Jonathan Nott, James Cook UniversityTropical Cyclone Seroja battered parts of Western Australia’s coast on Sunday night, badly damaging buildings and leaving thousands of people without power. While the full extent of the damage caused by the Category 3 system is not yet known, the event was unusual.
I specialise in reconstructing long-term natural records of extreme events, and my historic and prehistoric data show cyclones of this intensity rarely travel as far south as this one did. In fact, it has happened only 26 times in the past 5,000 years.
Severe wind gusts hit the towns of Geraldton and Kalbarri – towns not built to withstand such conditions.
Unfortunately, climate change is likely to mean disasters such as Cyclone Seroja will become more intense, and will be seen further south in Australia more often. In this regard, Seroja may be a timely wake-up call.
Seroja: bucking the cyclone trend
Cyclone Seroja initially piqued interest because as it developed off WA, it interacted with another tropical low, Cyclone Odette. This rare phenomenon is known as the Fujiwhara Effect.
Cyclone Seroja hit the WA coast between the towns of Kalbarri and Gregory at about 8pm local time on Sunday. According to the Bureau of Meteorology it produced wind gusts up to 170 km/hour.
Seroja then moved inland north of Geraldton, weakening to a category 2 system with wind gusts up to 120 km/hour. It then tracked further east and has since been downgraded to a tropical low.
The cyclone’s southward track was historically unusual. For Geraldton, it was the first Category 2 cyclone impact since 1956. Cyclones that make landfall so far south on the WA coast are usually less intense, for several reasons.
First, intense cyclones draw their energy from warm sea surface temperatures. These temperatures typically become cooler the further south of the tropics you go, depleting a cyclone of its power.
Second, cyclones need relatively low speed winds in the middle to upper troposphere – the part of the atmosphere closest to Earth, where the weather occurs. Higher-speed winds there cause the cyclone to tilt and weaken. In the Australian region, these higher wind speeds are more likely the further south a cyclone travels.
Third, most cyclones make landfall in the northern half of WA where the coast protrudes far into the Indian Ocean. Cyclones here typically form in the Timor Sea and move southward or south-west away from WA before curving southeast, towards the landmass.
For a cyclone to cross the coast south of about Carnarvon, it must travel a considerable distance towards the south-west into the Indian Ocean. This was the case with Seroja – winds steered it away from the WA coast before they weakened, allowing the cyclone to curve back towards land.
Reading the ridges
My colleagues and I have devised a method to estimate how often and where cyclones make landfall in Australia.
As cyclones approach the coast, they generate storm surge – abnormal sea level rise – and large waves. The surge and waves pick up sand and shells from the beaches and transport them inland, sometimes for several hundred metres.
These materials are deposited into ridges which stand many metres above sea level. By examining these ridges and geologically dating the materials within them, we can determine how often and intense the cyclones have been over thousands of years.
At Shark Bay, just north of where Seroja hit the coast, a series of 26 ridges form a “ridge plain” made entirely of one species of a marine cockle shell (Fragum eragatum). The sand at beaches near the plain are also made entirely of this shell.
The ridge record shows over the past 5,000 years, cyclones of Seroja’s intensity, or higher, have crossed the coast in this region about every 190 years – so about 26 times. Some 14 of these cyclones were more intense than Seroja.
The record shows no Category 5 cyclones have made landfall here over this time. The ridge record prevents us from knowing the frequency of less intense storms. But Bureau of Meteorology cyclone records since the early 1970s shows only a few crossed the coast in this region, and all appear weaker than Seroja.
Cyclones under climate change
So why does all this matter? Cyclones can kill and injure people, damage homes and infrastructure, cause power and communication outages, contaminate water supplies and more. Often, the most disadvantaged populations are worst affected. It’s important to understand past and future cyclone behaviour, so communities can prepare.
Climate change is expected to alter cyclone patterns. The overall number of tropical cyclones in the Australian region is expected to decrease. But their intensity will likely increase, bringing stronger wind and heavier rain. And they may form further south as the Earth warms and the tropical zone expands poleward.
This may mean cyclones of Seroja’s intensity are likely to become frequent, and communities further south on the WA coast may become more prone to cyclone damage. This has big implications for coastal planning, engineering and disaster management planning.
In particular, it may mean homes further south must be built to cope with stronger winds. Storm surge may also worsen, inundating low-lying coastal land.
Global climate models are developing all the time. As they improve, we will gain a more certain picture of how tropical cyclones will change as the planet warms. But for now, Seroja may be a sign of things to come.
This article is part of Conversation series on the nexus between disaster, disadvantage and resilience. Read the rest of the stories here.
