Participants demonstrated improvements in food security status (p = 0.030), cooking confidence (p = 0.001), food preparation behaviours (p = 0.006), nutrition knowledge (p = 0.033), vegetable consumption (p = 0.043), and a reduction in intake of sugar-sweetened beverages (p = 0.017), and salty snack foods (p = 0.011). The interviews revealed that participants learned to stretch their food budgets and make meaningful changes to their food utilisation (a key dimension of food security). Interviews also identified enablers  and barriers  to achieving food security. Acknowledging the need for a multi-faceted approach that also addresses upstream determinants, interventions like NEST may play a role in promoting food security and food literacy.Food literacy interventions are widely implemented to improve the food security and health of low-socioeconomic adults. The purpose of this study was to conduct an inquiry into the value of OzHarvest’s six-week NEST (Nutrition Education and Skills Training) program in promoting food security and food literacy, and to identify the barriers and enablers that participants experienced in sustaining food security, and in utilising their food literacy skills beyond the program. A descriptive evaluation study with pre-post surveys ( Globally, one in five deaths are attributed to a poor diet , with obFood insecurity is defined as the ‘limited or uncertain availability of nutritionally adequate and safe foods, or [the] limited or uncertain ability to acquire acceptable food in socially acceptable ways’  (p. 1). The term ‘food literacy’ has significantly increased in policy, practice, and research over the past decade . Vidgen There is evidence to suggest that improved food security and food literacy skills can result from these interventions ,13,14,15The Nutrition Education and Skills Training (NEST) program is a food literacy intervention founded in 2014, by OzHarvest, a national Australian not-for-profit food rescue organization. The NEST program is yet to be formally evaluated, hence, the aim of this study was to conduct a descriptive evaluation study into the value of OzHarvest’s NEST program in promoting food security and food literacy, and to identify the barriers and enablers that participants experienced in sustaining food security, and in utilising their food literacy skills beyond the NEST program.The NEST program is a 6-week, 15-h guided public health nutrition program, which aims to improve the nutrition, food literacy, and cooking skills of low-socioeconomic Australian adults. Trained NEST facilitators  travel to organisations, such as rehabilitation and health services, food pantries, community centres, and housing support services, with all food, equipment, and educational materials required for the program delivery. Each session integrates a series of nutrition activities, goal setting, and practical cooking lessons, utilising recipes from OzHarvest’s Everyday (photo-based) Cookbook, culminating in the sharing of a meal together. OzHarvest’s nutrition team developed the program to align with the Australian Dietary Guidelines (ADG) , and theNEST incorporates best practice and sustainable public health program evaluation approaches. A process and outcome evaluation framework was implemented to systematically monitor, sustain, and adapt the program, to ensure sustainability, integrity, and fidelity . All NESThe objectives of the program are to: (1) improve participants’ food literacy, (2) increase consumption of core foods aligned with the ADG, (3) decrease consumption of discretionary foods and drinks, (4) reduce household food insecurity, and (5) increase social engagement  checklist  see Sup. The mixn = 24) and incomplete surveys (n = 11), the final data set included 21 matched pre-post survey responses.OzHarvest provided pre-existing, de-identified pre-post survey data, with no control group, from a convenience sample of seven NEST programs that were held in Melbourne, Sydney, and Newcastle. The organisations hosting the NEST programs were responsible for the recruitment of participants; the only eligibility criteria provided to agencies was age (18+ years). When organisations sign up to the program, they are provided with a toolkit of posters and flyers to assist in promotion and recruitment of participants that are accessing their services. Each NEST program consisted of groups of 6 to 15 participants. NEST facilitators were trained to distribute the surveys and data was collected from participants before the NEST intervention (baseline), and immediately after the last NEST session (March–June 2019). Fifty-six participants were recruited into the NEST program and completed the pre-survey, and 32 participants completed the post-survey. After removal for attrition  food security measure . This 6-Cooking confidence and self-efficacy were measured using a tool that was adapted from Devine et al.  and BartChange in daily fruit and vegetable consumption was captured using self-reported questions of fruit and vegetable intake (serves per day), and based on the 1995 National Nutrition Survey . These qParticipants self-completed, except for those with low literacy (identified by the host organisation staff), to whom the survey was read aloud by trained NEST facilitators and volunteers for a verbal response. The surveys were designed to be completed in approximately 15 min.n = 56) from this sample of NEST program locations were notified of the opportunity to participate in the interviews, through recruitment posters and flyers that were distributed at the NEST program locations by NEST facilitators or the organisation staff that hosted the program, in April to August 2019. This was considered the most appropriate method of recruitment due to the ‘hard to reach’ nature of this demographic [Qualitative semi-structured interviews were conducted with a sub-set of participants who volunteered to be interviewed, from the same sample of seven NEST programs. All participants  or via video call (n = 1) [n = 11) some of the interviewees survey responses may have been removed from the final results.Nineteen participants elected to participate in the interviews; two did not met the eligibility criteria of attending at least four of the six program sessions, and so seventeen participants were interviewed by the lead author (EW). The interviews ranged from 13–59 min long (average time 29 min), and due to the contingencies of interstate fieldwork, interviews occurred face-to-face ( (n = 1) . This sa (n = 1) ,40,41. IA semi-structured interview guide see  was devep < 0.05 for all tests). Power calculations were not conducted, as this was an exploratory study.Statistical analyses were performed on survey data using STATA statistical software release IC 15.1  . Descripn = 3) or a transcription service (n = 14). A general inductive approach for the analysis of the qualitative part of this study was undertaken. The COREQ checklist was followed to strengthen analysis and interpretation conformability [After interview completion, the audio files were transcribed verbatim by the lead author , suggesting an improvement in participants’ food security, from baseline to post intervention.At baseline, 61.9% of participants were classified as food insecure, as low food security (score of 2–4: 47.6%), or very low food security (score 5–6: 14.3%) . At postp = 0.001). All individual cooking confidence measures improved, except confidence in one’s ability to buy healthy food on a budget. The combined average food behaviour score showed a significant increase in health-promoting behaviours from baseline to post-intervention (p = 0.006) (p = 0.033) (= 0.006) . Most fo= 0.033) . p = 0.043) (p = 0.017). The overall average consumption of discretionary foods decreased by almost half a serve, although this difference was not statistically significant  . There wnificant .The interview findings provided a deeper understanding of the pre-post survey results from the NEST participant’s perspectives. Seventeen interviews were conducted with past NEST participants, within two to ten weeks of program completion. The majority were male (64.7%), born in Australia (70.6%), living in social housing or rehabilitation centres (58.8%), with a household income of <$AUD 575 per week (58.8%) . Their aThe food literacy skills participants gained from the NEST program were reported to help achieve the food utilisation dimension of food security. The NEST participants described improvements to food literacy in terms of cooking confidence, food preparation and cooking methods, food selection and eating behaviours, and stretching food budgets and saving money.Participants described confidence in being able to shop for food, read and follow recipes, and prepare foods safely. Participant 5 explains, “the cooking experience… this was the first time… and you don’t realise how good you are until you have a go at it and I thought, there you go that proves that I can do something when I want to”. Participants described that this confidence brought feelings of pride and self-efficacy. According to Participant 14, “pride’s a big thing in life… I did this and the fact that I did it, I was proud of myself”. This new confidence in cooking motivated participants to utilise their new skills by increasing their cooking frequency. Increased cooking confidence also led some participants to experiment by cooking with new foods and recipes. Participant 14 shared, “I’ve been cooking things since I’ve done the program, which I wouldn’t have done before, like pasta and the way I prepare my vegie’s… I enjoy that, and I experiment with that… I did one yesterday, which was the nicest I’ve ever got it”. This improved confidence led some participants to share future plans to utilise these skills beyond their current circumstances, with plans to cook for their families once they were out of rehabilitation, or to cook for themselves once they left their assisted living residence .A shift to prepare meals using healthier ingredients and cooking methods was evident in the perceived outcomes since the NEST program. As described by Participant 10:From the fifteen months I had been in <rehabilitation> we used to have four or five days a week of fried foods… Mainly from awareness, mainly from affordability… So, what the NEST program was teaching us… we have been incorporating that into our weekly menus… a healthier way of cooking with healthier oils… to do chips steamed or oven… we don’t need to put everything in the deep fryer, which is what we were doing.Many participants shared that they were incorporating more vegetables, baking instead of frying, and choosing fresher products, rather than packaged or pre-prepared meals. Interviewees also described learning how to substitute more expensive ingredients for cheaper ones, to extend meals. Replacing meat or extending it by adding other protein sources (such as legumes) was a commonly reported strategy. Participant 3 described, “it’s sort of helped to eat—like before the program I wouldn’t know if you can replace this with this… You can have legumes or soybeans or