February 10th, 2012

Turtle economic value

4 minute read

by Chris Sherrington


A few days back I came across yet another article claiming that plastic bags really aren’t as bad as they are often made out to be – backed by the authoritative voice of last year’s Environment Agency Life Cycle Assessment (LCA) of supermarket carrier bags

The Agency’s study is focused on the carbon impacts of different bags. Important though this is, the report explicitly excludes from consideration effects such as littering. A ‘Life Cycle Assessment’ might sound impressively thorough to the press and the public, but I wonder whether a leatherback turtle would be equally convinced?

While LCA as a methodology is unable to account for a number of the downstream consequences of litter, Cost Benefit Analysis, although better placed to incorporate such effects, only rarely does so. The primary reason in the case of CBA is a lack of relevant studies relating to all the different impacts. For example, we don’t know much about what happens when plastics break down in the environment. Recent research, however, suggests that in the marine environment particles smaller than 1mm are being eaten by animals, and thus entering the food chain.

Understanding all of the ‘hidden costs’ of plastic bag litter may be impossible, but we could get to grips with some of the more obvious ones.


Charisma contest

For starters, plastic bags blowing about or stuck in trees look awful, and people don’t like to see them. A monetary value can be placed on this visual disamenity, broadly through asking people what they would be willing-to-pay for its removal. This value can then be compared against the expense of avoiding or clearing the litter.

But many of the negative impacts of plastic bags relate to what environmental economists term ‘non-use’ values. These are impacts that people don’t experience directly, but just knowing that they occur has a negative impact on how people feel. I’m thinking of tropical deforestation, or the extinction of a species.

CBA is unapologetically anthropocentric, and unsurprisingly people are typically willing-to-pay more to protect ‘charismatic mega-fauna’ (tigers, polar bears etc.), than for dung beetles. However, to the extent that preservation of a species requires preservation of its habitat, this willingness-to-pay can be considered to represent a wider desire for environmental protection. Policy development is a long way from applying principles such as biocentric egalitarianism, which accords nature an unqualified intrinsic value, and gives humans no privileged place. But accounting for non-use values that relates to human welfare at least starts to incorporate some of these wider aspects into the decision-making process.


Green turtle in Kona 2008

A Green Turtle (not a Leatherback, I know). By Mila Zinkova, via Wikimedia Commons

Turtle costs and benefits

Now to my mind, turtles are appealing, and in their own way, charismatic. Unfortunately, turtles have a habit of mistaking plastic bags for the jellyfish they feed on. I would rather that this didn’t happen, and I’m sure I’m not alone. Trying to gauge this feeling in monetary terms would begin to expose one of the hidden costs of carrier bags.

Plastic bag use has declined by over 90% in Ireland since the introduction of a levy. If such levies are introduced more widely, we can expect a gradual decline in marine carrier bag litter – and a reduction in the incidence of turtles ingesting bags. But would the benefits exceed the costs?

The Regulatory Impact Assessment for the recently introduced Welsh Carrier Bag Charge suggests that its monetised benefits will outweigh the costs – even without taking turtles into account. The reduced threat to marine wildlife and aesthetic benefits are noted as key non-monetised benefits that are currently deemed unquantifiable. But with a little additional research, a value could be placed on these effects, which would make the case for policy action even stronger.

2011 was a record year for leatherback turtles in the Irish Sea, supported by an increased population of jellyfish. If the Welsh charge leads to reductions similar to those achieved in Ireland, it will be good news for this summer’s expected influx, hopefully reduce the number whose dinners end in a fatal case of mistaken identity. I see value in that.


Chris Sherrington


Dr Chris Sherrington Senior Consultant

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Love the article, love the turtles and love the lovely green country side that is blighted by plastic rubbish and not just filthy bags. It makes me so mad, I boycott plastic. Yup, I wont have it in my bin. As a result I have sourced loads of plastic free products that I have listed over at the blog. You might find it useful if you want to reduce your plastic footprint even more.
Thanks for raising the issue and keeping it current.


Really interesting article. I make similar comments and thoughts on my blog sustainable seas about monetarisation of cultural ecosystem services on the coast.


keep it up!

Chris Sherrington
Chris Sherrington

Great blog Tavis – definitely one for us to keep an eye on