Every little doesn’t help. Environmental spill-over effects

I’ve taken quite a lot of flak for pointing out how trivial domestic recycling is compared to an individual’s overall carbon footprint (here). A common theme in the criticism has been the idea that carrying out one action (like recycling) raises environmental awareness and makes it more likely that the individual will undertake further environmental behaviours. This is known as spill-over; the impact that one behaviour has on another. Spill-over might be positive – one pro-environmental behaviour leads to another. However it might also be negative – the idea that because I am ‘doing my bit’ in respect of one issue, this somehow excuses me from undertaking other pro-environmental behaviours.

Pro-environmental behaviours and spill-over. In the top diagram, negative spill-over is illustrated. In the bottom diagram, mechanisms of positive spill-over are illustrated. From behaviourworksaustralia.org

It is clearly an important phenomenon to understand, because it has a huge impact on how we can encourage people to undertake pro-environmental behaviours. Positive spill-over simplifies environmental messaging a lot – one behaviour leads to another in an ever increasing virtuous circle. However, if negative spill-over occurs, then encouraging people to take simple but minor actions (e.g. recycling) can actually make them less likely to do more important things (like limiting meat intake, or stopping flying). Or there may simply be no spill-over at all, positive or negative.

There are many studies in the environmental literature on pro-environmental behaviour and spill-over, with varying results. Given that slightly different questions are addressed in each study, it is not unexpected that results differ, and fortunately there is a technique called meta-analysis, which allows wider conclusions to be reached by assessing a number of factors about each study and then combining the results. This blog post draws on the recent meta-analysis of Maki et al. (2019) published in Nature Sustainability. If you can’t get through the paywall, the final version of the manuscript is available here albeit without fancy formatting.

So what did they find?

Firstly, spill-over effects are very small; if 100 people undertake a particular pro-environmental behaviour, this would result in about 5 intending to undertake another pro-environmental behaviour. A crucial thing to take into account when looking at studies of this type is what exactly is being measured; attitude or behaviour. Whilst an attitude change often precedes a behavioural change, we cannot simply say that because someone intends to fly less that they actually act on that intention.

The analysis of Maki et al. showed that the spill-over effect was even smaller and in fact negative when it came to behaviour; of our initial 100 people undertaking a pro-environmental behaviour, it would make no difference to other behaviours in 99 of these people, and would result in 1 person actually not undertaking a second pro-environmental behaviour.

The authors also found that when positive spill-over effects did occur, they were more likely to happen with similar actions. This makes intuitive sense; if somebody starts paying attention to recycling their household waste, they may be more likely to look for recycling logos when they buy new products. But there is no evidence to suggest that the connection is then made with other pro-environmental behaviours – taking the train instead of driving is not a behaviour that follows on from recycling household waste.

So what can we do?

A constant frustration of mine is that individuals expend a lot of effort on actions that don’t make much difference to climate change – the obsession with coffee cups and water bottles being the archetypal examples. If these actions don’t result in positive spill-over, then they are little more than mechanisms for assuaging environmental guilt. And it seems from Maki et al. (2019) that spill-over is at best very small. It follows that we need to focus on the big things that will make the most difference. Calculate your carbon footprint, discover where your biggest impacts are, and then act on them. Simple really.

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