Farmland heterogeneity is associated with gains in some ecosystem services but also potential trade-offs

Abstract

The intensification of farming practices negatively impacts the provision of many non-food ecosystem services (ES), including pollination, pest regulation and water quality regulation. Incorporating greater landscape heterogeneity in cropped areas, especially by increasing crop diversity and the density of field edges (i.e. greater farmland heterogeneity), may be a key lever to increase non-food ES provision in agricultural landscapes. However, most work to date focuses on the effects of farmland heterogeneity on biodiversity or on a single ES at a single spatial scale. Understanding how farmland heterogeneity affects multiple ES across spatial scales is critical to exploring whether increasing this heterogeneity is a feasible management solution to increase ES provision in agricultural landscapes. We measured the effects of farmland heterogeneity on the provision of eight key ES (crop production, soil fertility, water quality regulation, carbon storage, bee and syrphid pollination, and aphid and defoliator regulation) in the Montérégie, an important agricultural region in Quebec, Canada. We sampled 32 soybean fields embedded within landscapes that fell along independent gradients of mean field size and crop diversity. We evaluated the effects of heterogeneity on these eight ES at two spatial scales (500 m and 1000 m radii around fields), while controlling for the effects of in-field management practices. We found that the mean size of agricultural fields had a stronger influence on ES provision than crop diversity, especially at the 500 m scale. We observed varying responses to mean field size for different ES, which may lead to trade-offs for landscape management. Landscapes with smaller fields benefitted from greater bee pollination, water quality regulation and defoliator regulation, but had less crop production and aphid regulation. To further explore these trade-offs, we calculated the multiple ecosystem service landscape index to assess multifunctionality, but found no significant relationship between mean field size and multifunctionality and a negative relationship between crop diversity and multifunctionality. Our findings show that different ES respond differently to changes in heterogeneity, and efforts to manage heterogeneity to improve ES provision will need to acknowledge and understand possible trade-offs, particularly for crop production and pest regulation services.