Buzzkill: Can native bees do the job?

Photo of Bumble Bee from Strange One\'s flickr collection With the health of honey bee colonies in dramatic decline, can farmers rely on native bees to pollinate their crops?

On the right kind of farm — one with nearby natural habitat and organic management — the answer is yes, according to UC Berkeley professor Clare Kremen, an expert on native bees. Kremen shared this finding and other interesting facts about bees in a talk at the Commonwealth Club in San Francisco a few weeks ago. (A recording of her talk appeared on the Commonwealth Club's podcast feed but isn't yet on their website.)

Bee prepared for disaster

If all of the world's pollinators were to suddenly disappear, there would be a massive disruption of plant communities, as most of them require active pollination to reproduce. Our food supply would see significant changes. Even though two-thirds of world crop production is not dependent on active pollination — grains like wheat, rice, millet and sorghum are pollinated by the wind — some of the most interesting and nutritious foods, such as almonds, cacao, coffee, avocados, and carrots, do depend on outside pollinators.

Photo of honey bee and native bee on onion flowerIn today's industrial agriculture system in the United States, the pollinators are primarily managed hives of honey bees (Apis mellifera). For example, according to a report from Cornell University (PDF), the U.S. almond crop is completely dependent on pollination by the honey bee; for avocados and carrots, honey bees provide about 90% of the pollination. Honey bees therefore provide tremendous economic value. The report from Cornell estimates that the marginal value of honey bees (the value of increased yield and quality caused by honey bee pollination) is over $14 billion annually. For a frame of reference, California's output of fruit, nuts, vegetables and melons in 2006 was about $17 billion (according to the California Department of Agriculture, PDF).

Kremen said that there are several thousand bee species native to the United States (maybe tens of thousands) and we don't know how many actually pollinate crops. Bees are exceptional pollinators for several reasons. First, they collect pollen, not only nectar like ants and other flower visitors. Second, bees are biologically adapted to carry pollen and therefore are effective collectors. Third, they exhibit "floral constancy," which means that they visit many individuals from the same species of flower on their foraging trips, making it more likely that pollen will be transferred.

For most of our agricultural history, humans have relied on native bees and unmanaged honey bees to pollinate our crops and ornamental plants. Trucking scores of bee hives across hundreds or thousands of miles as an on-demand pollination service is a recent development brought about by the ascendancy of industrial agriculture. Although this is the type of agriculture that most needs pollinators, it offers the worst habitat for them. Take almonds, an extreme example: they have a very short blossom period, and because of the similarity of the climate in almond-producing areas, most of the trees bloom at the same time. Thus, thousands of colonies converge on the central valley of California during the spring: in 2004, 60% of the 2.5 million "for-hire" honey bee colonies in the U.S. were involved in pollination of California almond orchards, according to the Agricultural and Resource Economics Update.

Honey bees have been struggling in recent decades because of the varroa mite, diseases, and most recently the mysterious Colony Collapse Disorder. (A Congressional Research Service report and an episode of PBS's Nature provides a good background of CCD.) Between 1945 and 2005, there was a a major decrease in the number of managed colonies, according to USDA data summarized in a report from the National Academies (on page 40). There is much effort underway to find the cause of CCD, and at the same time, some experts like Kremen are looking at ways to find local help for honey bees by improving the conditions for native bees.

Go native!

For 10 years, Kremen has studied wild bees. Some of her research has been in Yolo County, a rural county to the northeast of the S.F. Bay Area and home to some amazing farms that supply Bay Area markets and restaurants. Kremen and her collaborators are investigating the behavior of native bees along "gradients of agricultural intensification": one gradient starts with farms near natural habitat and ends in wall-to-wall agriculture. Another starts at organic and ends at industrial. Along this gradient, you have smaller farms with a polyculture, low use of pesticides, a tolerance of weeds (which often have flowers that provide food for pollinators) on one end, and monoculture, regular pesticide use, and a barren landscape on the other.

