Just like birds and mammals carrying seeds through a rainforest, green sea turtles and dugong spread the seeds of seagrass plants as they feed. Our team at James Cook University’s TropWATER Centre has uncovered a unique relationship in the seagrass meadows of the Great Barrier Reef.
We followed feeding sea turtle and dugong, collecting samples of their floating faecal matter. Samantha then had the unenviable job of sifting through hundreds of smelly samples to find any seagrass seeds. These seeds range in size from a few centimetres to a few millimetres, and therefore can require the assistance of a microscope to be found. Once any seeds were found, they were stained with a chemical dye (Tetrazolium) to see if they were still viable (capable of growing).
Why is this important for turtles and dugong?
Green sea turtles and dugong are iconic animals on the reef, and seagrass is their food. Dugong can eat as much as 35 kilograms of wet seagrass a day, while sea turtles can eat up to 2.5% of their body weight per day. Without productive seagrass meadows, they would not survive.
This relationship was highlighted in 2010-11 when heavy flooding and the impact of tropical cyclone Yasi led to drastic seagrass declines in north Queensland. In the year following this seagrass decline there was a spike in the number of starving and stranded sea turtles and dugong along the entire Queensland coast.
The seagrass team at James Cook University has been mapping, monitoring and researching the health of the Great Barrier Reef seagrasses for more than 30 years. While coral reefs are more attractive for tourists, the Great Barrier Reef World Heritage Area actually contains a greater area of seagrass than coral, encompassing around 20% of the world’s seagrass species. Seagrass ecosystems also maintain vibrant marine life, with many fish, crustaceans, sea stars, sea cucumbers, urchins and many more marine animals calling these meadows their home.
These underwater flowering plants are a vital component of the reef ecosystem. Seagrasses stabilise the sediment, sequester large amounts of carbon from the atmosphere and filter the water before it reaches the coral reefs. Further, the seagrass meadows in the Great Barrier Reef support one of the largest populations of sea turtles and dugong in the world.
Seagrass meadows are more connected than we thought
Samantha’s research was worth the effort. There were seeds of at least three seagrass species in the poo of both sea turtles and dugong. And lots of them – as many as two seeds per gram of poo. About one in ten were viable, meaning they could grow into new plants.
Based on estimates of the number of animals in the coastal waters, the time it takes for food to pass through their gut, and movement data collected from animals fitted with satellite tags, there are potentially as many as 500,000 viable seeds on the move each day in the Great Barrier Reef. These seeds can be transported distances of up to 650km in total.
This means turtles and dugong are connecting distant seagrass meadows by transporting seeds. Those seeds improve the genetic diversity of the meadows and may help meadows recover when they are damaged or lost after cyclones. These animals help to protect and nurture their own food supply, and in doing so make the reef ecosystem around them more resilient.
Understanding recovery after climate events
This research shows that these ecosystems have pathways for recovery. Provided we take care with the environment, seagrasses may yet recover without direct human intervention.
This work emphasises how much we still have to learn about how the reef systems interconnect and work together – and how much we need to protect every part of our marvellous and amazing reef environment.
Samantha J Tol, PhD Candidate, James Cook University; Alana Grech, Assistant Director, ARC Centre of Excellence for Coral Reef Studies, James Cook University; Paul York, Senior Research Scientist in Marine Biology, James Cook University, and Rob Coles, Team leader, Seagrass Habitats, TropWATER, James Cook University
On May 10, the 43.5-metre schooner Avontuur arrived in the port of Hamburg. This traditional sailing vessel, built in 1920, transported some 70 tonnes of coffee, cacao and rum across the Atlantic. The shipping company Timbercoast, which owns and operates Avontuur, says it aims to prove that sailing ships can offer an environmentally sustainable alternative to the heavily polluting shipping industry, despite being widely seen as a technology of yesteryear.
Similar initiatives exist across the world. In the Netherlands, Fairtransport operates two vessels on European and transatlantic routes. In France, Transoceanic Wind Transport sails multiple vessels across the English Channel and Atlantic Ocean, and along European coasts. The US-based vessel Kwai serves islands in the Pacific. And Sail Cargo, based in Costa Rica, is building Ceiba, a zero-emission cargo sailing ship.
