How much plastic does it take to kill a turtle? Typically just 14 pieces



File 20180913 133877 1l7r55a.jpeg?ixlib=rb 1.1
Plastic bags, balloons, and rope fragments were among more than 100 pieces of plastic in the gut of a single turtle.
Qamar Schuyler, Author provided

Britta Denise Hardesty, CSIRO; Chris Wilcox, CSIRO; Kathy Ann Townsend, University of the Sunshine Coast, and Qamar Schuyler, CSIRO

We know there is a lot of plastic in the ocean, and that turtles (and other endangered species) are eating it. It is not uncommon to find stranded dead turtles with guts full of plastic.

But we weren’t really sure whether plastic eaten by turtles actually kills them, or if they just happen to have plastic inside them when they die. Another way to look at it would be to ask: how much is too much plastic for turtles?

This is a really important question. Just because there’s a lot of plastic in the ocean, we can’t necessarily presume that animals are dying from eating it. Even if a few animals do, that doesn’t mean that every animal that eats plastic is going to die. If we can estimate how much plastic it takes to kill a turtle, we can start to answer the question of exactly how turtle populations are affected by eating plastic debris.




Read more:
Eight million tonnes of plastic are going into the ocean each year


In our research, published today in Nature Scientific Reports, we looked at nearly 1,000 turtles that had died and washed up on beaches around Australia or were found in nets. About 260 of them we examined ourselves; the others were reported to the Queensland Turtle Stranding Database. We carefully investigated why the turtles died, and for the ones we examined, we counted how many pieces of plastic they had eaten.

Some turtles died of causes that were nothing to do with plastic. They may have been killed by a boat strike, or become entangled in fishing lines or derelict nets. Turtles have even been known to die after accidentally eating a blue-ringed octopus. Others definitely died from eating plastic, with the plastic either puncturing or blocking their gut.

One of the first meals eaten by this sea turtle post-hatchling turned out to be deadly. It died from consuming more than 20 tiny pieces of plastic, many of which were about the same size as a grain of rice.
Kathy Townsend, Author provided

Some turtles that were killed by things like boat strikes or fishing nets nevertheless had large amounts of plastic in their guts, despite not having been killed by eating plastic. These turtles allow us to see how much plastic an animal can eat and still be alive and functioning.

The chart below sets out this idea. If an animal drowned in a fishing net, its chance of being killed by plastic is zero – and it falls in the lower left of the graph. If a turtle’s gut was blocked by a plastic bag, its chance of being killed by plastic is 100%, and it’s in the upper right.

The animals that were dead with plastic in their gut, but had other possible causes of death have a chance of death due to plastic somewhere between 0 and 100% – we just don’t know, and they can fall anywhere in the graph. Once we have all the animals in the plot, then we can ask whether we see an increase in the chance of death due to plastic as the amount of plastic in an animal goes up.

Conceptual framework for estimating the probability of death due to plastic debris ingestion. Figure provided by the authors.

We tested this idea using our turtle samples. We looked at the relationship between the likelihood of death due to plastic as determined by a turtle autopsy, and the number of pieces of plastic found inside the animals.

Unsurprisingly, we found that the more plastic pieces a turtle had inside it, the more likely it was to have been killed by plastic. We calculated that for an average-sized turtle (about 45cm long), eating 14 plastic items equates to a 50% chance of being fatal.




Read more:
Pristine paradise to rubbish dump: the same Pacific island, 23 years apart


That’s not to say that a turtle can eat 13 pieces of plastic without harm. Even a single piece can potentially kill a turtle. Two of the turtles we studied had eaten just one piece of plastic, which was enough to kill them. In one case, the gut was punctured, and in the other, the soft plastic had clogged the turtle’s gut. Our analyses suggest that a turtle has a 22% chance of dying if it eats just one piece of plastic.

A green sea turtle that died after consuming 13 pieces of soft plastic and balloons, which blocked its gastrointestinal system.
Kathy Townsend

A few other factors also affected the animals’ chance of being killed by plastic. Juveniles eat more debris than adults, and the rate also varies between different turtle species.

