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Consumers underestimate the emissions associated with food but are aided by labels

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Abstract and Figures

Food production is a major cause of energy use and GHG emissions, and therefore diet change is an important behavioural strategy for reducing associated environmental impacts. However, a severe obstacle to diet change may be consumers’ underestimation of the environmental impacts of different types of food. Here we show that energy consumption and GHG emission estimates are significantly underestimated for foods, suggesting a possible blind spot suitable for intervention. In a second study, we find that providing consumers with information regarding the GHG emissions associated with the life cycle of food, presented in terms of a familiar reference unit (light-bulb minutes), shifts their actual purchase choices away from higher-emission options. Thus, although consumers’ poor understanding of the food system is a barrier to reducing energy use and GHG emissions, it also represents a promising area for simple interventions such as a well-designed carbon label.
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1UTS Business School, University of Technology Sydney, Ultimo, New South Wales, Australia. 2Fuqua School of Business, Duke University, Durham, NC,
USA. 3Duke University School of Law, Duke University, Durham, NC, USA. 4Nicholas School of the Environment, Duke University, Durham, NC, USA.
There is a widespread scientific consensus regarding the
urgency to reduce GHG emissions1, and on the need to study
alternative interventions to do so. Much research has empha-
sized technological solutions such as greater energy efficiency and
increased use of renewable sources of energy2. More recently, it has
been recognized that diet change is also a potential solution worth
exploring35. Economic analysis has examined the virtues of mar-
ket-based mechanisms to influence demand, such as a carbon tax
that increases prices in line with social costs6. Increasingly, however,
social scientists have turned their attention to possible behavioural
interventions to influence demand7. For example, social psychologi-
cal research on social norms shows their effectiveness in producing
behaviour change in some contexts8,9. However, social norms are
problematic when the desired behaviour is rare10. Another interven-
tion approach is to ‘boost’ consumer decision-making by providing
relevant skills, knowledge and decision tools11. The efficacy of such
boosts requires first understanding the relevant knowledge gaps.
Attempts to modify behaviour typically presume that con-
sumers recognize the connection between their acts and the
consequences for energy consumption and GHG emissions12,13.
However, there is a growing body of research demonstrating
that consumers are often unaware or misinformed. For example,
Attari, et al.14 found that people had a rudimentary understanding
of the relative energy use of different electrical household appli-
ances (henceforth, appliances) and activities. On average, people
correctly recognized that refrigerators used more electricity than
light bulbs, but were insensitive to the true difference between
relatively high- and low-emitting appliances.
Research suggests that the food system contributes 19%–29%
of global GHG emissions15, which is similar to emissions from
US household electricity use16. Many factors combine to produce
such considerable emissions. Agriculture is highly industrialized.
Refrigeration and transportation tend to depend heavily on fos-
sil fuels. Natural gas is a key input in the manufacture of fertil-
izer. Cattle raised for beef and dairy products are major sources
of methane. Moreover, the process of raising meat is inherently
inefficient: fertilizer is used to grow feedstock, but only a small
portion of the feed becomes animal protein; the rest becomes
manure and methane. Thus, it takes 38 kg of plant-based protein
inputs to produce 1 kg of edible beef17. Finally, in many parts of
the world, burning forests to create grazing and agricultural land
also emits GHG emissions. A significant reduction in GHG emis-
sions from food could be achieved by changing consumers’ diet; in
particular, by moving toward more vegetarian or vegan meals18,19.
Even changing the type of meat consumed could have a large ben-
eficial environmental impact20.
Existing research, which typically asks consumers via survey
to indicate knowledge or agreement with facts about the environ-
mental impact of food, suggests that consumer awareness of the
environmental impact of meat production is low2124. Importantly,
however, those who believe that reducing meat consumption effec-
tively reduces GHG emissions are much more likely to intend to
reduce eating meat22,25.
Understanding consumersʼ perceptions of energy consump-
tion and GHG emissions of individual food items in a way similar
to Attari et al.14 is important because it can inform the design of
information interventions to help consumers understand the true
impact of their behaviours. Experimental studies investigating sim-
ple interventions to increase pro-environmental food consumption
behaviour have yielded only modest results26. Therefore, additional
research that identifies effective ‘boosts’ is needed.
One of the most straightforward ways to attempt to influence
food choice is through labels27. For example, a carbon label com-
municates information about the total amount of GHG emissions
from within a defined supply chain (for example, from cradle
to grave). Carbon labels provide information to consumers that
can be factored into purchase choices and also exert pressure on
manufacturers and retailers to provide consumers with lower-
emission options28.