These initiatives have an environmental objective: transporting cargo without generating greenhouse gas emissions. But are they really a viable alternative to today’s huge fossil-fuelled maritime cargo transport industry?
Shipping emission targets?
On April 13, 2018, the International Maritime Organization, the United Nations body that regulates shipping, agreed for the first time to limit the sector’s greenhouse emissions. It’s targeting a 50% reduction by 2050 (relative to 2008 levels), with the aim to phase out emissions entirely.
This was a breakthrough, given that both the 1997 Kyoto Protocol and the 2015 Paris Agreement exclude international shipping (and international aviation) from emissions targets, because these are so hard to attribute to individual countries.
Conventional seaborne cargo transport is relatively energy-efficient. It emits less greenhouse gas per tonne-kilometre (one tonne of goods transported over one kilometre) than transport by train, truck or plane. But because 80-90% of all goods we consume are transported by sea, the total emissions of the shipping industry are immense.
According to figures from the International Maritime Organization (IMO), shipping accounts for 2-3% of global emissions – outstripping the 2% share generated by civil aviation.
As the global demand for goods increases, so does the need for shipping. As a result, the IMO has projected that the sector’s greenhouse emissions will grow by anything between 50% and 250% between 2012 and 2050, despite improvements in fuel composition and efficiency. More worryingly, a commentary on that report in Nature Climate Change warns that “none of the anticipated shipping scenarios even approach what is necessary for the sector to make its ‘fair and proportionate’ contribution to avoiding 2℃ of warming”.
A recent report commissioned by the European Parliament raises further alarm bells, underscoring the fact that the sector’s huge growth is likely to swamp any carbon savings that come from improved operations. On top of this, the significant progress made in other industries means that the relative share of greenhouse gas emissions from cargo shipping is likely to increase from the current 2-3% to 17% by 2050.
The OECD International Transport Forum is less pessimistic. It projects a 23% increase in the sector’s emissions between 2015 and 2035 on current trends, but also argues that it will be possible to decarbonise maritime transport altogether by 2035, through the “maximum deployment of currently known technologies”.
These emissions-reducing propulsion technologies include kites, solar electricity, and advanced sail technology. Some of them, such as Flettner rotors, are already in use. But these will not be scaled up and become viable unless there is strict regulation, even if some shipping companies have taken steps to reduce their emissions ahead of a binding IMO target. Electricity-propelled container barges operate in Belgium and the Netherlands.
Meanwhile, the IMO faced a tricky balancing act in juggling the priorities of different countries. Climate-vulnerable nations such as the Marshall Islands want shipping emissions to be cut entirely by 2035. The European Union has proposed a reduction of 70-100% by 2050, while emerging economies such as Brazil, Saudi Arabia and India have argued against any emissions target at all. Despite these differences, the IMO did agree on a 50% reduction target by 2050 in April 2018.
It took Avontuur 126 days to sail from France to Honduras, Mexico, Cuba and home to Germany. But conventional container ships can cross the Atlantic in about a week. Avontuur was carrying more than 70 tonnes of cargo on arrival in Germany. But many cargo vessels now carry more than 20,000 standard shipping containers (TEU), each weighing more than 2 tonnes and able to hold more than 20 tonnes of cargo.
Given the relatively small capacity of sailing ships, it is expensive and labour-intensive to ship cargo this way. But despite these limitations, support for sail cargo initiatives is growing. A consortium of small North Sea ports, for example, will “create sail cargo hubs in small ports and harbours, giving local businesses direct access to ethically transported goods”.
These initiatives signal the revival of sail cargo with an explicit environmental agenda, although this effort is dwarfed by the scale of the global shipping industry. But while they don’t stack up in logistical terms, these voyages can help us see the possibilities for a world without fossil fuels. Sail cargo aims to rethink not only the means of propulsion for cargo vessels, but the entire scale, economy and ethics of cargo transport.
Traditional sailing vessels like Avontuur will not be able to compete with conventional cargo vessels on speed, scale or cost. But they help us focus on the underlying issue. We ship too much, too often and too far. The scale of shipping is unsustainable. That is why we need a change of mindset as much as a change of technology.
Sail cargo initiatives raise awareness about the devastating environmental effects of conventional cargo shipping. And they do so by showing that an alternative is possible. Indeed, it has been around for thousands of years.