something like that instead of meat”. Another strategy was substituting more expensive cuts of meat for cheaper ones, as Participant 16 explained, “I bought a chook but I roasted it myself and I’ve been using the roast chicken from that for my lunches during the week... Like instead of just buying…chicken fillets and cook them… A whole chook cost me like $4 or $5, where the chicken fillets are like $4 or $5 for three… just making slightly smarter options”. Substituting ingredients was a particularly important food literacy skill for participants that were receiving rescued food, as participant 12 (from an agency that receives a weekly food delivery) shared, “I <was> made aware of what you can substitute things for… what you can add in, what-you can change things for other things. As long as it’s similar… I look at squash being zucchini, they’re just a different shape, different colour but essentially…do the same thing”. The key benefit of substituting and replacing ingredients was that participants were able to more effectively utilise their ingredients to “make a big meal and have it stretched over a couple of nights or lunch and dinner”.Participants described that the NEST program increased their understanding of healthy eating practices and as a result were more mindful when selecting foods to eat. As participant 1 explains, “It gave me some insight into healthy eating, what are good options and what I should be eating…we got information on that thing about the salts and the sugars and all that … and how much is appropriate fat…and which ones are not so good and all that”. They continued to explain that when they buy food, they “look at those items and you say which ones are appropriate and which ones are not for your own overall health”. Several other participants reported that they “learnt about the reading on the packets” and “check the labels a bit more carefully now”. Increased variety “in different types of food” and “balance in cooking” were also reported, with participants explaining that they’ve swapped to wholemeal grains and cereals and choosing low fat varieties of dairy products.Several participants explained that in the NEST program, they learnt about affordable food options, food storage techniques, and shopping strategies , which assisted them to make their food budget stretch further. Acquiring food budget skills was particularly important for Participant 16:When I became unemployed it was like we can’t have those easy quick meals because they’re not cheap. So, I had to re-learn myself how to cook meals again and make them stretch… I just got so caught up in easy buy stuff, and like just for the convenience of it all. Because we went from having two fairly good wages to one wage that barely covered anything, we really had to learn how to–just the basics again. I know it sounds so silly, but it’s true…A key part of stretching budgets for interviewees was linked to food literacy skills of storing and utilising foods that participants already had, as Participant 11 described that NEST taught them, “How to make use what you have in the cupboard, which saved us a lot of money in the long run, and gave us healthier food… our money budget for shopping has reduced, and we are coming back with change as well, we used to run out”.Some participants experienced enablers that supported them to remain food secure (or less at risk of very low food security) beyond the NEST program. The enablers that participants reported were: (1) receiving and providing support to family or friends and (2) provision of charitable food.Participants described that regular support from family or friends was an enabler for sustaining food security or protecting from the worst aspects of food insecurity. Some participants shared that they had a family member or friend provide regular support through the provision of money, groceries, and/or cooked meals. For others, support was provided through disseminating the knowledge and skills gained in the NEST program. For Participant 16, this meant sharing the information she learnt from the program with her husband. She explained that her husband, “Is happy to go shopping for me sometimes too now which is amazing. He hates any type of shopping. So, to see him go grocery shopping is a big thing because… he knows now to look at the bargains, I’ve taught him how to do that as well”. For others, the knowledge and skills gained from the program were sustained after the program, because participants were motivated to support their family and friends. As Participant 13 shares: “I will stay on that path, you know, because it’s better. And I’ve got kids to play with… I found it very helpful to get some ideas… I think about when I come home, how will I cook and how healthy I can eat… I want to cook for my wife, my kids more healthy… and learn more about healthy living”.Most participants reported accessing some form of charitable organisation for food, but their reliance on it varied. Some interviewees obtained almost all of their food from food charities; most were accessing a food charity once a week. Meanwhile, for participant 16, food relief was accessed regularly, but only for a short-period of time; she shared, “So, up until recently I was unemployed… I was going to <organisation name> for food donations. Like a week under five months I was unemployed for. So, I was going to <organisation name> for all that time to help…. I felt that <organisation name> and OzHarvest were all there to help me and my husband get ourselves back on our feet and get us through this really bad, dark, <expletive> situation”. Interviewees were living in a rehabilitation centre that provided all ingredients and a meal roster, for all residents to take turns preparing meals. In these instances, the provision of food extended budgets and helped to save money, so that the organisation could “spend the money on other things that are necessary around the house, which is good. So OzHarvest does save us a lot of money around the place”.Participants still faced key barriers to food security, these were described as: (1) lack of economic access to food, (2) pre-existing health issues, and (3) provision of charitable food.Access to food includes economic access or affordability of food (17). It is evident from the themes above that the NEST program supported participants to stretch food budgets and save money, but the difficulty of not having enough income to afford food remained. Participant 8, for example, explained Unfortunately, due to the cost of living and expenses, making food and getting food is quite hard… you need a roof over your head and you need to be able to pay bills and stuff, so try and pay them off... Then food generally comes last. It just means lack of food a lot of the time… there’s no point in me saying, ‘Yes, I’ll cook three meals a day and I’ll make sure to include every type of food.’ Because of course, that would straight away be a fail because it’s not accessible.Many participants struggled to afford safe, nutritious, adequate, and culturally appropriate food. For many, this meant forgoing fresh fruit and vegetables. Participant 7 explained, lack of money meant that she “can’t really get the veggies you need in your diet, you can’t get a lot of the fruit you need”. As a result, she turned to cheaper foods, “that will fill you up, keep you energised for ages, but not break the ability to pay the bills”. She described that this “has been upsetting” as she and others want to eat healthier, but “it’s all about living with what you can”.Mental health issues were also reported by some participants as a barrier to food security. Participant 1 explains, “some barriers like to go out and shop and get my own healthy food. Sometimes the barrier’s a bit of anxiety… worried about people looking at me and all that”. Pre-existing mental health issues were found to not only impact the participant’s ability to physically access the food, it was also mentioned as a barrier to utilising the skills developed from NEST. Participant 8 explained that she and other participants “were facing barriers in regard to ability to get the food or have energy to cook”. This was echoed by Participant 2, who shared, “I haven’t been cooking much lately because I’ve been a bit depressed, but yeah, normally on Saturday’s I’ll cook a roast or something for me and <name of friend>”. Drug and alcohol addictions were also identified by participants as obstacles to them becoming both food secure and healthy. Participant 10 described that he “was a lot fitter when I was younger and I lost that due to my drug addiction, yeah umm I’ve lost a lot of sort of wants. The lifestyle I was living was nearly impossible to be doing healthy living you know”.As discussed above, most participants accessed food from charitable organisations, and some viewed this as an enabler for food security. However, for others, the types of food provided by charitable organisations were considered a barrier, as they were not necessarily nutritionally adequate. Participant 1 explained, “I haven’t really been cooking for myself that much. I haven’t changed that. Mainly we get meals here…. The meals here are not too bad, health wise. The desserts can be a barrier because we have dessert as well”. Participant 10 explained that, while NEST encouraged their household to “want change and want healthy eating, a lot of goodies come on the OzHarvest truck”. It is evident that the key nutritional messages from the NEST program were at odds with some of the rescued food provided by OzHarvest and other organisations. This was also reported by Participant 8, who shared: we’re given a bag of food and sometimes it’s quite simply a loaf of bread, a little bag of cereal, and some muesli bars and maybe one packet of pasta. Which means it doesn’t go far… as grateful as we are for the amount of food we get, it’s not possible to make certain recipes out of it. And quite simply put, if there’s no ability to cook… it’s just going to actually make you feel more upset.This descriptive evaluation study investigated the NEST Program’s impact on food security and food literacy, and identified key barriers and enablers that participants experienced in sustaining food security and utilising their food literacy skills beyond the program. Both interview and survey findings suggest that NEST had a significant effect on food security and food literacy. The pre-post survey data suggested an improvement in participants’ food security from baseline to post intervention. and improvements in food literacy , and some measures of dietary intake .The qualitative interview data analysis yielded themes that described how the NEST program changed participants’ food literacy and food insecurity, as well as the barriers and enablers to food security that participants experienced. The program was shown to improve food security and increase food literacy skills, enabling participants to stretch their food budgets, select and cook healthier foods, and save money. Support from family or friends and the provision of food from charitable organisations enabled some