Five ways to reduce waste (and save money) on your home renovation



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Sensible design can dramatically reduce waste of a renovation.
Photo by Nolan Issac on Unsplash, CC BY-SA

Deepika Mathur, Charles Darwin University

On average, renovating a home generates far more waste than building a new one from scratch.

This waste goes straight to landfill, damaging the environment. It also hurts your budget: first you have to pay for demolition, then the new materials, and then disposal of leftover building products.

By keeping waste in mind from the start and following some simple guidelines, you can reduce the waste created by your home renovation.




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1. It starts with the design

Waste is often treated as inevitable, factored into a building budget with no serious attempt to reduce it.

By raising the issue early with your architect, designer or builder, they can make decisions at the design stage that reduce waste later. Often the designers and architects don’t see their decisions contributing to waste – or rather, they don’t really think about it.

During my research on reducing construction waste, I asked one architect what he thought happens to the waste generated. He laughed with a glint in his eyes and said, “I think it disappears into pixie dust!”

One simple early decision that dramatically reduces waste is designing with material sizes in mind. If you have a ceiling height that does not match the plasterboard sheet, you end up with a tiny little strip that has to be cut out of a full sheet. In the case of bricks, not matching the ceiling height is even more wasteful.

Obviously not all materials will work together at their standard sizes (and you need to fit your renovation to the existing house). But sensitive design can make intelligent trade-offs, reducing overall waste.

When I asked architects why they don’t design zero-waste buildings more often, they said clients don’t ask for it. Make it part of your brief, and ask the architect how they can save money by using the materials efficiently.

2. Get your builder involved early

If you’re using an architect for your renovation, it’s common to have very little collaboration between them and the builder. Any errors or issues are usually spotted after construction has begun, requiring expensive and wasteful rework.

Instead, ask your architect and builder to collaborate on a waste management plan. Such integrated approaches have worked well in Australia and the United States.

This means clients, engineers and builders are collaborating, rather than taking adversarial roles. For such contracts to work, it’s important to involve all parties early in the project, and to encourage cooperation.

The briefing stage is an opportunity for architects, quantity surveyors and builders to work together to identify a waste minimisation target.

3. Whatever you do, don’t change your mind

One the biggest contributions to waste on sites is late design changes. Client-led design changes are identified in all literature as having far-reaching implications on waste.

These are mostly due to owners changing their mind once something is built. Reworking any part of a building due to design changes can account for as much as 50% of the cost overrun, as well as causing delays and generating waste.

The early work with your design and construction team outlined in the first steps gives you the chance to make sure you’re committed to your original design. Skimping in the planning stage can end up costing you far more in the long run.

4. Deconstruction, not demolition

Ask your builder not to demolish the building, but to deconstruct it. Deconstruction means taking a building apart and recovering materials for recycling and reuse. This provides opportunities for sorting materials on site.

Salvaged materials can be resold to the community or reused in the renovations. It greatly reduces the tip fees which are usually higher for mixed waste (typical from demolition process) and lower for sorted waste.

Of course this takes more time and has an additional cost. Therefore you do have to balance the cost of deconstruction against the savings.

Denmark, which recycles 86% of its construction waste, has made it mandatory for all government buildings to undergo selective demolition and sorting of construction waste. A good place to start in Australia is your state environment department, which may have guidelines on what is involved.

5. Choose materials carefully

Good-quality materials last longer, reducing maintenance later. Choosing manufacturers that use minimal packaging also reduces waste (be careful here to check the difference between “minimal” and “inadequate” packaging, as the latter can mean your material breaks).

Reusing materials from your renovation may also be an option (you will need to discuss this with architect and builder at the beginning of the project). Finally, using materials with recycled content is a great option, and boosts our recycling industry.