A proposed Kosciuszko Wild Horse Heritage Bill that rules out shooting horses is based on a flawed understanding of fertility control. Unfortunately, by ignoring scientific evidence and expert advice horses will be condemned to slow starvation.
The bill, which also proposes relocating horses within the park, or removal and domestication, intends to use fertility control for longer-term population control. But this simply isn’t feasible, and is unlikely to become so in the near future.
Vaccine darts are not a panacea
Immunocontraceptive vaccines that have been used for fertility control in wild horses in North America include the gonadotrophin releasing hormone (GnRH) vaccine, GonaCon, and porcine zona pellucida (PZP) vaccines. Administration requires injection: there is no effective oral vaccine. Injection requires either trapping horses and injecting them by hand, or darting them.
Immunocontraception has only been successfully used in smaller and more isolated populations (such as islands). Population modelling has estimated that over 50% of mares would need to be treated in KNP just to slow the rate of population increase within 2–5 years.
Although the precise number of horses in KNP is hotly debated, even at the lowest estimates almost 1,000 mares would need to be treated to have the desired impact on population growth – and it would still take 10–20 years before the population size was reduced substantially through natural mortality. And that is on the proviso that we could actually administer the vaccine to this number of mares.
Trapping enough horses across KNP (an area of about 700,000 hectares) would likely be impossible. Dart administration sounds intuitively appealing but is a complex process and will not be possible for large numbers of horses in difficult, mountainous terrain.
Staff must be extensively trained for licences before they can administer darts. More importantly, darting can only be safely performed within around 40 metres of a stationary horse, and with a clear line of vision. This must be done accurately and without causing ballistic injuries.
Injected animals must be marked (with dye, for example) so that they can be identified for booster shots as needed.
As demonstrated in a recent trial of fertility control darting for eastern grey kangaroos in the ACT, it is extremely challenging to manage all of these goals in the field. Helicopters can be used to dart animals, but this adds animal welfare impacts due to pursuit and lower levels of accuracy.
In other parts of the world where dart administration of immunocontraceptives has been successful, they have been applied to horses that are used to people, allowing staff to approach horses on foot. This is a very different situation to KNP.
Although it is possible to closely approach some horses in KNP, ongoing research has revealed that it is only possible to get within 200–500m of most horses in the larger populations.
Furthermore, it would be close to impossible to both identify and locate the same horses on multiple occasions, as required for booster vaccination injections. In more densely forested areas, it can be challenging to even see horses, let alone dart them.
There is no vehicle access to many parts of KNP where horses live, and long treks across challenging terrain would make attempts to locate all horses very labour-intensive. Furthermore, many areas of KNP are completely inaccessible in winter due to snow, making darting before the spring breeding season even more problematic.
What would we be vaccinating the horses with?
There’s also the question of what exactly the horses would be vaccinated with. GonaCon and PZP are not produced in commercial quantities, are not currently available in Australia and are not straightforward to import. Australian quarantine regulations may prevent the import of reagents derived from animals, such as conventional PZP which is derived from pig ovaries.
There are two alternative GnRH vaccines available in Australia. One has shown less effectiveness than required in a pilot trial and while the other is registered for use in domestic mares, it lasts a relatively short time and is prohibitively expensive.
Most contraceptive vaccines require an initial injection followed by a second injection about one month later to achieve maximum efficacy, and then annual booster injections. GonaCon is promoted as having 3-year efficacy after a single injection, but that significantly reduces after the first 12 months. Long-acting PZP formulations have been investigated in North America; while results appeared promising initially, more recent work showed a contraceptive efficacy of under 60% beyond one year after treatment. Furthermore, the viscous nature of these longer-acting formulations make administration by dart more challenging.
Alternative fertility control options such as surgical sterilisation or intra-uterine devices have even more practical hurdles. For all of these reasons, a recent peer-reviewed study by two Australian reproductive experts concluded that current fertility control methods are not feasible for halting the population growth of wild horses in Australia.
Although some newer technologies are undergoing investigation, realistically it will be a long time before contraception for wild horses becomes an effective reality in Australia.
‘No-kill’ bill means slow starvation
Without a feasible method for sterilising horses, the newly proposed bill will mean population control is mainly through food limitation.
While “no kill” is seemingly more compassionate, it may ultimately and unintentionally be crueller.
