See http://judson.blogs.nytimes.com/2009/01/27/guest-column-a-low-tech-treatment-for-bee-plague/?ref=opinion

Also many interesting comments on the site.

Best,

Michael

Guest Column: A Low-Tech Treatment for Bee Plague

BY AARON E. HIRSH
Aaron E. Hirsh

On a bright day last spring, I hiked at dawn into the foothills behind our house in Colorado. Snow still lay in the shadows beneath boulders and pine trees, but the morning was warm — so warm the honeybees I keep up there would soon awaken, emerge from their wooden boxes and begin searching out their first nectar of the new year.

As I climbed the final slope, I could see that two of the hilltop hives were already thrumming with activity: bees lifted off from the entry holes, catching the light and rising like sparks on a wind; and bees spiraled in for a landing, returning already from their first outings. The third hive, however, was conspicuously quiet — its entrance a small dark hole offering no sign of life.

Colony Collapse, I thought: The bee plague.

Bees crawl on a frame used in bee hives.Bees crawl on a frame used in bee hives. (Ann Johansson for The New York Times)

As you’ve probably heard, honeybees are disappearing. Across the country, beekeepers are cracking open their hives to discover the remnants of a sudden and mysterious desertion: the stores of honey are good; the brood are tucked as usual into their cells; but all the adults are gone. Last winter, over a third of the honeybee hives kept in the United States suffered the strange fate now called Colony Collapse Disorder.

What’s at stake here is not just our honey, or our favorite symbol of cooperative society, but our food. Most of our crops require pollination — deposition of a bit of male pollen on the female flower — to set fruit and ultimately produce the parts we eat. Out of 115 of the world’s leading crops, 87 depend on animals — predominantly bees — to perform that vital act of placing pollen.

And it is important to add that, here in the United States, the majority of our crops are pollinated not by wild bees, or even by honeybees like mine, which live in one location throughout the year, but by a vast mobile fleet of honeybees-for-rent.

From the almond trees of California to the blueberry bushes of Maine, hundreds of thousands of domestic honeybee hives travel the interstate highways on tractor-trailers. The trucks pull into a field or orchard just in time for the bloom; the hives are unloaded; and the bees are released. Then, when the work of pollination is done, the bees are loaded up, and the trucks pull out, heading for the next crop due to bloom.

The mobile fleets have been hit exceptionally hard by Colony Collapse Disorder, and if the epidemic continues, crop yields will soon decline. The consequences of CCD are therefore very clear. The causes, however, are not.

A recent survey of all the foreign DNA that could be found in honeybee hives discovered that a certain virus was present in 85 percent of hives that had fallen to CCD, but only 5 percent of hives that had not. That’s a strong association. But it’s not perfect, and there is surely more to the story.

Many of us have had the experience of contracting a cold shortly after an intense stretch of work. The lesson in this common ordeal — that the transition from health to disease is rarely so simple as exposure to the wrong bug — is probably as true for honeybees as it is for people. And CCD hit a honeybee population that was already feeling worn down: a large mite that attaches to bees and sucks their fluids, a tiny mite that inhabits the bee trachea, and a pair of fungal infections were all taking a toll when CCD first appeared. Not surprisingly, evidence of this grim company also showed up in the survey of foreign DNA.

But those plagues, too, could be part of a broader erosion of honeybee health. If you hang around beekeepers, from the hobbyists on up to the managers of mobile fleets, you’ll hear a variety of hypotheses about CCD. The mobile hives, some say, are overworked: for a species that evolved with an off-season and a steady home, year-round migratory labor must be taxing.

What’s more, each time they fly out into a new workplace, the itinerant honeybees encounter a variety of insecticides, herbicides and crops engineered to produce insecticidal proteins. And between jobs, they get a road-trip diet of pure corn syrup, which lacks many nutrients.

Some keepers say the problem isn’t just with the honeybees’ lifestyle, but with their genetics, as well, since they’ve been bred for traits that make them easier to handle, but may also render them more vulnerable to disease.

The list of plausible risk factors goes on. But if the cause of CCD truly is complex and multi-factorial, or if it simply remains obscure, what is there to do?

I’d like to back up a bit, because here we may need a brief history of bees. Honeybees first came to the New World on European ships. Once they’d hitched a ride across the Atlantic, however, they required no further assistance. They went feral, expanding swiftly — on their own — across the American landscape.