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The return of the breeze block


In March 2017 the Housing Industry Association released data suggesting the Australian residential building industry will increasingly become more dependent on renovation work rather than new construction,

If you’re renovating your home, making efficiency and low waste a priority helps cut costs and reduce landfill.The Conversation

Deepika Mathur, Researcher in sustainable architecture, Charles Darwin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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‘The worst kind of pain you can imagine’ – what it’s like to be stung by a stinging tree



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Even the slightest touch of a D. moroides leaf can cause excruciating pain. An intense stinging, burning pain is felt immediately, then intensifies, reaching a peak after 20 – 30 minutes.
Marina Hurley, Author provided, Author provided

Marina Hurley, UNSW

Sign up to the Beating Around the Bush newsletter here, and suggest a plant we should cover at batb@theconversation.edu.au.


Stinging trees grow in rainforests throughout Queensland and northern NSW. The most commonly known (and most painful) species is Dendrocnide moroides (Family Urticaceae), first named “gympie bush” by gold miners near the town of Gympie in the 1860s.

My first sting was from a different species Dendrocnide photinophylla (the shiny-leaf stinging tree). It was like being stung by 30 wasps at once but not as painful as being stung by D. moroides, which I once described as the worst kind of pain you can imagine – like being burnt with hot acid and electrocuted at the same time.

An excerpt from a French documentary ‘Plant Secrets’ by director François-Xavier Vives.

I agreed to study stinging trees even after being badly stung. The puzzle was – what was eating the stinging tree? Stinging trees often have huge holes but no-one knew what was eating them. What could possibly eat the leaves that were so painful to touch? (Read to the end to discover the answer).

My first sting was from a different species Dendrocnide photinophylla (the shiny-leaf stinging tree)
Marina Hurley, Author provided



Read more:
Grass trees aren’t a grass (and they’re not trees)


Stinging trees grow in light-filled gaps in the rainforest understorey and come in many different shapes, sizes and species (seven in Australia).

Dendrocnide moroides
Marina Hurley, Author provided

I studied two species for my PhD, Dendrocnide moroides and Dendrocnide cordifolia which is often mistaken for Dendrocnide moroides. Both species are shrubs that grow to three metres with heart-shaped, serrated-edged, dark-green leaves that can grow from the size of a thumbnail to over 50 cm wide.

The sting is caused by stinging hairs that contain toxin and densely cover the leaves, stems and fruit. The thick covering of the hairs makes the leaves look as though they are covered with soft, downy, fur and may give the impression they are inviting to touch.

The fruit of D. moroides is similar to a bright red-dark purple raspberry with long stems, while the fruit of D. cordifolia is always green with short stems that give the fruit a clumped appearance.

The fruit and leaves of Dendrocnide cordifolia.
© Marina Hurley

What it’s like to be stung

Even the slightest touch of a D. moroides leaf can cause excruciating pain. An intense stinging, burning pain is felt immediately, then intensifies, reaching a peak after 20 – 30 minutes.

The hairs can remain in the skin for up to six months, with stings recurring if the skin is pressed hard or washed with hot or cold water.

Not only do you feel pain from where you are stung, if it is a really bad sting, within about 20 minutes your lymph nodes under your arms swell and throb painfully and feel like they are being slammed between two blocks of wood.

The intense throbbing pain from both the sting and from your lymph nodes can last anywhere from 1-4 hours, depending upon what species you touched, the amount of skin that was stung, and how hard you came into contact with the plant.

How it works

The stinging hair structure is complex and consists of a tip, shaft and bulb composed of silica, calcium carbonate and calcium phosphate.

The tip of the hair is a small bulb that breaks off on contact, then the hair penetrates the skin injecting toxin. The structure and function of Dendrocnide stinging hairs is similar across five plant families and is described as similar to a hypodermic needle.

The composition of the toxin is also complex and still not well understood, including exactly what components actually cause the stinging sensation.

The toxin is stable and heat resistant and retains its pain-producing properties for decades. Dried botanical specimens collected over 100 years ago, can still sting you.

