Floral resource strips enhance parasitoid abundance and diversity in apple orchards and promote agroecological advances in a South African biosphere reserve

Agricultural intensification drives insect declines, including those of
parasitoids, through landscape simplification and extensive use of
synthetic pesticides. Spatially heterogeneous agricultural landscapes are
potentially important biodiversity reservoirs where non-crop habitats may
support populations providing ecosystem services to farming. However,
there is a need to find methods to support this transition to more
sustainable farming and support the progressive concept of biosphere
reserves. We focus here on the relationship between apple orchards and
sclerophyllous natural fynbos vegetation in the megadiverse Kogelberg
Biosphere Reserve, Cape Floristic Region, South Africa.  We
established patches of floral resources within apple orchards, which are
embedded in landscapes, equivalent to the transition zone of the KBR, with
varying proportions of natural habitat in a 500 m radius around orchards.
We assessed the role of these enhanced floral resources for supporting
parasitoid abundance, species richness, and diversity inside orchards, and
compared these metrics to those in ruderal vegetation around orchards and
in nearby natural vegetation. Further, we assessed the effect of
semi-natural vegetation in the surrounding landscape mosaic on parasitoids
in orchards. Floral enhancement improved parasitoid abundance and
influenced assemblage composition within apple orchards. However, non-crop
ruderal habitat immediately adjacent to orchards supported greater
abundance and richness of parasitoid species, while natural fynbos
supported even richer parasitoid assemblages. Vegetation within orchards
and landscape complexity enhanced parasitoid assemblages inside and
surrounding the orchards. Our study shows that increasing floral resources
within orchards improves local diversity of parasitoids within
agroecosystems in the Biosphere Reserve. In doing so, this improves levels
of biodiversity and increases parasitoid richness within the biosphere
transition zone, supporting a shift from conventional production to a more
biodiversity-friendly agroecological approach.