Now that we know how much is too much plastic, the next step is to apply this to global estimates of debris ingestion rates by turtles, and figure out just how much of a threat plastic is to endangered sea turtle populations.The Conversation

Britta Denise Hardesty, Principal Research Scientist, Oceans and Atmosphere Flagship, CSIRO; Chris Wilcox, Senior Research Scientist, CSIRO; Kathy Ann Townsend, Lecturer in Animal Ecology, University of the Sunshine Coast, and Qamar Schuyler, Research Scientist, Oceans and Atmospheres, CSIRO

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

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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.




Read more:
Why plastic bag bans triggered such a huge reaction


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?




Read more:
How to break up with plastics (using behavioural science)


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


Read more:
Why can’t all plastic waste be recycled?


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

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

Curious Kids: How do plastic bags harm our environment and sea life?


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Sea turtle eating a plastic bag.
from www.shutterstock.com

Britta Denise Hardesty, CSIRO and Qamar Schuyler, CSIRO

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.


My name is Sanuki and I’m 8 years old. I live in Melbourne. My question is how do plastic bags harm our environment and sea life? – Sanuki, age 8, Melbourne.


Good question, Sanuki!

Plastic bags harm marine (and land) environments in a few ways.

Turtles (and other animals) may mistake plastic bags for food. Turtles like to eat jellyfish, and we think turtles eat the plastic bags because they resemble jellyfish.

When turtles eat plastic, it can block their intestinal system (their guts). Therefore, they can no longer eat properly, which can kill them. The plastics in their tummy may also leak chemicals into the turtle. We don’t know whether this causes long term problems for the turtle, but it’s probably not good for them.




Read more:
Australian waters polluted by harmful tiny plastics


How plastic impacts the ecosystems

Plastic bags can also smother corals and other seabed communities. When plastic bags end up in our oceans, animals (including seals, dolphins and seabirds) can get tangled up in them. An animal with a plastic bag around its neck will have trouble moving through the water, catching its prey or feeding, and escaping predators.

Plastic can smother seabed and coral, impacting ecosystems.
from www.shutterstock.com

On land, plastic bags are an eyesore. They get stuck in trees, along fence lines, or as litter at our parks and beaches.

Many people don’t realise that plastic bags can also cause flooding. Previously in Ghana (in West Africa), plastic bags blocked storm water drains during a big rainstorm. This caused flooding so bad that people were killed.

Making plastic requires a lot of energy and work

Plastic bags can even be harmful before they are used. It takes a lot of resources and energy to create a plastic bag. A key ingredient is oil. As a fossil fuel, oil must be extracted from the ground. Do we want to use fossil fuel resources to make a product that is only used once (we call this a “single use plastic”)?

Many millions of barrels of oil are used to make plastic bags every year. A lot of energy is also used to make and transport plastic bags. It is better for the environment if we reduce our energy use.




Read more:
This South Pacific island of rubbish shows why we need to quit our plastic habit


The push towards plastic-free

Lately, lots of people recognise the impacts that plastic bags have, and they are working on alternatives. Many local and state governments have passed plastic bag bans here in Australia, which helps stop the use of single use plastic bags.

In fact, New South Wales is the only state in Australia where you can still get thin, single use plastic bags at the grocery store.

So, remind your parents to bring their reusable cloth bags whenever you go shopping. You just might save a turtle.


Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:

* Email your question to curiouskids@theconversation.edu.au

* Tell us on Twitter


CC BY-ND

The ConversationPlease tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.

Britta Denise Hardesty, Principal Research Scientist, Oceans and Atmosphere Flagship, CSIRO and Qamar Schuyler, Research Scientist, Oceans and Atmospheres, CSIRO

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

How the ‘yeah-but’ mentality stalls progress on bag bans and other green issues



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Is forgetting your bags really such an inconvenience?
AAP Image/Peter Rae

Anne Lane, Queensland University of Technology

The debacle over the removal of single-use plastic bags from supermarkets has been analysed from a range of different perspectives. Supermarkets have been described as breaking a psychological trust contract with their customers and cynically using environmental concerns to reduce their costs and increase their profits. The pushback by Australian shoppers has been the cause of much amusement and bewildered head-shaking.