Photo of a bumble bee on lavender flower from Velodenz\'s flickrAt each study site, Kremen's team documented bee diversity by collecting specimens, counting visitors, and measuring pollen efficiency. They did some clever and painstaking experiments to determine how much pollination comes from native bees, such as watching an individual watermelon flower, or carrying around a watermelon flower as 'bait' and then counting what landed.

On farms near natural areas, they found 30 species of native bees active in the fields and orchards; in wall-to-wall agricultural areas, just a few. They also discovered that the most efficient native pollinators live closest to the natural areas. In sum:

  • 80% of organic farms near natural habitat received enough pollination from wild bees
  • 50% of conventional farms near natural habitat received enough pollination from wild bees
  • 0% of conventional farms in exclusively agricultural areas received pollination from wild bees
  • Little pollination (she didn't give a number) was provided by native bees on organic farms located in exclusively agricultural areas

The team also looked at farms in New Jersey and Pennsylvania, two states with smaller-scale and more diverse agricultural systems. In both places, the in-place bee communities (native bees, non-mobile honey bees, and feral honey bees) handle the pollination.

Bumbling attempts to help

Near the end of her talk Kremen asked, "Can wild bees pollinate modern agriculture?" Her answer was no. Modern agriculture provides too few nesting sites, too little floral resources, and too many flowers to pollinate at once.

But that doesn't mean that farmers should give up on native bees. They can create suitable habitat and nesting sites by allowing weeds and cover crops to flower, by growing a variety of crops, planting strips of flowering vegetation between fields, restoring patches of native habitat around the farm, and through creating nest sites (leaving soil undisturbed, keeping dead trees in place, and installing nest blocks).  Unfortunately, these very practices have come under attack by industrial food-safety advocates who think that farms should be sterile sites devoid of anything natural except for the crops, as an op ed from 2007 by Full Belly Farms co-owner Judith Redmond points out (PDF).

Kremen has been working with the Xerxes Society and several other organizations to test some of these ideas on real farms in Yolo County. The group started a project in a wall-to-wall agricultural area that involves planting hedgerows of native flowering plants and installing nesting boxes for bees. An interesting feature of the project is that they are enlisting "citizen scientists" to monitor parts of the project and have been very happy with the quality of their work. (Part of a segment of the television program Quest is about the project.)

She concluded the talk by saying that it will take many actions to help native bees provide more pollination services to our crops. We will need improved conservation programs in agricultural areas, restoration of degraded lands, and changes in farm management practices (like more polycultures and reduced pesticide use).

More information

Photo of bumble bee on a lavender flower from velodenz's flickr collection, subject to a Creative Commons License; photo of a bumble bee on a pink flower from Strange One's flickr collection, subject to a Creative Commons License;photo of bees on an onion flower by the author.

4 Responsesto “Buzzkill: Can native bees do the job?”

  1. There's also the added dimension of territoriality of bees. They will actually knock each other off of flowers trying to get them to leave the area (and leave the flowers to themselves is the interpretation), resulting in more pollen spread, interestingly.
    I'm also a beekeeper, and having just met with the CSA farmers last night, on whose farm I keep my bees, one thing that beekeepers could try to do is establish relationships with farmers that will keep their bees around for longer. Diverse farms are probably good for the bees, and they may be able to more effectively pollinate flowers that open at different dates.
    Native bees can help, but the kind of floral concentration that is present in agriculture may be too much for them, not just modern monocultures. There has been research on what kind of pollinator density is necessary to fully pollinate various crops, and honeybees are still going to be needed, IMO.
    Also, if anyone is interested, I did an interview on bee diseases with Eric Mussen at UC Davis a few years ago:

  2. Buzzy Beez says:

    If the actual numbers were anything close to what Ms. Kremen claimed, growers would not be paying beekeepers so much money to bring hives of honey bees to their crops.

