Pollinationsberoende och skördeskillnader mellan ekologiskt och konventionellt jordbruk

Sammanfattning

Pollinators contribute substantially to crop production, yet many pollinator populations are declining due to agricultural intensification and land-use change. Conventional farming systems generally achieve higher yields than organic systems, although the magnitude of this yield gap varies among crops. Organic farming often supports higher pollinator abundance and diversity, which may improve pollination success and thereby reduce yield differences for pollinator-dependent crops. In addition to pollinator dependence, nitrogen fixation may also influence yield differences between farming systems, as nitrogen-fixing crops can be less dependent on external nutrient inputs. This study investigated whether yield differences between organic and conventional agriculture decrease with increasing crop pollinator dependence, while accounting for nitrogen fixation as a potential explanatory factor. It was hypothesized that both pollinator-dependent and nitrogen-fixing crops would show smaller yield differences between farming systems. Secondary yield data for 12 crops grown in Sweden between 2010 and 2024 were obtained from Jordbruksverket. Pollinator dependence values were assigned based on published literature, and a linear mixed model was used to examine the relationship between pollinator dependence and yield difference between organic and conventional systems, with crop identity included as a random effect. Nitrogen fixation was included as an additional explanatory variable. Contrary to expectations, a weak positive relationship between pollinator dependence and yield gap was observed, indicating slightly larger yield differences in more pollinator-dependent crops. However, this relationship disappeared when strawberries, which showed both the highest pollinator dependence and the largest yield gap, were excluded from the analysis. The uneven distribution of pollinator dependence among crops and the limited dataset may have reduced the ability to detect broader patterns. Nitrogen fixation had no significant effect on yield differences, although nitrogen-fixing crops tended to exhibit smaller yield gaps. The results did not support the hypothesis that pollinator dependence reduces yield gaps between organic and conventional agriculture. Instead, the findings suggest that the relationship between pollination and crop yield is complex and likely influenced by multiple interacting biological and agricultural factors beyond pollination alone.