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 article examines the potential of reduced meat and dairy consumption to meet stringent climate change targets. It employs a biophysical approach, constructing regionalized food consumption scenarios and calculating crop and livestock production in each region. The study analyzes the impact of various mitigation scenarios, including increased livestock productivity, technical mitigation measures, and dietary changes, on long-term agricultural greenhouse gas (GHG) emissions. The methodology involves estimating emissions from agricultural soils, enteric fermentation, and manure management, with a focus on emissions up to 2070. The study relates these emission levels to those compatible with the 2°C temperature target, exploring how changes in the food system can contribute to achieving climate goals. The research aims to understand global agricultural GHG mitigation by estimating emissions under different scenarios and comparing them with global temperature targets. Specifically, the study assesses mitigation potentials from livestock productivity increases, technical measures, and dietary changes, as well as the compatibility of emissions from the agricultural sector with the 2°C target.
Key Findings & Statistics
- The study finds that baseline agricultural CO2-equivalent emissions will be approximately 13 Gton CO2eq/year in 2070, 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.
- 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.
- The study examines five different scenarios.
- The reference (baseline) scenario (REF) is based on FAO projections.
- The increased productivity (IP) scenario involves global average feed-to-product ratio improvements.
- The technical mitigation (TM) scenario adds improved N efficiency, altered manure management, fat additives to ruminants, and reduced methane from rice to the IP scenario.
- The climate carnivore (CC) scenario involves 75% of ruminant meat and dairy products being replaced by other meat.
- The flexitarian (FL) scenario involves 75% of animal food being replaced by pulses and cereals.
- N₂O emissions associated with fertilizer and manure application are estimated from 28% (for rice in China) to about 75% in forages.
- 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, assumed to be 7% for permanent pasture, 6.5 % for forages, 5% for protein concentrates and 3.5% for cereal grains in gross energy terms.
- Emissions in the REF scenario 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 scenario.
- In the TM 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 CC scenario the annual emissions are 4.9 Gton CO2eq, while in the FL scenario the total emissions are about 3.1 Gton CO2eq/year.
- In the REF scenario, emissions from ruminant meat were projected to be 189 MJ GE feed/MJ ME product in 2050, whereas in the IP scenario, this was reduced to 148.
Other Important Findings
- The study concludes that reduced ruminant meat and dairy consumption is indispensable for reaching the 2°C target with a high probability, unless unprecedented advances in technology take place.
- Technical measures alone may not offer sufficiently deep emission reductions in the long term.
- Increased productivity is likely to be a major GHG mitigation option in many low and middle-income countries.
- Dietary changes that substitute vegetable products for animal products may hold a large mitigation potential.
- The actual mitigation level is highly sensitive to which products that are substituted.
- The potential for productivity increases may be limited.
- Realizing the productivity potentials that do exist will be associated with higher N turnover per area unit and intensified livestock production, which both may counteract GHG emission reductions.
- In the TM scenario, the potential for productivity improvements and mitigation measures is more restricted in the ruminant sector than for dairy, other meat and vegetables.
- Changing diets cuts the emissions further.
- The study generated two emission pathways, using two different assumptions on climate sensitivity (being either 3 or 4 °C for a doubling of the CO2 concentration).
Limitations Noted in the Document
- The approach in this study is bio-physical and does not explicitly include any economic factors.
- The scenario results presented should be seen as descriptive rather than predictive.
- The study excluded some GHG emission sources (see 2.1), most notably CO2 from changes in land use.
- Plausible levels of long-term CO2 emissions from land-use change span over a wide range, since they depend on several highly uncertain factors.
- The potential for technical mitigation of CH4 from ruminants and N₂O from soils are conservative by design; currently known mitigation technology does not seem to promise large reductions.
- Stronger advancement of mitigation technology than that assumed in this study could avoid the assertion that dietary changes may be needed for meeting the 2 °C target.
- The authors note the difficulty in predicting how microorganisms would evolve to circumvent blocked pathways (such as nitrification inhibitors).
Conclusion
The study emphasizes the critical role of reduced ruminant meat and dairy consumption in achieving stringent climate change targets. The research reveals that while technological advancements and productivity improvements in agriculture can contribute to emissions reductions, dietary changes are crucial for meeting the 2°C target with a high probability. The authors’ findings underscore the significance of altering food consumption patterns to mitigate climate change, particularly given the limitations of solely relying on technological solutions. The study highlights that meeting climate targets requires a multifaceted approach, including technological advancements, productivity increases, and dietary shifts. The authors suggest that policy interventions driving dietary changes may be essential, especially as technological advancements alone may not be sufficient. The study acknowledges the complex interplay of factors affecting emissions, including productivity, technical measures, and dietary preferences. This research contributes valuable insights into the challenges and opportunities for achieving significant reductions in agricultural GHG emissions and underscores the urgent need for innovative solutions to address climate change effectively.