Abstract
Climate change mitigation policies tend to focus on the energy sector, while the livestock sector receives surprisingly little attention, despite the fact that it accounts for 18% of the greenhouse gas emissions and for 80% of total anthropogenic land use. From a dietary perspective, new insights in the adverse health effects of beef and pork have lead to a revision of meat consumption recommendations. Here, we explored the potential impact of dietary changes on achieving ambitious climate stabilization levels. By using an integrated assessment model, we found a global food transition to less meat, or even a complete switch to plant-based protein food to have a dramatic effect on land use. Up to 2,700 Mha of pasture and 100 Mha of cropland could be abandoned, resulting in a large carbon uptake from regrowing vegetation. Additionally, methane and nitrous oxide emission would be reduced substantially. A global transition to a low meat-diet as recommended for health reasons would reduce the mitigation costs to achieve a 450 ppm CO2-eq. stabilisation target by about 50% in 2050 compared to the reference case. Dietary changes could therefore not only create substantial benefits for human health and global land use, but can also play an important role in future climate change mitigation policies.
Generated Summary
This study investigates the potential impact of dietary changes on achieving ambitious climate stabilization levels. The research employs an integrated assessment model to explore the effects of transitioning to diets with reduced meat consumption or complete switches to plant-based protein sources. The primary goal is to assess how these dietary shifts influence greenhouse gas emissions, land use, and the associated costs of achieving climate stabilization targets. The research provides a detailed analysis of various dietary scenarios, including complete substitution of meat from ruminants, complete substitution of all meat, complete substitution of all animal products, and a partial substitution based on a healthy diet. The study uses the IMAGE 2.4 model, a global integrated assessment model, to simulate the long-term dynamics of global change. The model incorporates detailed representations of the energy system, agricultural production, land use change, and the carbon cycle. The researchers examine the impact of these dietary changes on greenhouse gas emissions, land use, and mitigation costs, offering insights into the potential role of dietary choices in climate change mitigation policies.
Key Findings & Statistics
- The livestock sector accounts for 18% of global greenhouse gas emissions and 80% of total anthropogenic land use.
- A global food transition to less meat could result in the abandonment of up to 2,700 Mha of pasture and 100 Mha of cropland.
- A global transition to a low meat-diet would reduce mitigation costs to achieve a 450 ppm CO2-eq. stabilization target by about 50% in 2050 compared to the reference case.
- Greenhouse gas emissions in 2050 in the reference scenario are projected to be 19.7 GtC-eq.
- In the reference scenario, global average GDP per capita is projected to almost triple, from $5,500 to $16,000 between 2000 and 2050.
- In the reference scenario, greenhouse gas emissions are projected to increase by 78% from 2000 to 2050.
- Total annual land-use related greenhouse gas emissions increase by 10% from 3 GtC-eq to 3.3 GtC-eq. between 2000 and 2030, remaining constant thereafter.
- In 2000, methane emissions from animal waste were 0.5 g CH4 per kg meat and decreased to 0.4 g CH4 per kg meat in 2050.
- The carbon price would increase to $650 US per tonne C-eq in 2050 to induce the required emission reductions.
- The strongest impacts occur for pasture area, which is reduced by 80% or 2,700 Mha (in NoRM and NoM) and by 100% or 3,200 Mha (in NoAP) compared to the reference scenario.
- In the NoRM variant, there is a 6% reduction in global cropland area.
- The NoM variant results in a 4% decrease in global crop area.
- The cumulative emission reduction in the 2010-2050 period amounts to 17% for CO2, 24% for CH4, and 21% for N2O in the NoAP scenario.
- The reduction of greenhouse gas concentrations is 57 to 76 ppm CO2-eq., and a reduction of radiative forcing of about 0.5 W m−2 compared to the reference scenario in 2050.
- In the HealthyDiet variant, crop and pasture area are reduced by 135 and 1360 Mha, respectively, compared to the reference case.
