A group of international scientists launched a campaign in Toronto this week to identify the world's bees, an effort they hope will help track and better understand these important pollinators of food crops.

Experts from Canada, the United Nations and nine other countries attending a conference at York University say they want to get a "DNA barcode" of the close to 20,000 bee species.

DNA barcoding, a technique conceived at the University of Guelph five years ago, involves using a short sequence of DNA from a standard segment found in all animals to quickly identify a species. Similar barcoding efforts have already found new bird, butterfly and fish species.

York University biology Prof. Laurence Packer told CBC News that bees are important to understand and monitor because of their prominence in our food chain.

"About one-third of the food we eat has been pollinated either directly or indirectly by bees," said Packer. "Even if you only ate beef, cattle often forage alfalfa in the winter, and alfalfa is pollinated by bees."

They are also, he said, an excellent indicator of the state of the environment, both on a global scale and to regions in particular.

It's a worrisome thought, given that honeybee populations have been declining, particularly in North America, in the past few years.

The Apiary Inspectors of America said in a report earlier this month that the total loss of the insects among 384 beekeeping operations surveyed was 31.8 per cent between September 2006 and May 2007, with 51.9 per cent reporting abnormally heavy losses. In Ontario, almost 27,000 of the 76,000 hives were killed in 2006, according to the Ontario Beekeepers' Association, and many of the remaining colonies were badly weakened.

The causes of colony losses in the U.S. and Canada have been shown to be unrelated ailments.

Packer says part of the problem is that bees are uniquely vulnerable to extinction because of a genetic quirk they share with wasps that turns some females sterile.

Tracking extinct species

Understanding this and other aspects of bee biology would be one benefit of barcoding the world's species. But another more basic purpose is to take a census of what's out there so that if more species become extinct, scientists will be able to track it.

He said the scientists have identified 19,231 known species of bees, of which between 1,500 and 2,000 are already barcoded. Samples can be obtained from live specimens or some museum specimens, particularly those less than 15 years old.

Making the task a mammoth enterprise is the comprehensive nature of the effort, requiring participation of regions such as Central Africa or war-torn nations such as Afghanistan where access to samples is difficult, he said.

The insects themselves are also elusive, said Packer.

"Many species are known only from their male or female specimens, and until we see them mating, we won't know for sure if they are the same species. Also, some species appear identical but have different DNA.

"So there is a fair bit of chaos," he said. "We're looking to create some real order."