Speaking of Science Column May 17, 2009
Cause and effect as blurry as bee’s wings
It was clearly my wife’s fault that I sliced open my hand. If she hadn’t scheduled a party for 21 little girls at our house, I wouldn’t have been on the roof trying to get the air conditioner operating in such a hurry. The wet roof, the slick shoes and working too fast had nothing to do with it.
The determination of cause haunts science. It is a surprisingly difficult concept to prove. Even when the accident was clearly because driver A ran a red light, there is a reason that driver A ran the red light and a reason driver B was in the intersection. What was the real cause?
Children quickly learn to use this slippery concept when they claim, “He hit me first,” or “I didn’t turn my homework in because the dog ate it.” It’s never anyone’s fault.
The determination of cause is a difficult problem with disease because the assessment of exposure to a disease agent is often imprecise, and the mechanism that connects exposure to outcome is not yet known.
Consider the effort to prove that cigarettes cause some forms of cancer. It took a long time to prove, even though everyone was pretty sure that they did.
Honeybee Colony Collapse Syndrome has led to massive declines in the number of bees in recent years. This is significant because honeybees are the major commercial pollinators in the world and, without their pollination services, our world would be altered radically and detrimentally. But the cause of this bee disease has not been known, although there have been numerous hypotheses.
As is often the case, there may be more than one contributor to the problem, but it now appears that colony collapse may be caused by an imported, emerging bee disease, Nosema ceranae.
Three recent papers by Mariano Higes from the Bee Pathology Laboratory in Marchamalo, Spain, suggest that a new species of Nosema has spread throughout the world and may be causing the disease. Higes has identified Nosema ceranae in several commercial outbreaks in Spain where they were able to rule out numerous other potential causes such as pesticides or other diseases.
In a companion paper, he and his research team also found N. ceranae causing death in bumblebees, another important pollinator.
In his third publication, they were able to show that N. ceranae has developed into an important pathogen because of better reproductive response at higher temperatures. So the cause of colony collapse disorder may be Nosema ceranae.
But if Nosema ceranae causes colony collapse disorder, what causes Nosema ceranae? That may be the fault of Dr. Robert Atkins and Dr. Arthur Agatston: the creators of the Atkins diet and the South Beach diet respectively, because both have recommended almonds as healthy snack foods. For that and other reasons, almond production has exploded in recent years, and in the United States almonds are grown mostly in southern California.
First, the expansion in almond orchards surpassed the ability of local beekeepers to pollinate the crops. Then beekeepers began trucking bees into southern California from all across the nation.
Eventually, some bees were brought in from New Zealand. Unfortunately, some of those bees had originated in China, where Nosema ceranae has been in existence for a long time and where Chinese bees are more or less resistant.
But the disease spread into susceptible American bees and was then disseminated across the nation by the migratory pollination practices of commercial beekeepers.
But whatever caused these two physicians to recommend almonds to the public? Well, that was partially because of concern over obesity in modern Americans.
Obesity appears to be largely because of sugar consumption. But sugar consumption increased historically because it was cheaper than honey. Honey is expensive in part because of bee diseases. Oh, never mind. This is causing me to have a headache.
Gary McCallister is professor of biology at Mesa State College and also owner/operator of Flaming Moth Productions and the “Bee bar Bee Ranch,” supplier of native bees, native bee nests and native bee information.