Climate change shifts Arabica coffee suitability upslope and constrains long-term cultivable land: implications for coffee cultivation and forest conservation in montane northern Vietnam

Arabica coffee is highly sensitive to warming, yet its suitability is rarely assessed alongside the ecological and legal limits on forest conversion. We mapped land suitability in montane northern Vietnam on a 30 m grid from twelve climatic, topographic and soil criteria, weighted by a literature-based fuzzy analytic hierarchy process and screened by a non-compensatory ecological exclusion overriding high scores elsewhere. Projections cover 2041–2070 under two high-emission pathways (SSP3-7.0, SSP5-8.5) with five global climate models. Climatically suitable land covers 55,182 km²; the exclusion removed 26.6% of the domain. On the ensemble mean it contracts by 19.9–24.4%, and by 16.7–19.8% where at least three of five models agree; the highly suitable class loses 64–69%, and the median elevation of suitable land rises 127–161 m. Intersected with the baseline and a non-agricultural mask, that area yields long-term cultivable land of 44,094 km² (SSP3-7.0) and 41,862 km² (SSP5-8.5). Of that, 6.5% lies in special-use forest, treated as legally unavailable for coffee; 30.4% in protection forest, where statutory ceilings leave of the order of 4,000 km² usable; about 60% is under tree cover, leaving 17,815 km² unforested. Discrimination is good (AUC = 0.846, 95% CI 0.820–0.872), but absence data come from one province and absolute areas respond more to classification thresholds than to the climate signal: these maps screen rather than authorise land. Because the suitable belt rises while the topographic ceiling and forest estate do not, adaptation itself risks driving forest conversion; it should favour shade-grown coffee on farmland, not standing forest.