Does land abandonment decrease species richness and abundance of plants and animals in Mediterranean pastures, arable lands and permanent croplands?

Background: Obscured by the more prevalent discussion of intensification and expansion of agricultural land, the impacts of the abandonment of many grasslands and croplands of the world in recent decades have received limited attention in the literature. Land abandonment is a common phenomenon in the Mediterranean Basin, a global biodiversity hotspot, but little is known about the impacts of this process on biodiversity. To upscale existing case-study insight to a Pan-Mediterranean level, we plan to perform a systematic review of the effects of land abandonment on plant and animal richness and abundance in pastures, arable lands and permanent crops of the Mediterranean Basin. In particular, we ask (1) which taxonomic groups are most affected by land abandonment; (2) whether different spatial and temporal scales of studies influence species richness and abundance outcomes; (3) whether previous land use and current anthropogenic impacts on abandoned lands determine differences in the number and abundance of species; and (4) whether landscape context modifies the impacts. Methods: Our review will be based on searching scientific databases as well as the internet for empirical studies on the effects of land abandonment on biodiversity in the Mediterranean Basin. Study selection follows a three-stage process and includes study quality assessment. Extracted data will be synthesized through meta-analysis. Results will be presented in the form of a quantitative (e.g. figures indicating effect sizes, tables summarizing heterogeneity statistics) and narrative synthesis. Additional aspects will be addressed through meta-regression and sub-group analyses.