The research associated with environmental labels on foods
is mixed. Some research suggests that consumers desire carbon
labels29,30. However, other research suggests that consumers barely
use environmental labels when making food choices31. Still other
research indicates that environmental labels can move consumption
Consumers underestimate the emissions
associated with food but are aided by labels
AdrianR.Camilleri 1*, RichardP.Larrick2, ShajutiHossain3 and DaliaPatino-Echeverri4
Food production is a major cause of energy use and GHG emissions, and therefore diet change is an important behavioural
strategy for reducing associated environmental impacts. However, a severe obstacle to diet change may be consumers’ under-
estimation of the environmental impacts of different types of food. Here we show that energy consumption and GHG emission
estimates are significantly underestimated for foods, suggesting a possible blind spot suitable for intervention. In a second
study, we find that providing consumers with information regarding the GHG emissions associated with the life cycle of food,
presented in terms of a familiar reference unit (light-bulb minutes), shifts their actual purchase choices away from higher-
emission options. Thus, although consumers’ poor understanding of the food system is a barrier to reducing energy use and
GHG emissions, it also represents a promising area for simple interventions such as a well-designed carbon label.
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... On the one hand, adding information about the ecological impact of the dishes is feasible and both customers and restaurants have expressed an interest in such information [14,15]. Carbon labels that provide information about products' GHG emissions have the potential to reduce the carbon footprint of consumer choices [16,17]. Analogously, the field of health promotion has provided meta-analytic evidence that health-related labels move people toward healthier food choices [18]. ...
... According to a recent review of behaviorally informed interventions aimed at climate-friendly food consumption [10], carbon labels can be classified as disclosures when they provide ecological information about a food item (e.g., GHG emissions) and as warnings when the label features salient information connoted with emotional value (e.g., traffic-light colors). There are several studies in the context of health- [18,[23][24][25] and environment-related food choice [16,17,[23][24][25][26][27] in which the examined labels combined these two types of nudging. In other studies, default and non-default dishes were varied systematically on menus or board menus [28][29][30][31]. ...
... Labels that indicate food items' GHG emissions have been examined in dining [23,26,27,42,43] and grocery shopping [16,17,24,25,44] settings. In most cases, such labels combine explicit information (disclosure) with a color signal (warning; [10]). ...
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In this study, we aimed to understand how restaurants can contribute to climate change mitigation via menu design. We investigated two types of interventions: changing the configuration of menu entries with variable side dishes so that the most climate-friendly option is set as the default and indicating the greenhouse gas emission of each dish via carbon labels . In an online simulation experiment, 265 participants were shown the menus of nine different restaurants and had to choose exactly one dish per menu. In six menus, the main dishes were presented with different default options: the side dish was associated either with the highest or with the lowest greenhouse gas emissions. The other three menus consisted of unitary dishes for which the default rules did not apply. All menus were presented either with or without carbon labels for each dish option. The results indicated that more climate-friendly dish choices resulting in lower greenhouse gas emissions were made with the low-emission than the high-emission default condition, and when carbon labels were present rather than absent. The effects of both interventions interacted, which indicates that the interventions partly overlap with regard to cognitive predecessors of choice behavior, such as attentional focus and social norms. The results suggest that the design of restaurant menus has a considerable effect on the carbon footprint of dining.
... Other changes attempt to address externalities, promoting the creation of public goods (for example, deceased organ availability 7 and charitable giving 8 ). In the domain of climate change mitigation, such interventions can strongly increase the number of consumers who sign up for a green energy contract 9,10 , reduce their residential energy use 11,12 , switch to a more cost-effective energy contract 13 or increase their willingness-to-buy environmentally friendly consumer goods 14 . In previous studies, behavioural 'nudges' either led to financial improvements for households (for example, resulting in a reduction of one's energy bill) or had no or only trivially negative impact on one's financial wellbeing. ...
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Behavioural public policy has received broad research attention, particularly in the domain of motivating pro-environmental behaviours. We investigate how far the efficacy of arguably one the most popular behavioural policy tools (green ‘default change’ nudges) depends on the associated cost. On the basis of a field study involving carbon offsets for over 30,000 flights booked by more than 11,000 airline customers, we show that green defaults have a large effect on voluntary climate action, even when several hundreds of Euros are at stake. The effect fully vanishes only as costs approach approximately €800. Berger et al. investigate green defaults under varying prices. Using field data from a flight compensation platform, they show that green defaults are effective. Their effectiveness, however, vanishes when costs become too high.