participants to feel more food secure beyond the program. Participants still faced key barriers that were linked to other dimensions of food security, including lack of economic access to food, and pre-existing health issues. Interestingly, the provision of charitable food was also considered a barrier to some participants, due to the lack of variety and nutritionally adequate foods, which hindered participants in utilising the skills and knowledge they reported obtaining from the NEST program.Food security improved by 28% from baseline to post-intervention among participants. This is slightly higher than that reported in other similar interventions, which have found a 12.9% to 25% improvement in food security ,15, or nThe NEST program is underpinned by social cognitive theory, and the program aims to build self-efficacy in its participants. Increased self-efficacy has been shown to improve an individual’s capability across both the access and utilisation dimensions of food security ,12. HoweThe results of the NEST program on food insecurity are promising, however, understanding the enablers and barriers to food security for these participants is essential to properly consider the role interventions like NEST play in promoting food security. There is evidence that the provision of food assistance together with a food literacy intervention improves food security ,18. ThisUnlike the US, Australia has no national system of welfare food provision based on income, rather, charitable food is available, but can vary in quantity and quality. Acquiring food from charitable organisations in this way is widely considered as a socially unacceptable way of procuring food ,53,54,55Both quantitative and qualitative data demonstrated that NEST improved the utilisation dimension of food security. However, the qualitative data revealed that lack of economic access due to the price and affordability of foods remained a key barrier to food security. This is not surprising, as most interviewees 58.8%) reported very low income levels, relying on ≤AUD $575 per week, compared to the average weekly wage of approximately AUD $1250 in 2019 in Australia . Recent .8% reporThis study adds to the body of literature around food literacy interventions, which to date, has shown a varying effectiveness of impact on food security ,13,18,20Further research is also required, that investigates and addresses the food environment and external factors related to food security. For example, programs should ensure that food literacy intervention participants can access affordable high-quality foods in the regions where interventions are conducted . As foodFood insecurity occurs at a global, national, community, household, and individual level, and is the result of multiple and complex environmental and individual factors ,64. EnviThis enquiry into the NEST program suggested an improvement in participant’s food security from baseline to post intervention. However, education alone cannot change food prices or address other upstream determinants of food security. The barriers to food security that participants faced were related to other dimensions of food security, indicating the need for multiple approaches to food insecurity, including immediate food assistance, food literacy interventions, and structural level initiatives. Economic access to nutritious food was highlighted as a key barrier to food security, hence the core part of this structural level initiative would ensure that all citizens have a ‘right to food’, achieved through the provision of an adequate living wage . This stThis study found that a theoretically grounded program that caters to the needs of low-income groups can play at least a short-term role in building skills and addressing food literacy and food security. Therefore, such programs could comprise a part of broader community-based approaches to addressing food insecurity. However, aspects of the program could be improved. For example, the key nutritional messages from the NEST program were at odds with some of the rescued food provided by OzHarvest and other organisations. There is a need for charitable food organisations to develop nutrition guidelines, to ensure that they are providing a healthy food environment for their participants.The qualitative findings found that mental health issues were barriers to food security. There is an increasing amount of research exploring the bidirectional impact of mental health issues and nutrition . CookingSupport from friends and family was reported as an enabler for sustaining food security or protecting from the worst aspects of food insecurity. There is sound evidence that engagement from social support can increase the effectiveness of dietary interventions . HoweverThe pre-post surveys reported insignificant changes in participant’s confidence to cook healthy on a budget, whilst the qualitative results showed that tips on stretching food budgets were beneficial to participants. This provided an opportunity to review the way NEST facilitators were delivering the content and amendments to the NEST facilitator handbook were made to ensure useful advice on budget healthy eating was explicitly incorporated into each module. For example, highlighting that adding lentils to spaghetti bolognaise not only provides additional protein and fibre, it also can save money, as 500 g of beef mince costs AUD$8.00, whilst a 475 g tin of lentils costs AUD$2.00.Overall, these findings support the current public health research that food literacy interventions can play a small, but important role in the adoption of healthier food behaviours .This descriptive evaluation study was strengthened by its mixed methods approach, through the use of qualitative data that provided some explanatory framework to the quantitative results. The first author is an employee of OzHarvest in the role of National NEST Program Manager, and was involved in the development and delivery of the NEST program. The consequent familiarity with the program and experience working with people experiencing food insecurity is often seen as a strength in qualitative research ,71. ThisA limitation of this study is the relatively small sample size, and the lack of control or comparison group. The strongest level of evidence of a food literacy intervention’s impact is generated from randomised control trials that include a control group . HoweverThis descriptive evaluation study explored the value of OzHarvest’s NEST program in improving participants’ food security and food literacy. The results of this study indicate that the NEST program may improve food security and food literacy. The program was shown to increase food literacy skills, enabling participants to stretch their food budgets, select and cook healthier foods, and save money. Despite the positive findings of this study, the obstacles to food security reported by participants confirm that food literacy interventions alone cannot impact the other determinants of food insecurity . NEST pr


Countries generally agree that global greenhouse gas emissions are too high, but prefer other countries reduce emissions rather than reducing their own. The Paris Agreement is intended to solve this collective action problem, but is likely insufficient. One proposed solution is a matching-commitment agreement, through which countries can change each other’s incentives by committing to conditional emissions reductions, before countries decide on their unconditional reductions. Here, we study matching-commitment agreements between two heterogeneous countries. We find that such agreements (1) incentivize both countries to make matching commitments that in turn incentivize efficient emissions reductions, (2) reduce emissions from those expected without an agreement, and (3) increase both countries’ welfare. Matching-commitment agreements are attractive because they do not require a central enforcing authority and only require countries to fulfil their promises; countries are left to choose their conditional and unconditional emissions reductions according to their own interests. In the Paris Agreement, countries overwhelmingly agree to limiting “the increase in the global average temperature to well below 2 °C […] and pursuing efforts to limit the temperature increase to 1.5 °C above pre-industrial levels”2. To do so, they must curb GHG emissions; yet according to recent assessments of present and future global GHG emissions, the Earth is still expected to warm by more than 2 °C6.Anthropogenic emissions of greenhouse gases (GHGs) have been identified as comprising a key factor in climate change7: each country benefits from reduced global emissions, but curbing its own emissions carries an economic cost. Countries thus prefer to free-ride on the emissions abatement  of others over reducing their own emissions9. The implied tragedy is that if countries pursue their own interests in this way, everyone will be worse off than if they had cooperated and acted in their collective interest.Achieving the necessary reduction in GHG emissions is difficult, primarily because it is an instance of Hardin’s classic “tragedy of the commons”10. The cause for this discrepancy between the Paris Agreement’s goal and individual countries’ abatement targets is that, because countries are sovereign, their participation must be voluntary. Thus, countries chose their own abatement targets, and had little incentive to make very ambitious pledges. Moreover, the abatement targets that countries have pledged are not legally binding, so countries are not incentivized to fulfill them; consequently some countries’ current policies are insufficient to fulfill even their modest pledges10. So, while, in principle, “prompt and substantial reductions in greenhouse gas emissions on a global scale” could limit warming to meet the 1.5 °C target set in Paris, at 2015 rates of emissions the global carbon budget for this goal will be exhausted already in 202111.To manage shared resources (or to resolve other collective action problems) within a single country, rules are typically agreed upon and enforced, making cooperation the rational choice by shaping individual incentives. In contrast, the Paris Agreement details countries’ voluntarily pledged emission reductions in the hope of averting a “climate tragedy”, but this agreement will likely fall short of its goal. For example, even if countries reduced their emissions by the amounts they pledged, the Earth would still be an estimated 3.2 °C warmer by 2100 12 for a review). Most of the resulting proposals involve establishing a central authority that can punish non-participation and noncompliance or otherwise redistribute money or resources (either directly or by approving sanctions imposed by countries)16. But enforcement is difficult to achieve in practice, because, as pointed out by Nordhaus8, it conflicts with the principles of countries’ sovereignty, equality and right to manage internal affairs without intervention, first established in the 1648 Treaty of Westphalia. Consequently, Nordhaus has suggested that international trade