Pollinators

Pollinator Habitat Conservation Activity Plan for Boulder County

Boulder County Parks & Open Space manages 25,000 acres of agricultural land of which about 16,000 acres is considered cropland. To help establish policies that support sustainable agricultural practices on these lands, the Department created the “Cropland Policy,” This document was developed in several stages, including the participation of a nine-member citizen advisory board. In 2011, the Board of County Commissioners voted unanimously to adopt the Cropland Policy.

A key consideration of this policy is to minimize any negative impacts of agricultural practices on pollinators (bees, wasps and other pollinators). In order to determine if we are achieving this goal, we recognize the need to have good baseline data that would identify trends in pollinator abundance and diversity. While there is much research from around the country and the world, we are interested in local research that that is applicable in Boulder County. Through our investigations we found that the Xerces Society for Invertebrate Conservation is fulfilling this role. In addition to practical applications in and around the Front Range, Xerces has partnered with other governmental agencies, including NRCS, to help develop site specific pollinator habitat.

This Xerces project resulted in a two-day pollinator short course for Boulder County staff and invited guests, as well as a custom Conservation Action Plan (CAP) for pollinators using one of our county-owned agricultural properties as an example (ERTL). These CAP guidelines, and the extensive supplemental documents, are now available for Parks and Open Space staff to draw upon for best practices. It is our hope that the public and other farmers can use these materials for their own pollinator conservation practices and to identify funding opportunities to implement these kinds of actions.

• Pollinator Habitat Conservation Activity Plan for Boulder County
• List of Supporting Documents

The conservation value of woody debris for cavity-nesting bees on Boulder County Open Space

About a third of Boulder County’s bee species use holes in woody debris created by other insects to nest in and provision pollen for their offspring; however little is known about the value of woody debris as habitat for bees on Boulder County Open Spaces or how its management impacts the bee community. The goal of this study was to evaluate the conservation value of woody debris on Boulder County Parks and Open Space riparian properties along the St. Vrain River. To do so, we estimated the amount of woody debris as bee nesting habitat at 25 sites across 12 different properties, sampled the abundance and diversity of bees in each site, and investigated the relationships between woody debris and bee community dynamics. We collected 3,662 bee specimens from hand-netting, representing 33 bee genera and ~96 different species, and recorded 664 individual bee nests in wooden and bamboo nest blocks.

In areas where Open Space reported removing woody debris we found 50% less woody debris compared to unmanaged sites and 40% fewer bees overall. We also found a positive relationship between woody debris and bee abundance, though this was driven mostly by soil and ground nesting bees. Where woody debris was abundant, cavity-nesting bee use of nest blocks was lower than when woody debris was scarce, suggesting that wood nesting bees are likely limited by suitable woody nesting habitat, and in areas where it is available prefer it over artificial nests. Conversely, where wood is lacking or must be removed, many cavity-nesting bees will readily nest in artificial substrates. Together, these results suggest that woody debris benefits the entire bee community and its management should be considered wherever pollinator conservation is a primary management goal.

The conservation value of woody debris for cavity-nesting bees on Boulder County Open Space

Riparian Pollinators on Boulder County Open Space: Good News and Current Findings

Riparian habitats are extremely important for pollinators, providing crucial floral and nesting resources for a wide diversity of native bees. However, native bees vary tremendously in their ecologies and natural histories, and the effectiveness of management strategies to promote native bees likely depend on species- or guild-specific responses of the bee community to habitat changes.

As part of a study to evaluate the conservation value of woody debris on Open Space riparian lands, a team of researchers led by Dr. Adrian Carper is surveying native bees along the St. Vrain Creek corridor. They are quantifying the amount and quality of woody debris as bee nesting habitat and will use these data to explore the relationship between woody habitat availability and cavity-nesting bee abundance and diversity. Ultimately, they hope to make recommendations on the value of woody debris on open spaces for native pollinator conservation, and means to preserve or enhance this habitat in the future. In the meantime, they have made a number of interesting observations, and will discuss these and some preliminary findings in terms of native bee ecology and conservation.

Riparian Pollinators Study Presentation

Agricultural Practices on Boulder County Open Space: Implications for Pollinator Conservation

Abstract: Declines and local extinctions of insect pollinators have been reported around the globe. This phenomenon is of great concern as insects, in particular bees, are important pollinators of native plants and agricultural crops. We are interested in examining the bee populations on land used for agriculture. Boulder County Parks and Open Space (BCPOS) owns approximately 25,000 acres of crop land in Boulder, and it is entrusted with managing these properties for both public and private use. Ensuring the conservation of bee communities is one component of its land-use policy. Our proposed study will compare bee communities on open space lands using conventional agricultural practices with open space lands using organic cultivation practices. As part of our investigations, we will explore factors important in bee abundance and diversity.

Agricultural Practices on Boulder County Open Space: Implications for Pollinator Conservation