Can we fight climate change by convincing people to change the way they treat leftovers and plan their shopping lists?
While public policy, technology and corporate actions play a large role in influencing the trajectory of emissions, the daily choices billions of consumers make about whether to walk or drive, or the temperature they set in their homes, can be just as impactful. According to the Intergovernmental Panel on Climate Change’s Sixth Assessment Report, changing consumer behavior can potentially reduce greenhouse gas emissions 40-70% by 2050.
That includes changing consumer behavior around food waste. Today, an estimated 17% of all food produced in the world is wasted at the consumer end of the food supply chain — in retail, food service and households. If current trends persist, food waste will double by 2050.
Reducing food waste is an important strategy for ensuring adequate global supply of food at a moment when conflict and rising prices are contributing to a looming food security crisis. But it’s also a potentially powerful lever to combat climate change, as rotting food is a major emitter of methane, a potent greenhouse gas. The potential is so great, in fact, that Project Drawdown identified reducing food waste as the single-best solution to limit global warming.
Food waste is a multi-faceted challenge that results from a sequence of seemingly small decisions that households make every day — which is why behavioral science interventions have the potential to help us reduce the amount of food that ends up in landfills and the associated emissions. As new WRI research finds, making food waste socially unacceptable through the right type of messaging can elevate the importance of this issue in consumers’ lives. When people were informed that many others are making efforts to reduce food waste at home, it changed attitudes, raised awareness, and encouraged consumers to talk about it.
The Role of Social Norms in Human Behavior
Social norms are rules and standards commonly understood by a group that guide or constrain social behavior. Whether the goal is to use less energy, choose sustainable foods or conserve water, research has shown that shifting social norms is an effective strategy for motivating people to change their habits and actions.
Hotels, for example, have encouraged guests to reduce water use by including social norms messages on door hangers that mention how other guests reuse their bath towels (rather than send them to be washed every day). The implication is that new guests should do the same.
These messages have been proven to work in reducing excess laundry. In two studies, WRI researchers set out to understand whether social norms messages are just as effective in nudging people to prevent household food waste. We found that while norms messages, by themselves, are not sufficient to change behavior, they can contribute to significant reductions in waste when included in in multi-component interventions.
Measuring Food Waste
In one study, food waste produced by 250 households in Washington, D.C. was weighed over six weeks. Households were randomized into one of three groups. A control group received no intervention. A first intervention group received standard education materials from the National Resource Defense Council’s “Save the Food” campaign. And a second intervention group received Save the Food materials along with specially tailored social norms messages. These included messages about a relevant local group of households, such as: “More than three-quarters of DC residents report storing food properly to maximize its shelf life,” and “More than half of DC residents reorganize their refrigerators, freezers, and pantries to avoid forgetting about food at home.”
Over the study period, the control group wasted 25% more food by the end of measurement than at the start. By contrast, the two intervention groups did not see any increase in their food waste over the period. In follow-up surveys, households in the social norm intervention group reported that they were more likely than both other groups to engage in behaviors to prevent food waste at home, including planning meals, using a list when grocery shopping, and eating their leftovers, among other actions.
This study did not show that social norms messages worked better than standard education intervention materials when it came to changing measured food waste. But the messages did influence householders’ stated beliefs that they could make a change through their own actions. Participants in the social norms intervention group also reported engaging in food waste prevention at home — such as meal planning and avoiding eating out when food in the fridge needs to be finished — more frequently than those in the control group.
Discouraging Food Waste on Social Networks
To better understand whether certain social norms messages are more impactful than others, we conducted a second study. We tested whether different norm messages delivered through Facebook advertising had differential influence on consumers’ food waste knowledge, attitudes and behavior on the platform.
During the study, 20 million Facebook users in the UK and 20 million users in Germany received one of four ads containing a social norms message, or no ad at all. The messages either included a “descriptive” norm (what others are currently doing in relation to food waste at home), an “injunctive” norm (what others think is the right thing to do in relation to food waste at home), or a “dynamic” norm (how others are beginning to change their behavior in relation to food waste at home). Participants were then presented with poll questions that measured their knowledge, attitudes and behaviors regarding food waste.
None of the messages was a clear winner. But each had a distinct effect on Facebook users’ knowledge, attitudes and behaviors. Together, the messages encouraged more than 60,000 users to visit WRI’s website to access further information on how to prevent food waste at home. And the findings were consistent across both countries. Dynamic norms messages worked best to encourage Facebook users to share information on food waste. Injunctive norms messages changed people’s views regarding what each of us should do to reduce waste. And descriptive norms messages increased agreement with the statement that individual actions to reduce waste can make a difference.
However, when it came to clicking to learn more about food waste, users responded differently based on their location. German users responded most to a dynamic norms message, whereas British users were least swayed by a dynamic norms message.
Preventing Food Waste, Curbing Climate Change
These intriguing findings represent a beginning. Further research is now needed to fully understand why some message types were more impactful for different outcomes, why the messages impacted residents in each country differently, and to what extent such messages lead to observable behavior change on household food waste.
Regardless, it’s clear that incorporating social norms messaging into consumer education campaigns is a low-cost, low-risk strategy that should be part of the suite of tactics to tackle the growing food waste problem.
