UBC Theses and Dissertations
Impacts of semi-natural habitat restoration in agro-ecosystems on the diversity and abundance of pest and beneficial insects Tsuruda, Matthew Kirin
As agricultural intensification accelerates around the world, the proportion of natural habitat in and around agricultural ecosystems has decreased. Restoration of these habitats may lead to an increase in the abundance and diversity of natural enemy insects that play a key role in agricultural pest control. However, these effects have been shown to be system-specific and depend upon climatic conditions, landscape structure, the local species pool, etc. To evaluate the response of the insect community to semi-natural habitat enhancement, I surveyed insects in the Lower Mainland region of British Columbia, Canada across two growing seasons and in four distinct types of restored on-farm habitat (differently managed hedgerows and grassland set-asides). I sampled insects using a variety of trapping techniques to obtain metrics of diversity and abundance and subsequently identified them to a taxonomic level where a functional guild could be assigned (family in most cases and lower when possible). I found that habitat type mostly did not determine the overall and intra-guild family diversity of arthropods. Grassland set-asides designed to support pollinators supported a higher abundance of ground-dwelling natural enemy arthropods and pests compared to unenhanced fields. I was better able to detect differences among habitat types in more taxonomically resolved groups. Grassland set-asides supported a greater abundance and diversity of predatory carabid beetle genera compared to control fields. Both hedgerow types showed higher average abundances of Drosophila suzukii, an invasive pest of fruit crops in British Columbia, compared to unenhanced grassy margins. These findings indicate that some economically important taxa (predaceous ground beetles, invasive Drosophila suzukii) respond strongly to semi-natural habitat elements in agro-ecosystems. However, it is possible that broad-level taxonomic analyses of these responses are not sufficiently sensitive to quantify these responses. It is likely that focusing biodiversity studies on a few highly resolved and representative taxa will yield more insightful conclusions. Further research will be required to determine if these changes in the insect community driven by semi-natural habitat restoration will impact levels of pest pressure and biocontrol within cropped fields.
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