What has happened to the bees? Across the planet, the honey bee population is in a state of collapse. In Britain, the bee population has already fallen by 25 per cent and the farming minister Lord Rooker has warned that our remaining 270,000 colonies could be wiped out over the next decade. In the United States, the problem is worse, with one-third of bees having mysteriously died. Scientists are baffled. Their research has come up with nothing.

Bees don't just make honey and provide the pollination that flowers need. Albert Einstein is supposed to have said: "If the bee disappeared from the surface of the earth, man would have no more than four years to live. No more pollination, no more plants, no more animals, no more man." There is confusion as to whether he actually did say this, as no reference seems to exist for quite where and when he said it. But the general logic of the sentiment has not been seriously challenged.

In the annual Earthwatch debate, scientists argued the case for which species would have the greatest impact on our planet if it was lost.

The bees won (beating plankton, bats, primates and fungi). Their champion, Dr George McGavin, of the Oxford University Museum of Natural History, declared: "The partnership between flowering plants and pollinating insects, especially bees, is one of the most widespread and significant symbiotic interactions on Earth. This 100-million-year-old collaboration has spawned a rich diversity of species and promoted the rise to dominance of humans."

Given the cataclysmic potential for colony collapse disorder, as the sharp bee depopulation has been named, there is an understandable reluctance to take the blame for it. Could it be that radiation from mobile phone masts interferes with the bees' navigational system? Possible but no proof as yet. Are pesticides to blame? But there has also been a population collapse where no pesticides are used.