title: The impact of land abandonment on species richness and abundance in the Mediterranean Basin: a meta-analysis.
abstract: Land abandonment is common in the Mediterranean Basin, a global biodiversity hotspot, but little is known about its impacts on biodiversity. To upscale existing case-study insights to the Pan-Mediterranean level, we conducted a meta-analysis of the effects of land abandonment on plant and animal species richness and abundance in agroforestry, arable land, pastures, and permanent crops of the Mediterranean Basin. In particular, we investigated (1) which taxonomic groups (arthropods, birds, lichen, vascular plants) are more affected by land abandonment; (2) at which spatial and temporal scales the effect of land abandonment on species richness and abundance is pronounced; (3) whether previous land use and current protected area status affect the magnitude of changes in the number and abundance of species; and (4) how prevailing landforms and climate modify the impacts of land abandonment. After identifying 1240 potential studies, 154 cases from 51 studies that offered comparisons of species richness and abundance and had results relevant to our four areas of investigation were selected for meta-analysis. Results are that land abandonment showed slightly increased (effect size  = 0.2109, P<0.0001) plant and animal species richness and abundance overall, though results were heterogeneous, with differences in effect size between taxa, spatial-temporal scales, land uses, landforms, and climate. In conclusion, there is no "one-size-fits-all" conservation approach that applies to the diverse contexts of land abandonment in the Mediterranean Basin. Instead, conservation policies should strive to increase awareness of this heterogeneity and the potential trade-offs after abandonment. The strong role of factors at the farm and landscape scales that was revealed by the analysis indicates that purposeful management at these scales can have a powerful impact on biodiversity.
authors.affiliation: Department of Geosciences and Natural Resource Management, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Tobias
authors.initials: T
authors.lastname: Plieninger
authors.affiliation: Centre for Invasion Biology, Department of Mathematical Sciences, Stellenbosch University, Matieland, South Africa; Mathematical and Physical Biosciences, African Institute for Mathematical Sciences, Cape Town, South Africa.
authors.forename: Cang
authors.initials: C
authors.lastname: Hui
authors.affiliation: Centre for Invasion Biology, Department of Mathematical Sciences, Stellenbosch University, Matieland, South Africa.
authors.forename: Mirijam
authors.initials: M
authors.lastname: Gaertner
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America.
authors.forename: Lynn
authors.initials: L
authors.lastname: Huntsinger
mesh_terms: D000818:Animals; D001181:Arthropods / Q000145:classification / Q000254:growth & development*; D058448:Biota; D001717:Birds / Q000145:classification / Q000254:growth & development*; D002980:Climate; D056727:Endangered Species / Q000331:legislation & jurisprudence; D008011:Lichens / Q000145:classification / Q000254:growth & development*; D009792:Oceans and Seas; D063245:Plant Development; D010944:Plants / Q000145:classification; D011156:Population Density