Carbon Farming and Agroforestry: Synergies, Trade‑Offs, and a Decision Framework for Climate‑Smart Landscapes

Carbon farming through agroforestry and biochar amendment is widely recognised as a climate‑smart strategy, yet the quantitative integration of their combined effects on soil organic carbon (SOC) and the operationalisation of monitoring, reporting, and verification (MRV) remain fragmented across the literature. This review synthesises published meta‑analytical evidence, mechanistic studies, and case examples to assess SOC sequestration potentials, synergies, and trade‑offs of integrated agroforestry–biochar systems. We draw on 127 field studies and ten global meta‑analyses to quantify carbon pool dynamics and to construct a nexus analysis linking carbon gains to seven dimensions of sustainability. Tropical silvopasture combined with biochar shows the highest average SOC accrual (2.6 Mg C ha⁻¹ yr⁻¹), while temperate alley‑cropping with biochar achieves 1.8 Mg C ha⁻¹ yr⁻¹. Trade‑offs such as water competition (yield reductions of 10–25% in semi‑arid settings) can be mitigated by AI‑assisted irrigation scheduling and nano‑enabled soil amendments. A novel four‑phase decision‑support framework is developed and illustrated with a hypothetical Sahelian case study, embedding digital MRV, blockchain verification, and community‑based benefit‑sharing mechanisms. By bridging the gap between scientific evidence and market‑ready carbon removal, this framework provides a practical pathway for scaling carbon farming in diverse smallholder landscapes. Limitations and priority research directions are clearly identified.