grow.
Reaching for the canopy
Most trees lay down concentric rings of vascular tissue as they mature, thickening over time. This enables them to grow tall, yet maintain enough structural integrity to avoid toppling over. It is also arguably the most important evolutionary innovation that has enabled trees to colonise most of terrestrial Earth.
Together with palms, bamboo and yucca, pandans belong to a group known as monocots, because their seedlings produce a single embryonic leaf.
Their vascular tissue is not compartmentalised in the same way. It forms bundles that are positioned somewhat haphazardly within the stem. Consequently, monocots are unable to produce true secondary growth and thicken like other trees do – and reaching the canopy becomes a much more ambitious endeavour.
The canopy offers a good life. The sun is shining, seed-dispersing birds are abundant, and the herbivores of the forest floor are a distant concern. In monocots, natural selection has favoured some inventive ways of stretching to the top.
Palms overcome the limitations imposed by their physiology by spending their younger years laying down enough vascular girth to support their future stature. Think of it like putting aside money for your retirement. You may not need it now, but you will likely later depend on it.
Once thick enough, palms shift their efforts to vertical growth. The palm’s tactic of delayed vertical growth may be slow, but it functions well enough to thrust Columbian wax palms (Ceroxylon quindiuense) – the world’s tallest monocot – 45 meters into the clouds.
Pandans, on the other hand, are less patient. Unlike palms, they prefer a sort of “pay-as-you-go” method. They produce stilt roots that extend from the trunk to the ground for support as the crown matures. The end result gives the appearance of an ice cream cone perched on a tepee of stilts. It’s an odd strategy, but it works.
However, on Lord Howe Island, something quite remarkable has transpired. Isolated some 600 kilometres off the east coast of Australia, one species of screw pine has evolved into an island giant.
Most screw pines are lucky to reach four or five meters. Pandanus forsteri trees, however, regularly exceed 15 meters. These kinds of size changes are not uncommon on isolated islands. They are part of a repeated evolutionary phenomenon known as the island syndrome.
Species on isolated islands are free from the stressors of continental life, and they subsequently converge on a more optimal, ancestral form. Large continental species evolve into island dwarfs, while smaller species become comparatively gigantic. Support for the island syndrome primarily comes from animals. However, a growing body of evidence suggests island plants follow a similar evolutionary path.
While gigantism may be favourable, it doesn’t come without risks – and for P. forsteri, they are serious. Thanks to their new-found stature, P. forsteri trees must produce enormous stilt roots to support themselves. This process that can take years. Exposed to the air, roots can form air bubbles, and an air bubble in a plant is bad in the same way it is bad in your artery. It is potentially lethal.
Nature appears to have solved this problem through the evolution of a rainwater harvesting system that enables P. forsteri to water its own stilt roots before they reach the ground.
Gutter-like leaves collect rainwater and transport it to the trunk, where it descends. The flow of water is then couriered by a network of aqueducts formed by the root surface. Finally, water is stored in a specialised organ of absorptive tissue encasing the growing root tip.
Back to the drawing board
This is dramatically different from how we traditionally think about plants. It is far from our concept of sessile beings that passively absorb everything they need from the soil, thanks to the capillary action of their vascular tissues. Never before has a plant species been shown to possess a system of traits that operate jointly to capture, transport and store water external to itself.
This species has opened our eyes to an entirely new field of scientific inquiry. It forces scientists to rethink the function of organs like leaves and roots outside of the contexts of photosynthesis and the conduction of soil water.
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Do other plants harvest rainwater in this way? Why have we only just discovered this? Has our overly simplistic view of plants hindered our ability to comprehend their true complexity? Only time, and more research, will tell.
This is an edited extract from Sunlight and Seaweed: An Argument for How to Feed, Power and Clean Up the World by Tim Flannery, published by Text Publishing.
Bren Smith, an ex-industrial trawler man, operates a farm in Long Island Sound, near New Haven, Connecticut. Fish are not the focus of his new enterprise, but rather kelp and high-value shellfish. The seaweed and mussels grow on floating ropes, from which hang baskets filled with scallops and oysters. The technology allows for the production of about 40 tonnes of kelp and a million bivalves per hectare per year.