An electron micrograph of stinging hairs.
© Marina Hurley



Read more:
Welcome to Beating Around the Bush, wherein we yell about plants


Sting stories

My worst sting was from a dead, dried-up leaf on the forest floor. I dropped my glove and then drove my finger through the leaf when I went to pick it up. As I was alone at the time, I had to drive to the hospital with one hand.

During my research in the late 80s-early 90s, I heard dozens of stories about people getting badly stung including a letter from an ex-serviceman, Cyril Bromley, who said he was stung after falling into a stinging tree while crossing a creek near the Barron River (North Queensland) in 1941. He said the pain was so bad they had to tie him to his hospital bed for three weeks. He also recounted how an officer had shot himself because he could not stand the pain.

The less well-known and very disturbing thing about stinging trees is they cause intense sneezing, nose bleeds, and possibly major respiratory damage, if you stay close to them for more than about 20 minutes without protection.

The reaction starts with your nose tingling, then dripping continuously. After a short period, you start to sneeze – not just mild sneezing but intense, harsh and continuous bouts of sneezing.

Marina Hurley wore a particle face mask and welding gloves when working with stinging trees.
© Marina Hurley

This happened to me and my field assistants when in close proximity to the plant, either in the rainforest or in the laboratory. Wearing particle face masks helps but they need to be regularly replaced. I believe that this reaction is caused by breathing in the hairs that become air-borne but I have never been able to substantiate this.

Researcher W.V. MacFarlane described his reaction in detail when working with hairs and leaves of D. moroides:

Mucous membranes are affected by dust or spray from the leaves… Initially they produced sneezing, but within three hours there was diffuse nasopharyngeal pain, and after 26 hours a sensation of an acute sore throat… aching sensations in the sinuses occurred… and a watery nasal discharge that persists for two days. The nasal mucous membranes then begin to slough together with blood, pus and inspissated (thickened) mucus… and discharge of sloughing tissue for 10 days.

Dozens of these nocturnal beetles (Prasyptera mastersi) were found eating the leaves.
© Marina Hurley

The mystery solved

I found out what was eating them: a nocturnal leaf-eating chrysomelid beetle and many other leaf-chewing insects and sap-suckers.

Also, surprisingly, both species of stinging tree were voraciously eaten by the red-legged pademelons that occasionally stripped entire plants of their leaves overnight.

A red-legged pademelon. These tough guys eat stinging leaves.
Shutterstock

Meanwhile, if you are out and about in the rainforest, stay on the designated paths, and wear closed shoes and long pants.The Conversation

Marina Hurley, Visiting Fellow, Lecturer & Consultant (Writing Clear Science), UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Trust Me, I’m An Expert: Australia’s extreme weather



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Australia’s cyclone season lies ahead.
NASA / ESRSU / Seán Doran, CC BY-NC-SA

Madeleine De Gabriele, The Conversation and Wes Mountain, The Conversation

It’s easy to write off Australia’s extreme weather as business as usual. We deal with floods, droughts, cyclones and other wild events every year. But as climate change raises global temperatures, are the droughts happening more often? Are the floods getting worse?

The October episode of Trust Me, I’m An Expert looks back through colonial evidence and prehistoric records, and forward to the Bureau of Meteorology’s Cyclone Weather Outlook for the year ahead.

The full episode will be released on October 8, but today you can catch a little of our interview with the Bureau of Meteorology’s Andrew Watkins. Keep an eye out for the full episode, where we ask: are we in uncharted territory, or is this life as usual on a changeable continent?




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Trust Me I’m An Expert is a monthly podcast from The Conversation, where we bring you stories, ideas and insights from the world of academic research.

You can download previous episodes of Trust Me here. And please do check out other podcasts from The Conversation – including The Conversation US’ Heat and Light, about 1968 in the US, and The Anthill from The Conversation UK, as well as Media Files, a brand new podcast all about the media.

You can find all our podcasts over here.