Australia’s wetlands are home to a huge range of stunning flora and fauna, with large snakes often at the top of the food chain.
Many wetlands are located near urban areas. This makes them particularly susceptible to contamination as stormwater, urban drainage and groundwater can wash metals — such as arsenic, cadmium, lead and mercury — into the delicate ecosystem.
We know many metals can travel up the food chain when they’re present in the environment. So to assess contamination levels, we caught highly venomous tiger snakes across wetlands in Perth, and repurposed laser technology to measure the metals they accumulated.
In our new paper, we show metal contamination in wild wetland tiger snakes is chronic, and highest in human-disturbed wetlands. This suggests all other plants and animals in these wetlands are likely contaminated as well.
34 times more arsenic in wild wetland snakes than captive snakes
Urban growth and landscape modification often introduces metals into the surrounding environment, such as mining, landfill and waste dumps, vehicles and roadworks, and agriculture.
When they reach wetlands, sediments collect and store these metals for hundreds of years. And if a wetland’s natural water levels are lowered, from agricultural draining for example, sediments can become exposed and erode. This releases the metals they’ve been storing into the ecosystem.
This is what we suspect happened in Yanchep National Park’s wetland, which was supposed to be our “clean” comparison site to more urban wetlands. But in a 2020 study looking at sediment contamination, we found this wetland had higher levels of selenium, mercury, chromium and cadmium compared to urban wetlands we tested.
And at Herdsman Lake, our most urban wetland five minutes from the Perth city centre, we found concentrations of arsenic, lead, copper and zinc in sediment up to four times higher than government guidelines.
In our new study on tiger snake scales, we compared the metal concentrations in wild wetland tiger snakes to the concentrations that naturally occurs in captive-bred tiger snakes, and to the sediment in the previous study.
We found arsenic was 20-34 times higher in wild snakes from Herdsman Lake and Yanchep National Park’s wetland. And snakes from Herdsman Lake had, on average, eight times the amount of uranium in their scales compared to their captive-bred counterparts.
Tiger snakes usually prey on frogs, so our results suggest frogs at these lakes are equally as contaminated.
We know for many organisms, exposure to a high concentration of metals is fatally toxic. And when contamination is chronic, it can be “neurotoxic”. This can, for example, change an organism’s behaviour so they eat less, or don’t want to breed. It can also interfere with their normal cellular function, compromising immune systems, DNA repair or reproductive processes, to name a few.
Snakes in general appear relatively resistant to the toxic effects of metal contamination, but we’re currently investigating what these levels of contamination are doing to tiger snakes’ health and well-being.
Our method keeps snakes alive
Snakes can be a great indicator of environmental contamination because they generally live for a long time (over 10 years) and don’t travel too far from home. So by measuring metals in older snakes, we can assess the contamination history of the area they were collected from.
Typically, scientists use liver tissue to measure biological contamination since it acts like a filter and retains a substantial amount of the contaminants an animal is exposed to.
But a big problem with testing the liver is the animal usually has to be sacrificed. This is often not possible when studying threatened species, monitoring populations or working with top predators.
In more recent years, studies have taken to measuring metals in external “keratin” tissues instead, which include bird feathers, mammal hair and nails, and reptile scales. As it grows, keratin can accumulate metals from inside the body, and scientists can measure this without needing to kill the animal.
Our research used “laser ablation” analysis, which involves firing a focused laser beam at a solid sample to create a small crater or trench. Material is excavated from the crater and sent to a mass spectrometer (analytical machine) where all the elements are measured.
This technology was originally designed for geologists to analyse rocks, but we’re among the first researchers applying it to snake scales.
Laser ablation atomises the keratin of snake scales, and allowed us to accurately measure 19 contaminants from each tiger snake caught over three years around different wetlands.
We need to minimise pollution
Our research has confirmed snake scales are a good indicator of environmental contamination, but this is only the first step.
Further research could allow us to better use laser ablation as a cost-effective technology to measure a larger suite of metals in different parts of the ecosystem, such as in different animals at varying levels in the food chain.
This could map how metals move throughout the ecosystem and help determine whether the health of snakes (and other top predators) is actually at risk by these metal levels, or if they just passively record the metal concentrations in their environment.
It’s difficult to prevent contaminants from washing into urban wetlands, but there are a number of things that can help minimise pollution.
This includes industries developing strict spill management requirements, and local and state governments deploying storm-water filters to catch urban waste. Likewise, thick vegetation buffer zones around the wetlands can filter incoming water.
The destruction of 46,000-year-old Juukan Gorge sites in the Pilbara has created great distress for their traditional owners, seismic shockwaves for heritage professionals and appalled the general public.