law be amended to allow sanctions against non-participants, while prohibiting retaliation by the latter8. This would require the comprehensive renegotiation of trade laws, which will be a difficult and lengthy process. Moreover, Barrett also stresses the importance of enforcement, but warns that even if countries agree to a treaty with strong enforcement mechanisms, they will likely do so at the expense of lowering their abatement targets “to ensure that punishments are not imposed”14. Hence, solutions that encourage countries to cooperate without encroaching on their sovereignty would be desirable, since the global carbon budget for 1.5 °C warming is quickly running out.Seeking possible mechanisms for lowering global emissions, many researchers have turned to game theory  Assuming countries can commit to the matching factors they declare (see the section “Commitment” for a justification of this assumption), this program allows countries to alter the incentives of other countries without invoking a central authority.Barrettet al’s21 inspirational analysis considers an arbitrary number of heterogeneous countries and arrives at an optimistic result. They show that a matching-commitment agreement can lead to new equilibrium emission levels that are locally Pareto efficient and unique and reduce emissions relative to the status quo. However, Boadway et al. consider the status quo emissions in the absence of an agreement to be exogenously determined, and their results require that at least one country has an incentive to unilaterally reduce emissions from this status quo even in the absence of an agreement. A more realistic scenario would be that countries follow their Nash equilibrium emissions strategy in the absence of an agreement, so that no country has an incentive to either increase or decrease their emissions23. In that case, Boadway et al.’s optimistic results disappear. In other words, in Boadway et al.’s analysis, without an agreement, at least one country’s emissions are irrationally high, even for its pure self-interest; matching-commitment agreements reduce emissions because they allow countries to respond to their incentives and thus lower their emissions. Thus, we do not know whether matching-commitment agreements can work to reduce emissions if countries are able to freely select emissions levels that align with their incentives in the absence of an agreement. Furthermore, Boadway et al. do not consider the question of global efficiency, i.e., whether the agreement improves global welfare, the payoff of all countries, or indeed any single country’s payoff, relative to the outcome in the absence of an agreement .Boadway et al.’s21 formulation, but require the baseline scenario—that is, countries’ emissions in the absence of an agreement for reducing them—to be a Nash equilibrium determined endogenously by the countries’ strategic decisions. For arbitrarily many countries that may differ in their economic and climate-related properties, and that choose their emissions independently, we find conditions guaranteeing that such a Nash equilibrium emissions profile exists and is unique—i.e., the baseline scenario is well-defined. Next, we analyze the effects of a matching-commitment agreement on the emissions of two such countries. We show that a matching-commitment agreement generates a new, unique equilibrium emissions profile.  At this equilibrium emissions profile, both countries’ emissions are lower and their payoffs are higher than at baseline, i.e., at the equilibrium without a matching-commitment agreement. Lastly, we show that the equilibrium emissions profile with matching-commitment agreements is locally Pareto efficient.Against this background, this paper addresses two main questions: First, can a matching-commitment agreement incentivize countries to reduce their emissions relative to a baseline scenario without an agreement, and in which countries’ choices align with their incentives? Second, are countries better off with such an agreement than without? We build on Boadway et al.’s21 results broke new ground and motivated all that we have done, there are subtle problems with their arguments for both the existence and the uniqueness of the equilibrium, and hence the claims for the general case do not hold up ))et al.’set al.’s21 model, which in turn is similar to one described by Finus  and an example of Folmer and von Mouche’s25 transboundary pollution games. As is often the case for game-theoretical models of international cooperation, we focus on two countries, to retain mathematical tractability .We start by describing a model for the public goods problem of global GHG emissions between two countries , building on Boadway emissions profile, i.e., the vector of countries’ emissions, by total emissions by 33. We denote by i  when its own emissions level is ei and the total emissions are i’s total payoff as a function of the emissions profile e isWe consider two countries deciding on their emissions levels, basic climate game (BCG), representing the absence of any international agreement to curb emissions, countries independently and simultaneously choose their own emissions levels. When countries play the BCG and there is a unique Nash equilibrium, we view it as the baseline scenario, as it represents the predicted emissions profile for rational countries in the absence of any agreement to limit emissions. Unfortunately, and not surprisingly, the Nash equilibrium of the BCG does not maximize global welfare, i.e., the total payoff of both countries, ∏ = ∏1 + ∏2, and is hence not socially optimal. Indeed, we show in Appendix social optimum (SO), i.e., at an emissions profile that maximizes global welfare, must be lower than the total baseline emissions , so that its actual emissions level isOne suggested approach to establishing an accord that incentivizes a reduction in GHG emissions is to use a matching-commitment schemei’s abatement Ai is the sum of its unconditional abatement ai, and the conditional abatement that it performs in response to the other country’s unconditional abatement,mi is the proportionality factor at which country i matches country j’s unconditional abatement and i, j = 1, 2, i ≠ j . The countries then play the following game, henceforth referred to as the matching climate game (MCG)  matching factors, ai, with full knowledge of the matching factors chosen in stage I.Stage II: Countries independently and simultaneously choose their unconditional abatement levels, Denoting the total baseline emissions and the total abatement by i’s payoff becomes the nonlinear functionCountry Note that the baseline emissions levels The process by which national abatements arise from the unconditional abatements and matching factors is visualized in Figs. In this paper, we aim to compare the equilibrium outcomes of the basic climate game (BCG) and the matching climate game (MCG). Since such a comparison is predicated on the existence of well-defined equilibrium outcomes for these two games, additional assumptions are needed to guarantee this. For example, in the BCG, it may be advantageous for countries to emit or abate without bound, in which case no Nash equilibrium exists. In the MCG, matching may incentivize a country to abate without bound, in which case the best-response functions for stage II (given matching factors chosen in stage I) need not even be well-defined.bounded global emissions (BGE) , because it guarantees that no matching factors can incentivize infinite abatement. Henceforth we assume the benefit and damage functions are such that BAM holds and that global emissions are bounded. It turns out that (at least for the case of two countries) the BAM condition is sufficient to ensure a unique equilibrium outcome for the MCG, in the sense described in our “Results” section. In Appendix n ≥ 2, the BGE and BAM assumptions (resp.) ensure the existence and uniqueness of a Nash equilibrium for the BCG, and that the MCG’s stage-II best-response functions are well-defined. Regardless of the number of countries, these properties are necessary to sensibly ask whether and when the MCG yields equilibria that improve on the baseline emissions profile.While the model described above and the results that follow involve two countries only, note that for any number of countries, 24, Ch. 4). The matching climate game (MCG), on the other hand, is a two-stage game in which a strategy for country i  specifies its choice of a matching factor, mi = μi in stage I, and of an unconditional abatement level for any combination of matching factors chosen by both countries in stage II, ai  . A natural choice of solution concept for the MCG is therefore the subgame-perfect equilibrium , which yields Nash equilibria at every subgame . For the MCG, an SPE must then satisfy two conditions: first, it must constitute a Nash equilibrium for the full MCG, and second, for any pair of matching factors , the abatements , a2 ) must constitute a Nash equilibrium of stage II. For any choice of matching factors played in stage I, an SPE selects abatements that are Nash equilibria for stage II, so this solution concept avoids Nash equilibria (for the full MCG game) that are sustained by incredible threats or other irrational behaviour in stage II. We focus on SPEs precisely because they avoid such irrational behaviour, and our main aim is to identify and compare SPEs of the MCG with the baseline emissions profile.The relevant solution concept for the basic climate game (BCG) is the Nash equilibrium, i.e., an emissions profile from which no country has an incentive to deviate unilaterally ; we then find which strategies will be played in stage I. A more detailed account of the process follows below, and the full details are given in Appendix B.We first use backward induction to find subgame-perfect equilibria (SPEs) for the matching climate game  m1 = m2 = 0, for which the unique stage-II Nash equilibrium is no abatement (baseline), and (2) a pair of matching factors The functions  by Eqs.  and 6)  ϕ1 and ϕa1- and a2-axes:ϕ1 (resp. ϕ2) and the a2-axis (a1-axis), there is a stage-II Nash equilibrium at which only country 1 (2) abates unconditionally.On or between ϕ1 and ϕ2, there is a stage-II Nash equilibrium at which both countries abate unconditionally.Between the curves Furthermore, we find that for pairs of matching factors other than i  can be determined assuming that a Nash equilibrium is played in stage II; we ascribe these payoffs to pairs of matching factors and obtain payoff functions ∏i that we then use to find matching factors that are Nash equilibria of stage I . These Nash equilibrium matching factors, along with the choice of Nash equilibria played in stage II that was used to calculate the stage I payoff functions, constitute SPEs.Next, for any pair of non-negative matching factors, i given  may then not be uniquely defined even under the assumption that only Nash equilibria are played in stage II   determined by a particular choice of stage-II equilibria .However, the multiplicity of stage-II Nash equilibria for some pairs of matching factors