Global food systems need significant changes to support human and environmental health. Swiss agriculture, with high environmental and health costs, presents a case study. Livestock production, responsible for a significant portion of Switzerland's greenhouse gas emissions, necessitates a decrease in meat consumption and a shift towards sustainable protein sources. Legumes offer a promising alternative due to their lower environmental footprint (significantly less GHG emissions compared to meat and eggs), nitrogen-fixing capabilities (reducing fertilizer needs), and high nutritional value (dietary fiber, essential amino acids, low glycemic index). Increased demand for plant-based protein contrasts sharply with Switzerland's negligible grain legume production, resulting in high import dependence. This study aims to quantify the potential for increasing domestic grain legume production and its impact on protein self-sufficiency in Switzerland. The study combines qualitative expert assessment to identify challenges and opportunities, with quantitative analysis to estimate the potential land area suitable for legume cultivation under different scenarios and the consequent impact on Switzerland's protein supply chain and environmental footprint.

Existing literature highlights the urgent need for sustainable food systems and the high environmental costs associated with Swiss agriculture, particularly livestock production. Studies emphasize the advantages of legumes as a sustainable protein source due to their lower GHG emissions, nitrogen fixation capabilities, and nutritional benefits. Research indicates the effectiveness of integrating legumes into crop rotations to mitigate nitrogen pollution. However, literature also notes challenges, including antinutrients in some legumes and the economic and policy barriers hindering wider legume adoption. Existing data reveals Switzerland's significant dependence on imported soy and other legumes to support its livestock industry, emphasizing the need for increased domestic production to enhance sustainability and self-sufficiency. Prior research in Europe highlights the potential for increased legume production but also notes the lack of successful policy interventions to support this change. Successful examples from other countries such as Canada and Australia involve supply chain integration, policy support, and breeding efforts.

This study employed a mixed-methods approach. First, a qualitative assessment was conducted through expert interviews (15 experts) and a survey (29 experts) focusing on the challenges and opportunities related to grain legume cultivation in Switzerland across the entire food value chain (from producers to consumers). Second, a quantitative analysis estimated the potential production area of three grain legumes—soybean, faba bean, and pea—based on agronomic factors (soil properties, altitude, climate expressed as growing degree days (GDD)). Two scenarios were developed: Scenario I considered only currently arable land, and Scenario II included suitable permanent grassland. The analysis considered cultivation breaks for each legume. Yield data were analyzed to assess the potential for protein production. Finally, the study modeled the impact of increased legume production on Switzerland's protein self-sufficiency, adjusting for reductions in livestock production and feed imports. The model balanced legume protein allocation between food and feed, while maintaining existing feed composition and distribution amongst livestock. A sensitivity analysis was performed to assess the robustness of the model's results under fluctuating legume and roughage yields. The model incorporated data on agricultural area, fodder usage, animal protein consumption, and feed imports. The study also calculated changes in gross and net self-sufficiency, plant-based protein consumption, and the environmental impact of reduced livestock production.

The qualitative expert assessment identified pricing structures and the political framework as major challenges for increased grain legume production in Switzerland. Lack of breeding programs leading to a shortage of site-adapted varieties and the underdeveloped supply chain were also highlighted. Common pea and soybean were identified as having the greatest potential. The quantitative analysis revealed a significant untapped potential for grain legume cultivation. Scenario I (using existing arable land) showed a substantial increase in legume production area and the potential to replace a significant portion (84%) of meat protein consumption. Scenario II (including suitable permanent grassland) demonstrated even greater potential, with legume production potentially exceeding current meat protein consumption and allowing for a decrease in the area dedicated to temporary grassland and fodder maize. The sensitivity analysis revealed that the model was relatively robust, with minor variations in self-sufficiency despite fluctuating legume and roughage yields. Under the improved self-sufficiency scenario, domestic legume production could significantly reduce reliance on imported concentrated feed and animal protein, leading to an overall increase in both gross and net self-sufficiency. The shift towards increased legume production would also lead to a considerable reduction in livestock production (approximately 33%), contributing to lower GHG emissions.

The findings demonstrate a considerable potential to enhance the sustainability and self-sufficiency of Swiss agriculture by shifting towards increased grain legume production. The results address the research question by quantifying the substantial untapped potential of grain legume cultivation in Switzerland and its impact on the national protein supply. The significant potential for replacing a considerable proportion of meat protein consumption with domestically produced legume protein is crucial for reducing environmental impact (GHGs, fertilizer use) and improving food security. The identified challenges across the value chain highlight the need for concerted efforts in breeding, policy, market development, and consumer education to fully realize this potential. The study suggests that a transition towards a plant-based protein-rich diet is not only environmentally beneficial but also economically viable when considering economic competitiveness with other crops, provided adequate policy and market mechanisms are in place.

This study concludes that increasing grain legume production in Switzerland offers a promising pathway towards more sustainable and self-sufficient agriculture. The potential for replacing substantial amounts of meat protein consumption with domestically produced legumes is significant, contributing to reduced environmental impacts and improved food security. Success hinges on addressing the identified challenges through collaborative efforts across the value chain, including targeted breeding programs, supportive policies, efficient processing infrastructure, and increased consumer acceptance of plant-based proteins. Future research should focus on detailed economic impact assessments, further refinement of yield predictions incorporating various climatic factors, and in-depth studies on the long-term effects of intensified legume production on soil health.

While the study provides a robust estimation of potential legume production, certain limitations exist. Yield estimates were based on average values, potentially overlooking variations across different areas. The focus on protein might underrepresent the contributions of other nutrients. The modeling assumes a specific crop rotation, and economic implications beyond protein production were not extensively analyzed. Lastly, the potential for carbon sequestration resulting from changes in land use needs further investigation.