solution_plant_rich_diets2.jpg

Lefteris Kallergis | Unsplash

Plant-Rich Diets

Animal agriculture is a significant source of greenhouse gas emissions. Favoring plant-based foods reduces demand, thereby reducing land clearing, fertilizer use, and greenhouse gas emissions.

Reduce SourcesFood, Agriculture, and Land UseAddress Waste and Diets
Support SinksLand SinksAddress Waste and Diets
78.33 to 103.11
Gigatons
CO2 Equivalent
Reduced/Sequestered
2020–2050
Research Fellows: Zak Accuardi, Susan Miller Davis, Karthik Mukkavilli, Jon Schroeder; Senior Director: Chad Frischmann

Impact

Using country-level data from the Food and Agriculture Organization of the United Nations, we estimated the growth in global food consumption by 2050, assuming that people in lower-income countries will consume more food and higher quantities of meat as economies grow. If 50–75 percent of people adopt a healthy diet of an average 2,300 calories per day and reduce meat consumption overall, we estimate at least 54.19–78.48 gigatons of emissions could be avoided from dietary change alone. Since agriculture, particularly for cattle and animal feed production, is the leading driver of tropical deforestation, reducing meat consumption can avoid additional forest loss and associated greenhouse gas emissions. 

Introduction

Plant-rich diets hold enormous potential for climate change mitigation if adopted on a global scale. They also tend to be healthier than animal-rich diets. A plant-rich diet can be adopted incrementally with small behavioral changes that together lead to globally significant reductions in greenhouse gas emissions.

Project Drawdown’s Plant-Rich Diets solution involves the individual choice to 1) maintain a 2,300-calorie-per-day nutritional regime; 2) meet daily protein requirements while decreasing meat consumption in favor of plant-based food items; and 3) purchase locally produced food when available. This solution replaces projected dietary trends.

In terms of cost, the solution appears to yield significant savings at the individual level, and indirectly at the national level through lower health-care costs. Moreover, the burden of change seems highly equitable and implementable, because developing nations already consume fewer calories and do not need to shift their diets much, whereas developed nations need to address issues such as obesity.

Bringing about dietary change is not simple because eating is personal and cultural, but promising strategies abound. Plant-based options must be available, visible, and enticing. Also critical: ending price-distorting government subsidies so the prices of animal protein more accurately reflect their true cost.

Methodology

To evaluate the impact of a plant-rich diet, we created an independent model outside our core model framework that projects food consumption and waste from 2020 to 2050. This was required due to the complexity of estimating country- and regional-scale food consumption and waste trends.

Total Addressable Market

We defined the global market for the Plant-Rich Diets solution as the total human demand for food based on estimated kilocalories supplied per year for consumption. We projected the baseline food consumption for all countries up to 2060 in kilocalories per capita per year, using data compiled by the Food and Agriculture Organization (FAO) for 2013. We forecast future consumption using growth factors from Alexandratos et al. (2012), which reflect projected dietary changes. The projected dietary changes show significant impacts for countries such as India and China, where people are expected to demand more carbon-intensive foods over the next 30 years.

Adoption Scenarios

We calculated impacts of increased adoption of the Plant-Rich Diets solution from 2020 to 2050 by comparing two growth scenarios with a reference scenario in which the food demand reflects future “business-as-usual” dietary changes based on projected regional growth factors (Alexandratos et al., 2012).

To meet our definition of plant-rich, a diet must include:

  1. consuming 2,300 kilocalories per day
  2. consuming reduced quantities of animal-based protein (particularly red meat, which is constrained to 57 grams per day)
  3. purchasing locally produced food when possible (a 5 percent localization factor is applied globally).

The caloric breakdown comes from Bajželj et al. (2014). It takes projected regional data and optimizes it according to a number of nutritional studies to create a “healthy” diet.

Adoption scenarios in this model grow linearly over time starting from the base year of 2014, and are considered “complete” in 2050. Linear growth trends were chosen because of the lack of country or regional data; additional behavioral research at more granular scales can reveal more representative adoption estimates.

The following scenarios were considered:

  • Scenario 1: 50 percent of people adopt a plant-rich diet by 2050.
  • Scenario 2: 75 percent of people adopt a plant-rich diet by 2050.

Emissions Model

To estimate emissions, we drew commodity-specific carbon dioxide equivalent per-calorie values from several sources (see Audsley et al., 2010; Heller and Keoleian, 2014; Hoolohan et al., 2013; Tilman and Clark, 2014; Vieux et al., 2012) and used them to determine minimum, average, and maximum estimated emissions factors per commodity. We multiplied the emissions factors by the baseline annual food demand by country and commodity to get the carbon dioxide equivalent values for food items over time. We aggregated emissions estimates by commodity type (cereals, roots and tubers, oilseeds and pulses, fruits and vegetables, meat, fish and seafood, and milk) and region as classified by the FAO (2011), and aligned them with regions used by Project Drawdown.