introduces a complication, because the payoff to country i  obtained assuming equilibrium stage-II play  for the MCG are uniquely defined in the sense that they do not depend on which SPE is chosen. Specifically, with m and a denoting the unique positive solutions ofDespite this complication, it turns out that there is a unique SPE emissions profile. In particular, analyzing all possible pairs of payoff functions ∏At the equilibrium emissions profile of the MCG, both countries’ emissions are lower, but their payoffs are higher, than at the baseline equilibrium .The equilibrium emissions profile of the MCG is locally Pareto efficient, i.e., a small deviation from the MCG’s equilibrium abatement levels cannot increase both countries’ payoffs.The MCG’s equilibrium emissions profile is socially optimal iff the two countries’ marginal benefits at the equilibrium emissions profile are equal, which need not generally be the case; it then follows that from the perspective of a social planner, the country having lower marginal benefits at the subgame-perfect emissions profile emits too much, while the one with higher marginal benefits emits too little Lemma .Comparing the subgame-perfect emissions profile of the matching climate game (MCG) given by Eq.  with theMatching-commitment agreements have been garnering increasing interest as a way to construct international agreements to lower global greenhouse gas (GHG) emissions without requiring extensive international monitoring and enforcement. Our main contribution in this paper is to show the theoretical viability of such an approach assuming that countries behave strategically in the absence of an agreement. We show that matching-commitment agreements can indeed result in increased abatement and welfare for the countries involved, relative to a baseline of strategic behavior in the absence of agreements. Our results suggest that matching-commitment agreements can be a promising option for addressing other public goods problems when enforcement is difficult.To conclude, in the next few subsections we position our results in a broader context. First, we highlight some appealing features of the matching climate game (MCG). Next, we touch on related models from the literature on matching-commitment agreements. We then discuss the main simplifying assumptions made in our model, and mention how our assumptions regarding the damage and benefit functions could be relaxed. Lastly, we discuss how our methods can be applied to the provision of public goods in general.In addition to improving on the baseline scenario, the matching climate game (MCG) has a number of attractive features in comparison with other mechanisms (including other matching mechanisms) suggested to address international public goods problems such as reducing global GHG emissions, which we describe below.9 approach, including a clause stipulating that the matching agreement does not come into force unless all countries are signatories can help assuage countries’ fears that their environmental policies would be undone by defecting countries, and hence stabilize participation in the treaty and avoid leakage.) Second, unlike many other climate-agreement schemes , signatories are not asked to expose themselves to the possibility of economic sanctions. Third, countries decide on their own policies for matching factors and unconditional abatements, rather than submitting to the authority of an institution or coalition of countries . Fourth, countries are only asked to commit to conditional actions (as opposed to the Paris Agreement’s pledges), and to refrain from emitting more than they would in the absence of an agreement. In other words, the only encroachments on national sovereignty that the MCG makes is requiring countries to keep their word and fulfill a conditional commitment that they choose to make.The MCG asks countries to relinquish very little of their sovereignty and entails no negotiation. First, a country that agrees to participate in the MCG may still choose not to match, and hence does not commit to any policy change, other than refraining from increasing its emissions in response to other countries’ emissions reductions, a phenomenon known as carbon leakage. .The fact that the MCG does not employ costly punishments is also appealing, because it sidesteps the second-order free-riding problem: when punishment is costly, players are tempted to let others do the punishingn identical countries, Rübbelke39 points out that, because countries commit only to matching factors, they can still adjust their unconditional abatements if they discover (after having made their matching commitments) that they underestimated the benefits of abatement. This flexibility allows countries to at least partially (and sometimes fully) correct their emissions abatements based on updated estimates of benefits, avoiding the need for costly renegotiations. Although we do not repeat Rübbelke’s analysis for our model, the flexibility in the choice of unconditional abatements in the MCG is likely to give rise to a similar ability to compensate for updated estimates of the benefits of abatement.In an analysis of a similar matching-commitment agreement between 42. The MCG similarly subsidizes abatements in that positive matching factors effectively reduce the marginal costs of abatements. However, in the MCG, countries’ subsidies are implemented not by transferring resources, but through additional abatements provided conditionally. This type of subsidy is essentially unilateral and seems more likely to be implemented than one that involves monetary or in-kind transfers, especially in the case of countries between which diplomatic relations are tense or nonexistent.Lastly, many suggestions for climate agreements involve international monetary (or in-kind) transfers through which countries pay to subsidize the abatement efforts of other countries39 was the first to analyze a matching-commitment agreement to reduce GHG emissions, in which each country declares a single matching factor at which it will match any other country’s abatement. As is common in the literature on matching-commitment agreements, his analysis is restricted to identical countries and symmetric equilibria, whereas we allow for heterogeneous countries and asymmetric equilibria. The style of our model is also different from Rübbelke’s39 in that—similarly to Boadway et al.21—we use Finus’s22 well-established emissions game to specify payoffs from emissions profiles . Our analysis is closest in spirit to Boadway et al.’s21, with the most important difference being this: Boadway et al.’s main result concerns the efficacy of the matching climate game (MCG) in emissions reductions relative to an exogenously-determined baseline scenario in which at least one country would benefit from unilaterally reducing its emissions—in which case emissions would be reduced even without an agreement, if this country simply followed its incentives. By contrast, our main contribution here is to show that the MCG incentivizes countries to lower emissions relative to an endogenously-determined baseline scenario from which they have no incentive to deviate.To our knowledge, Rübbelke’s44. However, those authors (a) show that a subgame-perfect equilibrium (SPE) exists for positive externalities, and show that their approach may not work for negative externalities , and (b) do not establish that matching commitments yield unique equilibrium actions , whereas we are able to do so. Note also that in the context of public goods provision, Buchholz et al.46 have shown that when players are heterogeneous, matching often leads to inefficient equilibria at which not all players contribute. Our analysis shows that this problem is avoided in our approach, regardless of any possible inequalities between the countries.Matching mechanisms are most commonly studied in the general context of public goods or externality problems, and in that context our analysis is closest to Guttman and Schnytzer47 for a review, or ref. 48 for a notable example). Broadly, this literature takes a dynamic, evolutionary game-theoretic perspective, in which the independent agents  interact many times, and over time alter their strategies based on the payoffs they and others receive . To our knowledge, these methods have not yet been applied to matching-commitment agreements, and are a promising avenue for circumventing the technical difficulty of analyzing matching-commitment agreements among many countries in the “classical” game-theoretic setting.Lastly, we mention that another growing branch of the research into social dilemmas in general, and climate governance in particular, involves the application of methods from statistical physics  yield significant improvements in public good provision in repeated public goods games played in groups, and between pairs, respectively .There is, however, some experimental evidence that matching-commitment agreements can increase the provision of public goods. In particular, Guttmanm2 = 0 and a2 = 0. This is because, even if country 1 continues to play Because our model is a one-shot game, it only addresses the issue of commitment in a limited fashion: even if country 2 could renege on the matching factor it committed to in stage I, it has no incentive to do so, and in particular, it does better playing a cooperative subgame-perfect equilibrium (SPE) than it does by reverting to its baseline emissions, i.e., choosing 14, the ability of countries to commit assumes the “enforcement problem” is solved. As Barrett49 notes, this is justified by the international-law custom of treaties being binding, pacta sunt servanda. This custom is codified in the Vienna Convention on the Law of Treaties: “Every treaty in force is binding upon the parties to it and must be performed by them in good faith” . Thus, if countries can agree that whatever matching commitments they themselves select be legally binding, they are more likely to keep their word. Since countries are also free to refrain from any matching , and since the matching commitments are conditional on other countries’ actions, such commitments are weaker—and hence safer from being exploited, and thus more likely to be kept—than commitments to specific emissions abatements.In the language of Barrett56; this suggests that countries ascribe more weight to commitments that are explicitly legally binding, possibly due to the risk of reputation loss57. Second, although the Paris Agreement’s emissions targets are not binding, other aspects of the agreement are, and even the withdrawal of the US from the Paris Agreement will conform to the agreement’s rules for withdrawal58.Two recent examples suggest that legally binding commitments to match emissions reductions would likely be an improvement on the status quo, even without an explicit enforcement mechanism in place. First, some parties to both the Kyoto Protocol and the Paris Agreement rejected legally binding targets3. We leave the analysis of matching-commitment agreements among many countries for future work, but note that a number of studies