The following is an excerpt from Attracting Native Pollinators: Protecting North America's Bees and Butterflies by The Xerces Society (Storey, 2011). The excerpt is from Chapter 5: Strategies to Help Pollinators.
Critical Mass of Habitat
Although many pollinating insects can adapt to changing conditions and often rebound from the effects of natural changes in their environment — including fires, floods, droughts, and windstorms — it’s impossible to protect a diversity of pollinators without a critical mass of diverse habitats. That critical mass is being lost in many landscapes.
Not only is there less natural habitat than ever before, but the land that surrounds it may also be inhospitable to pollinating insects because it lacks food plants or nesting sites. In rural areas, the fields created by large-scale agriculture are too big for some bee species to cross to reach forage or nests. Tilling can destroy shallow bee nests or block the emergence of bees deeper in the ground. The crops grown on many farms are wind-pollinated members of the Grass family (wheat, corn, rice, grass, barley, oats, and so on) and have no value as bee forage, while those crops that do offer nectar and pollen usually provide them only in a brief, though abundant, burst.
In urban areas, landscapes around developments tend to be dominated by easy-to-maintain lawns and shrubs chosen for their colorful foliage rather than for their flowers. When there are flowers, often they are nonnative plants or highly ornamental varieties that provide little or no food value for native pollinators.
You can improve these conditions where you live if you consciously plan, create, and maintain habitat patches — the bigger the better — in urban, suburban, and rural areas. We can plant a diversity and abundance of nectar- and pollen-laden native plants, we can provide nesting habitat, and we can choose not to use pesticides, or at least exercise extreme caution.
Provide New Habitat for Pollinating Insects
Whether you are a homeowner working in your own garden, a land manager for a city park, a farmer with field margins, or a superintendent of a nature preserve, the principles for establishing pollinator habitat are the same.
First, increase the available foraging habitat to include a range of plants (especially native species) blooming at different times. This will provide nectar and pollen throughout the seasons, as well as host plants for butterflies. For your backyard, this may simply involve browsing a seed catalog or wandering the paths of your local nursery. Larger areas, especially public ones, will require significantly more planning because of factors such as size, public use, weed control, or the cost of management.
You will have to balance the details of pollinator conservation with the other goals and uses of the site. If your site protects migratory birds, for example, providing for pollinating insects may take second place.
Second, create nesting and overwintering sites by providing suitable ground conditions or tunnel-filled lumber and appropriate nesting materials. Building and managing these nests may involve clearing some plants from warm, dry, gently sloping ground, or bundling paper straws, or drilling holes in pieces of wood.
Third, reduce the use of insecticides and herbicides, which directly kill pollinators or the plants they rely on. Select less-toxic insecticides or utilize alternative strategies to manage pest insects, and eliminate or minimize the use of insecticides.
Excerpted from Attracting Native Pollinators by The Xerces Society, Copyright © 2011 by The Xerces Society. Used with permission from Storey Publishing, LLC