The kelp draw in so much carbon dioxide that they help de-acidify the water, providing an ideal environment for shell growth. The CO₂ is taken out of the water in much the same way that a land plant takes CO₂ out of the air. But because CO₂ has an acidifying effect on seawater, as the kelp absorb the CO₂ the water becomes less acid. And the kelp itself has some value as a feedstock in agriculture and various industrial purposes.
After starting his farm in 2011, Smith lost 90% of his crop twice – when the region was hit by hurricanes Irene and Sandy – but he persisted, and
now runs a profitable business.
His team at 3D Ocean Farming believe so strongly in the environmental and economic benefits of their model that, in order to help others establish similar operations, they have established a not-for-profit called Green Wave. Green Wave’s vision is to create clusters of kelp-and-shellfish farms utilising the entire water column, which are strategically located near seafood transporting or consumption hubs.
The general concepts embodied by 3D Ocean Farming have long been practised in China, where over 500 square kilometres of seaweed farms exist in the Yellow Sea. The seaweed farms buffer the ocean’s growing acidity and provide ideal conditions for the cultivation of a variety of shellfish. Despite the huge expansion in aquaculture, and the experiences gained in the United States and China of integrating kelp into sustainable marine farms, this farming methodology is still at an early stage of development.
Yet it seems inevitable that a new generation of ocean farming will build on the experiences gained in these enterprises to develop a method of aquaculture with the potential not only to feed humanity, but to play a large role in solving one of our most dire issues – climate change.
Globally, around 12 million tonnes of seaweed is grown and harvested annually, about three-quarters of which comes from China. The current market value of the global crop is between US$5 billion and US$5.6 billion, of which US$5 billion comes from sale for human consumption. Production, however, is expanding very rapidly.
Seaweeds can grow very fast – at rates more than 30 times those of land-based plants. Because they de-acidify seawater, making it easier for anything with a shell to grow, they are also the key to shellfish production. And by drawing CO₂
out of the ocean waters (thereby allowing the oceans to absorb more CO₂ from the atmosphere) they help fight climate change.
The stupendous potential of seaweed farming as a tool to combat climate change was outlined in 2012 by the University of the South Pacific’s Dr Antoine De Ramon N’Yeurt and his team. Their analysis reveals that if 9% of the ocean were to be covered in seaweed farms, the farmed seaweed could produce 12 gigatonnes per year of biodigested methane which could be burned as a substitute for natural gas. The seaweed growth involved would capture 19 gigatonnes of CO₂. A further 34 gigatonnes per year of CO₂ could be taken from the atmosphere if the methane is burned to generate electricity and the CO₂ generated captured and stored. This, they say:
…could produce sufficient biomethane to replace all of today’s needs in fossil-fuel energy, while removing 53 billion tonnes of CO₂ per year from
the atmosphere… This amount of biomass could also increase sustainable fish production to potentially provide 200 kilograms per year, per person, for 10 billion people. Additional benefits are reduction in ocean acidification and increased ocean primary productivity and biodiversity.
Nine per cent of the world’s oceans is not a small area. It is equivalent to about four and a half times the area of Australia. But even at smaller scales,
kelp farming has the potential to substantially lower atmospheric CO₂, and this realisation has had an energising impact on the research and commercial
development of sustainable aquaculture. But kelp farming is not solely about reducing CO₂. In fact, it is being driven, from a commercial perspective, by sustainable production of high-quality protein.
What might a kelp farming facility of the future look like? Dr Brian von Hertzen of the Climate Foundation has outlined one vision: a frame structure, most likely composed of a carbon polymer, up to a square kilometre in extent and sunk far enough below the surface (about 25 metres) to avoid being a shipping hazard. Planted with kelp, the frame would be interspersed with containers for shellfish and other kinds of fish as well. There would be no netting, but a kind of free-range aquaculture based on providing habitat to keep fish on location. Robotic removal of encrusting organisms would probably also be part of the facility. The marine permaculture would be designed to clip the bottom of the waves during heavy seas. Below it, a pipe reaching down to 200–500 metres would bring cool, nutrient-rich water to the frame, where it would be reticulated over the growing kelp.