suggest that such agreements among many countries can also be effective in reducing emissions. For instance, encouraging analytical results include those of Fujita35 and Rübbelke39 (described in the sections “Advantages over other climate-agreement schemes” and “Related literature”). Using the STACO model40 to estimate countries’ damages and benefits from emissions, Kawamata and Horita59 simulate a matching scheme similar to the matching climate game (MCG) for six countries and regions and show that emissions are substantially reduced. Lastly, in Guttman’s50 experimental study, matching commitments also increased public good provision in repeated games in groups of 3–6 players.While it is widely acknowledged that an effective agreement must include as parties the two largest emitters, the US and China, their combined emissions amount to about 45% of global emissions, so a climate agreement between only these countries will likely be insufficientall countries be signatories. This is because although matching-commitment agreements do not strictly require signatories to perform any abatement, they do require that countries refrain from emitting more than they would in the absence of an agreement. If some countries opt out of the agreement, and signatories collectively abate their total emissions, then non-signatories will have an incentive to increase their emissions from their no-agreement baseline emissions (this is the carbon leakage mentioned in the section “Advantages over other climate-agreement schemes”).In the context of multilateral matching-commitment agreements, it will likely be imperative that et al.60 recently estimated the country-level social cost of carbon (CSCC)—a measure of the long-run economic cost of a tonne of CO2 emitted in 2020. The CSCC is analogous to the marginal damage suffered by each country, additional pulse of one tonne of CO2 emissions, but is otherwise identical to the reference pathway. Ricke et al.60 repeat these calculations for a variety of different socioeconomic scenarios (that result in different emissions pathways) and for different empirical estimates of the economic impacts of warming. .Ricke et al.’s60 model specifications results in a negative CSCC  for some countries, they note that “[t]hese results are among the most sensitive in the analysis, as under the BHM long-run and DJO damage model specifications all countries have positive CSCC”, where BHM and DJO refer to the damage-function estimates of Burke et al.63 and Dell et al.64, respectively. Moreover, they find that “under the long-run impact model specifications [...] countries like Russia, Canada, Germany and France that have negative CSCC under the reference case switch to having among the highest positive CSCCs”. Another analysis by Kompas et al.65 applies a “computable general equilibrium” approach and finds that all of the 139 countries included in their analysis benefit from complying with the Paris Agreement, providing additional support for our assumption that the marginal damages of emissions are positive.While one of Ricke The assumption that global emissions are bounded  and our analysis are framed in terms of climate agreements, they can be applied equally well to other public goods problems. The public good provided in our model is the Electronic supplementary material.


In this comment, we analyse the conceptual framework proposed by Aguirre de Cárcer , introducing the novel concept of Phylogenetic Core Groups (PCGs). This notion aims to complement the traditional classification in operational taxonomic units (OTUs), widely used in microbial ecology, to provide a more intrinsic taxonomical classification which avoids the use of pre-determined thresholds. However, to introduce this concept, the author frames his proposal in a wider theoretical framework based on a conceptualization of selection that we argue is a tautology. This blurs the subsequent formulation of an assembly principle for microbial communities, favouring that some contradictory examples introduced to support the framework appear aligned in their conclusions. And more importantly, under this framework and its derived methodology, it is not possible to infer PCGs from data in a consistent way. We reanalyse the proposal to identify its logical and methodological flaws and, through the analysis of synthetic scenarios, we propose a number of methodological refinements to contribute towards the determination of PCGs in a consistent way. We hope our analysis will promote the exploration of PCGs as a potentially valuable tool, helping to bridge the gap between environmental conditions and community composition in microbial ecology.Video AbstractThe online version contains supplementary material available at (10.1186/s40168-021-01023-y). HeadingThanks to the development of new technologies such as next generation sequencing, we are in a privileged position to start deciphering the mechanisms underlying microbial communities’ assemblage, and novel conceptual frameworks, as the one presented by Aguirre de Cárcer in , are verx, and the two statements conceptualizing it will be described with the variables a= “statement (i)” and b= “statement (ii)”. Since the statements a and b are mutually exclusive , this means that selection is simultaneously one thing and the contrary, x={a,¬a}. Therefore, selection (x) can escape from being a tautology if any of these possibilities are realistic alternative models: if there exist environments containing only phylo-niches (x={a}), if there exist environments containing only nonphylo-niches (x={¬a}), or if there are niches whose occupancy does not require specific sets of traits . The mentioned possibilities are evaluated below.In the article , Aguirrx={a}, or x={¬a} are valid alternatives. Secondly, we note that the author refers to phylogenetically conserved sets of traits . This means that the proposed conceptualization of selection x={a,¬a} suffers from the same weakness as Diamond’s first rule  are expected to lead to phylo-niches or nonphylo-niches (which would be of a great interest). Therefore, we do not find arguments to substantiate that Blomberg ) and not nature” ): it onl nature” , it seemx={a,¬a} (note that the existence of PCGs is a direct consequence of the definition of phylo-niche), confirming that this conceptualization and its predictions constitute a logical trap.One still may argue that this conceptualization is not “the principle” but just a description of the niches that can be observed, which is needed to build the principle and to bring testable predictions. In this respect, the author continues presenting the following statements as predictions: (a) “any microbial ecosystem can present phylo-niches and nonphylo-niches; (b) for each phylo-niche there must be a discrete portion of the phylogeny (from now on a ‘phylogenetic core group’ or PCG) whose members share a phylogenetically conserved set of traits allowing the occupancy of their respective phylo-niche. (c) For each nonphylo-niche there must be a group of microbial populations sharing a set of traits not showing phylogenetic conservation allowing the occupancy of their respective nonphylo-niche.” It is easy to see that these are not predictions, because they are true by construction of the principle x={a}, and x={¬a} would reject the principle). The text then continues noting that, independently of the type of niche considered, species occupying a niche have similar traits and, hence, each group “should present a high degree of intra-group ecological coherence” (understood as similar life-strategies), and he postulates that the assembly within these niches “should be governed by neutral processes, and likely show intra-group competition.”At the end of the section above mentioned, we find a candidate-formulation of the principle: “Each instance of the same microbial ecosystem type should present populations from each PCG (occupying phylo-niches), and non-phylogenetic-core populations (occupying nonphylo-niches)”. As we anticipated, the reason why each “instance” “should” present both types of populations is not justified, although it is a testable prediction , with tFor instance, our understanding of this formulation nicely fits the competitive lottery model , in whicLeaving aside the conceptual weaknesses of the formulation, Aguirre de Cárcer presents a potentially sound proposal under the notion of Phylogenetic Core Groups (PCGs). Given a set of 16S rRNA samples, he proposes to cluster 16S rRNA sequences as follows : OTUs arThe idea departs from a simple assumption: if some microbes in a given sample are observed, they must have traits which encode the functions that are needed to occupy the environment from which they were sampled. However, it is unclear why determining PCGs will lead to a better understanding of which are the underlying environmental conditions or how to identify the relevant traits with them. For example, convergent evolution may lead to different traits being used by unrelated species to cope with a given environment. In addition, the procedure strongly depends on the number of samples considered, as we anticipated.To better understand these caveats, in Fig. Following the above conceptualization of selection, to occupy a niche requires a set of traits (conserved or not), and this map allows us to label a niche by using the required set of traits , each of which contains different scenarios Fig. . Each scScenario 4 samples two niches and, without further analysis, the search for a common PCG would lead us to conclude that the rectangle is again the relevant trait, with the PCG being the whole family F (first row). Moreover, it is clear that this conclusion depends on the number of samples considered, because subsets of samples within this scenario may lead to scenarios 2 or 3 if only two species are found in these subsets, a caveat acknowledged by the author in his proposal, but not solved in practice. A possibility to conclude which is the scenario, is to perform a neutrality test in which all the samples are considered to build a metacommunity (see e.g. ) and, siIn case B Fig. , we explLet us finally consider two additional scenarios, 5 and 6, in which the star-trait is required to occupy the niche. Scenario 5 suffers from the same ambiguities than scenarios 1–3, and only increasing the number of samples may allow us to resolve them. For instance, finding samples in which species from a different family appear  will allow us to identify the scenario as a nonphylo-niche. We may find phylogenetic overdispersion in this situation, as in . ScenariNavigating the examples presented by Aguirre de Cárcer to support his principle, it is possible to observe that the lack of precision in its formulation facilitates the consideration of very different examples as a support for his theory. For instance, results as those presented in , 14 possThere are two last important questions that remain unclear in the theory. Firstly, the role of cooperative interactions and facilitation, whose important role is increasingly recognized (see e.g. ), and thFrom the previous