Abstract. We present a modelling framework to simulate probabilistic futures of global cropland areas that are conditional on the SSP (shared socio-economic pathway) scenarios. Simulations are based on the Parsimonious Land Use Model (PLUM) linked with the global dynamic vegetation model LPJ-GUESS (Lund-Potsdam-Jena General Ecosystem Simulator) using socio-economic data from the SSPs and climate data from the RCPs (representative concentration pathways). The simulated range of global cropland is 893-2380 Mha in 2100 (± 1 standard deviation), with the main uncertainties arising from differences in the socio-economic conditions prescribed by the SSP scenarios and the assumptions that underpin the translation of qualitative SSP storylines into quantitative model input parameters. Uncertainties in the assumptions for population growth, technological change and cropland degradation were found to be the most important for global cropland, while uncertainty in food consumption had less influence on the results. The uncertainties arising from climate variability and the differences between climate change scenarios do not strongly affect the range of global cropland futures. Some overlap occurred across all of the conditional probabilistic futures, except for those based on SSP3. We conclude that completely different socio-economic and climate change futures, although sharing low to medium population development, can result in very similar cropland areas on the aggregated global scale.

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Land degradation, as a threat to smallholders in the tropics, attracts less attention than other global challenges. In addition, gaps between scientific understandings of land degradation and international policy regimes are problematic. We identify the three most significant debates including their different policy implications: desertification in the Sahel, nutrient depletion in Africa, and rural reforms in China. Using a political ecology frame across disciplines, scales of inquiry, and regional experiences, we nuance the often polarized scientific debate while seeking to bridge the gap between science and policy. Three main findings emerge: State-led rural reforms in China represent an important approach to land degradation; a renewed focus on agriculture and sustainability in development discourses opens new ways for tackling nutrient depletion with combined sociotechnological reforms; and a policy void in Africa paves the way for market mechanisms, such as payment for environmental services, that are insufficiently understood and put fairness at risk.

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