Particularities of climate protection in the agri-food system - what do we need to rethink?

The global agri-food system is responsible for one third of all greenhouse gas emissions worldwide, and significant climate protection measures in the agri-food sector are essential to achieve our climate goals. On the question of how to assess different climate impacts and which climate mitigation measures should be pursued, there is currently extensive debate, including the reassessment of biogenic methane emissions from livestock (GWP*). On closer examination, however, it becomes clear that even when using GWP*, a reduction of methane emissions represents a necessary and rapidly effective contribution to climate protection. Therefore, a fundamental change in direction of the measures proposed so far for methane emission reduction in agriculture does not seem reasonable. In addition to this debate, two concepts for assessing the climate impact of the agri-food system have been proposed and discussed which have clear limitations: first, the simplistic view of greenhouse gases as national external costs, which ignores leakage effects. Second, the consideration of short-term CO2 sequestration in harvested products, which cannot be reconciled with carbon accounting systems in use. In contrast to these concepts, the inclusion of carbon opportunity costs is a new approach that has been applied several times in peer-reviewed publications to a wide variety of issues and to which no fundamental limitations have been identified to date. Underlying this approach is the peculiarity in agriculture that when agricultural activities are ceased, emissions not only decline to zero, but a positive climate impact arises from the carbon sequestration capacity of natural vegetation. The carbon opportunity cost quantifies this foregone carbon sequestration capacity in tons of CO2 per ton of agricultural product. This leads to the following principles, which should be more strongly integrated into the discussion on the climate impact of agriculture: (1) Inclusion of carbon opportunity costs: this is the only way to achieve an efficient use of globally scarce land from a climate perspective. (2) Separate efficiency analysis of supply and demand side to identify optimized options for action with subsequent market modeling to account for market responses with respect to supply and demand side. (3) Focus on the overall consideration of landscapes to comprehensively include more complex environmental impacts, especially the challenge of biodicversity decline. The following recommendations for action can be derived: (1) The conversion of natural vegetation to agricultural land should be ended globally as soon as possible. (2) On the supply side, production emissions per unit of product should be reduced - in agriculture, especially methane and nitrous oxide. On the demand side, more plant-based diets are needed to reduce food-related production emissions and land requirements. (3) Land that provides greater climate benefits in its natural state than when used for agriculture should be restored. (4) Producing more food on existing agricultural land provides climate benefits that should be exploited.