Music:




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The Conversation


Madeleine De Gabriele, Deputy Editor: Energy + Environment, The Conversation and Wes Mountain, Deputy Multimedia Editor, The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The planned national waste policy won’t deliver a truly circular economy



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The proposed policy doesn’t quite fit all the pieces together.
Shutterstock.com

Jenni Downes, University of Technology Sydney

Australia’s government has announced new planned waste recycling targets, as part of its response to the crisis prompted by China’s decision to crack down on recycling imports earlier this year.

The wider goal of Australia’s plan to update the National Waste Policy is to embrace circular economy principles.

That process is now in train. Following engagement with industry and government working groups, a proposed update to the policy is now open for public comment.

So how well does the proposed new policy incorporate circular economy principles? The short answer is, not well enough.




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Explainer: what is the circular economy?


A circular economy is centred on keeping products, components and materials circulating in use for as long as possible, through long-lasting design, repair, reuse, re-manufacturing and recycling. The ultimate aim is to minimise the amount of resources consumed, and waste generated, by our economic activities.

The proposed principles, targets and strategies are a good start. They will help tackle a range of issues, including:

  • dealing with China’s recycling imports crackdown by improving local capacity
  • increasing the currently limited responsibility for products at end of life
  • focusing on organic waste (such as food and textiles), one of the major obstacles to current recovery rates
  • reducing litter and marine plastic debris
  • harmonising the various disparate state policies.
Synthesis of proposed National Waste Policy.
UTS Institute for Sustainable futures adapted from Department of Environment and Energy

Yet these proposals, while all crucial, represent only a moderate evolution from our current situation, rather than the revolution needed to truly embrace the circular economy.

The policy’s major focus is still on recycling and recovery, and while recycling is certainly a “circular” activity, the circular economy involves so much more than simply improving how we reclaim and reprocess unwanted materials.

A truly circular society aims to transform our whole system of production and consumption, with innovative approaches like “products as services” (through leasing or collaborative consumption) and designing for next life and new life (through repairability, modularity and disassembly).

Linear, recycling and circular economies.
Adapted by ISF from Netherlands Government-wide Programme for a Circular Economy

Global changes, local opportunities

The proposed policy misses the opportunity to focus on innovation and create a step change in not only the resource recovery industry, but our whole economy and broader society.

The public arguably has more awareness of this issue than ever before, thanks to the continuing emergence of sustainability as a concept, combined with China’s shock to our recycling industry and the media focus afforded by campaigns such as the ABC’s War on Waste documentary series.

Public awareness and expectation is one thing, but to deliver on these goals the national waste policy must strengthen the explicit adoption of circular economy principles and significantly increase support to transition towards it.

This includes such things as:

  • appointment of a Commissioner for Circular Economy
  • explicit targets for reuse, repair, reassembly and remanufacture
  • “Circular” procurement of goods and infrastructure
  • support for innovation in business models for circular economy
  • standards for imports, not just local production
  • federal tax incentives, funding, and research and development to enable all of the above.

Australia has a unique opportunity to lay the building blocks for the type of economy and society we want. Let’s hope we can get it right.The Conversation

Jenni Downes, Senior Research Consultant, Institute for Sustainable Futures, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

We must strengthen, not weaken, environmental protections during drought – or face irreversible loss



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The Flock Bronzewing is an inland species that is vulnerable to drought. Those vulnerabilities are heightened in an era of climate change and increased risks from feral predators.
Shutterstock

John Woinarski, Charles Darwin University; Chris Dickman, University of Sydney; Richard Kingsford, UNSW, and Sarah Legge, Australian National University

Australian rural communities face hardships during extended drought, and it is generally appropriate that governments then provide special support for affected landholders and communities.

However, some politicians and commentators have recently claimed that such circumstances should be addressed by circumventing environmental laws or management – by, for example, reallocating environmental water to grow fodder or opening up conservation reserves for livestock grazing.

But subverting or weakening existing protective conservation management practices and policies will exacerbate the impacts of drought on natural environments and biodiversity.