... Research has indicated that consumers have a poor understanding of the carbon footprint of different grocery products (Camilleri et al., 2019;Panzone et al., 2016;Sale, 2012). In the third experiment, we wanted to investigate whether repeated visits to a shop where graphical feedback was given about basket carbon footprint would result in more accurate representations of product carbon footprint through non-verbal (e.g., associative) ...
I investigated the impact of economic and non-monetary instruments on sustainable grocery consumption. I tested whether these instruments reduce carbon footprint of shopping baskets and increase CO2 knowledge in an experimental online grocery shop. In the first empirical chapter, I disentangled the price effect and psychological impact of carbon tax by testing the effect of price adjustments, injunctive norms, and tax salience on basket CO2. In the second experiment, the impact of traffic lights carbon labels were also tested. Over two experiments, little or no impact of carbon tax on consumption was found. However, I found that carbon labels decreased basket CO2. While tax signposts did not improve knowledge, carbon labels and norms did. In the second empirical chapter, I decomposed the psychological and price effect of bonus-malus tax by testing the effect of price adjustments, tax salience, and tax justification messages on basket CO2. In the second experiment, I tested whether carbon labels had an impact on basket CO2 and knowledge. Over two experiments, no effect of bonus-malus on basket CO2 was found. However, carbon labels decreased basket CO2 and improved knowledge. I found evidence for the impact of tax signposts on knowledge. Additionally, in these first two empirical chapters, it was found that knowledge was a mediator of the relationship between labels and consumption. In the third empirical chapter, I investigated the impact of goal setting techniques and of the provision of carbon footprint information about the products and the basket on consumption and compared their effectiveness. Over three experiments, it was found that goal-setting techniques were effective in reducing basket CO2. Multiple visits ameliorated knowledge, in the goal setting condition, even though it did not decrease basket CO2. While colour coded labels, on their own, did not have an impact on basket CO2, numerical labels did, after combing the data of two experiments.
... There is ample research studying which arguments convince people to consume less meat apart from the impact of nudges or social norms. In incentive compatible experiments, carbon labels are found to reduce meat consumption (Camilleri et al. 2019;Perino et al. 2014). Comparing nutritional, climate protection and animal welfare appeals, the latter is more effective in reducing meat consumption than the other two (Palomo-Vélez et al. 2018). ...
... Data collection and analytic approach. The sample sizes for studies 1a, 1b and 2a were determined based on similar research on consumer misperceptions of the energy consumption related to food and household appliances 60 . The sample size for study 2b was determined to be at least twice the sample size of study 2a per experimental group to allow for a sufficiently powered replication and extension. ...
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All-electric vehicles remain far from reaching the market share required to meaningfully reduce transportation-related CO2 emissions. While financial and technological adoption barriers are increasingly being removed, psychological barriers remain insufficiently addressed. Here we show that car owners systematically underestimate the compatibility of available battery ranges with their annual mobility needs and that this underestimation is associated with increased demand for long battery ranges and reduced willingness to adopt electric vehicles. We tested a simple intervention to counteract this bias: providing tailored compatibility information reduced range concern and increased willingness to pay for electric vehicles with battery ranges between 60 and 240 miles, relative to a 50-mile-range baseline model. Compatibility information more strongly increased willingness to pay than did information about easy access to charging infrastructure, and it selectively increased willingness to pay for car owners who would derive greater financial benefits from adopting an electric vehicle. This scalable intervention may complement classical policy approaches to promote the electrification of mobility.
... Despite the available data on the factual environmental consequences of meat production, many people still seem unaware of the effects of their meat consumption on the environment (Macdiarmid et al., 2016;Camilleri et al., 2019;Bschaden et al., 2020). Recent reviews conclude that most consumers are not ready to make food choices based on environmental arguments (Austgulen et al., 2018;Sanchez-Sabate et al., 2019). ...