Von Herzen’s objective is to create what he calls “permaculture arrays” – marine permaculture at a scale that will have an impact on the climate by growing kelp and bringing cooler ocean water to the surface. His vision also entails providing habitat for fish, generating food, feedstocks for animals, fertiliser and biofuels. He also hopes to help exploited fish populations rebound and to create jobs. “Given the transformative effect that marine permaculture can have on the ocean, there is much reason for hope that permaculture arrays can play a major part in globally balancing carbon,” he says.
The addition of a floating platform supporting solar panels, facilities such as accommodation (if the farms are not fully automated), refrigeration and processing equipment tethered to the floating framework would enhance the efficiency and viability of the permaculture arrays, as well as a dock for ships
carrying produce to market.
Given its phenomenal growth rate, the kelp could be cut on a 90-day rotation basis. It’s possible that the only processing required would be the cutting of the kelp from the buoyancy devices and the disposal of the fronds overboard to sink. Once in the ocean depths, the carbon the kelp contains is essentially out of circulation and cannot return to the atmosphere.
The deep waters of the central Pacific are exceptionally still. A friend who explores mid-ocean ridges in a submersible once told me about filleting a fish for dinner, then discovering the filleted remains the next morning, four kilometres down and directly below his ship. So it’s likely that the seaweed fronds would sink, at least initially, though gases from decomposition may later cause some to rise if they are not consumed quickly. Alternatively, the seaweed
could be converted to biochar to produce energy and the char pelletised and discarded overboard. Char, having a mineralised carbon structure, is likely to last well on the seafloor. Likewise, shells and any encrusting organisms could be sunk as a carbon store.
Once at the bottom of the sea three or more kilometres below, it’s likely that raw kelp, and possibly even to some extent biochar, would be utilised as a food source by bottom-dwelling bacteria and larger organisms such as sea cucumbers. Provided that the decomposing material did not float, this would not matter, because once sunk below about one kilometre from the surface, the carbon in these materials would effectively be removed from the atmosphere for at least 1,000 years. If present in large volumes, however, decomposing matter may reduce oxygen levels in the surrounding seawater.
Large volumes of kelp already reach the ocean floor. Storms in the North Atlantic may deliver enormous volumes of kelp – by some estimates as much as 7 gigatonnes at a time – to the 1.8km-deep ocean floor off the Bahamian Shelf.
Submarine canyons may also convey large volumes at a more regular rate to the deep ocean floor. The Carmel Canyon, off California, for example, exports large volumes of giant kelp to the ocean depths, and 660 major submarine canyons have been documented worldwide, suggesting that canyons play a significant role in marine carbon transport.
These natural instances of large-scale sequestration of kelp in the deep ocean offer splendid opportunities to investigate the fate of kelp, and the carbon it contains, in the ocean. They should prepare us well in anticipating any negative or indeed positive impacts on the ocean deep of offshore kelp farming.
Only entrepreneurs with vision and deep pockets could make such mid-ocean kelp farming a reality. But of course where there are great rewards, there are also considerable risks. One obstacle potential entrepreneurs need not fear, however, is bureaucratic red tape, for much of the mid-oceans remain a global commons. If a global carbon price is ever introduced, the exercise of disposing of the carbon captured by the kelp would transform that part of the business from a small cost to a profit generator. Even without a carbon price, the opportunity to supply huge volumes of high-quality seafood at the same time as making a substantial impact on the climate crisis are considerable incentives for investment in seaweed farming.
Last Friday, world-famous entrepreneur Elon Musk jetted into Adelaide to kick off Australia’s long-delayed battery revolution.
The Tesla founder joined South Australian Premier Jay Weatherill and the international chief executive of French windfarm developer Neoen, Romain Desrousseaux, to announce what will be the world’s largest battery installation.
The battery tender won by Tesla was a key measure enacted by the South Australian government in response to the statewide blackout in September 2016, together with the construction of a 250 megawatt gas-fired power station.
The project will incorporate a 100MW peak output battery with 129 megawatt hours of storage alongside Neoen’s Hornsdale windfarm, near Jamestown. When fully charged, we estimate that this will be enough to power 8,000 homes for one full day, or more than 20,000 houses for a few hours at grid failure, but this is not the complete picture.
