PS 20-20 - Pollinator diversity decreases with distance to the edge and a lower proportion of natural habitats in the rural landscape—the case of apple and sweet cherry orchards in central Mediterranean Chile

Abstract: Wild insects play an essential role in pollinating wild plants and crops. However, the expansion of agriculture has caused a reduction in natural areas and, therefore, a decrease in pollinator diversity with potentially negative consequences for crop productivity. The Mediterranean area of central Chile has been globally recognized as a biodiversity hotspot by the proportion of endemism that inhabits the dominant sclerophyllous vegetation. However, this vegetation is threatened by the expansion of agriculture, particularly fruit crops. Therefore, our goal was to evaluate how the proportion of natural areas and the distance to them influence pollinators' diversity in orchards of two important crops, sweet cherry and apple. For this, 27 orchards of each crop were selected along a latitudinal gradient, with different percentages of natural areas within a 1 km radius around each orchard (i.e., < 35%, between 36-70%, and >71%). At each orchard, we sampled at three distances from the edge of the crops (e.g., edge, 70 and 140 m to the edge). Pan traps (one blue, yellow, and white) were used to sample pollinators at each site during crop blossom in 2021. A density of 10 hives per ha was used in all sampled farms. A generalized linear mixed model was used for the wild pollinator richness, an abundance of wild species, and Apis mellifera as a response variable, with the proportion of natural areas and distance as fixed factors and latitudinal gradient and crop, as random factors. Finally, an ANOSIM analysis was used to evaluate if the proportion of natural areas changes wild pollinators' composition.

Wild pollinator's richness and abundance were significantly higher in orchards surrounded by a high proportion of natural area (< 71%). Moreover, wild pollinator richness and abundance decreased with increasing distance from the edge to the crop, independent of the proportion of the natural area. On the other hand, Apis mellifera did not change with either distance or of the natural areas. Furthermore, we found that pollinator composition changes between orchards with different proportions of surrounding natural areas. Therefore, a higher proportion of natural areas and a closer distance to wild areas helps to promote a higher diversity of wild pollinators in orchards. Thus, we suggested that pollinator conservation approaches in agricultural landscapes should be synchronized at both landscape and local scales.