As horse populations reach the carrying capacity of their habitats, they become malnourished and their fertility declines. Horses in very poor condition will not produce foals. When malnutrition persists, many horses will die young and many will die slowly.
This was dramatically demonstrated four years ago, when researchers discovered emaciated brumbies in the Snowy Mountains cannibalising their fellows and more emerging research is further confirming that extreme malnutrition is ongoing in parts of KNP.
In time, the number of horses suffering chronic malnutrition and dying of starvation is likely to increase. Is this truly humane population control?
Andrea Harvey, Veterinary Specialist, PhD scholar (wild horse ecology & welfare), University of Technology Sydney; Carolynne Joone, , James Cook University, and Jordan Hampton, Adjunct Lecturer, Murdoch University
Over the past few weeks we’ve seen increasingly spectacular images reported in the news of the ongoing eruption at Kilauea volcano, on the Pacific island of Hawai’i.
These have been tempered by reports of growing destruction, with houses and infrastructure bulldozed, buried or burned by lava flows.
Yet Kilauea is one of the world’s most active volcanoes, and has been erupting continually since 1983. So what has triggered this sudden change in activity, threatening homes and livelihoods? The answer relates to what is happening beneath the volcano.
Activity at Kilauea is driven by the buoyant upwelling of a plume of hot mantle, which provides the heat to generate magma beneath the volcano. This magma has the potential to erupt from several different locations, or vents, on the volcano.
Typically, the crater at the summit of the volcano is where eruptions are expected to occur, but the geology of Kilauea is complex and a rift on the eastern side of the volcano also allows magma to erupt from its flanks.
Over the past decade both the summit crater and a vent on the eastern rift, called Pu’u O’o, have been continually active. The summit crater has hosted a lava lake since March 2008.
Lava lakes are relatively rare features seen at only a handful of volcanoes around the world. The fact that they do not cool and solidify tells us that lava lakes are regularly replenished by fresh magma from below.
In contrast, Pu’u O’o, 18km east of the summit crater, has been pouring out lava flows since 1983. In the first 20 years of this eruption, 2.1km³ of lava flows were produced, equivalent in volume to 840,000 Olympic swimming pools. All of this tells us that Kilauea volcano regularly receives lots of magma to erupt.
Over the past three weeks activity at Pu’u O’o has stopped, while a series of fissures has opened roughly 20km further east in a subdivision known as Leilani Estates.
This area was previously affected by lava flows in 1955.
To date, 23 fissures have opened, starting off simply as cracks in the ground, with some developing into highly active vents from which significant lava flows are forming.
Meanwhile, at the summit of the volcano, the lava lake has drained from the crater, sparking fears of more explosive eruptions, as draining magma interacts with groundwater.
Satellite instruments and high-resolution GPS are being used to monitor changes in the shape of the volcano and have found that the summit region is deflating, while the lower east rift zone, where new fissures have opened in recent days, is inflating.
The magma reservoirs that feed eruptions on Kilauea can be imagined as balloons, which grow when they are filled and shrink when they are emptied. Deflation at the summit, combined with observations that the lava lake has drained (at a rate of up to 100m over two days!), suggest that the magma reservoir feeding the summit is emptying.
Where is the magma going? Observations of ground inflation around the newly opened fissures to the east indicate that the magma is being diverted down the east rift and accumulating and erupting there instead.
Exactly what has caused this rerouting of the magma is still not clear. A magnitude 6.9 earthquake occurred in the area on May 4 and this may have opened a new pathway for magma to erupt, influencing the geometry of the lower east rift zone.
Lessons for the future
By combining measurements from Kilauea of ground deformation, earthquake patterns and gas emissions during the current eruption, with observations of the lava that is erupted, volcanologists will be able to piece together a much clearer picture of what triggered this significant change in eruption over the past few weeks.
This knowledge will be crucial in planning for future eruptions, both at Kilauea and at other volcanoes.
Eruptions from the flanks of a volcano can pose a much more significant hazard for the local population than those from a volcano’s summit, as many more people live in the areas that are directly affected.
This has been amply displayed over the past few weeks on Kilauea by the fissures opening in people’s gardens and lava flows destroying homes and infrastructure.
But Kilauea is not the only volcano to have flank eruptions. For example, lava flows famously emerged from the lower slopes of Mt Etna in 1669, destroying villages and partially surrounding the regional centre of Catania, on the east coast of Sicily, Italy.