The fallout for Rio Tinto has been profound as has the groundswell of criticism of Western Australia’s outdated heritage laws. A path forward must ensure a pivotal role for Indigenous communities and secure Keeping Places for heritage items. More broadly, we need more Indigenous places added to the National Heritage List, ensuring them the highest form of heritage protection.
In a state heavily dependent on mining, the model for this could follow the successful seven-year heritage collaboration I have been part of on-country with Murujuga Aboriginal Corporation (MAC) and Rio Tinto in the Dampier Archipelago (Murujuga).
As Director of the Centre for Rock Art Research and Management at the University of Western Australia, I am funded to undertake research supported by Rio Tinto’s conservation agreement with the Commonwealth.
This Rio Tinto funding enables research documenting the significant scientific and community values of the archipelago, feeding into the management of this estate by MAC, who represent the local coastal Pilbara groups. It also resources Indigenous rangers and trains undergraduate students.
The Murujuga conservation agreements, made between the Commonwealth and both Rio Tinto and Woodside, were negotiated when the archipelago’s one million-plus engravings and stone features were added to Australia’s National Heritage List in 2007.
Murujuga is one of only seven Indigenous rock art places on the National Heritage List. There are 118 listings in total in Australia (only 20 of them Indigenous). Murujuga is the only listed Indigenous site here with a conservation agreement requiring industry to fund heritage protection.
Rio Tinto does not have a similar agreement with the traditional owners of Juukan Gorge, the Puutu Kunti Kurruma Pinikuru (PKKP) peoples — nor do any of the other Pilbara resource extraction companies with their host native title communities. These mining tenements are managed by a range of royalty agreements, which recognise native title rights but are flexible and require transparency.
Despite working closely with Rio Tinto, I have been dismayed by the Juukan incident and the fault lines it has revealed in Rio Tinto’s historically significant investment in heritage management and agreement-making with Aboriginal people.
Conserving Aboriginal heritage
Many of the changes in the WA Government’s new Aboriginal Cultural Heritage Bill 2020 are welcome: in particular, the recognition of native title, allowing “stop work orders” if an Indigenous community says mining work was begun without their permission, and increased penalties for damaging heritage.
But Aboriginal groups, including many in the Kimberley and south-west WA, fear the onus for this regulatory process will be passed onto them and — despite being the appropriate people to manage their own heritage — they will not be adequately resourced to do so.
The number of heritage sites likely to be at risk in the future will number in the thousands, given the current footprint of mining is a mere 1% of the planned expansion over the next century. A new paradigm is needed in managing heritage. There needs to be a process of identifying regionally significant landscapes and earmarking them for conservation before future development footprints are determined.
And there need to be more conservation agreements like the Murujuga one, with industry-funding heritage and conservation rather than just mining clearance work.
In the Pilbara, for instance, there are three national parks, Karajini, Millstream-Chichester and Murujuga, where mining cannot occur. But more are needed in other native title areas. They need to be resourced so Aboriginal heritage rangers can manage them, with appropriate facilities for tourists.
Mining compliance surveys, which “manage harm” to heritage are a significant economy for many Aboriginal communities.
But a number of Pilbara Aboriginal Corporations, including Wintawari Gurama, with whom I have developed a rock art research project, don’t want to just participate in the mining economy, which is tantamount to destroying their heritage.
They want to train local rangers, and document, record and manage their own heritage estates, enabling elders and young people to earn a living on country.
This approach is equally required in places like the Kimberley, where fracking could be the next resources “boom”.
Aboriginal communities need Keeping Places.
These, too, could be funded by industry, becoming the focus of heritage tourism and ranger training, and hosting collaborative research on heritage, biodiversity and conservation.
The state government and industry stakeholders are funding the Murujuga Rock Art Strategy, which will monitor and assess emissions from nearby industry. There are, however, concerning plans to introduce new industry in the adjacent Burrup Industrial Estate. This is an issue, too, for the federal government, which has ultimate oversight of heritage on the national list.
In WA, the state government asserts that heritage can co-exist with industry. But this will only be possible if the state recognises heritage is non-renewable — just like the mineral wealth of this country.
Significant coral bleaching at one of Western Australia’s healthiest coral reefs was found during a survey carried out in April and May.
The survey took a combined effort of several organisations, together with tour operators more used to taking tourists, but with time spare during the coronavirus lockdown.
WA’s arid and remote setting means many reefs there have escaped some of the pressures affecting parts of the east coast’s Great Barrier Reef), such as degraded water quality and outbreaks of crown of thorns starfish.
