From the BeeSpotter Project:
"Over 75% of the planet's flowering plants depend on animal pollinators in order to reproduce and the majority of those animal pollinators are insects. Among the most important pollinators in both natural and managed systems are the 5000+ species of bees in the family Apidae, a group that includes honey bees and bumble bees. Concern about pollinator declines has increased in recent years, and, where pollinator status has been monitored over time, as in Europe, reductions in numbers, in some cases dramatic, have been documented.
Apis mellifera, the western honey bee, is the principal managed pollinator worldwide and is responsible for pollinating over 90 commercially grown crops in North America. The number of colonies reported in the 2005 survey, 2.41 million, represents a 28% reduction relative to colony numbers in 1981; numbers continued to decline in 2006 and in the winter of 2006-7 beekeepers in over 20 states reported further steep losses attributable to what appears to be a new phenomenon called colony collapse disorder. Given the importance of A. mellifera in contributing pollination services to agriculture, activities estimated to be worth over $14 billion annually, the inexplicable disappearance of honey bees has caused concern not only in the apiculture industry but across the agricultural enterprise and among the general public.
Bumble bees also appear to be experiencing significant reductions in number. Of the 49 species of Bombus native to North America, many are important pollinators of flowers in natural landscapes; they also function as complementary pollinators of some crops, including cucumber and melons and certain species are actively managed, mostly for pollination of greenhouse tomatoes. Regional declines and even disappearances of some species have been documented and as a consequence four bumble bee species have been placed on the Xerces Society for Invertebrate Conservation Red List of at-risk pollinator insects of North America."