The world of plastics, in numbers



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Millions of tons of plastic are manufactured every year.
Bert Kaufmann/Wikimedia, CC BY

Eric Beckman, University of Pittsburgh

From its early beginnings during and after World War II, the commercial industry for polymers – long chain synthetic molecules of which “plastics” are a common misnomer – has grown rapidly. In 2015, over 320 million tons of polymers, excluding fibers, were manufactured across the globe.

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Until the last five years, polymer product designers have typically not considered what will happen after the end of their product’s initial lifetime. This is beginning to change, and this issue will require increasing focus in the years ahead.

The plastics industry

“Plastic” has become a somewhat misguided way to describe polymers. Typically derived from petroleum or natural gas, these are long chain molecules with hundreds to thousands of links in each chain. Long chains convey important physical properties, such as strength and toughness, that short molecules simply cannot match.

“Plastic” is actually a shortened form of “thermoplastic,” a term that describes polymeric materials that can be shaped and reshaped using heat.

The modern polymer industry was effectively created by Wallace Carothers at DuPont in the 1930s. His painstaking work on polyamides led to the commercialization of nylon, as a wartime shortage of silk forced women to look elsewhere for stockings.

When other materials became scarce during World War II, researchers looked to synthetic polymers to fill the gaps. For example, the supply of natural rubber for vehicle tires was cut off by the Japanese conquest of Southeast Asia, leading to a synthetic polymer equivalent.

Curiosity-driven breakthroughs in chemistry led to further development of synthetic polymers, including the now widely used polypropylene and high-density polyethylene. Some polymers, such as Teflon, were stumbled upon by accident.

Eventually, the combination of need, scientific advances and serendipity led to the full suite of polymers that you can now readily recognize as “plastics.” These polymers were rapidly commercialized, thanks to a desire to reduce products’ weight and to provide inexpensive alternatives to natural materials like cellulose or cotton.

Types of plastic

The production of synthetic polymers globally is dominated by the polyolefins – polyethylene and polypropylene.

Polyethylene comes in two types: “high density” and “low density.” On the molecular scale, high-density polyethylene looks like a comb with regularly spaced, short teeth. The low-density version, on the other hand, looks like a comb with irregularly spaced teeth of random length – somewhat like a river and its tributaries if seen from high above. Although they’re both polyethylene, the differences in shape make these materials behave differently when molded into films or other products.

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Polyolefins are dominant for a few reasons. First, they can be produced using relatively inexpensive natural gas. Second, they’re the lightest synthetic polymers produced at large scale; their density is so low that they float. Third, polyolefins resist damage by water, air, grease, cleaning solvents – all things that these polymers could encounter when in use. Finally, they’re easy to shape into products, while robust enough that packaging made from them won’t deform in a delivery truck sitting in the sun all day.

However, these materials have serious downsides. They degrade painfully slowly, meaning that polyolefins will survive in the environment for decades to centuries. Meanwhile, wave and wind action mechanically abrades them, creating microparticles that can be ingested by fish and animals, making their way up the food chain toward us.

Recycling polyolefins is not as straightforward as one would like owing to collection and cleaning issues. Oxygen and heat cause chain damage during reprocessing, while food and other materials contaminate the polyolefin. Continuing advances in chemistry have created new grades of polyolefins with enhanced strength and durability, but these cannot always mix with other grades during recycling. What’s more, polyolefins are often combined with other materials in multi-layer packaging; while these multi-layer constructs work well, they are impossible to recycle.

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Polymers are sometimes criticized for being produced from increasingly scarce petroleum and natural gas. However, the fraction of either natural gas or petroleum used to produce polymers is very low; less than 5 percent of either oil or natural gas produced each year is employed to generate plastics. Further, ethylene can be produced from sugarcane ethanol, as is done commercially by Braskem in Brazil.

How plastic is used

Depending upon the region, packaging consumes 35 to 45 percent of the synthetic polymer produced in total, where the polyolefins dominate. Polyethylene terephthalate, a polyester, dominates the market for beverage bottles and textile fibers.

Building and construction consumes another 20 percent of the total polymers produced, where PVC pipe and its chemical cousins dominate. PVC pipes are lightweight, can be glued rather than soldered or welded, and greatly resist the damaging effects of chlorine in water. Unfortunately, the chlorine atoms that confer PVC this advantage make it very difficult to recycle – most is discarded at the end of life.