The battery will support grid stability, rather than simply power homes on its own. It’s the first step towards a future in which renewable energy and storage work together.
How Tesla’s Powerpacks work
Tesla’s Powerpacks are lithium-ion batteries, similar to a laptop or a mobile phone battery.
In a Tesla Powerpack, the base unit is the size of a large thick tray. Around sixteen of these are inserted into a fridge-sized cabinet to make a single Tesla “Powerpack”.
With 210 kilowatt-hour per Tesla Powerpack, the full South Australian installation is estimated to be made up of several hundred units.
To connect the battery to South Australia’s grid, its DC power needs to be converted to AC. This is done using similar inverter technology to that used in rooftop solar panels to connect them to the grid.
A control system will also be needed to dictate the battery’s charging and discharging. This is both for the longevity of battery as well to maximise its economic benefit.
For example, the deeper the regular discharge, the shorter the lifetime of the battery, which has a warranty period of 15 years. To maximise economic benefits, the battery should be charged during low wholesale market price periods and discharged when the price is high, but these times are not easy to predict.
More research is needed into better battery scheduling algorithms that can predict the best charging and discharging times. This work, which we are undertaking at Monash Energy Materials and Systems Institute (MEMSI), is one way to deal with unreliable price forecasts, grid demand and renewable generation uncertainty.
The battery and the windfarm
Tesla’s battery will be built next to the Hornsdale wind farm and will most likely be connected directly to South Australia’s AC transmission grid in parallel to the wind farm.
Its charging and discharging operation will be based on grid stabilisation requirements.
This can happen in several ways. During times with high wind output but low demand, the surplus energy can be stored in the battery instead of overloading the grid or going to waste.
Conversely, at peak demand times with low wind output or a generator failure, stored energy could be dispatched into the grid to meet demand and prevent problems with voltage or frequency. Likewise, when the wind doesn’t blow, the battery could be charged from the grid.
The battery and the grid – will it save us?
In combination with South Australia’s proposed gas station, the battery can help provide stability during extreme events such as a large generator failure or during more common occurrences, such as days with low wind output.
At this scale, it is unlikely to have a large impact on the average consumer power price in South Australia. But it can help reduce the incidence of very high prices during tight supply-demand periods, if managed optimally.
For instance, if a very hot day is forecast during summer, the battery can be fully charged in advance, and then discharged to the grid during that hot afternoon when air conditioning use is high, helping to meet demand and keep wholesale prices stable.
More importantly, Tesla’s battery is likely to be the first of many such storage installations. As more renewables enter the grid, more storage will be needed – otherwise the surplus energy will have to be curtailed to avoid network overloading.
Another storage technology to watch is off-river pumped hydro energy storage (PHES), which we are modelling at the Australia-Indonesia Energy Cluster.
The South Australian Tesla-Neoen announcement is just the beginning. It is the first step of a significant journey towards meeting the Australian Climate Change Authority’s recommendation of zero emissions by at least 2050.
Ariel Liebman, Deputy Director, Monash Energy Materials and Systems Instutute, and Senior Lecturer, Faculty of Information Technology, Monash University and Kaveh Rajab Khalilpour, Senior Research Fellow, Caulfield School of Information Technology, Monash University
There’s plenty of excitement at the announcement overnight that a new planet is potentially waiting to be found at the extremes of our solar system.
The possible ninth planet is thought to be quite substantial with a mass around ten times that of Earth and a radius that’s two-to-four times bigger than Earth’s. This characterises it as a Neptune-like object.
What’s truly remarkable about Planet Nine, as it has been dubbed, is its very long orbit. It is estimated to take between 10,000 to 20,000 years to orbit our sun, on an elliptical orbit that stretches way beyond the Kuiper Belt.
The Kuiper Belt is a ring of icy objects (which includes Pluto) that circles the sun beyond the orbit of Neptune. Neptune orbits about 30 times further from the sun than the Earth and astronomers refer to Neptune’s distance from the sun as being 30 astronomical units (au) (where one au is the Earth-sun distance). Pluto follows an elliptical orbit that brings it as close as 29.7au from the sun, then out to almost 50au at its most distant point.