The lack of these local pressures reflects, in part, a sound investment by governments and communities into reef management. But climate change is now overwhelming these efforts on even our most remote coral reefs.
When the oceans warmed
As the 2020 mass bleaching unfolded across the Great Barrier Reef, a vast area of the WA coastline was bathed in hot water through summer and autumn. Heat stress at many WA reefs hovered around bleaching thresholds for weeks, but those in the far northwest were worst affected.
The remoteness of the region and shutdowns due to COVID-19 made it difficult to confirm which reefs had bleached, and how badly. But through these extraordinary times, a regional network of collaborators managed to access even our most remote coral reefs to provide some answers.
Australia’s Bureau of Meteorology provided regional estimates of heat stress, from which coral bleaching was predicted and surveys targeted.
At reefs along the Kimberley coastline, bleaching was confirmed by WA’s Department of Biodiversity, Conservation and Attractions (DBCA), Bardi Jawi Indigenous rangers, the Kimberley Marine Research Centre and tourist operators.
At remote oceanic reefs hundreds of kilometres from the coastline, bleaching was confirmed in aerial footage provided by Australian Border Force.
Subsequent surveys were conducted by local tourist operators, with no tourists through COVID-19 shutdown and eager to check the condition of reefs they’ve been visiting for many years.
The Rowley Shoals
Within just a few days, a tourist vessel chartered by the North West Shoals to Shore Research Program, with local operators and a DBCA officer, departed from Broome for the Rowley Shoals. These three reef atolls span 100km near the edge of the continental shelf, about 260km west-north-west offshore.
One of only two reef systems in WA with high and stable coral cover in the last decade, the Rowley Shoals is a reminder of beauty and value of healthy, well managed coral reefs.
But the in-water surveys and resulting footage confirmed the Rowley Shoals has experienced its worst bleaching event on record.
All parts of the reef and groups of corals were affected; most sites had between 10% and 30% of their corals bleached. Some sites had more than 60% bleaching and others less than 10%.
The heat stress also caused bleaching at Ashmore Reef, Scott Reef and some parts of the inshore Kimberley and Pilbara regions, all of which were badly affected during the 2016/17 global bleaching event.
This most recent event (2019/20) is significant because of the extent and duration of heat stress. It’s also notable because it occurred outside the extreme El Niño–Southern Oscillation phases – warming or cooling of the ocean’s surface that has damaged the northern and southern reefs in the past.
A reef crisis
The impacts from climate change are not restricted to WA or the Great Barrier Reef – a similar scenario is playing out on reefs around the world, including those already degraded by local pressures.
By global standards, WA still has healthy coral reefs. They provide a critical reminder of what reefs offer in terms of natural beauty, jobs and income from fisheries and tourism.
But we’ve spent two decades following the trajectories of some of WA’s most remote coral reefs. We’ve seen how climate change and coral bleaching can devastate entire reef systems, killing most corals and dramatically altering associated communities of plants and animals.
And we’ve seen the same reefs recover over just one or two decades, only to again be devastated by mass bleaching – this time with little chance of a full recovery in the future climate.
Reducing greenhouse gas emissions is the only way to alleviate these pressures. In the meantime, scientists will work to slow the rate of coral reef degradation though new collaborations, and innovative, rigorous approaches to reef management.
Western Australia boasts seemingly endless fields of pink, white and yellow everlasting daisies. But while there might seem to be an infinite number, one species in particular is actually endangered. The showy everlasting (or Schoenia filifolia subsp. subulifolia) once grew in the Mid West of WA. Now it is found in just a few spots around the tiny inland town of Mingenew.
But a WA primary school is helping my colleagues and me save the beautiful showy everlasting. With new seed banks, a genetic project and a whole lot of digging, we’re hopeful we can keep this gorgeous native daisy around for the next generation.
A grower and a shower
The first European to collect the showy everlasting was eminent botanist James Drummond, most likely in the mid-1800s. Initially the species was placed in the Helichrysum family (a group of plants also known as everlastings), but in 1992 botanist Paul Wilson formally described the species based on a specimen collected from Geraldton.
The genus name Schoenia is in honour of the 19th-century eye specialist and botanical illustrator Johannes Schoen, and the species name filifolia refers to its long, slender leaves.
Everlastings get their name from the fact that that the flowers hold their colour long after they have been picked and dried. The species is known as the showy everlasting because its large, brightly coloured flowers put on a spectacular show when in bloom.
