Wednesday, June 08, 2011

Review: Attracting Native Pollinators

In 2006, the importance of pollinators broke into the media with reports of colony collapse disorder in honeybees. Suddenly Americans were faced with the specter of whole honeybee colonies disappearing and leaving important food crops unpollinated and unproductive. While colony collapse disorder is unsettling, incidents of it are relatively isolated. A much larger, but less reported problem is the long-term decline of pollinator populations, both in introduced honeybees (Apis mellifera) and in native bees and other pollinating insects.

The long-term decline of pollinating insects has many causes. Habitat loss, indiscriminate pesticide use, disease, and introduced parasites all contribute. Other factors may be in play as well. Numerous native pollinator species have declined enough to cause concern, and some may even have become extinct.

Fortunately, there are large-scale and small-scale actions that can address and perhaps reverse the pollinator decline. Some need to be taken by public agencies, like planting highway medians with native wildflowers or changing the land management at public parks or nature reserves. Farmers can take some steps, like providing habitat for native bees along the margins of cultivated fields; in that case, native bees would be assist with pollinating their crops. Finally, homeowners and gardeners can attract native bees (and other pollinators) by providing appropriate foraging and nesting habitat for the pollinators in their area.

To encourage such steps, the Xerces Society* has released a new guide, Attracting Native Pollinators: Protecting North America's Bees and Butterflies, by Eric Mader, Matthew Shepherd, Mace Vaughan, Scott Hoffman Black, and Gretchen LeBuhn.

The book attempts to meet several goals:
  • educate readers about the process and importance of pollination;
  • introduce the many types of pollinating insects;
  • help readers to recognize and identify native bees;
  • suggest ways to make a variety of land types more pollinator-friendly;
  • encourage activism to improve conservation on local and national levels.
The most interesting parts for me were those that described a bee's life cycle and the habitat needs at each stage of that cycle. While I knew the basic steps of a bee's life cycle, I had not thought much about what their needs are beyond flowers for foraging, and how taking away one or another of those requirements could damage a local bee population. Bees need nectar for foraging, of course, but they also collect pollen to provide food for their larvae, they need places to nest and pupate, and they need places for overwintering. (Which stage overwinters varies from family to family.) Those elements are explained several times through the text, and the sections on habitat management suggest ways to support all of those needs.

The section on bee diversity, particularly the descriptions of bee families and genera in Part 3, will serve as a useful supplement to my insect field guides when it comes to identifying bees. Attracting Native Pollinators provides more detail on how to distinguish one genus from another than the Hymenoptera section in my Kaufman guide, and I find the family and genus descriptions easier to follow than my (old) Peterson guide. (However, it is not a field guide and does not provide a true identification key.) The illustrations in Part 3 do not always support the text as well as they could. For example, the accounts on Agapostemon and Augochlora reference a character on the rear of the thorax, but the difference is not clearly illustrated.

The book recommends specific plants as being useful to pollinators, and a separate list of recommendations is given for each region. The regional lists are comprised of native plants that bloom at different times of year and grow to different heights. There is also a list of beneficial (and non-invasive) ornamental flowers, such as crab apple (Malus spp.) and sunflower (Helianthus annuus). For my area, I found that I was already familiar with many of the recommended plants. I see plants like Joe-Pye Weed (Eupatorium fistulosum), New England Aster (Symphyotrichum novae-angliae), and Butterfly Weed (Asclepias tuberosa) – all recommended for the northeastern U.S. – very frequently in butterfly gardens and wildlife preserves. The book's recommendations are given as a starting point and will need to be adjusted depending on seed availability, soil conditions, and other factors. In addition to recommended forage plants, the guide also provides a list of butterfly host plants, ordered by butterfly species. This is a good resource if there are specific butterflies that you want to attract to your site.

Pollinator conservation may sound like a secondary concern to birders, but it really is beneficial to birdwatching. First, many birds eat pollinators, either in their larval stage (as grubs or caterpillars) or sometimes in their adult forms. Second, pollination is critical for the production of many fruits and seeds that birds depend on during the cooler months. Third, some birds, particularly hummingbirds, drink nectar from the same plants that many insect pollinators visit. Finally, aside from those considerations, insect watching can be a fun diversion for a birder, especially during the summer months once the birds quiet down and before southbound migration really gets going.

Attracting Native Pollinators: Protecting North America's Bees and Butterflies is a comprehensive introduction to pollinator conservation, from how the process works to how to support the diversity of insects that carry it out. This makes it a useful starting point for any home owner, land manager, or activist who wants to transform a given piece of property into quality wildlife habitat. The book has a broad scope, covering bees and other pollinators in habitats across North America. It should be a useful resource for educators and for non-specialists who are interested in insects.

* The Xerces Society was founded in 1971 to protect invertebrates and their habitats through advocacy, education, and research. The society is named for the Xerces Blue (Glaucopsyche xerces), a butterfly species that was endemic to the San Francisco area but became extinct in the early 1940s. Their website has a lot of useful resources, such as their Red List of Bees and a guide for making bee houses (pdf). See also The Great Sunflower Project, a citizen science project to gather information about bee activity in gardens.

This review was based on a review copy provided by the Xerces Society.