Spatial assessment and mapping of soil quality index for desertification in the semi-arid terrestrial ecosystem using MCDM in interval type-2 fuzzy environment

•Investigation of SQI for degradation and desertification in semiarid terrestrial ecosystem.•Solutions with MCDM for determination of importance levels of criteria that contradict for SQI.•Integration of type-2 fuzzy sets with AHP for the elimination of uncertainties in expert opinions. Land degradation is a significant phenomenon on the world particularly arid, semi-arid and semi-humid terrestrial ecosystem environments due to variety of factors such as through unsustainable land management, and through physical and climatic characteristics. One of the main indicators and commonly used in the land degradation and desertification is the soil quality index (SQI). Soil quality refers to the soil's capacity to function. The aim of this study is to determine SQI in terms of degradation and desertification in the Çorum Basin by taking into consideration of nine soil criteria in Desertification Model of Turkey (DTM). The study area includes semi-arid terrestrial ecosystem. Multi-criteria decision analysis was performed in Fuzzy environment integrated with GIS techniques and different interpolation models, which was chosen as the basis for the present study. In order to assign weighting value for each criterion, interval type-2 fuzzy-AHP approach was used to make sufficiently sensitive levels of importance of the criteria. Results classified more than 45% of the total area of approx. 68,755 ha as low and very low, while only about 31% of the study area’ soil indicated area high and very high by the SQI in terms of land degradation and desertification risk.