The effects of forest fragments and biodiversity on the provision of multiple ecosystem services

Background/Question/Methods

Human modified landscapes such as agroecosystems provide diverse ecosystem services (ES) including food, clean water and climate regulation. Human land use change alters the spatial structure of these landscapes, leading to changes in patterns of biodiversity and, in turn, changes to ecosystem function and ES provision. In particular, landscape connectivity – the degree to which a landscape facilitates species movement – is thought to play a critical role in influencing biodiversity, ecosystem function, and likely ES as well. Unfortunately, how different landscape components, their properties, and their connectivity interact to determine the provision of multiple ES across landscapes is currently not well understood. We investigated how the characteristics of forest fragments (i,e., size, connectivity and forest type) and the connectivity of soybean fields to these forest fragments (i.e., distance from forest) influenced biodiversity, ecosystem function and the provision of multiple ES in agroecosystems east of Montreal, Quebec. We estimated ES provision by measuring biophysical indicators for multiple ES, including pest regulation, crop yield, soil formation, climate regulation, and water quality regulation, as well as insect and forest plant diversity.

Results/Conclusions

Results suggest that insect pest regulation, herbivory, and crop yield in soybean fields all vary with distance to forest, but each in distinct ways. Forest fragment connectivity in some cases altered these patterns, while fragment size and forest type were less important. Crop yield was low close to forest fragments, but increased substantially at moderate distances, resulting in an overall positive effect of proximity to forest fragments for this ES. A negative relationship between insect diversity and crop yield with distance from forest was also present. We subsequently analysed the effects of the surrounding landscape at multiple scales (i.e., proportion of agriculture and landscape complexity), soybean planting method, field orientation, and forest fragment plant diversity on our biophysical indicators of ES provision. Insect pest regulation was affected by the amount of agriculture at the 500-1000m scale; both soybean aphid abundance and insect herbivory generally increased as the proportion of agriculture increased in the surrounding landscape. Field orientation, planting method and forest fragment plant diversity also impacted insect pest regulation. Understanding the effects of landscape structure on the provision of multiple ES is important both to identify the important ecological foundations of different ES and to accurately model and forecast the provision of multiple ES across increasingly human-dominated landscapes.