Abstract
For agriculture, there are three major options for mitigating greenhouse gas (GHG) emissions: 1) productivity improvements, particularly in the livestock sector; 2) dedicated technical mitigation measures; and 3) human dietary changes. The aim of the paper is to estimate long-term agricultural GHG emissions, under different mitigation scenarios, and to relate them to the emissions space compatible with the 2 °C temperature target. Our estimates include emissions up to 2070 from agricultural soils, manure management, enteric fermentation and paddy rice fields, and are based on IPCC Tier 2 methodology. We find that baseline agricultural CO2-equivalent emissions (using Global Warming Potentials with a 100 year time horizon) will be approximately 13 Gton CO2eq/year in 2070, compared to 7.1 Gton CO2eq/year 2000. However, if faster growth in livestock productivity is combined with dedicated technical mitigation measures, emissions may be kept to 7.7 Gton CO2eq/year in 2070. If structural changes in human diets are included, emissions may be reduced further, to 3–5 Gton CO2eq/year in 2070. The total annual emissions for meeting the 2 °C target with a chance above 50 % is in the order of 13 Gton CO2eq/year or less in 2070, for all sectors combined. We conclude that reduced ruminant meat and dairy consumption will be indispensable for reaching the 2 °C target with a high probability, unless unprecedented advances in technology take place.
Generated Summary
This research investigates the impact of reduced meat and dairy consumption on achieving stringent climate change targets. The study employs a biophysical approach to estimate long-term agricultural greenhouse gas (GHG) emissions under various mitigation scenarios, focusing on emissions up to 2070. The research explores three main avenues for mitigating agricultural GHG emissions: productivity improvements, technical mitigation measures, and dietary changes. The core methodology involves constructing regionalized food consumption scenarios and calculating corresponding crop and livestock production. The study assesses the potential for reducing emissions through increased livestock productivity, dedicated technical measures, and shifts in human diets. Furthermore, it relates these emission levels to those compatible with the 2°C temperature target, providing insights into the crucial role of dietary changes in achieving ambitious climate goals.
Key Findings & Statistics
- The study finds that baseline agricultural CO2-equivalent emissions in 2070, using Global Warming Potentials with a 100-year time horizon, will be approximately 13 Gton CO2eq/year, compared to 7.1 Gton CO2eq/year in 2000.
- If faster growth in livestock productivity is combined with dedicated technical mitigation measures, emissions may be kept to 7.7 Gton CO2eq/year in 2070.
- Including structural changes in human diets could further reduce emissions to 3–5 Gton CO2eq/year in 2070.
- The total annual emissions for meeting the 2 °C target with a chance above 50 % is in the order of 13 Gton CO2eq/year or less in 2070, for all sectors combined.
- In the REF (Reference) scenario, emissions amount to 12 Gton CO2eq in 2050; ruminant meat is responsible for around two thirds and animal products in total for about 80 %.
- Increased livestock productivity cuts the global emission by 2 Gton CO2eq in 2050 as seen in the IP (Increased productivity) scenario.
- In the TM (Technical mitigation) scenario, where technical mitigation options are added to the IP scenario, the emissions are reduced to about 8.3 Gton CO2eq/year in 2050.
- In the Climate Carnivore (CC) scenario, the annual emissions are 4.9 Gton CO2eq, while in the Flexitarian (FL) scenario the total emissions are about 3.1 Gton CO2eq/year.
- In the reference scenario (baseline), the N efficiency is assumed to remain constant in Europe and gradually converges to the European level in North America and Pacific OECD.
- Direct N2O emissions related to fertilizer and manure application were calculated using an emission factor of 1 % N2O-N per N applied (IPCC 2006).
- CH4 emissions from enteric fermentation is estimated as a fraction of feed intake in energy terms (IPCC 2006), assumed to be 7% for permanent pasture, 6.5% for forages (silage/hay), 5% for protein concentrates and 3.5 % for cereal grains in gross energy terms.
- In the REF scenario, global average feed-to-product ratio compared to REF: ruminant meat +20%, dairy +50%, other meat + 25% (IP).
- In the TM scenario, the N efficiency in crop production gradually increases so that all regions reach the efficiency level of Europe by 2050.
- The authors find that the emission pathway generated using the lower climate sensitivity (3 °C for a CO2 doubling) has about 50 % chance of staying below the temperature target.
- In the CC scenario, 75% of the ruminant meat and dairy consumption is replaced by other meat (in kcal terms). This scenario represents an increase in total meat consumption per capita by 45% compared to the baseline.
- In the Flexitarian (FL) scenario, 75 % of all meat and dairy products are replaced by cereals and pulses (in kcal terms).
Other Important Findings
- The study emphasizes that in the REF scenario, food-related GHG emissions alone are as high as, or higher than, the annual emissions in either one of the two emission pathways.
- The research highlights that stronger advancement of mitigation technology than assumed in this study could significantly relax the need for dietary changes.
- The potential for technical mitigation of CH4 from ruminants and N2O from soils are conservative by design.
- The study suggests that deep cuts in emissions from food and agriculture do not seem plausible without large changes in consumption towards less GHG intensive food, in particular less ruminant meat and dairy.
- The research finds that dietary changes are crucial for meeting the 2 °C target with high probability, given the constraints in achieving very large reductions in other sectors.
- The study indicates that, for baseline diets, long-term GHG emissions from the global food system will be dominated by CH4, with a strong link to ruminant meat and dairy consumption levels.
Limitations Noted in the Document
- The study acknowledges that the approach is bio-physical and does not explicitly include any economic factors.
- The scenario results are presented as descriptive rather than predictive.
- The study excludes some GHG emission sources, most notably CO2 from changes in land use.
- The study’s estimates of the potential for technical mitigation of CH4 from ruminants and N2O from soils are conservative by design.
- The study recognizes that the degree of substitution of 75 % is not based on any systematic analysis of limiting factors.
- The study assumes a gradual transition first from solid systems towards slurry systems, and thereafter to slurry systems with flaring, which can be a limitation.
Conclusion
The study’s primary conclusion underscores the critical importance of reduced meat and dairy consumption in meeting stringent climate change targets. The authors emphasize that, under current trends, agricultural emissions are projected to increase, potentially exceeding the emission levels compatible with the 2°C target. The research highlights that dietary changes are crucial for meeting the 2°C target with high probability. Furthermore, the study indicates that if overall emissions can be cut faster than in the illustrative pathways, this could compensate for higher sustained agricultural GHG emissions in the long-run. The study suggests that the food system’s emissions will be dominated by CH4, and the room for perpetual CH4 emissions from ruminants will depend on the level of CO2 emissions. While technical mitigation and increased livestock productivity can offer some relief, dietary changes, particularly reduced consumption of ruminant meat and dairy, are deemed indispensable for achieving the 2°C target with a high likelihood. The study emphasizes the need for substantial reductions in other GHG-emitting sectors, especially energy, for which the prospects for deep reductions by technology are more favorable. The researchers find that for baseline diets, long-term GHG emissions from the global food system will be dominated by CH4, with a strong link to ruminant meat and dairy consumption levels. The study indicates that, for a given temperature-increase target, any lowering of the cumulative CO2 emissions will give room for higher sustained emissions of CH4. The study concludes that, due to the constraints for emission reductions in the food system, it might be cost-effective to seek even deeper cuts in other sectors, especially energy and transport, for which the prospects for deep reductions by technology are more favorable.