The showy everlasting is an annual plant, growing around 30cm high, with long narrow leaves. Its bright yellow flowers bloom from August to October. The showy everlasting has two closely related sister species: the more common Schoenia filifolia subsp. filifolia, found throughout the WA Wheatbelt, and Schoenia filifolia subsp. arenicola, which grows around Carnarvon but hasn’t been collected for decades. The main differences between the showy everlasting and its sister species are the much larger flowers and the shape of the base of the flower, which is hemispherical rather than vase-shaped.
Collections of the showy everlasting housed in the Western Australian Herbarium indicate the species was once more widespread. It’s likely land clearing for farms and infrastructure led to the disappearance of the species from much of its known range.
It was listed as endangered in 2003. At that time the species was found in just three locations. At each of these sites, threats such as chemical drift from nearby agricultural land, grazing by animals, competition from weeds, and increasing soil salinity were all jeopardising the survival of the species.
Unfortunately, by the late 2000s two of these three populations had succumbed to these threats and were lost. However, continued search efforts since then have uncovered two new populations. The showy everlasting is hanging on, but a concerted conservation effort is needed to ensure its survival in the wild.
New populations needed
To ensure the long-term survival of the showy everlasting, we need to establish new populations – a process called translocation.
As an insurance policy, in 2007 seeds were collected and frozen in the Threatened Flora Seed Vault at the Western Australia Seed Centre. In 2015 my colleagues and I used some of these seeds in small-scale translocation trials, successfully getting new plants to grow, flower and seed in three small populations.
Despite this success, we knew the populations would need to be much, much larger and we would need many more populations to ensure persistence of the species. And for that we needed more information about the showy everlasting’s biology, and larger amounts of seed.
Currently a genetic study is underway to look at the difference between the showy everlasting in different locations and its sister species. As part of my PhD study with Murdoch University, I am running a glasshouse experiment to see whether different populations of the showy everlasting can cross and produce viable seed, and whether there are benefits or risks to such crosses.
The initial translocation trials have proved we can successfully establish new populations, but we’re currently limited by the amount of available seed. This is because our trials showed the most efficient way to establish the showy everlasting is by planting seeds directly into the ground. However, this process uses a lot of seeds – more than we have stored in the Seed Vault. Rather than denude the wild populations, we needed a new source.
Fortunately, at this time Andrew Crawford, manager of the Threatened Flora Seed Vault at the Western Australian Seed Centre, was approached by the principal of the Woodlupine Primary School, Trevor Phoebe. He was looking for a meaningful way to involve his students with plant conservation. This led to the establishment of a seed production area at the school which aims to grow and harvest seed of the showy everlasting. The students at the school are involved with planting, monitoring and taking care of the plants, and will help collect the seed when they ripen.
It is still early days for this project, however early signs are promising. Seedlings have established well and have begun flowering. Seed collection is planned for later in the year.
The seed harvested will be used in the future to boost plant numbers in the existing populations, and to establish new sites, hopefully securing this beautiful species in the wild so that everyone can enjoy the showy everlasting for decades to come.
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On a warm evening in early 1802, Robert Brown sat aboard the HMS Investigator describing several plant specimens collected that day. Brown was the botanist on Captain Matthew Flinders’ expedition, and they had been anchored in King George Sound for nearly a month documenting the remarkable flora of the area.
He keenly awaited the return of their gardener, Peter Good, who had left earlier in search of a curious “pitcher plant” discovered the previous morning by botanical artist Ferdinand Bauer and landscape artist William Westall.
Unbeknownst to him, in minutes he would be gazing upon a uniquely wondrous plant: Cephalotus follicularis, the Albany pitcher plant.
Named after the southwestern Australian port city around which it occurs, the Albany pitcher plant stands out as an oddity even by the standards of carnivorous plants. The species is instantly recognisable, as it produces distinctive insect-trapping pitcher leaves that sit on the ground almost expectantly waiting for prey.
The toothed mouth and overarching lid of these pitchers look superficially similar to those of the tropical pitcher plants (Nepenthes) and North American pitcher plants (Sarracenia). However, these plants are not related; this similarity is a remarkable example of convergent evolution. The Albany pitcher plant is unique.
C. follicularis is the only species in the genus Cephalotus, which is the only genus within the family Cephalotaceae. Its nearest living relatives are rainforest trees from tropical South America, from which it is separated by some 50 million years. Indeed, it is the only carnivorous plant among the 70,000 species, a quarter of all flowering plants, that make up one of the largest evolutionary plant groups, the rosid clade.
The Albany pitcher plant is more closely related to cabbages, roses and pumpkins than it is to other pitcher plants.
