The neglected role of abandoned cropland in supporting both food security and climate change mitigation

Global cropland expansion has historically accompanied population growth and increasing food demand. While yield improvements have been made, undernourishment remains a significant issue. Future cropland expansion is projected, posing risks to environmentally valuable areas. Simultaneously, the food sector contributes significantly to climate change, highlighting the need for land management strategies that mitigate emissions. Nature-based solutions, such as reforestation, are crucial for climate change mitigation, but compete with cropland expansion needs. However, cropland abandonment is also widespread globally due to factors such as land degradation, socioeconomic changes, and disasters. This presents an opportunity, as studies show that abandoned cropland can be recultivated for food production or restored to natural habitats for carbon sequestration. This paper addresses the potential and trade-offs of using abandoned cropland for both food production and climate change mitigation, considering the need for spatially prioritized land management strategies to maximize synergies.

Existing research highlights the feasibility of recultivating and reforesting abandoned cropland to support food production and climate change mitigation, respectively. However, comprehensive assessments of the trade-offs and synergies between these two purposes are lacking. Most assessments focus on a single purpose, neglecting the potential for alternative uses that might be more suitable given the spatial variability in crop yield and carbon sequestration rates. Studies indicate that land abandonment can be transient, shifting between different land uses. This underscores the importance of understanding the potential and trade-offs involved and developing better land-use management strategies, particularly those that prioritize spatially.

The study uses geospatial modeling, machine learning, and scenario simulation to assess the potential and trade-offs of using abandoned cropland for food production and climate change mitigation. Abandoned cropland was mapped using ESA-CCI land cover time series data and FAO's definition of abandonment (unused for at least five years). A machine learning model (MaxEnt) was trained to assess the suitability of abandoned cropland for recultivation, considering biophysical and socioeconomic factors. The food production potential was estimated using data on the productivity of 15 major food crops, accounting for food waste and loss. Suitability for reforestation was determined using a map of areas suitable for returning to native forest cover. Net climate change mitigation potential was estimated by considering carbon sequestration from natural reforestation and emissions from land clearing for recultivation. Scenario simulations were conducted to explore the trade-offs between maximizing food production, maximizing climate change mitigation, equal allocation, and maximizing combined potential. The impact of spatial prioritization strategies was also assessed by comparing outcomes with and without prioritization. Finally, the authors explored potential improvements to food production and climate change mitigation potential through various interventions such as improved water management, increased crop yields, reduced food waste and loss, and active reforestation.

The study identified 101 Mha of abandoned cropland globally between 1992 and 2020. 61 Mha was found suitable for recultivation, with a potential to yield 363 Pcal yr⁻¹ of food, enough to feed 292-476 million people annually. 83 Mha was suitable for reforestation, potentially sequestering 1080 MtCO₂ yr⁻¹. 50 Mha was suitable for both recultivation and reforestation. Scenario simulations showed that maximizing food production resulted in 363 Pcal yr⁻¹ and 290 MtCO₂ yr⁻¹ of mitigation, while maximizing climate change mitigation yielded 29 Pcal yr⁻¹ and 1066 MtCO₂ yr⁻¹. The 'maximizing combined potential' scenario achieved 81% of maximum food production and 62% of maximum climate change mitigation potential, demonstrating significant synergies. Spatial prioritization significantly increased food production and climate change mitigation potential, up to 59% and 43%, respectively. The benefits were most pronounced when only a portion of abandoned cropland was used. Analysis revealed that specific regions, notably Central and Eastern Europe, East and Southeast Asia, Central Africa, and South America, offer the greatest potential for food production and climate change mitigation through recultivation and reforestation.

The findings demonstrate the significant potential of abandoned cropland to contribute to both food security and climate change mitigation. Strategic recultivation and reforestation can unlock substantial resources and help to meet ambitious global goals. Reforestation via natural regrowth offers co-benefits like biodiversity enhancement and improved water and air quality. Recultivation helps to offset the environmental impacts associated with cropland expansion elsewhere. The potential of abandoned cropland to offset future land-use demands is considerable, easing competition between food production and climate mitigation efforts. However, various factors can hinder the utilization of abandoned cropland, including conflicts, economic conditions, dietary shifts towards meat consumption, and the need for policies to ensure the permanence of these land-use changes. While considerable potential exists, efforts must be made to improve access to, affordability of, and utilization of food products to address global food deficits. Similarly, global collaboration is needed to establish a reliable carbon market to ensure the benefits of carbon sequestration from reforestation are fully realized.

Abandoned cropland presents a valuable opportunity to improve food security and mitigate climate change. Strategic use of this land, guided by spatial prioritization and informed by scenario analysis, can maximize synergies between these goals. Future research should focus on refining the estimation of carbon sequestration and food production potentials at finer spatial scales, incorporating more detailed socioeconomic factors, and developing effective policies and incentives to facilitate the sustainable use of abandoned cropland in local contexts. Collaborations and detailed considerations are crucial to ensure positive outcomes for both environmental sustainability and human well-being.

The study's global scale introduces some limitations. Achieving globally optimized utilization requires overcoming challenges in global coordination and policy differences. Global maps may not always align perfectly with local land management practices. The estimations of food production and climate change mitigation potentials are conservative, as some possible improvements in practices are not included. The study does not account for all possible land uses for abandoned cropland, such as bioenergy crops, which warrants further investigation. Context-specific local data is crucial for translation of these global findings into effective local action, accounting for factors like land tenure, local policies, and cultural considerations.