Carbon Farming in Non-Tropical Dryland Wheat Systems: Sequestration, Co-Benefits, Trade-Offs, and Scalable MRV Pathways

Dryland wheat systems support food security in non-tropical drylands but face persistent water scarcity, soil degradation, and rising climate risks, contributing to yield stagnation and expected declines of 20–50% by 2050—1.2–1.8 times global wheat averages. Carbon farming, implemented through 20 climate-smart practices covering conservation agriculture (CA), regenerative approaches, and complementary soil–water–nutrient management (e.g., drought-resistant varieties for +10–30% stability, enhanced-efficiency fertilizers for –10–20% N₂O, crop-livestock integration for +0.5–1.0 Mg C ha⁻¹ yr⁻¹ and methane –10–15%, bioenergy rotations for 0.3–0.8 Mg C ha⁻¹ yr⁻¹), can deliver both mitigation and resilience benefits. However, dryland evidence is fragmented, context-dependent, and may be overestimated by 20–40% when short-term trials overlook reversals and biases. This study brings together biophysical and implementation evidence to quantify potential, co-benefits, trade-offs, and MRV pathways. We used AI-assisted mining of >10,000 records (Scopus/Web of Science/Google Scholar/), validated via manual screening/extraction of 145 core studies, yielding >300 harmonized points per indicator. Outcomes were analyzed using violin/bar plots for comparisons across hierarchies and an evidence map for trade-offs, with a conceptual framework linking drivers, practices, mechanisms, and enablers. Key findings include SOC sequestration (global 0.05–1.22 Mg C ha⁻¹ yr⁻¹; MENA/CWANA 0.15–0.82, 20–40% below humid averages), co-benefits (yields +20–88%, water productivity +18–100%, profitability +30–44%), and trade-offs (N₂O offsets 10–25%, reversals 20–40%). Bundles amplify effects 1.5–2.5× via enhanced biomass and reduced losses, with regional scaling potential ~0.1–0.5 Tg C yr⁻¹ over 5–15 Mha. MRV costs $10–50 ha⁻¹ (20–50% higher in drylands); tiered approaches that combine sampling, modeling, remote sensing, and digital tools are recommended. Carbon farming is most effective as integrated portfolios aligned with food security, but requires incentives, equitable MRV, and policy safeguards (e.g., subsidies for bundles, smallholder inclusion >50%) to address biases, equity gaps, and barriers to verifiable scaling toward SDGs 2, 13, and 15. Future priorities include data from long-term trials and digital innovations to reduce overestimation and enhance adoption.