California Coast & Ocean

Pollinators Feed People
The relationship between humans and honeybees goes back a long way. Cave paintings in Europe, Africa, Asia, and Australia show prehistoric people gathering honey. The art of beekeeping dates to at least 2400 B.C., and honey, beeswax, and propolis (bee “glue,” composed mainly of resins collected from plants and used to seal cracks in the hive) have been used medicinally since 2700 B.C. Bees and honey have figured in mythology and religion. In one Egyptian myth, the tears of the sun god Ra fell to earth as bees.

The bee everyone knows best is Apis mellifera, the Western or European honeybee, which humans have domesticated and transported around the globe. “It’s virtually everywhere humans have gone, except Antarctica,” said Robbin Thorp, professor emeritus of entomology at the University of California, Davis, who studies native bees. It’s one of only about seven species considered to be true honeybees (the exact number is disputed), among more than 20,000 known bee species worldwide. Brought to North America by settlers some 400 years ago, it is now one of the most valued species, although there are more than 4,000 native bee species on the continent, some 1,600 of which can be found in California.

Close to 100 flowering crop species in the United States rely to some degree on honeybees to reproduce. Among them are almonds, apples, avocados, peaches, strawberries, citrus, broccoli, cauliflower, carrots, and squash. A report released by the Congressional Research Service in March 2007 placed the value of these pollination services to agriculture at almost $15 billion.

California grows nearly 100 percent of the nation’s almonds and some 80 percent of the world’s. The state’s $2.3-billion almond crop, its fourth-most-valuable farm commodity in 2005, grows on 580,000 acres and depends on the services of about 1.4 million honeybee colonies, almost three-fourths of the commercial bee colonies available for pollination in the entire United States. Many colonies must be trucked to California for the bloom in February and March, some coming from as far as North Dakota. California’s almond acreage already requires the services of billions of individual honeybees, and is expected to grow by another 100,000 acres by 2010, requiring more pollinators even as the bee population declines.

Agriculture in the United States does not wholly depend upon honeybees for pollination services, but their loss would be “absolutely devastating to agriculture, no doubt about it,” Adams said. No one is suggesting that the honeybee might disappear from this continent, but “they certainly aren’t on a healthy trend.”

Return of the Natives
As the problems affecting honeybees have multiplied, scientists and farmers are realizing that it’s dangerous to rely too heavily on them for crop pollination. “There’s a lot of interest now in looking at our native bees and seeing which ones can be managed as pollinators,” said Thorp. Commercially managed native blue orchard bees, Osmia lignaria, are increasingly used for fruits and almonds. Alkali bees, which are native to North America, and alfalfa leaf-cutter bees, which were brought here in the first half of the 20th century, are used to pollinate alfalfa for seed.

Honeybees are good generalists--meaning they will pollinate a large variety of crops--but they’re not always the best pollinator for a particular crop. Bumblebees, for example--both native and non-native--typically pollinate greenhouse tomatoes because they are better than honeybees at the vibration or “buzz” pollination the plants require. Introducing exotic species of any animal or plant has potential pitfalls, however: Thorp and others fear that the virtual disappearance of two species of native bumblebee once common in western states may be due to a disease introduced by bumblebees imported from Europe for greenhouse pollination.