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Introduction In addition to being a source of valuable nutrients, meat consumption has several negative consequences; for the environment, for animal welfare, and for human health. To persuade people to lower their meat consumption, it is assumed that the personal relevance of the topic of lowering meat consumption is important as it determines how people perceive the quality of the arguments. Method In an experimental exploratory field study ( n = 139), participants recruited from the general Italian population were randomized to one of the four conditions with a text with pictures on the environmental, animal welfare, or health consequences of meat consumption, or a text on mustard (the control condition). The dependent variables were self-reported consumption of red meat and processed meat after 2 weeks. Personal relevance was assessed in the pre-test with self-reported meat consumption and intention. Results The interaction between pre-test meat consumption and condition was significant: In participants who scored high on pre-test meat consumption, the self-reported red meat consumption after 2 weeks in the health argument condition was significantly lower compared to the control condition and the environmental argument condition. The effects of pre-test intention as a moderator were less certain. Discussion The persuasive effects of the different arguments made a difference only in people who ate a relatively high level of meat in pre-test, and the type of arguments made a difference. Although the present outcomes are caused by the specific formulations of the arguments in this study, the results do show that it is relevant to choose the arguments carefully to ensure effectiveness.
Introduction The United States has among the highest per capita red meat consumption in the world. Reducing red meat consumption is crucial for minimizing the environmental impact of diets and improving health outcomes. Warning messages are effective for reducing purchases of products like sugary beverages but have not been developed for red meat. This study developed health and environmental warning messages about red meat and explored participants’ reactions to these messages. Methods A national convenience sample of US red meat consumers ( n = 1,199; mean age 45 years) completed an online survey in 2020 for this exploratory study. Participants were randomized to view a series of either health or environmental warning messages (between-subjects factor) about the risks associated with eating red meat. Messages were presented in random order (within-subjects factor; 8 health messages or 10 environmental messages). Participants rated each warning message on a validated 3-item scale measuring perceived message effectiveness (PME), ranging from 1 (low) to 5 (high). Participants then rated their intentions to reduce their red meat consumption in the next 7 days. Results Health warning messages elicited higher PME ratings than environmental messages (mean 2.66 vs. 2.26, p <0.001). Health warning messages also led to stronger intentions to reduce red meat consumption compared to environmental messages (mean 2.45 vs. 2.19, p< 0.001). Within category (health and environmental), most pairwise comparisons of harms were not statistically significant. Conclusions Health warning messages were perceived to be more effective than environmental warning messages. Future studies should measure the impact of these messages on behavioral outcomes.
We report evidence from a field experiment (N=561) on how different reasons for reducing the consumption of red meat (health, climate and animal welfare) impact intentions to change behavior, the consumption of red meat and the enjoyment of meals. Surprisingly, the three concepts are not aligned. On average, two treatments affect intentions to reduce meat consumption, only one affects behavior, while all affect enjoyment of meals containing red meat. This contributes to the emerging discussion of the welfare effects of nudging. We find that behavioral changes are driven by our female participants eating in company. This confirms the importance of the social environment both in explaining gender differences and the channels by which nudges affect behavior.
Food-related GHG emissions are ultimately driven by residents' dietary structures. Influenced by socio-economic development and consumer performances, modification for residents' dietary structures should reflect the variations in food demand and nutritional requirements. An integrated approach was developed by incorporating autoregressive integrated moving average (ARIMA), multiple linear regression, and interval linear programming models into a general life cycle analysis (LCA) framework. In detail, (a) the GHG emissions from agricultural system were assessed in the LCA framework; (b) the variations in food demand influenced by socio-economic development were identified; and (c) a dietary structure optimization model that considered GHG emission reduction and dietary nutritional balance was established. Seasonal changes in nutritional requirements among different age and gender groups were considered in the model. A case study was proposed to illustrate the application of the approach in Guangdong province. Compared with the predicted food demands based on multiple linear regression models, per capita cereal, fruit, and meat intake would be slightly smaller than predicted demands, as well as vegetable, beans and nuts intake would be more than predicted demands. Among different age and gender groups, adult and adolescent males would contribute the biggest GHG emissions of diets, due to their high daily energy requirements. Conversely, adult and older women would contribute the smallest GHG emissions in food consumption.
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In recent years, policy makers worldwide have begun to acknowledge the potential value of insights from psychology and behavioral economics into how people make decisions. These insights can inform the design of nonregulatory and nonmonetary policy interventions—as well as more traditional fiscal and coercive measures. To date, much of the discussion of behaviorally informed approaches has emphasized “nudges,” that is, interventions designed to steer people in a particular direction while preserving their freedom of choice. Yet behavioral science also provides support for a distinct kind of nonfiscal and noncoercive intervention, namely, “boosts.” The objective of boosts is to foster people’s competence to make their own choices—that is, to exercise their own agency. Building on this distinction, we further elaborate on how boosts are conceptually distinct from nudges: The two kinds of interventions differ with respect to (a) their immediate intervention targets, (b) their roots in different research programs, (c) the causal pathways through which they affect behavior, (d) their assumptions about human cognitive architecture, (e) the reversibility of their effects, (f) their programmatic ambitions, and (g) their normative implications. We discuss each of these dimensions, provide an initial taxonomy of boosts, and address some possible misconceptions.