But there’s one aspect of people’s resistance to this type of change that has major implications for every environmental initiative in the country. Let’s call it the “yeah-but” mentality.




Read more:
Why plastic bag bans triggered such a huge reaction


Yeah-buts know when things are bad for the environment. They know about the dangers of throwaway plastic, whether it be bags, straws or bottles. They know that eating farmed meat, leaving the tap running, and driving cars powered by fossil fuels are not good for the world we live in.

They know this situation is not sustainable and that someone must do something about it. They might even be willing to make an occasional donation to an environmental charity. But ask them to take action themselves, especially if that involves even a low level of inconvenience, and the Yeah-buts sound their call.

Yeah-buts know they shouldn’t really drive to work, but then again public transport takes longer and doesn’t go door-to-door.

Yeah-buts know that farmed meat has a large environmental footprint, but they like the taste, and anyway veggies are only really an accompaniment.

This mentality has significant implications for any organisation attempting to address environmental challenges in Australia, or any other democratic society.

Previous research – such as that into the low take-up of electric cars – has found that consumers can be resistant to eco-friendly innovations in products and behaviour where they perceive that the proposed alternative is more expensive and/or less practical.

A requirement for people to actually put in some effort to acquire new behaviour that helps the environment is almost certainly going to encounter resistance.

How to drive behaviour change

Encouraging people to adopt new behaviours – especially those that involve personal inconvenience – is traditionally done through a “standard learning hierarchy approach”. The first step is to provide people with new knowledge and information on a topic or issue, thus increasing their understanding. As a result they will change the way they feel about the topic, and ultimately change their behaviour to reflect this new understanding and feeling.

Research has shown, however, that giving people new knowledge doesn’t necessarily mean they’ll do the right thing.

For years, organisations have been telling us how bad plastic bags are for the environment. As a result, people have been feeling increasingly negative towards the use of plastic bags. But despite some shoppers changing their ways, many didn’t. Until this month, supermarkets were still supplying millions of single-use bags, and thousands of their customers were still using them.

Then came the prospect of a ban, and the yeah-but excuses began to flow. One shopper told A Current Affair:

It’s just one extra thing (to remember) and invariably as I get older my memory gets worse.

Clearly the standard learning hierarchy wasn’t working here. The Yeah-buts persisted because their unwillingness to be inconvenienced by the need to provide their own shopping bags triumphed over their knowledge of the harm that plastic bags do. For these people, the inconvenience of forgetting their bags is acute, whereas the guilt over using unnecessary plastic is more vague. So this is where the government stepped in and removed the option of single-use plastic bags altogether.

Under pressure from environmental groups and concerned individuals, governments introduced a legislated ban on single-use plastic bags. This is a different approach to the standard learning hierarchy, which seeks to change people’s perception first, and then their behaviour. Here, people’s behaviour was forcibly altered in the hope that their knowledge and feelings would catch up.

The idea that people will reject an opportunity to acquire a new habit that will bring positive environmental change because it inconveniences them is one that clearly needs more research. It’s hard to think of another example where this inconvenience has resulted from a government mandating the withdrawal of a legal product to benefit the environment.

The case of the plastic bag ban is still being analysed, but could it provoke copycat behaviour by other environmental agencies – lobbying for legislation to force people to take a particular course of action while waiting for them to realise it’s the “right” thing to do and it makes them feel good? It’s an avenue that has been explored by some over many years, with varying degrees of success.




Read more:
Target’s plastic bag backdown a loss for the silent majority


Only time will tell if the use of legislation makes the Yeah-buts’ resistance over the single-use plastic bag futile. If it does seem to work, watch out for a slew of applications from other environmental agencies and charities for similar levels of strong-arm government support.

The ConversationBut those organisations will have to be prepared to weather a severe storm of backlash and negative public sentiment if they think legislation is the way to go. It’s not the governments that will be held liable: just ask Coles and Woolies!

