The value of honey bees to commercial agriculture cannot be overstated. A couple of generations ago, managed honey bees may have been considered an "insurance policy" against shortages of wild bees, but the dramatic changes in agricultural practises since have turned the tables in favor of honey bees. For most crops, there is no other bee that can be provided on demand for a limited bloom period in adequate numbers, and then moved away so that they are not in the way of of farming.
There are a few crops for which managed alternatives exist. Alfalfa with the alkali bee (Nomia melanderi) and alfalfa leafcutter (Megachile rotundata) bee is an obvious example. Bumble bees are now extensively used for glass house crops of tomatoes and so on, though there are considerable concerns about the spread of diseases and escapes of nonnative species. Also, the blue orchard bee (Osmia lignaria) is increasingly finding a place in apple and cherry orchards; there are also some other species of Osmia that show a great deal of promise for cane fruits.
There is also a growing body of research that demonstrates the contribution of native, wild-living bees to crop pollination. Claire Kremen has led much of this work in recent years, focusing on comparative studies between farms in California's Central Valley. Her team's work has established the importance of native bees and begun to identify specific landscape features that influence the abundance and diversity of native bees needed to get fully pollinated crops. One of the key features is adequate habitat in and close to the farm that can support populations of bees. Obviously, some modern-day farm landscapes don't leave a lot of space for habitat, but where it exists -- or can be created -- native bees can provide a reliable source of pollination.
If you want to read more, Claire and her co-workers have published many papers, most of which are inaccessible unless you have the correct journal! She has also published in the Proceedings of the National Academy of Sciences, an archive of whose issues is freely available online (http://www.pnas.org/; it is searchable -- look for Kremen, Williams, and Thorp, 2002, Crop pollination from native bees at risk from agricultural intensification, vol 99, pp. 16812-16816) and also in "Fremontia," the magazine of the Californian Native Plant Society (http://www.cnps.org/publications/index.htm#fremontia; Vol 30 #3-4, Kremen et al, 2002, Native bees, native plants, and crop pollination in California, pp 41-49).
Another recent study estimated the value of non-managed insects to the U.S. economy. This calculated that wild bees were responsible for $3 billion of crop pollination. The study was published in Bioscience. A copy of the article can be down loaded from the Xerces Society website, at http://www.xerces.org/pubs_merch/Econ_Value_of_Insects.htm
Happy reading!
Matthew
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The Xerces Society for Invertebrate Conservation
Protecting wildlife through science-based advocacy, education,
and conservation projects since 1971. To join the Society, make a
contribution, or read about our work, please visit www.xerces.org.
Matthew Shepherd
Director, Pollinator Conservation Program
4828 SE Hawthorne Boulevard, Portland, OR 97215, USA
Tel: 503-232 6639 Fax: 503-233 6794
Email: [log in to unmask]
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