Plant biodiversity in Mediterranean orchards is related to historical land use: perspectives for biodiversity-friendly olive production

At a time when many questions are being raised about the future of rural landscapes and their ecosystem services, a better understanding of the effect of historical land use on their biodiversity is critical. We aim to verify to what extent the biodiversity in Mediterranean orchards, specifically olive groves, depends on past land use, similarly to some wooded ecosystems, as opposed to current conditions only, which is the case for farmlands. Using the Napoleonic cadaster (1825–1867) and aerial photographs (1947–2011), we characterized land-use trajectories across two centuries in 67 georeferenced olive plots selected across five terroirs in the South of France, and examined their similarities with land-use change at the regional level. We tested their relationships with botanical data, management, surrounding land use, and environmental conditions. Plant community parameters and species composition depend mainly on the effects of past land use. The highest numbers of species living in semi-natural ecosystems are found in orchards initially covered with natural vegetation, tilled over a short duration and recently rehabilitated by farmers (mean 62 species). Other farmed orchards host a significant mean floral richness (51–56). The lowest mean levels are encountered in long-cultivated orchards, due to intensive management (28), and in abandoned (42) and burnt (23) orchards, due to plant competition. The perceptions of olive growers are an indirect factor in the conservation of this biodiversity. The study suggests that the restoration of olive groves should be encouraged, as they provide ecosystem services and represent a promising prospect for Europe as a whole. Graphical Abstract