Anne Lane, Academic and researcher, Queensland University of Technology

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

Why Coles’ plastic bag backflip leaves us worse off than before


Kim Borg, Monash University and Edwin Ip, Monash University

One month after removing free lightweight plastic bags from checkouts, Australian supermarket giant Coles has decided to offer thicker reusable plastics bags for free, indefinitely. This unprecedented move is in response to strong backlash by customers who are struggling to switch to reusable bags.




Read more:
Why plastic bag bans triggered such a huge reaction


We know that offering free lightweight plastic bags causes excessive plastic use. We also know that banning lightweight bags can increase the use of heavier plastic bags (such as bin liners). Coles’ decision brings out the worst of both worlds: giving out heavier plastic bags for free.

Free vs. fee

Consumers respond to price changes: if prices go up, demand falls. Increasing the use of reusable bags by introducing a small fee has generally been successful around the world. This includes examples from Canada, Botswana, Portugal and Ireland, where introducing a €0.15 tax on plastic shopping bags reduced usage by over 90%.

An alarming example for Coles is that of South Africa. They removed lightweight plastic bags and introduced a fee of 46 rand cents for thicker plastic bags, later reducing it to 17 cents. The initial high price point almost halved the use of plastic bags, but when the price was lowered the use of plastic bags increased over time.




Read more:
In banning plastic bags we need to make sure we’re not creating new problems


Behavioural economics suggests that people are more sensitive to loss than gains, so financial disincentives for plastic bags are particularly useful. For example, it has been found that use of single-use bags can decrease substantially when a charge is framed as a tax, compared to a bonus for bringing reusable bags.

A habit of free bags

Cole’s backflip is particularly troubling from a behavioural economics perspective. The thicker reusable plastic bags were meant to cost 15c. Coles are essentially offering a 100% discount on these bags compared to rival supermarkets. This, combined with the “power of free”, means that people may take more bags than they need when shopping – increasing plastic usage.

Switching to reusable bags without an added cost means that they are conceptually very similar to the old single-use bags (but with more plastic content). This replacement will not help people to kick their old single-use habits. In fact, they may develop a new habit of using the reusable bags as single-use products. If consumers continue their old habits, this could lead to even more plastic going to landfill and entering the environment.




Read more:
There are some single-use plastics we truly need. The rest we can live without


Alternative solutions

Coles is in a difficult situation. Not only has this decision divided shoppers, but if they decide to charge for these bags in the future, they are likely to experience another round of backlash as consumers experience another bout of loss aversion – but this time the loss will be associated with a higher quality product.

Now that the decision is made, it is important that Coles is able to evaluate the impact: How many free bags are being distributed? How many bin liners are being sold? How are the thicker plastic bags being used?

Coles also has a responsibility to take alternative measures to reduce plastic use. Financial disincentives are not always the best option (for example charging for bags can cause additional hardships for low income households). They are also not the only option for reducing our reliance on plastic bags.




Read more:
How to break up with plastics (using behavioural science)


The ConversationA more equitable solution could be to use behavioural science to help consumers break their habits. For example, instead of giving out free plastic bags, Coles could loan their reusable canvas bags for a small fee that is refunded on return. This would encourage reuse while avoiding additional costs for low income households or backlash from customers – everybody wins.

Kim Borg, Doctoral Candidate & Research Officer at BehaviourWorks Australia, Monash Sustainable Development Institute, Monash University and Edwin Ip, Research Fellow, Monash University

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

Why plastic bag bans triggered such a huge reaction


Gary Mortimer, Queensland University of Technology and Rebekah Russell-Bennett, Queensland University of Technology

Woolworths’ and Coles’ bans on plastic bags have been applauded by environmental groups, but were reportedly met with abuse and assault and claims of profiteering. Even comedians saw value in the theatre of the bag ban.

This reaction is due to supermarkets breaching their “psychological contract” with customers. When both major supermarkets appeared to back flip in the face of irate customers it only compounded the problem”.

Unlike written legal contracts, psychological contracts are a set of “unwritten rules” or “expectations” exchanged between the parties in a transaction. This can be between an employee and employer, or a customer and a retailer.

