Abstract
With current diets and production practices, feeding 7.6 billion people is degrading terrestrial and aquatic ecosystems, depleting water resources, and driving climate change (1, 2). It is particularly challenging to find solutions that are effective across the large and diverse range of producers that characterize the agricultural sector. More than 570 million farms produce in almost all the world’s climates and soils (3), each using vastly different agronomic methods; average farm sizes vary from 0.5 ha in Bangladesh to 3000 ha in Australia (3); average mineral fertilizer use ranges from 1 kg of nitrogen per ha in Uganda to 300 kg in China (4); and although four crops provide half of the world’s food calories (4), more than 2 million distinct varieties are recorded in seed vaults (5). Further, products range from minimally to heavily processed and packaged, with 17 of every 100 kg of food produced transported internationally, increasing to 50 kg for nuts and 56 kg for oils (4). Previous studies have assessed aspects of this heterogeneity by using geospatial data sets (6–8), but global assessments using the inputs, outputs, and practices of actual producers have been limited by data. The recent rapid expansion of the life cycle assessment (LCA) literature is providing this information by surveying producers around the world. LCA then uses models to translate producer data into environmental impacts with sufficient accuracy for most decision-making (9–11). To date, efforts to consolidate these data or build new large-scale data sets have covered greenhouse gas (GHG) emissions only (8, 12, 13), agriculture only (13–16), small numbers of products (8, 14–16), and predominantly Western European producers (12–16) and have not corrected for important methodological differences between LCAs (12–16). Here, we present a globally reconciled and methodologically harmonized database on the variation in food’s multiple impacts. Our results show the need for far-reaching changes in how food’s environmental impacts are managed and communicated.
Generated Summary
This research article presents a comprehensive meta-analysis aimed at identifying effective solutions to reduce the environmental impacts of food production. The study consolidates data from 570 studies, covering five environmental indicators and analyzing data from approximately 38,700 farms, 1600 processors, packaging types, and retailers. The research focuses on the heterogeneity of food production, examining variations in impacts across different producers, and exploring the potential of mitigation strategies. The study’s methodology involved a multi-indicator approach, assessing land use, freshwater withdrawals, and greenhouse gas (GHG) emissions, among others. The scope of the study encompasses the entire food supply chain, from the initial inputs used by producers to the final retail stage where consumers make their choices. The study’s primary objective is to understand how environmental impacts vary among producers of the same product and identify effective strategies for reducing these impacts through both producer practices and consumer choices.
Key Findings & Statistics
- The food supply chain creates ~13.7 billion metric tons of carbon dioxide equivalents (CO₂eq), 26% of anthropogenic GHG emissions.
- Food production creates ~32% of global terrestrial acidification and ~78% of eutrophication.
- The farm stage dominates, representing 61% of food’s GHG emissions (81% including deforestation), 79% of acidification, and 95% of eutrophication.
- Today’s agricultural system covers ~43% of the world’s ice- and desert-free land.
- ~87% of this land is for food and 13% is for biofuels and textile crops or is allocated to nonfood uses such as wool and leather.
- Two-thirds of freshwater withdrawals are for irrigation.
- Ninetieth-percentile GHG emissions of beef are 105 kg of CO2eq per 100 g of protein.
- The highest-impact 25% of beef herd producers represent 56% of the beef herd’s GHG emissions and 61% of the land use (an estimated 1.3 billion metric tons of CO2eq and 950 million ha of land, primarily pasture).
- Across all products, 25% of producers contribute on average 53% of each product’s environmental impact.
- Producing just 5% of the world’s food calories creates ~40% of the environmental burden.
- For beef originating from beef herds, the highest-impact 25% of producers represent 56% of the beef herd’s GHG emissions and 61% of the land use.
- In the Australian wheat belt, the U.S. corn belt, and the Yangtze river basin, land use becomes less variable, but the same high levels of variation in all other indicators are observed.
- Halving land use can increase GHG emissions per kilogram of grain by 2.5 times and acidification by 3.7 times.
- For many producers, increasing cropping intensity can provide more economically viable and trade-off-free ways to boost productivity and reduce impacts.
- Freshwater aquaculture ponds create 0 to 450 g of methane per kg of liveweight (for context, enteric fermentation in dairy cows creates ~30 to 400 g per kg of liveweight).
- For every kilogram of nitrogen applied to crops, between 60 and 400 g is lost in reactive forms.
- 90th-percentile postfarm emissions are 2 to 140 times larger than 10th-percentile emissions.
- Returnable stainless steel kegs create just 20 g of CO₂eq per liter of beer, but recycled glass bottles create 300 to 750 g of CO2eq, and bottles sent to landfills create 450 to 2500 g of CO2eq.
- Moving from current diets to a diet that excludes animal products has transformative potential, reducing food’s land use by 3.1 (2.8 to 3.3) billion ha (a 76% reduction), including a 19% reduction in arable land; food’s GHG emissions by 6.6 (5.5 to 7.4) billion metric tons of CO2eq (a 49% reduction); acidification by 50% (45 to 54%); eutrophication by 49% (37 to 56%); and scarcity-weighted freshwater withdrawals by 19% (-5 to 32%).