Read more:
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Drought-related decline in wildlife

Impacts of severe weather on some natural systems are obvious and well-recognised. For example, during periods of elevated sea temperature, coral bleaching may conspicuously signal extensive environmental degradation and biodiversity loss.

On land, however, the impacts of comparable extreme climatic events on natural systems may be less obvious, even if of comparable magnitude.

Nonetheless, the record is clear: drought leads to extensive and severe declines in many wildlife species.

Early observers in Australia reported the collapse of bird communities (“the bush fell silent”) and other wildlife across vast areas during the Federation Drought.

There were comparable responses during the Millennium Drought.

Unsurprisingly, wetland environments, and species dependent on them, may bear the brunt of impacts. That said, impacts are pervasive across all landscapes exposed to drought.

Drought contributed to the extinction of one of Australia’s most beautiful birds, the Paradise Parrot. For example, the pastoralist and zoologist Charles Barnard noted:

Previous to the terrible drought of 1902 it was not uncommon to see a pair of these birds when out mustering … but since that year not a single specimen has been seen … For three years… there had been no wet season, and very little grass grew, consequently there was little seed; then the worst year came on, in which no grass grew, so that the birds could not find a living, and … perished … they have not found their way back.

Drought contributed to the extinction of one of Australia’s most beautiful birds, the Paradise Parrot.
Wikimedia, CC BY

After the long droughts break, native plant and animal species may take many years to recover, and some never recover or return to their former range.

Threatened plant and animal species – with an already tenuous toe-hold on existence – are often the most affected.

Days of extremely hot temperatures also exceed the thermoregulatory tolerance of some species. That means mass mortality for some animals; and large numbers of even hardy native trees may be killed by heat and lack of rain across extensive areas.

Furthermore, water sources can disappear from much of the landscape. Organisms dependent on floods are now more vulnerable, given that overallocation of water from rivers has increased drying of wetlands.

Drought is not new in Australia, but the stresses are greater now

Of course, drought has long been a recurrent characteristic of Australia. Indeed, many Australian plants and animals are among the most drought-adapted and resilient in the world. But drought impacts on wildlife are now likely to be of unprecedented severity and duration, for several reasons:

  1. with global climate change, droughts will be more severe and frequent. There will be less opportunity for wildlife to recover in the reduced interval between drought periods

  2. feral cats and introduced foxes now occur across most of Australia. In drought periods, these hunt more effectively because drought reduces the ground-layer vegetation that many native prey species rely upon for shelter. Cats and foxes also congregate and hunt more efficiently as wildlife cluster around the few water sources that are left

  3. prior to European settlement, the reduction in vegetation during drought would have been accompanied by natural feedback loops, notably reduction in the density of native herbivores. Now, livestock are often maintained in drought-affected areas, with supplementary food provided, but they also graze on what little native vegetation remains. Now, wildlife must compete with feral goats, camels and rabbits for the last vestiges of vegetation

  4. clearing of native vegetation across much of the eastern rangelands means it will now be much harder for species lost from some areas during drought to recolonise their former haunts after drought. The habitat connectivity has been lost

  5. many wildlife species could previously endure drought by maintaining a residue of their population in small refuge areas, where nutrients or moisture persisted in an otherwise hostile landscape. Now, livestock, feral herbivores and predators also congregate at these areas, making them less effective as native wildlife refuges

  6. in at least woodland and forest habitats, droughts may interact with other factors. Notably, drought increases the likelihood of high intensity and extensive bushfires that can cause long-lasting damage to wildlife and environments.




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Our intention here is not to downplay the needs or plight of rural communities affected by drought.