Polyurethanes, an entire family of related polymers, are widely used in foam insulation for homes and appliances, as well as in architectural coatings.

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The automotive sector uses increasing amounts of thermoplastics, primarily to reduce weight and hence achieve greater fuel efficiency standards. The European Union estimates that 16 percent of the weight of an average automobile is plastic components, most notably for interior parts and components.

Over 70 million tons of thermoplastics per year are used in textiles, mostly clothing and carpeting. More than 90 percent of synthetic fibers, largely polyethylene terephthalate, are produced in Asia. The growth in synthetic fiber use in clothing has come at the expense of natural fibers like cotton and wool, which require significant amounts of farmland to be produced. The synthetic fiber industry has seen dramatic growth for clothing and carpeting, thanks to interest in special properties like stretch, moisture-wicking and breathability.

The ConversationAs in the case of packaging, textiles are not commonly recycled. The average U.S. citizen generates over 90 pounds of textile waste each year. According to Greenpeace, the average person in 2016 bought 60 percent more items of clothing every year than the average person did 15 years earlier, and keeps the clothes for a shorter period of time.

Eric Beckman, Professor of Chem/Petroleum Engineering, University of Pittsburgh

This article was originally published on The Conversation. Read the original article.

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Why we’re watching the giant Australian cuttlefish



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Hello little ones! Juvenile giant Australian cuttlefish developing under rocks in the waters of South Australia.
Fred Bavendam, Author provided

Bronwyn GIllanders, University of Adelaide

Australia is home to the world’s only known site where cuttlefish gather to mate en masse.

From May to August, if you head into the water around Point Lowly, South Australia, it will be a chilly 12℃. But you’ll be able to observe what look like aliens – hundreds, even thousands of tentacled organisms with their unusual distinctive W-shaped eye pupils, and pulsating colours moving across their body.

Intent on mating, the cuttlefish will be totally oblivious to your presence.

Giant Australian cuttlefish can change the colour and texture of their skin.
David Wiltshire, Author provided



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But this population of cuttlefish dropped in abundance from an estimated 150,000 animals in the late 1990s to only 13,492 in 2013.

Although counts in recent years suggest the creatures have recovered, my research aims to determine what sorts of factors influence this very unique cuttlefish population. This may allow us to better manage and protect the species – important not just for science, but also for the local environment and economy.

Rockstars of the sea

Every time I head to the Point Lowly coastline and dive with the giant Australian cuttlefish I’m amazed and excited by their antics.

Giant Australian cuttlefish in an intimate embrace.
Matt McMillan, Author provided

The name “giant” is perhaps a misnomer. Giant Australian cuttlefish only ever reach about one metre in size. Most animals are much smaller, especially in South Australia.

Cephalopods have been described as rockstars of the sea for their “live fast, die young” life history strategy – they grow rapidly, reproduce early and die following reproduction. Giant Australian cuttlefish live for 1-2 years.

Although they are found in waters across southern Australia, giant Australian cuttlefish live in distinct populations that do not interact. We know from genetic studies that those breeding along that small area of Upper Spencer Gulf coastline are restricted to an area north from a line across the gulf from Wallaroo to Arno Bay (around 6,500 km²).

The most northern waters of Upper Spencer Gulf in South Australia host a unique population of giant Australian cuttlefish.
Ellen Rochelmeyer (using Google Maps), CC BY-NC-ND

Outside the breeding season of May to August they are distributed throughout this northern region. Come May they start to move towards a narrow 8km stretch of rocky coastline. At their peak you see literally one cuttlefish per square metre. It’s the sheer numbers that are impressive!

They come solely for one purpose over winter – to find mates to reproduce.

Cuttlefish gather to breed from May-August each year.
Tim Rogers, Author provided

Sudden drop in numbers

Around the late 1990s, the cuttlefish breeding aggregation in the Upper Spencer Gulf began to be targeted by fishers. Since then, a number of restrictions on taking cuttlefish and other cephalopods from these waters have been in place.