The Albany pitcher plant only grows in a very small area of Western Australia, and is thought to be an ancient Gondwanan relict from a period when this region was almost tropical. It grows in nutrient-poor soils of coastal swamps and lowlands, where it survives by luring insects into its traps to be digested in a pool of enzymes at the base of each pitcher. Each pitcher bears a lid to prevent rain from diluting the pool of enzymes, with translucent windows to disorient trapped prey and prevent escape.
Interestingly, one species of insect not only survives inside the fluid of the pitchers, but relies on it for survival. The wingless stilt fly Badisis ambulans lays its eggs in the pitchers, and the larvae develop in the pool of pitcher fluid, feeding on captured prey.
These stilt flies live only in the dense vegetation of the swamps inhabited by the Albany pitcher plant. They look more like an ant than a fly, which is probably a deliberate mimicry of the ant Iridomyrmex conifer, the primary prey of the pitcher plant. It is likely that these three species – plant, fly and ant – have co-evolved together over millions of years.
The Albany pitcher plant was probably widespread in the southwest corner of WA before European settlement, and almost 150 populations have been recorded throughout this region. However, the species has declined dramatically over the past century as extensive land has been cleared throughout the southwest for agriculture and urban development.
The Albany pitcher plant now occurs only as small, isolated populations in remnant habitat patches. It is thought that less than 3,000 hectares of habitat suitable for the species now remains in the greater Albany region. Recent survey efforts suggest that fewer than 20 populations of the Albany pitcher plant still exist, and fewer than 5,000 plants remain.
Despite the perilous state of the Albany pitcher plant, it still has no formal conservation status. Indeed, swamps containing the species have been bulldozed for housing development in the past 12 months. But habitat loss and changes to bushfire frequency and water flow are not the only threats to this amazing species. Current projections of a drying climate in the southwest of Western Australia may see the species pushed towards extinction in the coming decades.
Incredibly, the Albany pitcher plant is also at risk from poaching. The species is prized for its horticultural novelty, and unscrupulous individuals dig up plants from the wild either to grow or sell. At one accessible location where the species was known to grow in abundance, every single plant within reach has been removed. At other sites, entire populations have been dug up.
Without improved conservation measures, and tough penalties for removing this incredible species from its natural habitat, the Albany pitcher plant and its complex web of insect relationships face a potentially dire future.
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When you are in the northern part of Western Australia, one of nature’s joys is seeing a large boab tree close up, perhaps for the first time.
The boab (Adansonia gregorii) is a native to this part of Australia, but is related to the broader group of species called boababs that live in Madagascar and Africa – but more on that connection later.
Boabs are also called bottle trees, the tree of life, boababs and Australian boababs. Some of the indigenous Australian names include gadawon and larrgadi.
From their iconic swollen trunks, to living up to 2,000 years and the many uses for their “superfood” fruits, here’s what makes boab trees so fascinating.
The ‘upside-down tree’: trunks that save lives and lock up prisoners
While the boab in Australia is not quite as well-documented as the African species, specimens have been recorded at over 1,000 years of age. Some living trees have been estimated to be nearer to 2,000 years old.
And while it’s difficult to age the trees, several specimens of the African species have been dated at 2,000 or more years old.
Australian boabs can grow up to 15 metres tall at maturity and have swollen, attention-grabbing trunks called a caudex, which may be up to five metres in diameter.
The African boab species, A. digitata, can be much taller, at 25 metres high and with a diameter of up to 15 metres.
In such dry continents, the caudex is a life-saver, often containing water, which was tapped by Indigenous folk. It has been estimated that some of these huge old trees can hold more than 100,000 litres of water in their trunks.
In Africa, these massive trunks have been used as shelters, homes, farm sheds and, more recently, even shops and bars.
Sadly in Australia, legend has it the huge trunks were used to make lock-ups for Indigenous people and other prisoners.
It’s not just the trunk that can stop you in your tracks. The boab has a unique branching structure, one that looks more like a root system than a canopy.
Some locals in Africa will tell you the tree was dropped from heaven to earth and landed upside down. So the African species of boab is sometimes called the upside-down tree.
Boab fruits are ‘superfoods’ and its shell has many uses
A. gregorii, the Australian boab species, has large, attractive white flowers up to 75 millimetres in length. Its round fruits are edible and sought after by birds, mammals and humans. The fruit gives rise to some of the common names for the tree, such as monkey bread tree and dead rat tree. The latter comes from the appearance of older fruits in the canopy looking a bit like … well, dead rats?
In fact, there’s great interest in fruits from the African species, A. digitata, which are considered a “superfood” because of their high levels of antioxidants, calcium, potassium, magnesium, fibre and vitamin C. It’s assumed many of these traits will be shared by the Australian boab, but there is little research as yet to prove it.