analysis, we identify two key questions which deserve a closer look. To start with, a point we already highlighted, namely that this strategy strongly depends on the number of samples and their depth. Since this question is technical in nature, we will attempt to address it below. The second question would be what can be gained from this methodology that could not be addressed analysing directly all traits present in the set of samples under analysis.A possible answer for the second question comes from the low taxonomic resolution that can be achieved sequencing fragments of the 16S rRNA gene, which cannot reliably resolve ranks under the genus level , in partIn addition, to the best of our knowledge, it still remains largely unknown for natural microbial communities how the degree of phylogenetic conservation expected relates to the dominance of homogeneous or heterogeneous selection or neutral processes. Therefore, another potentially interesting justification for searching PCGs is if their structure (i.e. the number and similarity thresholds of the OTUs they host) is informative of the underlying ecological and evolutionary processes.In the following, we attempt to produce a pipeline to incorporate to Aguirre de Cárcer’s proposal a more consistent methodology that is less sensible to the number of samples in the dataset. In addition, we propose a number of tests, preceding the determination of PCGs, that would help establish bridges between different assembly ecological processes and the phylogenetic signal. We illustrate the proposal in Fig. β−diversity similarity within classes than between classes is an appropriate starting point to infer the processes driving this similarity (see e.g [β−diversity similarity should be computed using exact sequence variants (ESVs), i.e. sequences with single-nucleotide differences over the sequenced gene region [Our proposal starts observing that the large number of different taxa in most natural samples makes unlikely to systematically find similar communities by chance. As a consequence, the determination of clusters of communities (hereafter “community classes”) sharing a significantly higher . The region , to avoie region . The rate region .β−diversity analyses should be considered to understand the effects of these gradients . Anotheiewed in , and, heThe next step considers the realization of a neutrality test, which is affordable for large sets of samples with nowadays methods; see e.g. . If clasTaking together the results from the test of neutrality and from the search of classes, it is possible to interpret them as follows. If classes cannot be determined and the test of neutrality is positive, there is a single environmental filter  or from the community as a whole  to heterogeneous (degraded resources), see e.g. [An additional test that can help to disentangle the dichotomy between neutral processes and selection comes from the computation of the Nearest Taxon Index . The indsee e.g. . An openFinally, if neutrality is rejected, we are dealing with scenarios in which strong environmental selection, ecological interactions, or both, are dominant  are performed on each class. Both the identification of classes and the tests of neutrality are robust against an increasing number and depth of samples, provided that these are sufficient .It remains, however, unclear, which benefit may bring their characterization. Working with ESVs represents a better standard to compare biodiversity patterns across different environments  than anyA final possible application would come if it is shown that PCGs structure is determined by the underlying environmental and ecological processes structuring communities. This would allow us to characterize them directly without running into the different steps of the pipeline proposed here. To address this question, possible different scenarios could be simulated to determine null expectations, and if clear patterns appear for PCGs, it would be a valuable tool to link selection with the search of traits, a much needed approximation to investigate community-level function. Until these questions are addressed, PCGs will be an appealing concept, opening more questions than the answers it provides.


In recent decades, packaged fruit has gained market ground over loose fruit, and fruit containers have become a source of information for consumers. This study approaches three objectives related to consumer information needs for decision making when purchasing fruit: (1) Determine if consumers’ choice of packaged fruit rather than loose fruit is motivated by their interest in the information provided on packaging; (2) identify information gaps on fruit packaging labels; (3) identify those sensory attributes that consumers consider to be of major interest to be included in sensory labels of different fruit types. The study was based on an online questionnaire answered by 394 fruit consumers. Ninety percent of the participants stated having an interest in receiving information when purchasing fruit, but their choice between packaged or loose fruit was not conditioned by their information needs. Moreover, a gap between information interest and information use was detected as their final purchase decisions were not always based on the provided information. ‘Harvest date’, ‘production method’, ‘percentage of the price received by the farmer’, ‘applied treatments’, ‘sensory characteristics’, and ‘environmental information’ were identified as the major information gaps, as these labels were unavailable for a high percentage of consumers, who stated their interest in them. According to consumers, sensory labels should include information about ‘sweetness’ and ‘flavor intensity’ irrespectively of fruit type. ‘Sourness’ and ‘juiciness’ attributes were particularly interesting for citrus, as ‘sourness’ and ‘firmness’ were for kiwi. Information about texture properties was required for pome and stone fruit. Other attributes, such as easiness to peel, were important only for citrus fruit. In most occidental countries, the fruit market has undergone major changes in the last 50 years, and has moved from selling local production to commercializing fruit imported from countries worldwide. This change in fruit marketing has led supply to sharply increase, which is linked not only with the availability of off-season fruits, but also with the possibility of choosing among a wider range of varieties ,2,3,4. MIn parallel to this increasing offer, the way of commercializing fruit has also changed in recent decades. Thus, packaged fruit has gained market ground and presently co-exists with loose fruit on supermarket shelves. Apart from preserving fruit from mechanical damage, packaging has been claimed to extend the fresh fruit shelf life by prolonging freshness and food quality, and ensuring safety ,9. HowevTraditionally, loose fruit consumers have received fruit information orally when asking grocery sellers, or in writing in texts added to labels on shelves together with prices, or in fixtures or posters in supermarkets . HoweverTherefore, to a certain extent, information has become part of the fruit market offer. Factors like label information source ,17, labeTherefore, it is possible that consumers’ choice between loose and packaged fruit is conditioned by their information needs for purchase decisions and/or their trust in the provided information. Despite the relevance that clarifying this aspect may have for industry, to our knowledge this has not yet been investigated.However, different studies have elucidated the effect of specific label facts and packaging claims on consumer decisions when choosing among packaged fruit . Adding Different studies have highlighted the dominance of hedonic attributes in consumer food choices ,24,28, wIn this context, this study approaches three objectives: (1) Determine if consumer fruit choice (packaged vs. loose fruit) is conditioned by their information needs; (2) identify information gaps on fruit packaging labels; (3) establish the key attributes for sensory label designs depending on fruit type. www.googleforms.com). The participants were recruited using the consumer database of the Sensory and Consumer Science research group from the IVIA, Valencia (Spain). Only those people who buy fruit at least once a week were invited to participate, and all of them signed an informed consent form. Three hundred and ninety-four Spanish consumers participated in this study, which is based on an online questionnaire via the online platform Google forms ; Variety; Country of origin; Production area ; Size; Category ; Batch number; Presence/absence of seeds ; Treatments applied after harvest; Taste, aroma, and texture characteristics that are perceived when eaten; Recommended use ; Nutritional value; Production method ; Preservation method; Preparation recommendations ; Quality Seals ; Best before date; Environmental information ; Beneficial properties ; If it is “Ready to eat”; Net weight; Number of pieces; Packing date; % of the price received by the farmer; Harvest date; None of the above. To draw up the labels list, individual interviews were held with eight people (4 men and 4 women aged 18–57 years) who stated they eat fruit at least once a week. Consumers were asked to first list all the information they remembered they were provided with when they bought fresh fruit, and then include on the list that information they would like to know, but is not normally provided.The final labels list was drawn up after taking into account the information that must be mandatorily provided, the results of the individual interviews, and the evaluations of fruit packaging in supermarkets. The option ‘Others’ was also available if some participants wished to indicate any information missing on the list. Before conducting the final questionnaire, it was individually checked with six people in order be sure that all the vocabulary and concepts could be understood by regular consumers and no relevant information was missing.3. Finally, those participants who declared an interest in “Taste, aroma, and texture characteristics that are perceived when eaten”, were moved to the third questionnaire section.In this part, the participants were presented images of six different fruit types and were asked about the organoleptic characteristics they would like to know when they bought fruit. The different fruit types were shown in six pictures, which included: (1) Citrus fruit (mandarins and oranges); (2) stone fruit ; (3) pome fruit (different pear and apple varieties); (4) melon and watermelon; (5) different types of bananas; and (6) kiwi (yellow and green kiwis). A preliminary sensory attributes list was drawn up based on a fruit sensory studies bibliography ,4,35,36.Participants were presented the final list and asked to check all the attributes they would like to know when they purchase the different fruit types shown in the images. The order the images were presented in was randomized, as were the terms on the lists .At the end of the questionnaire, the participants answered some demographic questions, such