Around that time, a program of research through the University of Adelaide and SARDI Aquatic Sciences also began. Estimates of abundance and biomass of the breeding aggregation population suggested around 150,000 cuttlefish bred in the Upper Spencer Gulf. The surveys stopped after a few years.

Numbers of giant Australian cuttlefish in the Upper Spencer Gulf fell dramatically between the late 1990s and 2013.
Matt McMillan, Author provided

Then in 2005 anecdotal reports from SCUBA divers suggested cuttlefish were less abundant. A survey at that time and continual data collected since 2008 confirmed that numbers had dropped. In 2013 less than 15,000 individuals were estimated on the breeding aggregation.

Significant resources were put towards studying the cuttlefish to determine what might be causing such a decline. Changes in water temperature and salinity may be involved.




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We looked at data for other cephalopods over a similar time frame, and found no such decline. In fact, over the last 60 years many different types of cephalopod have been increasing in abundance – it’s not yet clear why.

The low numbers of 2013 seem to be unique to the giant Australian cuttlefish on the Upper Spencer Gulf.

Since this time there has been a recovery in this population, with numbers bouncing back towards their late 1990s levels.

Some giant Australian cuttlefish reach one metre in length – but most are smaller.
Nick Payne, Author provided

How cuttlefish breed

We know that cuttlefish come to this breeding aggregation to mate using a range of amazing strategies and behaviours – for example, small males impersonate females to avoid detection by larger males and gain access “under cover”.




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Because the population on the breeding aggregation is skewed towards males (an average o four to one), females have some choice over who they mate with.

After mating takes place, females deposit eggs on the underside of rocks.

Cuttlefish eggs deposited on the underside of rocks.
Fred Bavendam, Author provided

Cuttlefish eggs take three to five months to develop, hatching from mid-September through to early November. They emerge as miniature adults about the size of your thumbnail.

Baby cuttlefish disperse within the Upper Spencer Gulf with an even sex ratio.

Cuttlefish gather in only a few metres of water in the Upper Spencer Gulf.
Matt McMillan, Author provided

To work out why there was a difference in sex ratio between the broader region (1 male:1 female) and the breeding aggregation (4 males:1 female), we tagged male and female cuttlefish using trackable acoustic markers. We discovered that males spend around four times the length of time on the breeding aggregation compared to females, and that individuals are not present for the whole breeding season.

So the breeding aggregation is likely larger in size than fixed time frame counting estimates allow us to measure.

Positive influence on local economy

Although the apparently low population size in 2013 caused great concern, we are now cautiously optimistic for our giant Australian cuttlefish in Upper Spencer Gulf.

There’s something behind you!
Matt McMillan, Author provided

These creatures attract tourists from around the world, who come and snorkel or SCUBA dive on a unique breeding aggregation. This in turn injects money into the local economy and diversifies business in the region.

The cuttlefish are just one “user” of our shared marine environment along with the other activities and industries of South Australia.


The ConversationThis article is based on a presentation delivered by Bronwyn Gillanders at the South Australian Museum as part of the Sprigg Lecture Series.

Bronwyn GIllanders, Professor , University of Adelaide

This article was originally published on The Conversation. Read the original article.

From devils to superheroes: our complicated relationship with bats



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A “cloud” of Mexican freetail bats leaving their roost.
Wikimedia

Susan Lawler, La Trobe University

Review: Bat by Tessa Laird.


Did you know that the collective noun for bats is a “cloud”, or that in the first scientific classification of mammals, bats were placed close to humans because, like us, they have two nipples? The book Bat, by Tessa Laird, is full of similar tidbits that you will want to share with others. It is also engrossing, eloquent and beautifully illustrated.

Bat contains hundreds of delightful bat facts, but they are so grounded in context that the whole is much more than the sum of its parts. One cannot help but become intrigued and eventually transformed. I know I will never look at bats the same way again.

A chocolate wattled bat.
Flickr, CC BY

The author moves between Chiropteran (the scientific name for the bat group) biology, conservation, history, psychology and pop culture to capture the essence of bats, not only in all their marvellous diversity, but in our collective imagination.

Because their flight is erratic, bats are used as a symbol of insanity. Because they hang upside down and are active at night, bats can imply an inversion of normality. Their triumphant daily emergence from their caves can even represent rebirth.