These understandings are often tacit or implicit. They tend to be invisible, assumed, unspoken, informal or at best only partially vocalised.

The pre-ban psychological contract between supermarket and shopper was something like “I’ll shop with you and, in exchange, you’ll pack my purchases into a free plastic bag.”

There was an implicit financial exchange between parties. Shoppers spent money on groceries and the supermarket paid for providing a plastic bag.

With the bag ban the psychological contract changed: “I’ll shop with you and give up a plastic bag, you’ll also give up plastic in the store in other areas, and the environment will benefit.”

Supermarkets justified phasing out lightweight plastic bags with the idea of a corporate social responsibility strategy. Customers might have been glad to forgo single-use plastic bans to support a greener future, but this is where the problem occurred.

Shoppers began to realise that supermarkets were saving money (by no longer giving away bags for nothing), while they themselves incurred a cost (paying 15 cents or more, depending on the type of re-usable bag).

The supermarkets had not kept up their end of the psychological contract by reducing the use of plastic in the store, particularly in packaging. The social media comments largely reflect this.

When there is a psychological contract breach, people can engage in revenge and retaliation.

This can range from mild, such as venting on social media, to acts of sabotage like altering floor stock and stealing shopping baskets.

Compounding factors

A couple of other factors have compounded the perceived breach of contract.

Unlike smaller states and territories (South Australia, Tasmania, Northern Territory and the ACT) where state legislation has banned single-use plastic bags by all retailers, this was a retailer-imposed national ban.

Shoppers in these smaller states quickly became accustomed to not having free bags, as these were not available anywhere.

By simply backflipping soon after implementing the policy, the supermarkets also prompted shoppers to question their intentions and integrity.

While shoppers may have at first accepted the rationale for the ban, extended free bag periods sent the message that the supermarkets are not that serious about banning plastic bags for environmental reasons.




Read more:
Getting rid of plastic bags: a windfall for supermarkets but it won’t do much for the environment


While Woolworths has said it will channel “money made” from selling its “Bag for Good” scheme into a youth environmental scheme, customers also rightly question the cost savings and revenues generated.

Removing a single-use plastic bag is a positive first step, but it is only the beginning. Customers still walk in to supermarkets today and see many varieties of food wrapped in plastic, and they themselves place loose fruit and vegetables into plastic bags.

As a result of media coverage, customers are now more aware and sensitive of plastics throughout dry grocery departments. They see more and more unnecessary plastic packaging, like dry pasta in a box with a clear plastic window.

Fixing the plastic bag ban

There is certainly enough evidence that removing single-use bags leads to positive environmental outcomes. But a national, uniform approach is needed, supported by consumer awareness and education programs.

While many state and territory governments have legislated plastic bag bans, others have held out. The Victorian government last year announced plans to ban single-use plastic bags, but despite widespread consumer support, it is yet to come into effect.

Supermarkets need to be open about the financial aspects of plastic bags, both costs and revenues.

Consumers may understand the procurement and logistics costs of the replacement plastic bag options will be higher – because the bags are thicker and heavier, and it takes extra time to pack different-sized bag options.




Read more:
How to break up with plastics (using behavioural science)


The distribution of net profits (not gross profits) from the sale of all re-usable bag options should be channelled into sustainability programs, research grants and education schemes. Programs need to be benchmarked, measured and publicly announced.

Shoppers will be more accepting of change if they can comprehend how their small sacrifice (say 15 cents) is helping the environment.

Shoppers also have an important role to play in the scheme of things. While it will take some time to break old habits, responsibility rests with shoppers to remember to bring a bag. If they forget, they simply need to buy another one.

The ConversationUltimately, the psychological contract needs to once again be aligned and in balance. To do this governments, retailers and consumers need to work together to solve this important environmental issue.

Gary Mortimer, Associate Professor in Marketing and International Business, Queensland University of Technology and Rebekah Russell-Bennett, Social Marketing Professor, School of Advertising, Marketing and Public Relations, Queensland University of Technology

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