Can sustainable farming make olive groves carbon neutral? Empirical evidence from Mediterranean Portugal

Agriculture contributes to greenhouse gas emissions while also offering potential as a carbon sink. However, the capacity of Mediterranean olive groves to offset their emissions remains poorly quantified, particularly as different cultivation models may vary substantially in their contributions to carbon sequestration and emissions, highlighting the need for comparative assessment to inform sustainable management and climate mitigation. This study assessed the carbon balance and footprint of six olive groves in Alentejo, Portugal, managed under integrated, organic, and biodynamic-organic systems. The groves were classified as low or high carbon input systems based on annual soil carbon inputs. Results showed that soil organic matter was more strongly influenced by carbon inputs than by the management system. High-input groves consistently exhibited a positive carbon balance (around +1.0 Mg C ha−1 yr−1), whereas low-input groves showed more variable results, with values ranging from net carbon losses to modest gains. CO₂ emissions from agricultural operations were similar across systems (approximately 3200–3400 kg CO₂ eq ha−1 yr−1), but net emissions were substantially lower in high-input groves (∼140 kg CO₂ eq ha−1 yr−1) compared to low-input groves (∼1650 kg CO₂ eq ha−1 yr−1). These findings highlight that increasing annual carbon inputs is more effective than changing management type for enhancing carbon sequestration and reducing net CO₂ emissions in olive groves, supporting carbon farming as a key strategy for climate change mitigation in Mediterranean agricultural systems.