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Public understanding of the water system is vital in confronting contemporary water challenges, as public support is necessary for implementing measures to address shortages and repair infrastructure. In this study, university student participants (N = 457) were asked to draw diagrams illustrating how water reaches the tap in an average home in the U.S. and is then returned to the natural environment. We also conducted an expert elicitation (N = 15) to create a simplified, accurate diagram by which to code each student drawing. Results showed major gaps in understanding, where 29% of the student participants did not draw a water treatment plant, 64% did not draw a wastewater treatment plant, and 1 in 5 participants depicted untreated wastewater returning to the natural environment. For the majority of non-environmental students, the water system stops at the home. These gaps reveal a critical area for public environmental education efforts.
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Every attribute can be expressed in multiple ways. For example, car fuel economy can be expressed as fuel efficiency (“miles per gallon”), fuel cost in dollars, or tons of greenhouse gases emitted. Each expression, or “translation,” highlights a different aspect of the same attribute. We describe a new mechanism whereby translated attributes can serve as decision “signposts” because they (1) activate otherwise dormant objectives, such as proenvironmental values and goals, and (2) direct the person toward the option that best achieves the activated objective. Across three experiments, we provide evidence for the occurrence of such signpost effects as well as the underlying psychological mechanism. We demonstrate that expressing an attribute such as fuel economy in terms of multiple translations can increase preference for the option that is better aligned with objectives congruent with this attribute (e.g., the more fuel-efficient car for those with proenvironmental attitudes), even when the new information is derivable from other known attributes. We discuss how using translated attributes appropriately can help align a person’s choices with their personal objectives. The online appendix is available at This paper was accepted by Yuval Rottenstreich, judgment and decision making.
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Feeding a growing population while minimizing environmental degradation is a global challenge requiring thoroughly rethinking food production and consumption. Dietary choices control food availability and natural resource demands. In particular, reducing or avoiding consumption of low production efficiency animal-based products can spare resources that can then yield more food. In quantifying the potential food gains of specific dietary shifts, most earlier research focused on calories, with less attention to other important nutrients, notably protein. Moreover, despite the well-known environmental burdens of livestock, only a handful of national level feed-to-food conversion efficiency estimates of dairy, beef, poultry, pork, and eggs exist. Yet such high level estimates are essential for reducing diet related environmental impacts and identifying optimal food gain paths. Here we quantify caloric and protein conversion efficiencies for US livestock categories. We then use these efficiencies to calculate the food availability gains expected from replacing beef in the US diet with poultry, a more efficient meat, and a plant-based alternative. Averaged over all categories, caloric and protein efficiencies are 7%–8%. At 3% in both metrics, beef is by far the least efficient. We find that reallocating the agricultural land used for beef feed to poultry feed production can meet the caloric and protein demands of ≈120 and ≈140 million additional people consuming the mean American diet, respectively, roughly 40% of current US population.
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The consensus that humans are causing recent global warming is shared by 90%–100% of publishing climate scientists according to six independent studies by co-authors of this paper. Those results are consistent with the 97% consensus reported by Cook et al (Environ. Res. Lett. 8 024024) based on 11 944 abstracts of research papers, of which 4014 took a position on the cause of recent global warming. A survey of authors of those papers (N = 2412 papers) also supported a 97% consensus. Tol (2016 Environ. Res. Lett. 11 048001) comes to a different conclusion using results from surveys of non-experts such as economic geologists and a self-selected group of those who reject the consensus. We demonstrate that this outcome is not unexpected because the level of consensus correlates with expertise in climate science. At one point, Tol also reduces the apparent consensus by assuming that abstracts that do not explicitly state the cause of global warming ('no position') represent non-endorsement, an approach that if applied elsewhere would reject consensus on well-established theories such as plate tectonics. We examine the available studies and conclude that the finding of 97% consensus in published climate research is robust and consistent with other surveys of climate scientists and peer-reviewed studies.
