COS 70-5 - Pollination service for apple and cherry crops improves with a higher proportion of natural areas in the surrounding landscape.

Abstract: Recent studies have highlighted the role of wild insects in crop pollination and have shown that this ecosystem service increases when there is a greater proportion of natural areas surrounding the crop. However, this relationship has rarely been studied in the Southern Hemisphere, particularly in the globally recognized biodiversity hotspot of the Mediterranean area of central Chile, which is dominated by sclerophyll vegetation and currently threatened by the expansion of fruit crops. Therefore, our goal was to evaluate how the proportion and distance to natural areas in agricultural landscapes influence floral visits of wild insects and its consequences on cherry and apple yield.
For each crop, 18 orchards were selected along a latitudinal gradient with 3 different proportions of remnant natural areas within a 1 km radius (i.e., < 35%; 36-70%, >71%). Twelve trees were randomly selected in each orchard (6 close to the natural habitat and 6 at 140 m from the edge). On each tree, 2 inflorescences were selected, on one floral visitors were excluded using a mesh bag and the other inflorescence received no exclusion (open pollination). On inflorescence that received no exclusion, insect visits were observed for 5 min. Insect contribution to yield (pollination service) was calculated as the difference between the open pollination fruit set and the exclusion fruit set and a linear mixed model was used for the pollination service response variable, with the proportion of natural areas and distance as fixed factors and latitudinal gradient, year sampled (2021 and 2022), crop and trees as random factors.
The total rate of floral visits (Apis mellifera and wild insects) was significantly lower when the area of natural habitat was greater than 35%. However, when excluding Apis mellifera from the analysis, the rate of floral visits by wild insects was significantly higher in orchards with more than 70% of natural areas and significantly lower in the orchard centre in comparison to the border. Similarly, the contribution of floral visitors to fruit set was higher in orchards with more than 35% natural areas and was lower inside the orchard than on the edge. As, such, our results show that when the natural area is less than 35%, pollination service decreases, even when the Apis mellifera are present (10 hives/ha per orchard) and therefore, this suggests that the conservation of natural areas, especially close to orchards is essential to maintain effective crop pollination services and improve agricultural yield.