The soft part of the fruit is surrounded by a hard, coconut-like shell that’s initially covered in a velvety fur. The hard shell has been used for cups and bowls, but has also been intricately carved and decorated by Aboriginal artists in Africa and Australia. If the seeds are left inside the fruit as it dries, they can be used for toys like rattles.
On both continents, Aboriginal people have eaten the white powder that surrounds the seeds. The leaves are rich in iron and the pulp from the fruits tastes like cream of tartar.
The Indigenous people of both continents were also well aware of the medicinal uses of the fruits. The bark and leaves of the trees also treat various ailments, but particularly those associated with digestive disorders.
But at present there is very little modern research on the medicinal and dietary aspects of either the baobab or boab.
How the boab tree got to Australia
One of the mysteries surrounding the boab is how it got to Australia – the Australian species has clear affinities with related species in continental Africa and Madagascar.
There are three intriguing theories.
The first is that all of the boababs originate from the super-continent Gondwana – consisting of Africa, South America, Antarctica, Australia, India and Madagascar – before it fragmented almost 80 million years ago. But A. Gregorii and A. digitata are so similar genetically that, given the millions of years that have elapsed, this theory is now in question.
The second theory comes from recent DNA analysis of the species. It suggests they separated more recently, perhaps only 70,000 years ago, which raises the question, were humans involved in their journey? But did they come to Australia from Africa, or from Australia to Africa? The latter is a less likely scenario given the direction of ocean currents.
And the third theory is that fruits arrived on the Australian shore after an epic ocean voyage from Africa.
Boabs are usually found in the remote outback of Australia, but in 2008, a large 750-year-old boab was transported from Warmun in the Kimberley to Perth and transplanted in Kings Park.
Transplanting such a large tree is both daunting and fraught, with a high chance of failure, but the deciduousness and growth habit of the boab gave some cause for optimism about a successful outcome. For the reward of having a large old boab growing in Perth, it would be worth it.
After a period of stress, the tree appears to be coming good, reflecting the toughness of the species.
A large, mature boab is a splendid tree of arid Australia that inspires awe in all who experience them close up. They really are a beauty and a bottler of a tree!
When a threatened species is found only in one small area, conservationists often move some individuals to another suitable habitat. This practice, called “translocation”, makes the whole species less vulnerable to threats.
In the past, this approach has worked really well for some species, but climate change is creating new problems. Will the climate change at that location in the future, and will it remain suitable for the species of interest? On the other hand, some regions might become appropriate for a threatened species.
This fundamental question is important in a rapidly changing climate, yet it has seldom featured when picking new areas for translocations.
Saving the western ground parrot
Our recent research applied climate change modelling to translocation decisions for the critically endangered western ground parrot. This species is now restricted to a single population, with probably fewer than 150 birds, on the south coast of Western Australia.
It is enigmatic, in that it lives and nests entirely on the ground, unlike almost all other parrots except the closely related night parrot. And it is one of the many unique animals that make Australia so distinctive from all other parts of the world. But living on the ground has its drawbacks, as the parrot is very vulnerable to foxes and cats.
Its home near the south coast is particularly vulnerable to the effects of climate change. As southwestern Australia becomes warmer and drier, the risk of fire to the parrot increases.
Understanding potential climate change impacts is essential when selecting reintroduction sites. We developed high-precision species distribution models and used these to investigate the effect of climate change on current and historical distributions, and identify locations that will remain, or become, suitable habitat in the future.
Our findings predict that some of the western ground parrot’s former south coast range will become increasingly unsuitable in the future, so reintroductions there may not be a good idea. Four out of 13 potential release sites are likely to become inhospitable to these threatened birds.
On the other hand, many of the former or future sites are likely to become important refuge habitats as the climate continues to warm, and would make an excellent choice for any translocations or reintroductions.
We have given this information to an expert panel, who will use these predictions identify and prioritise areas for management and translocation.
The parrot in the coal mine
Fire is already a significant threat which, combined with predation by feral cats, may have led to the loss of this species from its former home at Fitzgerald River National Park. Many of these threats act together, so they must all be considered and managed alongside climate change.
What’s more, the western ground parrot may be an important indicator for the fate of many other species it currently (or formerly) shares its range with. These include the western whipbird, noisy scrub-bird, and a carnivorous marsupial, the dibbler.
These species are all likely to face the same threats and may be equally affected by the changing climate. Future studies will attempt to model these species and to assess whether all will benefit from similar management.
Many challenges remain for the western ground parrot, including the possible negative genetic impacts of the current small population size, and the increasing risk of damaging fires in a drying and warming climate.
