Abstract
A reduction in global meat consumption can significantly reduce the adverse environmental effects of the food system, but it would require widespread dietary changes. Such shifts to sustainable diets depend on several behavioural factors that have not yet been addressed in relation to the food system. This study links a behavioural diet shift model to an integrated assessment model to identify the main drivers of global diet change and its implications for the food system. The results show that the social norm effect (for instance, the extent of vegetarianism in the population that accelerates a further switch to a vegetarian diet) and self-efficacy are the main drivers of widespread dietary changes. These findings stress the importance of value-driven actions motivated either by intrinsic identity or by group dynamics over health and climate risk perceptions in steering diet change dynamics.
Generated Summary
This study investigates the factors that drive shifts toward lower meat consumption by linking a model of human behavior to an existing integrated assessment model. The research extends the functional enviro-economic linkages integrated nexus (FeliX) model with dietary choice population segmentation and models shifts between segments based on psychological theories used to explain individuals’ environmental actions. The study examined the environmental effects of numerous diet change scenarios and identified behavioral model elements most critical in obtaining widespread diet shifts. The study adopts a feedback perspective on climate mitigation, considering two main feedback mechanisms based on the Theory of Planned Behaviour and the Protection Motivation Theory. The study considers the impact of social norms and attitude towards diet change. The impact of climate change and health risk on diet change were also examined. The study used a public segmentation and innovation diffusion approach, dividing the population into meat-based diet followers and vegetarians and using global food demand resulting from these population dynamics reflected on the land use and climate modules of the FeliX model. The factors that steer diet changes towards lower meat consumption are investigated to identify the main drivers of global diet change and its implications for the food system.
Key Findings & Statistics
- A flexitarian diet (one serving of red meat per week) would reduce GHG emissions by around 50% by 2050.
- 1.8% of daily calories are obtained from red meat (beef and lamb) in the world’s average diet.
- In a flexitarian diet, one serving of red meat per week constitutes only 0.5% of daily caloric intake.
- Market research in the United Kingdom shows that around one third of consumers identify themselves as meat reducers.
- The study examines four diet composition scenarios.
- In Sc1, Sc2, and Sc3, the diet composition changed gradually from the reference diet type in 2020 to the given diet type in 2050.
- The study analyzed the environmental impact of diet change, showing a wide range for the ‘percentage of vegetarians’ in the total population, especially towards 2100; however, the population is mostly around 20% vegetarian.
- In the reference diet composition scenario, the emissions vary between 10 and 15 billion metric tons of carbon dioxide equivalents (GtCO2e) in 2100.
- The study finds that the highest reduction potential is in the third diet composition scenario.
- The study suggests that drastic shifts by a small group may not be sufficient to reap the environmental benefits of diet change.
- The study indicates high cropland use in the moderate-meat-consumption scenarios (Sc1, Sc2) compared to the reference diet composition scenario (Sc0).
- Sustainable diets (such as a flexitarian diet with one serving of red meat per week) have the potential to reduce deaths by 10.8-11.6 million per year.
Other Important Findings
- The social norm effect (e.g., vegetarianism in the population) and self-efficacy are the main drivers of widespread dietary changes.
- The study finds that the model parameters causing the variation in diet change are similar across the diet composition scenarios.
- The study found that the most distinguishing factors are: the parameter ‘x0 social norm’ of the young population, the ‘self-efficacy multiplier’ of the females, and the ‘normal fraction intended to change diet.’
- The responsiveness of the young population to increasing health risk is among the most distinguishing factors in 2050, whereas the factors affecting climate risk perception and response efficacy of the secondary education graduates appear more important in the long term.
- In the low-meat scenario (Sc3), none of the factors except the three above-mentioned parameters are distinctively influential on widespread diet changes.
Limitations Noted in the Document
- The study’s scope is limited to income, social norms, climate and health risk perception, and other psychological factors as drivers of diet change.
- Demographic heterogeneity is included in terms of gender, age, and education level, with population dynamics investigated in a globally aggregate manner.
- The study’s findings may not be directly applicable to local dynamics.
- The study acknowledges the uncertainties related to human behavior and data limitations.
- The study used a scenario-based approach and does not provide best-estimate projections.
- The model parameters are calibrated according to variables they are not directly linked to.
- Multiple sets of parameter combinations could match the historical data.
Conclusion
The study underscores the significance of value-driven actions motivated either by intrinsic identity or group dynamics over health and climate risk perceptions in steering diet change dynamics. The study highlights that behavioral change is crucial, and the environmental benefits of dietary shifts depend on the scale and nature of these changes, emphasizing the need for population-wide modifications rather than reliance on a small group of individuals. The research demonstrates the importance of the social norm effect, self-efficacy, and the need for a holistic approach that considers demographic factors. The study emphasizes the role of social norms and self-efficacy while suggesting that climate and health risk perceptions are less influential. It stresses the need for a population-wide shift, rather than reliance on a small group, and provides insights for policy interventions, such as empirical studies to quantify the relation between social norms and diet change behavior. The study’s findings can assist in prioritizing issues and factors to guide future model development and data collection. The study states that the modelling framework can be extended to capture cultural values and worldviews and may be customized to represent local settings.