Lessons learned from the current eruption of Kilauea can equally be applied to other volcanoes, like Etna, where more densely populated surroundings mean that the hazards posed by such an eruption would be even greater.
Welcome to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian. Read more about the series here or get in touch to pitch a plant at firstname.lastname@example.org.
Australia has about 42 native species of Ficus, that include vines, plants that grow on other plants (epiphytes), and woody trees.
In this article we will explore the unique features of the Sandpaper Figs, named so because of the rough texture of their leaves. From finishing tools, as the name suggests, to curing ringworm and making fire, these excellent trees do it all.
Can you grow it?
There are three species of sandpaper fig native to the South East Queensland area, although sandpaper figs grow all along the east coast and top end of Australia in gullies and rainforest. They are rarely found in southern Australia. Similar species with sandpaper-like leaves are found in other parts of the world such as Kenya, Africa and in Papua New Guinea.
The most common variation is the creek sandpaper fig, Ficus coronata. It has hairy, round, very sweet figs, turning purple to black as they ripen in the months of January to June, and a strong sandpapery texture on its leaves.
Less common is the sweet sandpaper fig, Ficus opposita. It grows squat-shaped, smooth, sweet figs (always in pairs) for the majority of the year, and knobbly branches, and the underside of its leaves have a hairy or velvety texture.
Lastly is the shiny sandpaper fig, Ficus fraseri. Its natural habitat is the rainforest, and also has a sandpaper texture, but more so on its branches than leaves. Its figs are egg-shaped, with a yellow-orange phase from June to November.
The immature, straggly Ficus coronata has a dark brown trunk and oval or elliptical leaves. It uses aerial roots that grow down from the branches to the ground while taking in nutrients and moisture from the air. These roots evolved so that the tree could germinate and grow in wet areas, barren soils and rocky outcrops. Once the roots have travelled to the ground, they expand to support the tree’s branches, creating some unusual shapes. The mature tree can grow up to 15 metres tall.
In your garden a sandpaper fig will attract birds, and is hardy and easy to grow. They prefer lots of light and moisture, free from frosts. As with all Ficus species that have large root systems, you must plant them well away from houses, ideally in a larger block (although they are relatively small compared to fig trees such as the Moreton Bay). They can tolerate heavy pruning so may be used as a hedge. Regular fertilising and addition of organic matter will ensure a healthy tree and production of fruit.
Don’t despair if you have a small block or are in a frost zone – you can try growing a Ficus in a large pot outdoors, a pot indoors or even create a bonsai tree.
Wasp’s my name
The fig tree is unique because its flower, made up of hundreds of tiny florets, is wrapped inside the fruit. You might then wonder how the flower can be pollinated. An amazing symbiotic feat of nature created the aptly names fig wasp to pollinate the figs, and in return the wasp can only mate inside the fig flower.
A female fig wasp recognises the special scent of the exact species of fig tree where she was born, and returns only to that species. She enters the fig by squeezing through a tiny hole near the top of the fruit (an ostiole), losing her wings and some of her antennae as she enters. She then dies inside the fruit after laying her eggs.
Male offspring are born without wings 20-100 days later, mate with the female offspring, and then die shortly after boring a hole through the fruit to make their escape. Only then can the female offspring collect the now ripe pollen and carry it to another fig tree of the same species.
The fruit gets the signal to ripen after the wasps have bored a hole and the carbon dioxide level inside has dropped, producing tasty sweet figs.
Historically many groups of indigenous people from mainland Australia ate these figs. Some were eaten raw and others were beaten to make a paste and then mixed with honey and water.
In bush medicine the sandpaper fig leaves were used in conjunction with stinking passion flower to relieve insect bites. The rough texture of the leaves would be used to rub the skin until it bled, and then the passion flower would be applied. The leaves of the Sandpaper Fig were also used as a cure for ringworm infections. The skin would again be rubbed raw with the leaves and the milky sap applied. This sap was additionally useful for treating wounds.
Indigenous people used the rough sandpapery texture of the leaves to finish off their tools and polish their wooden boomerangs and spears. Straight branches were used for fire starter sticks and string could also be made from the bark .
It provides food, medicine, fire and tools: a wonderful all-rounder in the Australian plant pantheon.