We calculated total global emissions reductions from agricultural production based on the incremental adoption of plant-rich diets by comparing the two adoption scenarios with the reference scenario.

Integration

We calculated the total change in food demand over time by weight and commodity type. We assumed that reduced demand in countries with consumption trends higher than 2,250 kilocalories per capita per day can be diverted to feed current and future undernourished populations. We used this diverted food as an input in our Integrated Yield model, which combines all agricultural production models to determine the required yield to meet the estimated food and bio-based product demand on an annual basis. Results from both demand-side solutions (i.e., Reduced Food Waste and Plant-Rich Diets) determine the need for land conversion to cropland and grassland in order to meet future food demand. We applied emissions reductions associated with land conversion to both Reduced Food Waste and Plant-Rich Diets according to the proportion of their contribution to diverted food supply.

Results

Between 2020 and 2050, Scenario 1 projects the total cumulative emissions reduction from adopting a plant-rich diet to be 78.33 gigatons of carbon dioxide equivalent gases: 54.19 gigatons due to diverted agricultural production, 23.99 gigatons from avoided land conversion, and 0.15 gigatons from sequestration from ecosystem protection.

Scenario 2 avoids 103.11 gigatons of emissions: 78.48 gigatons due to diverted agricultural production, 24.48 gigatons from avoided land conversion, and 0.14 gigatons from sequestration from ecosystem protection.

Discussion

High current per-capita meat consumption in high-income countries, paired with global diets that are forecasted to look increasingly Western, creates one of the most fundamental challenges of plant-rich diet adoption. How can we reduce livestock production in the face of high and rapidly increasing demand? Achieving some dietary change is reasonable, but more dramatic changes will be difficult to implement globally.

Scaling plant-rich diets globally is a challenge of communication and education as much as it is one of policy. Among the most fundamental research findings on this topic is that healthier diets tend to also be low-emission diets (Bajželj et al., 2014; Tilman and Clark, 2014; Stehfest et al., 2009). While plant-rich diets are not necessarily the lowest-emission diets, they represent a significant improvement over current dietary practices, particularly those in countries like the US and Australia where meat (especially beef) consumption is high. This overlap in desirable outcomes (healthier population, lower emissions) is a powerful communication and policy tool, particularly given that individuals are more likely to respond favorably to messaging that affects their health than they are to messaging relevant to their environmental impact.

References

Alexandratos, N., & Bruinsma, J. (2012). World agriculture towards 2030/2050: The 2012 revision. ESA Working Paper, 12–03. http://large.stanford.edu/courses/2014/ph240/yuan2/docs/ap106e.pdf

Audsley, E., Brander, M., Chatterton, J. C., Murphy-Bokern, D., Webster, C., and Williams, A. G. (2010). How low can we go? An assessment of greenhouse gas emissions from the UK food system and the scope reduction by 2050. World Wildlife Foundation and Food Climate Research Network. https://dspace.lib.cranfield.ac.uk/handle/1826/6503

Bajželj, B., Richards, K. S., Allwood, J. M., Smith, P., Dennis, J. S., Curmi, E., & Gilligan, C. A. (2014). Importance of food-demand management for climate mitigation. Nature Climate Change, 4(10), 924–929. https://doi.org/10.1038/nclimate2353

Heller, M. C. and Keoleian, G. A. (2014). Greenhouse Gas Emission Estimates of U.S. Dietary Choices and Food Loss: GHG Emissions of U.S. Dietary Choices and Food Loss. Journal of Industrial Ecology, 9(3) pp 391-401. http://doi.wiley.com/10.1111/jiec.12174

Hoolohan, C., Berners-Lee, M., McKinstry-West, J., & Hewitt, C. N. (2013). Mitigating the greenhouse gas emissions embodied in food through realistic consumer choices. Energy Policy, 63, 1065–1074. https://doi.org/10.1016/j.enpol.2013.09.046

Stehfest, E., Bouwman, L., van Vuuren, D. P., den Elzen, M. G. J., Eickhout, B., & Kabat, P. (2009). Climate benefits of changing diet. Climatic Change, 95(1–2), 83–102. https://doi.org/10.1007/s10584-008-9534-6

Tilman, D., & Clark, M. (2014). Global diets link environmental sustainability and human health. Nature, 515(7528), 518–522. https://doi.org/10.1038/nature13959

Vieux, F., Darmon, N., Touazi, D., and Soler, L. G. (2012). Greenhouse gas emissions of self-selected individual diets in France: Changing the diet structure or consuming less?. Ecological Economics 75, pp 91-101. http://linkinghub.elsevier.com/retrieve/pii/S0921800912000043