The global land-water-climate nexus of drought-tolerant succulent plants for bioenergy in abandoned croplands and arid marginal lands.

Bioenergy is considered among the main mitigation strategies to meet a green-growth development paradigm of 1.5 °C. However, climate change has been dramatically restructuring agriculture and damaging crops, threatening the achievement of global food security and bioenergy goals. Studies have shown that succulent plants through their water efficient and highly temperature-drought-tolerant Crassulacean Acid Metabolism (CAM) pathway, could be a key opportunity to meet future energy demands under global change scenarios. However, specific bioenergy potentials under alternative management conditions, irrigation, and land availability that minimize resource conflicts with food production, biodiversity transgressions, or water withdrawals in water scarce regions, remain unclear. Here, we estimate under a bottom-up approach the global bioenergy potentials of four relevant CAM species on recently abandoned croplands and arid marginal lands, unravelling the interdependencies between land availability, water requirements and climatic conditions at the global scale. We identify a potential of 16-36 Ej yr (27-62% of current bioenergy demand) in abandoned croplands depending on local and management factors. Rainfed CAM potentials (16 Ej yr) are comparable with the potentials of bioenergy crops such as miscanthus (19 Ej yr) under similar environmental conditions. However, the water requirement of CAM species to reach this potential is 24-30% of what is expected for C3 and C4 bioenergy crops. Additionally, we identify a carbon sequestration potential via plant growth of -3.09 Pg C yr between 1960 and 2020, which reveals an underestimated opportunity in arid marginal lands. We highlight the remarkable contribution of the CAM pathway as a nature-based solution under global change scenarios.