    Further, exploitation is not preservation.  The "native pollinator" enthusiasts have already put two species of bumblebees into extinction with their misguided attempts to exploit them in the rough-and-tumble of agriculture, just ask a real expert, like Robin Thorp
    ( )

    Sadly, the "news" presented here was misinformation.

  3. Buzzy Beez: 
    You missed the point of Dr. Kremen's research.  She has found that in order to have native bees do any substantial pollination, you need natural habitat.  In other words, we provide natural habitat to bees, and then they will spend some of their time pollinating our crops, and some of their time in the natural habitat.  It's not exploitation, but a mutually beneficial arrangement.  In the talk I attended, Kremen didn't say anything about trying to commercially raise bumblebees, much less export them to Europe, like the link you provide describes.  She's looking for a more natural solution for a certain type of farm, where humans work with nature, instead of trying to harness it. (If Kremen has written about commercial rearing of bumblebees, please let us know.)
    Huge almond groves, cranberry bogs, and other monocultured fields in industrial agriculture do not provide any habitat suitable for native bees, and consequently native bees cannot survive.  Thus, hives honeybees must be brought to the fields. 
    If you have concerns with the methodology used or conclusions reached by Dr. Kremen and her associates in their peer-reviewed literature (upon which her talk was based), please provide them, instead of a baseless attack of "misinformation."  And as for Dr. Kremen's qualifications, it's worth noting that Dr. Kremen is a member of the National Academies' "Committee on Status of Pollinators in North America", which wrote the study that I cited above.

  4. Buzzy Beez says:

    You hit on the exact problem with Dr. Kremen's research - the fatal flaw in her work was that she assumed a "natural habitat" that could only exist in such low-density agriculture that consumers like yourself would not survive the famine that would result from implementing that approach.  Dr. Kremen postulated a fantasy world.  One that has never existed.

    The only thing that will result from the misguided attempt to exploit native pollinators will be the further enrichment of large agribusiness concerns, who will "set aside" wasteland that cannot be farmed anyway, and call it "pollinator habitat" to get the tax credits

    The land will not be in large enough plots, nor will it be far enough away from intensive pesticide use to support even solitary bees placed there by beekeepers like myself (yes, surprise, we are also the experts on the practical husbandry and deployment of the "native bees" that enchant you so). Look at it from my point of view, and the point of view of every other experienced beekeeper.

    If we could get the job done with stingless, easy to transport, easy to lift bundles of tubes containing solitary bees, we certainly would be doing exactly that, wouldn't we?  Pollination stresses honey bee hives, and reduces honey crops, so we'd have one set of bees for the honey, and another set for pollination work.   What happens is that every decade or so, someone starts a splashy and very optimistic project to use "native bees" or "solitary bees", which is never again heard from when some hitherto unknown pathogen or parasite wipes out the breeding population of the "native bees".

    Recall that the crops pollinated by honey bees are ALSO NOT NATIVE to this continent.  One cannot expect the native bees to exist in sufficient density to be able to be useful in any level of agriculture from circa 1710 to today without the hand of man to culture them in sufficient density.   Sadly, this same density is what allows diseases to spread and wipe out entire operations. You really have to do more than attend a lecture to get a grasp on this complex aspect of agriculture.   I've been at it over 20 years, and no one with any sense is claiming to have a ready-made solution to the problems caused by invasive pests and diseases that have threatened beekeeping, and hence all of agriculture. To be blunt, the solitary bee with the most promise for applications East of the Rockies is the Japanese Hornfaced Bee, which is an import.   Various species of Osmia do fairly well West of the Rockies, but even those projects tend to be plauged by practical problems. Don't fall for the "Pollinat0r Protection Racket".

    The insect that puts food on your table is the same one that has done the work and been worth the investment of time and trouble for several thousand years  - the European honey bee.  Why would beekeepers put up with all the trouble of keeping them if any other insect could do the same job and NOT be a stinging insect?

    This is a complex agricultural issue, and one is well-advised to not argue with a beekeeper or farmer with one's mouth full.   :)