Rather, we seek to bring attention to the other life struggling in that landscape. Australia should bolster, not diminish, conservation efforts during drought times. If we don’t, we will suffer irretrievable losses to our nature.The Conversation

John Woinarski, Professor (conservation biology), Charles Darwin University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Richard Kingsford, Professor, School of Biological, Earth and Environmental Sciences, UNSW, and Sarah Legge, Associate Professor, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How did the fish cross the road? Our invention helps them get to the other side of a culvert



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When a stream enters a culvert, the flow can be concentrated so much that water flows incredibly fast. So fast, in fact, that small and juvenile fish are unable to swim against the flow and are prevented from reaching where they need to go to eat, reproduce or find safety.
Shutterstock

Jabin Watson, The University of Queensland; Craig E. Franklin, The University of Queensland; Harriet Goodrich, University of Exeter; Jaana Dielenberg, The University of Queensland, and Rebecca L. Cramp, The University of Queensland

Fish need to move to find food, escape predators and reach suitable habitat for reproduction. Too often, however, human activities get in the way. Dams, weirs and culverts (the tunnels and drains often found under roads) can create barriers that fragment habitats, isolating fish populations.

An Australian innovation, however, promises to help dwindling fish populations in Australia and worldwide. Our solution, recently described in Ecological Engineering, tackles one of the greatest impediments to fish migration in Australia: culverts.

A culvert crisis in our waterways

Freshwater ecosystems are one of the most heavily impacted by human activities.

Many freshwater species, such as the iconic barramundi, start their life as larvae in estuaries, then as small juveniles they make mammoth upstream migrations to freshwater habitats. In fact, about half of the freshwater fish species in southeast Australia need to migrate as part of their life cycle.

When fish are unable to pass human-made barriers, the decline in populations can be huge. For example, in the Murray-Darling Basin where there are thousands of barriers and flows are highly regulated, fish numbers are estimated to be at only 10% of pre-European numbers.

In New South Wales alone, there are more than 4,000 human-made barriers to fish passage. Over half of these are culverts. Culverts are most often installed to allow roads to cross waterways. They are designed to move water under the road, which they do quite efficiently, but often with no consideration of the requirements of the animals that live there.

When a stream enters a culvert, the flow can be concentrated so much that water flows incredibly fast. So fast, in fact, that small and juvenile fish are unable to swim against the flow and are prevented from reaching where they need to go to eat, reproduce or find safety.

A map of human-made barriers to fish passage in NSW. Image: Fisheries NSW.

Many current design ‘fixes’ come with problems

The problem culverts pose for fish is now well acknowledged by fisheries managers, and as a result efforts to make culverts fish-friendly are now widespread.

Where space allows, these new fish passage solutions can resemble a natural stream, where rocks of various sizes are added to break up the flow. Alternatively, artificial baffles (barriers to break up and slow the flow) are also commonly attached to the walls of the tunnel.

These designs do have some drawbacks. They may suit some fish sizes and species, but not all. They can be expensive to install. They also tend to catch debris, which increases maintenance costs and the risk of flooding upstream during high flow events.

A box culvert running under a road.
Shutterstock

Using physics to find a new solution

We took a new approach that harnesses a property of fluid mechanics that scientists call the “boundary layer”. When a fluid moves over a solid surface, friction causes the water to slow down next to the surface. This thin layer of slower-moving water is called the boundary layer.

Where two surfaces meet, such as in the corner of a square culvert, the boundary layers of the bed and wall merge. This creates a small area of slower-moving water – the “reduced velocity zone” – right in the corner. This is quite small, but little fish can still use it and are very good at finding it.

We wanted to expand this zone (to accommodate a wider range of fish sizes) and slow the water in it further.

So, we added a third surface, generating three boundary layers that then joined. This was done by adding a square beam running the length of the channel wall, close to the floor. The boundary layers of the floor, wall and bottom surface of the beam merged to create a reduced velocity channel along the side of the main flow.

In this GIF to the right hand side, the reduced velocity zone is revealed by adding a fluorescent dye, which lingers in the slower flowing water under the square beam we added to the channel.

Testing our design in a 12 metre channel (or flume) found that water velocity in the zone below the beam was slowed by up to 30%. For small fish, this is a huge reduction.

In tests, we focused on small-bodied species, or juveniles of larger growing species, because these are considered the weakest swimming size class and most vulnerable to high water velocities created within culverts. Every species tested saw significant improvements in their ability to swim and traverse up the channel.