- In the HealthyDiet variant, greenhouse gas emissions are about 10% lower than in the reference case.
- The reduction in emissions in the HealthyDiet variant leads to a lower carbon price needed to meet the emission pathway.
- The reduction of CO2 fertilization by a factor of two results in an approximately 12 ppm higher CO2 concentration in 2050 compared to the standard settings in both the reference case and the HealthyDiet variant.
- A slower recovery period of net primary productivity (NPP) for natural vegetation after the abandonment of pasture or cropland has a larger effect on CO2 concentrations in HealthyDiet than in the reference case (9 and 5 ppm, respectively).
- Under the HealthyDiet scenario, cumulative emissions are reduced by about 20%, while costs are reduced by more than 50% (both cumulated over the period 2010-2050).
- In the HealthyDiet variant, the total potential for bioenergy from woody biomass in 2050 increases to around 450 EJ.
- The total potential for bioenergy from woody biomass in 2050 increases from 170 EJ in the reference case.
- The abatement costs in the HealthyDiet variant are reduced by 54% compared to the reference case (i.e. 0.48% of GDP, all referring to net present values).
Other Important Findings
- The study uses four dietary variants: (a) complete substitution of meat from ruminants (NORM), (b) complete substitution of all meat (NoM), (c) complete substitution of all animal products (NoAP), and (d) partial substitution of meat based on a healthy diet (HealthyDiet, HDiet).
- The scenarios of dietary change involve the complete or partial substitution of meat with plant proteins.
- The study found that dietary changes can lead to substantial benefits for human health and global land use.
- The shift to low-meat diets induces a reduction in agricultural area.
- The study’s findings show that the potential for bioenergy from woody biomass increases in the HealthyDiet variant.
- The re-establishment of temperate, boreal and warm mixed forest, as well as tropical savannah, scrubland, woodland, and forest, results in more biomass than under managed grazing land.
- The study found that the largest reduction of greenhouse gas emissions by product category is caused by the substitution of ruminant meat.
- The reduction in emissions in the HealthyDiet variant also leads to a lower carbon price needed to meet the emission pathway.
Limitations Noted in the Document
- The transition to alternative diets was assumed to take place between 2010 and 2030, without implementation or other costs being accounted for.
- The implementation of the HealthyDiet was implemented globally in the model, without regional differentiation, which may lead to higher meat intake than in the reference case in some areas of the world.
- The study acknowledges uncertainties in the biosphere and agro-economic systems, particularly regarding the carbon cycle and land abandonment.
- The study did not analyze the agro-economic consequences of the dietary changes and their implications, such as transition costs or impacts on land prices.
- The study ignores potential socio-economic implications, such as effects on health changes on GDP and population numbers.
Conclusion
The study’s findings underscore the significant impact of dietary changes on climate change mitigation and the potential for substantial benefits for human health and global land use. The study shows that the transition to low-meat diets can lead to substantial emission reductions, primarily through reduced agricultural land use and changes in livestock production systems. The study emphasizes the role of the terrestrial carbon cycle and the importance of the carbon uptake of abandoned cropland and pasture in these scenarios. Furthermore, the study demonstrates that dietary changes can significantly reduce the costs of achieving climate stabilization targets. The HealthyDiet variant, in particular, presents a realistic and impactful approach to mitigation, offering considerable emission reductions while also reducing mitigation costs. The reduction in greenhouse gas emissions, coupled with the potential for increased bioenergy production, highlights the multifaceted benefits of dietary shifts. The study indicates that the benefits of dietary change extend beyond climate mitigation, influencing health outcomes and land-use patterns. The study’s conclusions suggest that dietary changes, particularly the shift towards low-meat diets, present a feasible and cost-effective pathway to achieve ambitious climate goals. The findings support the inclusion of dietary interventions in climate policy agendas, as these changes can contribute to both climate change mitigation and improved public health outcomes.