Environmental challenges of intensive woody crops: The case of super high-density olive groves

Super high-density olive groves (>800 trees ha^-1) are rapidly expanding in olive oil producer countries, which entails a strong modification of the olive growing system with important agronomic, economic, sociocultural, and environmental consequences. Among them, the latter is particularly unknown. The aim of this paper is to bring the attention on the environmental impacts of super high-density olive groves, by systematically reviewing the current evidence and identifying knowledge gaps yet to be filled. As a result, we can argue that new super high-density olive plantations reduce habitat heterogeneity and complexity, and the younger trees of these plantations impoverish habitat quality for farmland biodiversity. In addition, the high input use (e.g. phytosanitary treatments, fertilisers and water supply) may entail ecological impacts as well. Therefore, we conclude that i) new highly intensive olive groves should be limited to areas with lower ecological value; ii) consumers should have more information concerning how is produced the olive oil they buy, including the environmental impacts produced; iii) agricultural policies should be reformulated following the provider-gets principle; iv) input use (fertilisers, pesticides, water, etc.) should be gradually optimised to reduce the environmental impact; and finally, v) more research is necessary to foster decisions based on science.