Traditional vineyards in Spain are being upgraded to trellis vineyards. A key question is to what extent the transition to trellis vineyards is compatible with the environmental preservation goals in Special Protection Areas. This paper presents a GIS-based model to assess the suitability of Special Protection Areas for the development of trellis systems. The model was applied in a Special Protection Area for steppe birds in Castilla-La Mancha, Spain, a region with the largest concentration of vineyards in the world. The model includes three components: (1) a vineyard structure analysis, (2) an analysis of habitat fragmentation, and (3) a suitability analysis. The results showed that 50.9% of the study area, including 82.1% of the existing vineyards, was classified as suitable for transition to trellis systems. In the remaining unsuitable areas an increase in trellis systems should be avoided. The model is a stepping stone for improving the sustainable land use development of Mediterranean agricultural landscapes. Further research is needed to include wider socio-economic and environmental consequences of modernizing viticulture practices.