Planet Nine’s proposed elliptical orbit takes it from 200au at its closest to the sun (or perihelion) and between 500au to 1,200au at its furthest (aphelion). When it comes in close, it should be bright enough for high-spec backyard telescopes to pick it up.
But unfortunately, most of the time the planet will be much more distant and that represents a greater challenge. It will require the world’s largest telescopes, such as the 10m diameter Keck telescopes and Japan’s 8.2m Subaru telescope (both located on Mauna Kea in Hawaii) to have a hope of seeing it.
Ghostly pull of gravity
The planet has yet to be seen. So why is it thought to be out there? And how can we know so much about it? Planet Nine is the best fit to explain the orbits of six distant objects.
What’s odd about these six objects is that they have peculiar but remarkably similar orbits. These objects have been nudged off kilter and yet they are all shepherded together in the same region of space.
The first of these objects to be discovered was Sedna. It was observed in 2003, as it approached perihelion. When its 11,400-year orbit was calculated, the discovery team realised that this object was orbiting in a kind of “no man’s land” (or more correctly “no person’s land”).
It was too distant to belong to the Kuiper Belt and not far enough away to be among the sphere of comets orbiting the sun in the Oort Cloud.
Sedna was also beyond the gravitational pull of Neptune, so something else, perhaps a large planet or possibly even a passing star (one of the sun’s many siblings perhaps), might have nudged it off course. What makes Planet Nine feasible is that it can explain the orbit of Sedna along with the other five objects.
At their closest approach to the sun, these six objects sit within the plane of the solar system. Planet Nine would have an orbit that is anti-aligned to the six objects and provides the gravitational tug needed to keep those planets in check.
And there’s more. What makes good science is when a proposed model explains something above and beyond its original intention. Simulations of Planet Nine predict that there should also be objects in the Kuiper Belt that have orbits perpendicularly inclined to the plane of the solar system.
Turns out, these objects exist. Five such objects have been known about since 2002, although their orbits have been unexplained until now.
Haven’t we seen this before?
If Planet Nine does exist, it’s not the first time that a planet in our solar system has been discovered theoretically before being directly observed. In 1845, deviations in the orbit of Uranus, suggested there might be an eighth planet to the solar system and in 1846, Neptune was observed exactly where it was predicted to be.
There have also been predictions that haven’t stood the test of time. Back in the 1980s, scientists proposed that the sun might be a binary, with a dim undiscovered companion moving along on elongated orbit. Every 23 million years (or so), this star named Nemesis would pass through the solar system causing a deluge of comets to impact Earth and produce mass extinctions.
More recently, around the turn of the millennium, astronomers noticed an asymmetry in the distribution of new comets coming in from the Oort Cloud. In theory, comets should come evenly from all directions, but there was a slight excess distributed around a great circle on the sky. One of the explanations was that there could be a Jupiter-mass planet in the Oort cloud, known as Tyche.
In 2014, NASA’s Wide-Field Infrared Survey Explorer (WISE) examined the entire sky across infrared wavelengths. It was the perfect telescope to detect Nemesis or Tyche, but failed to find any evidence of either.
Will we find Planet Nine?
Scientists are sceptical by nature. It’s exciting to have a model that predicts the existence of Planet Nine but this prediction must also be tested. Astronomers have begun searching through astronomical surveys, such as the WISE survey, the Catalina Sky Survey, and the Pan STARRS surveys in the hope of making a sighting.
So far, nothing has been seen. The conclusion, as described in a blog by astronomer, Mike Brown (who proposed Planet Nine along with colleague Konstantin Batygin) is that Planet Nine, if it exists, is likely in the hardest place to find.
It seems to currently be at its furthest point from the sun, at least 500au away; it’s probably fainter than 22nd magnitude (that’s 1,500 times fainter than Pluto); and very possibly it’s aligned with the plane of the Milky Way Galaxy (meaning that Planet Nine may currently be hidden against the background stars of our Galaxy).
Regardless, the hunt is on and there just may be a great discovery out there, waiting to happen.
Tanya Hill, Honorary Fellow of the University of Melbourne and Senior Curator (Astronomy), Museum Victoria and Jonti Horner, Vice Chancellor’s Senior Research Fellow, University of Southern Queensland