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.

Evaluating population and community structure against climate and land-use determinants to improve the conservation of the rare <em>Narcissus pseudonarcissus</em> subsp. <em>nobilis</em>

“…Accordingly, higher species diversity would be expected, as plant competitors would not be able to dominate, and thus an assortment of ecological niches for plant species with distinct resource needs and preferences becomes available (Enyedi & al., 2008;Wallin & Svensson, 2012). Shifts in these traditional practices, towards intensification or abandonment, have been reported as major determinants of plant diversity (Kleijn & al., 2011;Plieninger & al., 2014). This has been more explicit for land-use intensification, promoting landscape/habitat homogenisation (e.g., monoculture production; Bielsa & al., 2005), fragmentation (e.g., patchiness of agricultural fields; Bratli & al., 2006) and degradation (e.g., input of fertilisers or animal effluents; Vassilev & al., 2011;Lomba & al., 2012).…”

“…Still, these landscapes are under several pressures, from climate change to land-use modifications (Deutschewitz & al., 2003;Lomba & al., 2012). Specifically, the abandonment of traditional land-use and the intensification of already intensively managed land are among the main determinants of plant diversity (Vassilev & al., 2011;Plieninger & al., 2014).…”

Relevance of secondary forest successions and their possible management

“…Plieninger et al (2014) discovered that land abandonment shows slightly increased plant and animal species richness and overall abundance. Results are however heterogeneous, with differences in the effect size between taxa, spatialtemporal scales, land uses, landforms, and climate.…”

Agricultural land abandonment in Mediterranean environment provides ecosystem services via soil carbon sequestration

“…This is mainly found in Europe, where numerous research studies have been published (Hatna and Bakker, 2011;MacDonald et al, 2000). This abandonment is most extensive and studied in the European Mediterranean belt (Plieninger et al, 2014;Romero-Díaz et al, 2016;Sheffer, 2012), and most of the research focuses on the mountainous regions that were abandoned as a consequence of the low income and loss of population (Lasanta et al, 2015a). The abandonment of land not only results in changes to the soil system, but also in the hydrological cycle and fauna and flora resources (Dixon-Coppage et al, 2005;de Araújo et al, 2015;Keesstra et al, 2016).…”