But locating “future-proofed” sites is giving us some hope we can ensure the long term persistence of this enigmatic species, and the myriad other unusual species that occur in the biodiversity hotspot of southwestern Australia.
The authors would like to thank Allan Burbidge and Sarah Comer from the WA Department of Biodiversity Conservation and Attractions for their invaluable help and guidance in putting together this article.
Diving on the remote coral reefs in the north of Western Australia during the world’s worst bleaching event in 2016, the first thing I noticed was the heat. It was like diving into a warm bath, with surface temperatures of 34⁰C.
Then I noticed the expanse of bleached colonies. Their bright white skeletons were visible through the translucent tissue following the loss of the algae with which they share a biological relationship. The coral skeletons had not yet eroded and collapsed, a grim reminder of what it looked like just a few months before.
I spent the past 15 years documenting the recovery of these reefs following the first global coral bleaching event in 1998, only to see them devastated again in the third global bleaching event in 2016.
The WA coral reefs may not be as well known as the Great Barrier Reef, but they’re just as large and diverse. And they too have been affected by cyclones and coral bleaching. Our recent study found many WA reefs now have the lowest coral cover on record.
When my colleague, Rebecca Green, witnessed that mass bleaching for the first time, she asked me how long it would take the reefs to recover.
The worst mass bleaching on record
A similar scene is playing out around the world as researchers document the decline of ecosystems they have spent a lifetime studying.
Our study, published in the journal Coral Reefs, is the first to establish a long-term history of changes in coral cover across eight reef systems, and to document the effects of the 2016 mass bleaching event at 401 sites across WA.
Given the vast expanse of WA coral reefs, our assessment included data from several monitoring programs and researchers from 19 institutions.
These reefs exist in some of the most remote and inaccessible parts of the
world, so our study also relied on important observations of coral bleaching from regional managers, tourist operators and Bardi Jawi Indigenous Rangers in the Kimberley.
Our aim was to establish the effects of climate change on coral reefs along Western Australia’s vast coastline and their current condition.
The heat stress in 2016 was the worst on record, causing mass bleaching and large reductions in coral cover at Christmas Island, Ashmore Reef and Scott Reef. This was also the first time mass bleaching was recorded in the southern parts of the inshore Kimberley region, including in the long oral history of Indigenous Australians who have managed this sea-country for thousands of years.
The mass bleaching events we documented were triggered by a global increase in temperature of 1⁰C above pre-industrial levels, whereas temperatures are predicted to rise by 1.5⁰C between 2030 and 2052.
In that scenario, the reefs that have bleached badly will unlikely have the capacity to fully recover, and mass bleaching will occur at the reefs that have so far escaped the worst impacts.
The future of WA’s coral reefs is uncertain, but until carbon emissions can be reduced, coral bleaching will continue to increase.
Surviving coral reef refuges must be protected
The extreme El Niño conditions in 2016 severely affected the northern reefs, and a similar pattern was seen in the long-term records.
The more southern reefs were affected by extreme La Niña conditions – most significantly by a heatwave in 2011 that caused coral bleaching, impacted fisheries and devastated other marine and terrestrial ecosystems.
Since 2010, all of WA’s reefs systems have bleached at least once.
Frequent bleaching and cyclone damage have stalled the recovery of reefs at Shark Bay, Ningaloo and at the Montebello and Barrow Islands. And coral cover at Scott Reef, Ashmore Reef and at Christmas Island is low following the 2016 mass bleaching.
In fact, average coral cover at most (75%) reef systems is at or near the lowest on record. But not all WA reefs have been affected equally.
In 2016 there was little (around 10%) bleaching recorded at the northern inshore Kimberley Reefs, at the Cocos Keeling Islands, and at the Rowley Shoals. Coral cover and diversity at these reefs remain high.
And during mass bleaching there were patches of reef that were less affected by heat stress.
These patches of reef will hopefully escape the worst impacts and retain moderate coral cover and diversity as the world warms, acting as refuges. There are also corals that have adapted to survive in parts of the reef where temperatures are naturally hotter.
Some reefs across WA will persist, thanks to these refuges from heat stress, their ability to adapt and to expand their range. These refuges must be protected from any additional stress, such as poor water quality and overfishing.
In any case, the longer it takes to curb carbon emissions and other pressures to coral reefs, the greater the loss will be.
Coral reefs support critical food stocks for fisheries around the world and provide a significant contribution to Australia’s Blue Economy, worth an estimated A$68.1 billion.
We are handing environmental uncertainty to the next generation of scientists, and we must better articulate to everyone that their dependence on nature is the most fundamental of all the scientific concepts we explore.