Agricultural mosaics maintain significant flower and visiting insect biodiversity in a global hotspot

Agricultural expansion requires mitigation to conserve biodiversity and maintain functional interactions across the transformed mosaic. Conservation outside protected areas (PAs) means providing increased spatial opportunities for populations to survive over the long-term. Here we assess the capacity of agricultural mosaics for maintaining indigenous biodiversity against the benchmark levels in neighbouring PAs. We do this in three geographical areas in the major biodiversity hotspot, the Cape Floristic Region. We focus on two functionally related groups, indigenous flowers and their associated native insects, to assess the biodiversity value of certain components of agricultural mosaics. These components include agriculturally disturbed land, semi-transformed, disturbed land, and remnant patches of natural land, as well as adjacent PAs as reference sites. Overall, species richness across the agricultural mosaics outside PAs was similar to that within PAs for insects, although more variable for plants. Nevertheless, sites outside PAs still retained great diversity of flowering plants. Across the agricultural mosaic, sites shared 20–38 % of their insect species, and 12–28 % of plant species, indicating substantial species turnover. Each particular agricultural component retained species not sampled elsewhere in the landscape, indicating that habitats outside PAs can make a significant contribution to the compositional biodiversity of an area. Our findings are positive for biodiversity conservation across these agricultural mosaics, with these semi-natural components within the production landscape, in effect, extending the size of the PAs for many species. Conservation planning should recognize the value of such agricultural mosaics.