Landscape-moderated biodiversity effects of ground herb cover in olive groves: Implications for regional biodiversity conservation

Studies assessing the effect of extensive versus intensive agricultural practices and addressing how biodiversity patterns and the effectiveness of agri-environmental practices (AES) to recover biodiversity are moderated by the landscape complexity (LMB framework), underlie large-scale biodiversity conservation programs and policies in anthropogenic landscapes. Such studies are numerous with annual crops and grasslands yet infrequent in more complex and structurally stable arboreal croplands, where high capacity to retain biodiversity is expected. Here, we explore to what extent landscape complexity and extensification of agricultural practices enhance biodiversity in olive groves of Andalusia (southern Spain). We monitored birds, ants and herbs in paired olive farms (extensive versus intensive ground herb cover management) from 20 localities spread over Andalusia and along a landscape complexity gradient. For each biological group, we obtained gamma diversity (diversity at the olive farm level), beta diversity (between the productive and unproductive areas located within the olive farm) and infield alpha diversity (in the productive area within the olive farm). We tested for multi-diversity, and for each group separately, three major hypotheses of the LMB: the intermediate-landscape complexity, the dominance of beta diversity, and the landscape species pool hypotheses. These hypotheses were corroborated with multi-diversity, which was affected by intensification of weed management and landscape simplification, suffering a combined impact of 26% of gamma biodiversity loss. The effectiveness of extensification to recover biodiversity depended on the landscape context and peaked at intermediate-complexity landscapes. Beta multi-diversity and infield alpha-diversity increased with landscape complexity. Birds, ants and weeds responded differently but were negatively affected either by landscape simplification or by management intensification. Birds mirrored better than other groups the multi-diversity pattern and were the best candidates for a rapid indicator of the impact of agriculture and land conversion on biodiversity. We provide recommendations for biodiversity conservation in olive groves-dominated landscapes and show that, if adequately managed, olive groves' landscapes have potential for the conservation of biodiversity in the Mediterranean region. Our results illustrate the need to reformulate the future EU-Common Agricultural Policy and particularly, to adapt AES to each landscape.