Legume-based cropping systems for biodiversity enhancement: a review of functional mechanisms for life cycle sustainability assessment

Introduction: Agriculture intensification has driven biodiversity loss, with monocultures occupying 80% of the arable land and causing crop diversity loss. Legumes enhance biodiversity through six mechanisms: (1) breaking pest cycles via crop diversification, enabling predator recovery; (2) providing high-protein floral resources that sustain wild pollinators; (3) releasing root exudates that enrich beneficial soil microbes; (4) contributing with nitrogen fixation, reducing synthetic fertilizer by 19–36% and N₂O emissions by 35%; (5) improving soil structure and preventing erosion by 50%, creating microhabitats for soil fauna; and (6) enriching non-rhizobia endophytes that suppress pathogens and improve plants resilience.

Methods: A systematic PRISMA review was undertaken of studies (from 2015-2025) on LCA, Life Cycle Costing, and Social LCA of legume-based systems, assessing how biodiversity-related mechanisms are included within sustainability pillars .

Results: A systematic review revealed that there are 148 methods for ecosystem services assessment, where 81.8% of methods relate to Regulation & Maintenance services and none of them relate to Cultural services. It is important to note that biodiversity maintenance, pollination and pest control lack LCA methodology. Integration of environmental, economic, and social assessment (LCSA) exists in just 5% of studies in agriculture.

Conclusions: We propose integrating biodiversity indicators (predator-pest interactions, pollinator abundance, and soil microbial biodiversity) into LCSA using environmental DNA. It is particularly relevant since existing LCSAs favor simplified and pesticide-intensive systems without quantifying the 30-35% yield increase, 20-25% pest infestation decrease, and 25-30% nutrient efficiency boost achieved by legume crops. Improved LCSA would support EU Biodiversity Strategy for 2030.

Acknowledgements: This research is funded by the www.legumESproject.eu (Grant Agreement N^o. 101135512).