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Bats suffer from not fitting comfortably into familiar categories. In Aesop’s Fables, the bat switched allegiance in the war between birds and beasts, so that when it was over the bat was shunned by both and forced to live at night. Their apparently hybrid nature was first noted by the Comte de Buffon in the 1780s when he wrote that the bat is an “imperfect quadruped and a still more imperfect bird”.

In Christian iconography, devils often have bat wings. Hans Memling, Hell, circa 1485.
Wikimedia

Early Christian iconography used bat wings for demons, to contrast with the bird wings that we see on angels. This may have something to do with the European prejudice against bats. When a sailor from Captain Cook’s Endeavour saw an Australian flying fox for the first time, he ran back to camp terrified, claiming to have met a real live devil.

Bats have been misunderstood throughout human history. It is, on reflection, extraordinary that we still use the phrase “blind as a bat”, knowing that they catch insects on the wing in the dark. Echolocation was not discovered until 1938, and because we cannot hear their calls, we did not know that bats basically spend their lives yelling at the world.

Even now, few people realise that bats are socially sophisticated; they share food, information, and maintain lifelong friendships within their colonies. They even engage in oral sex!

Yet bats are celebrated in some cultures. In China, bats are a symbol of luck, in part because the words “bat” and “luck” sound like each other in Chinese. They are also beloved in indigenous cultures from Mexico to Samoa to Papua New Guinea. Interestingly, cultures that venerate ancestors tend to love bats.

The demon queller Zhong Kui (鍾馗) and five bats representing the five blessings (五福).
Wikimedia

And just when you think that this book is about bats, it flips perspective and shines a light on humanity and our own foibles. Such as the second world war project to drop bats with incendiary devices strapped to them so they would crawl into the enemy’s roof cavities and explode.

Or when someone threw a live bat on stage and Ozzy Osbourne bit its head off thinking it was a toy – he was rushed to hospital for shots but apparently privately wondered if anyone would have noticed a change if he had contracted rabies.

There are pages dedicated to an analysis of the Batman superhero and his many incarnations, the Dracula story and its evolution since Bram Stoker’s publication in 1897, as well as more contemporary bat-inspired art.

For example, the 2015 installation in Federation Square in Melbourne, titled Batmania, consisted of 200 life sized flying foxes made from black plastic rubbish bags with holes burned in a filigreed pattern so that they looked like the stars of the night sky shining through. Each bat was juxtaposed with a collapsed parachute, as if to emphasise man’s inability to fly unaided. If we do not yearn for the freedom of flight, perhaps we dream of the immortality of vampires or the strength and anonymity of Batman himself.

Ben Affleck in Batman v Superman: Dawn of Justice.
IMDB

The bad reputation bats have in the human world has not been without consequences for them. Blamed for disease outbreaks from Ebola to rabies to SARS, bats have been killed in great numbers due to fear and ignorance. Their habitats are fragile and shrinking, and it is hard to overstate the planetary implications of their demise.




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Bats eat many tons of insect pests and are responsible for the pollination of some important and beautiful plants: mangoes, bananas, saguaro cactus. The conservation movement for bats has taken off in recent years, due in part to some excellent photography and a new appreciation of the cuteness of baby bats.

If you read this book you cannot fail to care more about bats, which I hope means that more people will become active in bat conservation. In the author’s own words:

The ConversationAs we have seen, bats have been variously associated with sexuality, diversity and sociability, combined with intuition and an ability to navigate through dark places, all of which seem like desirable qualities at the start of the twenty-first century.

Susan Lawler, Associate Professor, Department of Ecology, Environment and Evolution, La Trobe University

This article was originally published on The Conversation. Read the original article.

Figs, ferns and featherwoods: learn all about Australia’s native trees and plants


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You love Australian plants, I love Australian plants, we all love Australian plants!
Percita/Flickr

Madeleine De Gabriele, The Conversation and Molly Glassey, The Conversation

Sign up to the special Beating Around the Bush newsletter here.


Australia is classified as “megadiverse” meaning it’s a global hotspot for plant and animal diversity, and has vast numbers of unique species found nowhere else on Earth. With this newsletter we want you to be able to wander down the garden path, off the beaten track, and smell the gum leaves. Specifically, what kind of gum leaf? What is it from? Where does it grow?