All of the species benefited, regardless of their body shape or swimming style.

The GIF on the right hand side here shows a juvenile Murray cod swimming upstream using the reduced velocity zone we created by adding the beam.

Creating a slower-flowing zone

Our novel fish passage design is highly effective, yet very simple. It’s a square beam installed along the length of a culvert wall, so it’s easy to incorporate into new structures and cheap to retrofit into existing culverts.

It is also much less likely to trap debris than baffles or rocks embedded in the floor of a culvert.

This is a totally new approach that has the potential for widespread application, helping to restore the connectivity of freshwater fish populations here in Australia, and overseas.

A Crimson-spotted rainbowfish navigates the fast flow by swimming under the beam we added to channel.
Harriet Goodrich, Author provided
You can see the beam more clearly here. A Crimson-spotted rainbowfish swims under the beam we added to slow the water flow in that area.
Harriet Goodrich, Author provided

More research lies ahead. We’re hoping that by optimising the dimensions of the beam we can get even more fish through the channels, with even greater ease. We’re also planning field testing to check our laboratory findings work in the real world.

Freshwater biodiversity is greatest in the tropics. Here, developing countries are having drastic impacts on their freshwater ecosystems. The simplicity of this design may make it an affordable approach to help maintain and restore habitat connectivity in developing regions.

Matthew Gordos from NSW Fisheries contributed to this article.The Conversation

Jabin Watson, Postdoctoral researcher, The University of Queensland; Craig E. Franklin, Professor in Zoology, The University of Queensland; Harriet Goodrich, PhD student, University of Exeter; Jaana Dielenberg, Science Communication Manager, The University of Queensland, and Rebecca L. Cramp, Senior Research Fellow, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Grass trees aren’t a grass (and they’re not trees)



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Xanthorrhoea have no real trunk – just tightly packed leaves.
CC BY-SA

John Patykowski, Deakin University

Sign up to the Beating Around the Bush newsletter here, and suggest a plant we should cover at batb@theconversation.edu.au.


Grass trees (genus Xanthorrhoea) look like they were imagined by Dr Seuss. An unmistakable tuft of wiry, grass-like leaves atop a blackened, fire-charred trunk. Of all the wonderfully unique plants in Australia, surely grass trees rank among the most iconic.

The common name grass tree is a misnomer: Xanthorrhoea are not grasses, nor are they trees. Actually, they are distantly related to lilies. Xanthorrhoea translates to “yellow flow”, the genus named in reference to the ample resin produced at the bases of their leaves.

All 28 species of grass tree are native only to Australia. Xanthorrhoea started diversifying around 24-35 million years ago – shortly after the Eocene/Oligocene mass extinctions – so they have had quite some time to adapt to Australian conditions.

Wander through remnant heathland or dry sclerophyll forest, particularly throughout the eastern and south-western regions of Australia, and you’ll likely find a grass tree.


CC BY

Perfectly adapted to their environment

Xanthorrhoea are perfectly adapted to the Australian environment, and in turn, the environment has adapted to Xanthorrhoea. Let’s start the story from when a grass tree begins as a seed.

After germination, Xanthorrhoea seedlings develop roots that pull the growing tip of the plant up to 12cm below the soil surface, protecting the young plant from damage. These roots quickly bond with fungi that help supply water and minerals.

Once the tip of the young plant emerges above ground, it is protected from damage by moist, tightly packed leaf bases, although shoots may develop if it is damaged. The leaves of Xanthorrhoea are tough, but they lack prickles or spines to deter passing herbivores. Instead, they produce toxic chemicals with anaesthetising effects.

