24 May 2008

Why are honeybees declining?

Bees continue to die in droves in both the US and the UK. Both wild bees and domesticated honey bees are affected. Similar episodes of Colony Collapse Disorder (or Mary Celeste Syndrome in the UK...) were also noted last year, although the numbers appear to be larger this year. I haven't read any reports from other parts of the world.

While the cause remain somewhat unknown, ongoing research is shining some light onto the source of this ailment.

In fall 2007, a team led by Diana Cox-Foster, professor of entomology, reported a strong correlation between CCD and the presence of Israeli acute paralysis virus, making the pathogen a prime suspect in the disease. Since that time, researchers have introduced IAPV to healthy honey bee colonies in a controlled greenhouse environment in an effort to induce a collapse.

Cox-Foster noted that within a month, infected colonies had declined to small clusters of bees, many of which had lost their queens. "These data indicate that IAPV is a highly pathogenic virus," she said. "But they do not yet support a finding of IAPV as the sole cause of Colony Collapse Disorder. We still suspect that additional stresses are needed to trigger CCD."

I would not be surprised if further research implicates human meddling as being an ultimate source of these stresses. We have profoundly altered the environment on a very rapid time scale; just some of notable changes are: enhanced CO2, land use, and pesticides along with other persistent chemical pollution.

A post on TreeHugger notes this about enhanced CO2 and how it affects bees:

Curiously, 80 years ago bee scientists noted that CO2 was the controlling factor in bee colonies. Later scientists observed that bees exposed to high CO2 become incapable of performing their normally incredible navigation skills and become lost bees. It can be no wonder that with our recently imposed 44% higher CO2, - often 2-4 times higher locally - bees have no means to know that their time tested last gasp means to protect the colony will not suffice.

This is certainly an interesting hypothesis, although there are a few quibbles (e.g. The CO2 increase is exaggerated; CO2 has not gone up 44% in less than 80 years...). It seems improbable, though, unless there is some hard biological threshold that has been crossed in the last few years. Make no mistake, year-to-year increases in CO2 are alarming, but I wouldn't imagine that they are so rapid as to cause this sort of sudden onset. (I could easily be wrong about that, though...)

Habitat loss is undoubtedly important in some cases. This seems to be important in the loss of the wild bees (repeat link). But most of the honey bees are domesticated, so they don't really have a 'habitat' per se; they go wherever the managers put them.

Pesticides (linked earlier) seem a likely contributor, though.

[S]cientists analyzing pollen, wax, adult bees and brood (larvae) have found the presence of dozens of chemicals, including pesticides used by agricultural producers to protect crops and by beekeepers to control hive pests such as parasitic mites.

...Some of these compounds could react with each other to cause toxic effects or could combine with viruses or poor nutrition to weaken immunity and cause colony collapse. We also need to do more research to understand these chemicals' sub-lethal effects on bees."

"With the sheer number of compounds we're finding in hives, it's hard to believe that pesticides aren't contributing to the general decline in bee health,

Whatever the cause, the sustained loss of bees -- both wild and domesticated -- at this rate will certainly be Cataclysm-level event, particularly if is (or becomes) global in extent. Bees provide direct services to humanity, playing a vital role in agriculture (among other things). It would be hard to argue that humanity didn't cause it ('It's all the Sun's fault,' won't really cut it in this instance!), and it would hit 'doubt manufacturers' right where it hurt. It's a race against time, one of many we must win to avoid living on planet doom.


image: Shaun Curry /AFP. Extracted from The Guardian. I also know it's not a honeybee, but hey...it's a nice piccy anyway

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