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What we eat greatly influences our personal health and the environment we all share. Recent analyses have highlighted the likely dual health and environmental benefits of reducing the fraction of animal-sourced foods in our diets. Here, we couple for the first time, to our knowledge, a region-specific global health model based on dietary and weight-related risk factors with emissions accounting and economic valuation modules to quantify the linked health and environmental consequences of dietary changes. We find that the impacts of dietary changes toward less meat and more plant-based diets vary greatly among regions. The largest absolute environmental and health benefits result from diet shifts in developing countries whereas Western high-income and middle-income countries gain most in per capita terms. Transitioning toward more plant-based diets that are in line with standard dietary guidelines could reduce global mortality by 6-10% and food-related greenhouse gas emissions by 29-70% compared with a reference scenario in 2050. We find that the monetized value of the improvements in health would be comparable with, or exceed, the value of the environmental benefits although the exact valuation method used considerably affects the estimated amounts. Overall, we estimate the economic benefits of improving diets to be 1-31 trillion US dollars, which is equivalent to 0.4-13% of global gross domestic product (GDP) in 2050. However, significant changes in the global food system would be necessary for regional diets to match the dietary patterns studied here.
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Consumers are often poorly informed about the energy consumed by different technologies and products. Traditionally, consumers have been provided with limited and flawed energy metrics, such as miles per gallon, to quantify energy use. We propose four principles for designing better energy metrics. Better measurements would describe the amount of energy consumed by a device or activity, not its energy efficiency; relate that information to important objectives, such as reducing costs or environmental impacts; use relative comparisons to put energy consumption in context; and provide information on expanded scales. We review insights from psychology underlying the recommendations and the empirical evidence supporting their effectiveness. These interventions should be attractive to a broad political spectrum because they are low cost and designed to improve consumer decisionmaking.
Background Our daily food choices have a huge impact on the environment. Production of meat has a much larger impact compared with the production of vegetable-based proteins. In order to create a food production and supply system that is more sustainable and environmentally friendly, food consumption behaviour needs to change. A reduction of meat intake is necessary. The introduction of alternative protein sources (e.g., insects or cultured meat) might be one possibility to replace meat. Scope and approach The present systematic review identified 38 articles to answer the following three research questions: 1) Are consumers aware that meat consumption has a large environmental impact? 2) Are consumers willing to reduce meat consumption or substitute meat with an alternative? 3) Are consumers willing to accept meat substitutes and alternative proteins, such as insects or cultured meat? Key findings and conclusion Consumer awareness of the environmental impact of meat production is surprisingly low. This is true for consumers in various European countries. Likewise, willingness to change meat consumption behaviour in terms of reducing or substituting meat (e.g., by eating insects or meat substitutes) is low as well. How people can be motivated to decrease their meat consumption behaviour has been underexplored. In particular, experimental studies are lacking and further investigations should focus on strategies (e.g., nudging interventions) that might help to motivate pro-environmentally friendly meat consumption behaviour. Moreover, population-based studies are scarce, and we need more in-depth studies on the factors that increase people’s willingness to reduce or to substitute meat consumption.
This paper presents the results of a systematic literature review of greenhouse gas emissions for different food categories from life cycle assessment (LCA) studies, to enable streamline calculations that could inform dietary choice. The motivation for completing the paper was the inadequate synthesis of food greenhouse gas emissions available in the public domain. The paper reviewed 369 published studies that provided 1,718 global warming potential (GWP) values for 168 varieties of fresh produce. A meta-analysis of the LCA studies was completed for the following categories: fresh vegetables (root vegetables, brassica, leaves and stems); fresh fruits, (pepo, hesperidium, true berries, pomes, aggregates fruits and drupes); staples (grains, legumes, nuts, seeds and rice); dairy (almond/coconut milk, soy milk, dairy milk, butter and cheese); non-ruminant livestock (chicken, fish, pork); and ruminant livestock (lamb and beef). The meta-analysis indicates a clear greenhouse gas hierarchy emerging across the food categories, with grains, fruit and vegetables having the lowest impact and meat from ruminants having the highest impact. The meta-analysis presents the median, mean, standard deviation, upper and lower quartile, minimum and maximum results for each food category. The resultant data enables streamline calculations of the global warming potential of human diets, and is illustrated by a short case study of an Australian family’s weekly shop. The database is provided in the Appendix as a resource for practitioners. The paper concludes with recommendations for future LCA studies to focus upon with respect to content and approach