as their fruit consumption frequency, gender, and age . Packaged fruit in Spain is mainly sold in supermarkets, and suppliers normally provide consumers with more information than is mandatory, often for marketing purposes. Thus, in order to know what kind of non-mandatory information is normally included on package labels, we performed a prospective study by visiting 10 supermarkets belonging to five main chains. This allowed us to collect in situ all the information provided on fruit packaging to gain the main insights received by consumers. Examinations were made of the principal fruits herein included. The first objective of this study was to evaluate consumer interest in fruit information and to determine if it conditions fruit selections (packaged vs. loose fruit). To this end, we asked the participants about their usual way of buying fruit and their interest in receiving information about it. Our results showed that for 80% of the participants, fruit purchases habitually include both packaged and loose fruit, while the other 20% only bought loose fruit . Our data revealed that for both consumer groups, the same percentage of them  were interested in receiving information about fruit when they purchase. So, despite packaging labels being a relevant source of information, consumer information needs were revealed to be a non-decisive factor for deciding to choose packaged or loose fruit. When we took the question a step further and asked the participants if their purchase decisions depended on labeled information, we found that not all consumers were interested in the provided information to base their final decisions on it. According to our data, 41% of people who stated they were interested in information do not use the information they receive for purchase decisions. This result shows that for a high percentage of consumers, labels do not play an important role in their fruit purchases.Of the 59% participants who affirmed that their decisions were conditioned by label information, 28% declared that this was always the case, while 31% stated that information influence depended on the day . TherefoOur results also showed that a higher percentage of females  than males  based their purchase decisions on available information. Moreover, the effect of label cues on choice decisions was stronger for the participants aged over 40 years than among younger participants. Accordingly, it has been reported that women spend more time reading food labels than men, as do older people ,38, whicInformation provided to consumers is effective only when it addresses specific information needs, matches certain interests, and can be processed and used by its target audience. Hence, insights into consumer needs for, and interest in, information are required before needs can be effectively addressed . If we bA 20% difference between those consumers who declared they wished to receive a specific label and those who stated having received was established as the threshold to identify gaps. It is important to clarify that the fact that the participants who declared not receiving specific information does not necessarily imply that it was left as not provided. Perhaps a certain number of responses in this regard came from people who received information, but did not assimilate it. These cases form part of the information gap concept, as it is assumed that the information which consumers stated they are interested in could not be processed and used because it was not properly conveyed. However, to gain a clearer view about this, while this study was underway, we visited 10 supermarkets to detect first-hand the non-mandatory labels that are habitually included on fruit packaging. The obtained results are discussed together with consumer data. As seen in the right column of Of the three labels herein identified as the most interesting ones for consumers , the only one that must be mandatorily included on packaging is the country of origin . HoweverFruit name and variety, together with labels associated with fruit freshness , were also relevant for a high percentage of consumers (60–75%). Within the same range of importance, we found information about the percentage of price perceived by farmers, quality seals, and net weight. Of all these labels, three must be included on packaging: Fruit name, variety, and net weight (fruit name only if product content cannot be seen) . Two majConsumers’ need to know the fruit harvest date before purchase is related to the “freshness” concept. Indeed, freshness has been reported as one of the main drivers for consumer choices of different fruit ,47. RegaInformation on postharvest treatments, environmental aspects, organoleptic attributes and nutritional values were interesting for 50–60% of the participants, and were all identified as major information gaps. Consumer interest in the environmental-related aspects herein detected agrees with previous studies, which have reported a growing consumer awareness of the environmental impact of their purchasing decisions . ConsumeIn line with this, our data showed that all the participants declared buying loose fruit to a greater or lesser extent . However, no consumers reported that they based their fruit purchase on only packaged fruit . TherefoIn this context, the food industry is making an effort to find new alternative materials to plastic, such as biodegradable film and other materials like biocomposite, which preserve product quality, but cut the use of non-renewable resources and prevent plastic waste from accumulating ,55. Similarly, consumer awareness of the food impact on health has considerably increased in the last few decades , and con2 footprint”, etc. Our observations also indicated that providing nutritional labels was quite unusual. The environmental, nutritional, and organoleptic-information gaps revealed by consumer data coincided with the reality perceived in supermarkets. That is, the only mandatory information in this regard is to specify the postharvest treatments applied to citrus fruit, but not to other fruit . A commoWith regard to sensory attributes, it has been reported that consumer decisions may be modified by providing fruit sensory label . When seOf the five supermarket chains that we visited, three were highlighted for providing sensory labels, but they were restricted to only a few types of fruits, mainly apples, pears, grapes, and pineapple. Most claims referred to only one attribute, generally level of sweetness. Only in apples did labels cover attributes related to different properties, like flavor , texture, and aroma. Availability of such sensory labels may allow consumers to make easier selections from among apple varieties.Finally, four gaps were identified among the labels that aroused the interest of less than 50% of consumers: ‘Preservation method’, ‘beneficial properties for health’, ‘if it is ready to eat’, and ‘preparation methods’. Indeed, we corroborated that such information was generally lacking in supermarkets, and recommendations about preservation method were exceptional and limited to storage temperature. Claims related to beneficial properties were scarce and linked with only the high vitamin C and fiber content of kiwi and coconut. Preparation recommendation was available only for big-sized fruit like pineapple, melon and watermelon, and only one claim that referred to the ‘ready to eat’ state of pineapples was identified.It is also interesting to highlight that the opposite happened with ‘brand’ as 73% of consumers were aware of finding this information on labels, but only 43% of them were interested in it. According to this result, brand name should not occupy a priority position on labels, which should be left for other more relevant information for consumers so that it can be more clearly visualized.However, we must keep in mind the importance of information for food safety that is not very interesting for consumers. Thus, food traceability linked with batch numbers is key to avoid public health risks. Nowadays, information behind batch numbers or barcodes is not generally accessible for consumers. Quick Response Codes (QR codes) have been reported as useful tools to not only save information traceability, but also provide consumers with further information than that printed on packaging ,59,60. QAccording to ASTM International (2016) , a sensoAnother flavor-related attribute, level of sourness, was also pointed out as key information for facilitating consumer choice decisions with citrus or kiwi fruit A,C. It wThe identification of sweetness as a sensory attribute of special relevance is in accordance with that reported in sensory studies. In such studies, consumer preferences and purchase intentions after tasting fruit were related to fruit sensory properties, and in such a way that the attributes which acted as drivers of liking were identified. Thus, sweetness has been reported to be a driver of liking for pome fruit, such as apples and pears ,63, stonOur results related to sourness fell in line with those reported by Jaeger et al. (2011)  and TaraAs can be observed in Other texture attributes, such as mealiness and crunchiness, were selected only for pome fruit (between 30–45% of consumers) E, while Aroma intensity was selected for all the fruit types, but only for 40% of consumers. This data indicates that aroma properties are less relevant for consumer liking expectations than flavor or texture attributes.Finally, aspects as to whether fruit being easy to peel or containing seeds were only significant for citrus and watermelons/melons, and the latter only for seeds A,D. The The information herein collected is very useful for a sensory label design that responds to consumer information needs. However, it is important to bear in mind that during the shelf-life period and home storage, fruit may undergo metabolic changes that lead to sensory modification in relation to harvest time . Thus, tBased on our results, we conclude that Spanish consumers are very interested in receiving information when they purchase fruit. However, their choice between packaged and loose fruit does not depend on their information needs. In fact, a gap between information interest and information use was detected as their final purchase decisions are not always based on the provided information. ‘Harvest date’, ‘production method’, ‘percentage of the price received by farmers’, ‘postharvest treatments’, ‘sensory properties’, and ‘environmental information’ were identified as the major information gaps and, therefore, the industry should make efforts to provide this information or make it clearer than it currently is. For a correct design of sensory labels, they should include information on ‘sweetness’ and ‘flavor intensity’ irrespectively of fruit type. ‘Sourness’ and ‘juiciness’ levels must be included on citrus fruit labels, while ‘sourness’ and ‘firmness’ are relevant for kiwis. Information on texture properties must be provided to help consumers choose pome and stone fruit. Other attributes, such as easiness to peel, are important only for citrus fruit.