All Xanthorrhoea are perennial; some species are estimated to live for over 600 years. Most grow slowly (0.86 cm in height per year), but increase their rate of growth in response to season and rainfall. The most “tree-like” species grow “trunks” up to 6 metres tall, while trunkless species grow from subterranean stems.
Grass trees don’t shed their old leaves. The bases of their leaves are packed tightly around their stem, and are held together by a strong, water-proof resin.
As the old leaves accumulate, they form a thick bushy “skirt” around the trunk. This skirt is excellent habitat for native mammals. It’s also highly flammable. However, in a bushfire, the tightly-packed leaf bases shield the stem from heat, and allow grass trees to survive the passage of fire.

Fire burns the outside leaves but the centre survives.
John Patykowski, Author provided

Xanthorrhoea can recover quickly after a fire thanks to reserves of starch stored in their stem. By examining the size of a grass tree’s skirt, we can estimate when a fire last occurred.

It can take over 20 years before a grass tree produces its first flowers. When they do flower it can be spectacular, producing a spike and scape up to four metres long advertising hundreds of nectar-rich, creamy-white flowers to all manner of fauna. Flowering is not dependent on fire, but it stimulates the process. The ability of grass trees to resprout after fire and quickly produce flowers makes them a vital life-line for fauna living in recently-burnt landscapes.

Grass trees provide food for birds, insects, and mammals, which feast on the nectar, pollen, and seeds. Beetle larvae living within the flower spikes are a delicacy for cockatoos. Invertebrates such as green carpenter bees build nests inside the hollowed out scapes of flowers. Small native mammals become more abundant where grass trees are found, for the dense, unburnt skirt of leaves around the trunk provides shelter and sites for nesting.

Indigenous use of grass trees

For Indigenous people living where grass trees grow, they were (and remain) a resource of great importance.

The resin secreted by the leaf-bases was used as an adhesive to attach tool heads to handles and could be used as a sealant for water containers. This valuable and versatile resin was an important item of trade.

The base of the flowering stem was used as the base of composite spear shafts, and when dried was used to generate fire by hand-drill friction. The flowers themselves could be soaked in water to dissolve the nectar, making a sweet drink that could be fermented to create a lightly alcoholic beverage.

When young, the leaves of subspecies Xanthorrhoea australis arise from an underground stem which is seasonally surrounded by sweet, succulent roots that can be eaten. The soft leaf bases also were eaten, and the seeds were collected and ground into flour. Edible insect larvae residing at the base of grass tree stems could be collected. Honey could be collected from flower stems containing the hives of carpenter bees.

European exploitation

European settlers were quick to clue onto the usefulness of the resin , using it in the production of medicines, as a glue and varnish, and burning it as incense in churches. It was even used as a coating on metal surfaces and telephone poles, and used in the production of wine, soap, perfume and gramophone records.

The versatile resin had been used in everything from medicine to gramophones.
John Patykowski, Author provided

Resin can easily be collected from around the trunk of plants, but early settlers used more destructive methods, removing whole plants on an industrial scale. The resin was exported worldwide; during 1928-29, exported resin was valued at over £25,000 (equivalent to A$2 million today!).

We still have much to learn about grass trees. Current research indicates an extract from one subspecies can be used as a cheap, environmentally-friendly agent to synthesise silver nanoparticles that are useful for their antibacterial properties.

Threats to grass trees

Many of the oldest grass trees have been lost to land clearing, illegal collection, and changes to fire regimes. It’s vital we care for those remaining. Grass trees are particularly sensitive to Phytophthora cinnamomi, a widespread plant pathogen that is difficult to detect and control, and kills plants by restricting movement of water and nutrients through the vascular tissue.

Growing native plants can be a wonderful way to contribute to the conservation of genetic diversity, and attract native fauna into your garden. Grass trees certainly make an interesting conversation plant!




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It’s hard to spread the idiot fruit


They can easily be grown at home, provided they’re sourced from a reputable supplier. The best way is to grow from seed, but patience is required as growth can be slow. Despite being relatively hardy, grass trees do not like being moved once large or established, so translocation of plants is not advised. In my opinion, the best way to see grass trees in their true splendour is to visit them in their natural habitat.The Conversation

John Patykowski, Plant ecologist, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.