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We’ll let you know every time a new edition in our Beating Around the Bush series comes out, putting the spotlight on a different native plant every time. We’re on a roughly fortnightly schedule, but like any garden there might be a few surprises along the way. I’ll also be rounding up some of the greatest hits from our archives, and talking about what’s new in the plant world.

This one is for all you floraphiles out there.
Felicity Burke/The Conversation

The ConversationIf someone else in your life might enjoy this mix in their inbox, please let them know about it. And if you have any feedback, feel free to let us know in the comments.

Madeleine De Gabriele, Deputy Editor: Energy + Environment, The Conversation and Molly Glassey, Audience Development Manager, The Conversation

This article was originally published on The Conversation. Read the original article.

Here’s how many times you actually need to reuse your shopping bags



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Jeremy Piehler/Flickr, CC BY-NC

Trevor Thornton, Deakin University

The plastic bag ban by the major supermarkets (and Coles’ pivot away from its ban after backlash, then pivot back to the ban after a backlash to the backlash) has left plenty of people scratching their heads.




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What are the best replacements for single-use plastic bags? Given that reusable bags are much sturdier, how many times must we use them to compensate for their larger environmental impact?

The simple answer is that there is no simple answer. However, a kind of research called “life cycle assessment” can help us work out the impact of common types of reusable bags.

Life cycle assessments

I am not aware of any Australian studies of plastic-bag substitutes. Research conducted overseas can offer a basic guide.

Life cycle assessments consider a wide range of factors, including raw materials, manufacturing, transport, and eventual disposal.

Looking at all of these elements, researchers calculate greenhouse gas emissions, waste disposal, water and energy consumption and a variety of other impacts.

To complicate the decision further, if you choose a plastic bag, is it made from virgin resin or from recycled plastic? Even if the bag is recycled, transport is an issue – where was it made? Printing on the bag also adds to the environmental burden.

Finally, what happens to the bags when they can no longer meet their purpose? Are they recycled, reused as bin liners, or thrown away immediately?




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How many times must a bag be reused?

Once all of this information has been distilled, scientists can usually offer a fairly straightforward guide: the number of times a given bag should be reused when compared to the standard supermarket plastic bag.

A 2018 Danish study, looking at the number of times a bag should be reused before being used as a bin liner and then discarded, found that:

  • polypropylene bags (most of the green reusable bags found at supermarkets) should be used 37 times
  • paper bags should be used 43 times
  • cotton bags should be used 7,100 times.

Another UK study, which only considered the climate change impact, found that to have lower global warming potential than single-use plastic bags:

  • paper bags should be used three times
  • low-density polyethylene bags (the thicker plastic bags commonly used in supermarkets) should be used four times
  • non-woven polypropylene bags should be used 11 times
  • cotton bags should be used 131 times.

Note, however, that if a plastic bag is reused (even as a bin liner) the number of times an alternative needs to be used increases.

It’s worth noting that, according to the 2018 Danish study, using organic cotton has a greater environmental impact than non-organic due to higher production costs. Our assumptions about what is environmentally friendly don’t always stand up to scrutiny.

A 2014 study in the United States found that reusable LDPE and polypropylene bags do have a lower environmental impact than the usual plastic bags found in supermarkets – but only if they are reused enough times. This study found that about 40% of shoppers forgot to bring their reusable bags and therefore end up using the plastic bags. This then adds to the environmental burden of shopping.

One final consideration is how many bags you need. The Danish researchers equalised the volume of the bags so that evaluations were made on the same volume of space (this meant that for some assessments it was necessary to consider the impact of two bags).

As with all matters environmental, it’s essential that we have the right knowledge to make informed decisions. After looking at all this data, here are the things I’d like you to remember:

  1. whatever bag type you use, use it as many times as possible

  2. choose bags made from recyclable materials

  3. avoid bags that have printing or decorations – these alone can add significantly to the environmental burden of the bag

  4. never allow a bag to become litter – recycle, reuse and repurpose your bags.


The Conversation


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Trevor Thornton, Lecturer, School of Life and Environmental Sciences, Deakin University

This article was originally published on The Conversation. Read the original article.

