Claire Kremen

The world has been undergoing an unprecedented loss of biodiversity with agriculture being one of the primary drivers, as it results in widespread habitat loss and fragmentation. Evidence suggests that sustainable, diversified agricultural systems can alleviate this issue by increasing biodiversity, without compromising agricultural production. However, it is still unclear whether these same systems facilitate ecological movement (i.e., the physical process of individuals or propagules actively or passively changing their spatial location over time) and functional connectivity (i.e., the extent to which the landscape facilitates ecological movement). Additionally, there is limited knowledge as to which specific diversification scales and practices affect movement and connectivity, and whether this varies across different scales and taxa. Therefore, my thesis aims to understand whether diversified agricultural systems can meaningfully affect movement and functional connectivity. I first conducted a systematic literature review to assess the relationship between diversified agricultural systems and movement/connectivity while answering four questions. Overall, 68% of 87 studies reported diversified agricultural systems having positive effects on movement and connectivity, with most studies focusing on management around the border of agricultural fields. It was also found that species characteristics such as differing ecological niche breadth (i.e., generalist versus specialist species), mating systems, and life-history traits influenced movement in diversified agricultural systems with I then utilized GPS tracking data to parameterize step selection functions (SSFs) and omnidirectional connectivity models to assess how European diversified agricultural systems – termed High Nature Value farmlands (HNVs) – influenced the movement/connectivity of three ungulate species, red deer (Cervus elaphus), European roe deer (Capreolus capreolus), and wild boar (Sus scrofa) across different landscape contexts. Results indicated that while movement through HNVs is influenced by the spatial composition and configuration of the surrounding land cover types, HNVs, by and large, represent intact, permeable areas of movement for all three species. All three species generally selected HNVs and had higher predicted movement probabilities than conventional, intensive agricultural systems in agricultural matrix contexts. These findings help show how diversified agricultural practices can maintain important functional processes like movement and connectivity.

View record

Solutions to environmental and social problems are often framed in dichotomous ways, which can be counterproductive. Instead, multiple solutions are often needed to fully address these problems. Here we examine how framing influences people’s preference for multiple solutions. In a pre-registered experiment, participants (N=1,432) were randomly assigned to one of four framing conditions. In the first three conditions, participants were presented with eight problems, each framed with multiple causes, multiple impacts, or multiple solutions to the problem. The control condition did not present any framing information. Participants indicated their preferred solution, perceived severity and urgency of the problem, and their dichotomous thinking tendency. Pre-registered analyses showed that none of the three frames had a significant impact on preference for multiple solutions, perceived severity, perceived urgency, or dichotomous thinking. However, exploratory analyses showed that perceived severity and urgency of the problem were positively correlated with people’s preference for multiple solutions, while dichotomous thinking was negatively correlated. These findings show a limited impact of framing on multi-solution preference. Future interventions should focus on addressing perceived severity and urgency, or decreasing dichotomous thinking to encourage people to adopt multiple solutions to address complex environmental and social problems.

View record

Insects are in decline worldwide, with Hymenoptera being especially affected. Pollinator decline is driven by conventional farming practices such as intensive insecticide and herbicide use that negatively affect pollinator health and limit the availability of floral resources. With agricultural intensification and habitat loss further driving pollinator decline, growers have begun to rely on managed honey bees (Apis mellifera) to meet the pollination needs of their crops. Honey bees, however, cannot pollinate certain crops as effectively as wild pollinators. Highbush blueberry (Vaccinium corymbosum), a widely grown crop in British Columbia (BC), Canada, is one such crop that benefits from pollination by wild Bombus species. BC blueberry growers have previously been found to face limited crop yields and revenue due to insufficient pollination, but it is unknown how pollination limitation is affected by blueberry varieties and management practices. Research on other methods for growers to maximize yield, such as inter-varietal block design is also limited. I conducted a two year study on highbush blueberry fields with varying management practices within the Lower Mainland of BC. I ran pollen limitation experiments along transects set at varying distances from the field’s edge and surveyed pollinators visiting blueberry flowers on these transects to determine which taxa contributed the most to pollination. I also ran a pilot study in which I evaluated the effects of inter-varietal pollination on two different blueberry varieties. Results indicated fruit set and weight deficits are strongly related to bumble bee visitation rather than honey bee visitation and that growers who used clover as a cover crop experienced higher visitation than growers who did not. It was also found that growers may further increase yield by considering inter-varietal pollination during block design, but the level of yield increase depends on the blueberry varieties involved. These findings indicate that establishing floral resources beyond those offered by crops can encourage pollination services from wild Bombus sp., adding to a growing body of evidence that diversification of agricultural land can promote ecosystem services while contributing to conservation.

View record

Wild insect communities are key contributors to agriculture through crop pollination. However, many conventional practices in crop production harm insect populations; pesticides have toxic health effects for pollinators, herbicide applications diminish their access to foraging resources, and the frequent disturbance or removal of natural areas destroys habitat. There is growing evidence suggesting that the establishment of functional plant species within semi-natural agricultural areas supports pollinators, either by providing foraging or habitat resources. Planted hedgerows of native shrub and tree species within crop margins, as well as set-aside lands sowed with either grasses or a mix of grasses and flowering herbaceous plants, are examples of such semi-natural habitat enhancements. However, planted hedgerows have shown varying support of pollinating insect communities, and grassland set-asides have not been assessed for their pollinator conservation potential across management types.I conducted a three-phase research study to investigate the conservation potential of enhanced semi-natural areas in the Lower Fraser Valley of British Columbia. First, I assessed pollinator community diversity in three agricultural margins (planted hedgerows, remnant hedgerows, unplanted margins) to evaluate the success of enhanced margins to support pollinators compared to unplanted weedy margins. I found that pollinators visited flowers in hedgerows more often than in weedy margins, but beyond floral visits, I did not observe overall community differences among margin types, suggesting that weedy crop margins are also valuable for pollinators. Second, I evaluated pollinator diversity in three agricultural field types (traditional grassland set-asides, grassland set-asides with added flowers, and active crop control fields) and concluded that both set-asides practices supported pollinators better than crop fields did. Finally, I explored management considerations for enhancement practices, focusing on plant species selection used in seeding set-aside fields or floral strips for pollinators, through a series of literature reviews and expert interviews. Results indicated that floral identity and floral diversity are both important management considerations for floral establishments. These findings provide evidence that semi-natural habitat enhancements supply key resources for insect pollinators in agricultural matrices. The adoption of these practices can promote both the ecological and productive sustainability of agriculture.

View record