As the feral honeybees extended their range, they took up residence alongside thousands of native species of bees that were already here. There were the carpenter bees, which bored holes to nest in; the bumblebees, which formed small seasonal colonies; the orchard bees, which moved into the holes abandoned by others; the alkali bees, which burrowed in hardpan soil; and many, many others — all here before the honeybee.

For bees, the next important historical development was the transformation of landscapes. The immigrant humans set about remaking the continent — clearing land, building, sowing crops — and we have done so, at an accelerating rate, ever since. Obviously, a parking lot is a hard place for bees to live. Less obviously, a huge field of a single crop is equally unsuitable, for it lacks nesting sites, and yields its nectar as a sudden flood that soon recedes. Consequently, if a bee isn’t traveling the interstates by truck from one blooming field to the next, the American landscape is a tough place to make a living.

And yet, the wild bees — both the feral honeybees and many of the native species — have persisted. To this day, they are stowed away in our attics, hidden in holes in our wood siding and our dirt roads, and mostly, subsisting in the thin, semi-natural interstices of our transformed landscapes.

What does this mean for our current pollination crisis?

Those remnant wild bees, feral and native alike, might just be the seeds of a solution. And to sow those seeds and foster their growth, we must not till the earth, but do just the opposite: we must take patches of agricultural land out of production, and restore them to natural habitat.

At present, wild bee populations are too small, too few and too far between to take on the task of pollinating our crops. That, of course, is why fleets of domestic honeybee hives must be trucked in to do the job. But if the wild bees were provided with habitat of the right kind and in the right geographic arrangement, they could achieve pollination both reliably and effectively.

As the swift expansion of feral honeybees across the Americas shows, they are not especially picky about their habitat; most anything outside of parking lot or vast monoculture will do. And for native bees, habitat could be restored to suit the needs of whichever species are exceptionally good pollinators of local crops. Bumblebees, for instance, are the best pollinators of Maine blueberries, whereas blue orchard bees work well for California almonds.

The right geographic arrangement of habitat would also depend on which native species are desired for a certain crop. Many native species are willing to fly relatively far from their home habitat — a kilometer or so — to visit flowers; accordingly, patches of habitat for these bees could be placed relatively far apart.

Other species are homebodies, reluctant to fly more than a few hundred meters; to provide their services to an entire agricultural field, habitat patches would need to be closer together. Feral honeybees, for their part, are relatively fleet-winged, so whatever arrangement works for the natives will work for them, too.

Admittedly, there are costs of this rather low-tech solution to our pollination crisis: the opportunity cost of not cultivating those patches of land; the investment in restoration of habitat; the extra care required in applying insecticides close to established habitat.

But restoring bee habitat provides many offsetting benefits.

First, it allows us to foster the most effective pollinators for each crop, potentially increasing yields over levels achieved with pollination by domestic honeybees alone.

Second, habitat restoration is a singularly robust solution: It builds a diversified portfolio of potential pollinators, thus reducing our exposure to any one population’s collapse.

And third, a feral honeybee population distributed across a broad network of patches would harbor genetic diversity and inhabit a wide variety of environments — a wise insurance policy against problems with domestically bred hives.

As I arrived beside my own silent hive, I knelt and put my ear to the wooden box: Nothing. In a vague gesture of apology or consolation, I placed my hand on the box. Strangely, I received an answer: a gentle hum. And just then, from the dark entry hole, a bee emerged into the early light. Not dead, I realized. Just sleeping in.

**********

NOTES:

Thanks to D.G. Burnett, O. Judson, J. Maximon, T.H. Ricketts and V.H. Volny for helpful discussions.

The DNA survey of honeybee hives is reported in D.L. Cox-Foster et al. (2007) “A metagenomic survey of microbes in honey bee colony collapse disorder.” Science 318: 283-7. A good summary of current thinking on the causation of CCD is M.E. Watanabe (2008) “Colony collapse disorder: many suspects, no smoking gun.” BioScience 58: 384-8. For a review of the role of animal pollinators in our food supply, see A. M. Klein et al. (2007) “Importance of pollinators in changing landscapes for world crops.” Proc. R. Soc. B 274: 303-313. Two excellent papers on the services of native pollinators are T.H. Ricketts et al. (2008) “Landscape effects on crop pollination services: are there general patterns?” Ecology Letters 11: 499-515 and R. Winfree et al. (2007) “Native bees provide insurance against ongoing honey bee losses.” Ecology Letters 10: 1105-13.

For a guide to fostering native bees in your neighborhood, see “Alternative Pollinators: Native Bees.”