- The land no longer required for food production could remove ~8.1 billion metric tons of CO2 from the atmosphere each year over 100 years as natural vegetation reestablishes and soil carbon re-accumulates.
- Halving consumption of each animal product by replacing production with above-median GHG emissions would achieve 71% of the previous scenario’s GHG reduction (a reduction of ~10.4 billion metric tons of CO2eq per year, including atmospheric CO2 removal by regrowing vegetation) and 67, 64, and 55% of the land use, acidification, and eutrophication reductions.
Other Important Findings
- Impact can vary 50-fold among producers of the same product, creating substantial mitigation opportunities.
- Impacts of the lowest-impact animal products typically exceed those of vegetable substitutes, highlighting the importance of dietary change.
- Most proxies for predicting farm-stage impacts have limited predictive power when used alone.
- Setting regional and sector-specific targets will help producers navigate trade-offs and make choices that align with local and global priorities.
- Multiple sources contribute to the variance in each product’s impact.
- The environmental and social importance of different impacts also varies locally, given land scarcity, endemic biodiversity, and water quality, among other factors.
- Emissions from deforestation and cultivated organic soils drive on average 42% of the variance in each product’s agricultural GHG emissions.
- Deforestation for agriculture is dominated (67%) by feed, particularly soy, maize, and pasture.
- Moving from current diets to a diet that excludes animal products has transformative potential.
- Processors, distributors, and retailers can substantially reduce their own impacts.
Limitations Noted in the Document
- The study acknowledges that prior research has been limited by data availability and methodological differences.
- The predictive power of common proxies for farm-stage impacts is limited.
- Setting and incentivizing mitigation targets involves trade-offs, and the effectiveness of specific practices can vary.
- The research relies on existing LCA methodologies, which may have limitations in capturing the full range of environmental impacts.
- The effectiveness of mitigation strategies may be influenced by local conditions and regional variations.
Conclusion
The findings emphasize the need for a comprehensive approach to mitigate the environmental impacts of food production, involving producers, processors, retailers, and consumers. The study underscores the significant variability in environmental impacts among producers, even for the same product, creating opportunities for targeted mitigation. The study supports the implementation of environmental standards, the communication of producer impacts to consumers, and consumer education around the environmental impacts of the food system. One of the most striking findings is the environmental benefits that could be achieved by shifts in dietary choices. The research emphasizes that dietary change can deliver environmental benefits on a scale not achievable by producers alone. Furthermore, the environmental benefits of dietary changes can be scaled up by communicating average product impacts to consumers, which enables dietary changes. The paper concludes with a call for an integrated mitigation framework. The paper suggests that a multi-faceted approach is needed, including producer monitoring, policy-driven incentives, and consumer awareness, to drive significant and lasting change in the food system. By integrating these strategies, the food system can be transformed to reduce its environmental footprint and contribute to a more sustainable future.
IFFS Team Summary
- Analysis drawing on 570 studies with data covering 38,700 commercial farms
- 43% of the globe’s ice-and desert-free land surface is used for agriculture, and the
- Food production, upstream of the consumer, accounts for ~31% of global GHGs
- There is marked variation between farms
- Cattle raised only for meat without any dairy co-production (main model in USA):
- Has the highest GHG and land use impact.
- Beef from dairy herds is also very high
- Dairy uses less resources than beef
- But somewhat worse than most other animal products
- Lowest impact animal products (eggs, poultry meat, some farmed
- Animal products provide 37% of protein and 18% of calories,
- but are responsible for 83% of agricultural land use
- and 56-58% of food-related emissions.
- A global dietary shift to a completely animal-free diet
- would reduce food-related GHGs by~49% and farmland by ~76%.
- Just eliminating beef (globally) would still reduce food GHGs by 33%.
- A dietary shift away from all animal products in the US, where per capita meat consumption is thrice the world average, could reduce food emissions 61-73%.
- Between plant proteins
- Uses Tofu and not whole soybeans – interesting choice
- Tofu is the most efficient for land and GHG emissions amongst other plant proteins
- Interesting since there are other papers often list pulses as more efficient than soy, and lower relative ratings than in this paper
- This full impact assessment on not just GHG emissions, but also land use, freshwater use, and water pollution, led to their conclusions that a vegan diet shows to be the best way to reduce an ecological footprint.
- Indirectly stated that 28% of global GHG can be mitigated with an entire shift away from animal agriculture.
- GT of CO2e/yr of direct GHGs is 6.6 and carbon opportunity cost of land is 8.1
- If you divide that by the total of CO2e per year it works out to 28% of global anthropogenic GHG emissions based on their year of analysis.
- Excellent presentation by author Joseph Poore at the Cambridge Climate Lecture Series breaking down paper: https://www.youtube.com/watch?v=8miQs3mPGu8