Selection and testing of plant species for pollinator habitat, from decision analysis to validation

Hedgerows, wildflower strips and other pollinator-friendly habitat can provide critical resources to support native and managed pollinator populations within intensive agricultural lands.  These habitats have the potential to augment pollinator diversity, improve pollinator health and enhance pollination services.  The enhancement schemes also are currently supported by government incentives in the US and Europe.  Two questions common to such schemes are: (1) what plant species are “best” to include and (2) within such enhancements which plant species are providing greatest benefit.  We present a formal decision tool with an embedded optimization model that can be used to help define goals and objectives, as well as streamline plant selection.  We then present results from field trials designed to test the function of various native wildflowers in their ability to support wild bees and honey bees in northern California.  We show that the identity and diversity of plant species needed to support pollinators depends strongly on the specific objectives of the plantings.  Plant species selected by the decision tool to support maximum bee diversity also supported important crop pollinators, but the same crop pollinators could be supported with a much reduced set of plant species if pollination is the primary objective.  Field trials likewise reveal varying importance of different plant species depending on the specific objective.  Such tools and testing are a key part of developing guidelines for conservation of pollinators and the pollination services they provide.