Three reasons why it’s a bad idea to ramp up Adelaide’s desalination plant


Sarah Ann Wheeler, University of Adelaide

Drought-affected farmers in New South Wales have called for South Australia to increase the use of its desalination plant to enable an increase in water allocations for other users along the Murray River.

The farmers’ argument is that if Adelaide in particular draws less water from the river more will be available for agriculture in NSW and Victoria.

The logic may sound appealing, but there are three good reasons why it’s not a good idea. Not only is desalination an incredibly expensive project, there are other strategies – like water pricing – that can more effectively reduce water demand.




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It’s also important to remember that the water flowing to South Australia is not “wasted” if it’s not diverted for industry. Stream flows are vital for keeping many ecosystems alive, and there are already serious concerns about current levels.

Adelaide doesn’t use that much water

First, Adelaide uses a very small amount of water from the River Murray. Over the past two decades, average diversions for metropolitan Adelaide and associated country areas have been just over 100 gigalitres (GL). This represents an average 1.25% of the water diversions in the Murray-Darling Basin.

SA in general (including irrigator use) has used an average 11% of water diversions over the past two decades. NSW has diverted 52% of surface water in the Murray-Darling Basin over the same period. Hence, the reality is that ramping up SA’s desal plant will have very little actual impact on NSW irrigators’ water allocations.

South Australia (the grey line) receives much less water from the Murray River than other states.
MDBA Water Audit Monitoring reports, CC BY

Desalination is expensive

Second, increasing desalination has heavy financial and environmental costs. The financial cost is why the plant has been run at only about 10% capacity (the minimum needed to maintain its working condition).

Previous economic analysis by consultants has suggested the desalination plant should only be used to increase water allocations to SA irrigators when temporary water market prices are above A$510 per megalitre (ML).

Given that temporary water prices are now trading around A$300/ML (albeit increasing due to increased water scarcity), we’re still a long way from a financial argument for turning to the desal plant, let alone considering the cost of its negative environmental impacts.




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Water is always variable

Third, we need to take into account the variable nature of Australia’s irrigation sector.

Farmers in NSW are complaining that they are on zero percentages of water allocations at the start of the water year (August 1). This sounds like a big problem. But it doesn’t mean the farmers will get no water from the river at all.

At the start of the season, water managers allot water in districts to irrigators every two weeks. Depending on the type of water entitlement owned, and given the current state of water conditions (e.g. storage, inflows, rainfall predictions), water managers will allocate a percentage of water to high security entitlements first, then general security, then low security. Only in high rainfall years will the low security group get any water. Most years they get none.

Since water was separated from land in the Murray-Darling Basin, this water is not tied to any particular use. Once allocated, irrigators can use their seasonal water for their crops, store it, sell it on the water market, or even choose to let it flow down the river.

It is not unusual for irrigators with low or general security entitlements to start the water year with low or no water allocated, especially in times of water scarcity. One reason is that these rights are traditionally associated with districts where farmers typically grow annual crops like rice and cotton. They have larger farms and more water rights – but also more flexibility about the amount they plant every year.

Low water allocations at the start of the water year act as a signal to these producers to think carefully about the amount of acreage to plant in the coming months. In addition, many NSW and Victorian farmers have access to carry-over water (unused stored water from the previous year).

The other option is the water market; irrigators can enter the water market to buy water. Current temporary water prices are still historically a lot lower than prices in the Millennium Drought, when temporary prices hit over A$1000/ML in many regions.

Finally, it is important to emphasise that water destined for urban use in SA is not “wasted water” for NSW and Victoria. It is still providing surface-water flows in the basin as it makes it way to SA.

Economic studies show that a healthy and sustainable river is worth millions of dollars in tourism and recreation, plus providing important cultural values, on which many small regional town economies are heavily dependent. And there is ongoing evidence that the Murray-Darling Basin is still far from being sustainable.




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Unfortunately, many of the people who support more sustainable water reallocation for the environment are widely dispersed. They often do not have the lobbying power or the resources to engage successfully in policy debate.

The ConversationOf course, farmers need support. But the calls for more water to be allocated to irrigators will sound loudly as the drought continues, and it’s important to remember that there are other, less costly, options that also protect our environment.

Sarah Ann Wheeler, Professor in Water Economics, University of Adelaide

This article was originally published on The Conversation. Read the original article.