[Pollinator] Agriculture unaffected by pollinator declines

Thu Oct 16 18:34:01 PDT 2008

Published online 16 October  2008 | Nature | doi:10.1038/news.2008.1175  
News 
Agriculture unaffected by  pollinator declines
Global crop yields have not suffered even  though key insect populations have 
shrunk. 
Anna Petherick  

Crops may  not need quite so many bees for pollination after all.Punchstock
Bees and many other insects may be in decline almost  everywhere — but 
agriculture that depends on pollinators has been surprisingly  unaffected at the 
global scale. 
That's the conclusion of a study by Alexandra Klein at  the University of 
California, Berkeley, and her colleagues. Using a data set of  global crop 
production — maintained by the Food and Agriculture Organisation of  the United 
Nations (FAO) — which spanned 1961 to 2006, they compared the yields  of crops 
that require pollinators with those that don't. 
They found that crop yields for both crop types have gone  up consistently, 
seeing average annual growth rates of about 1.5%. There was  also no difference 
when the researchers split the data into crops from  developing countries and 
crops from developed countries.  
And when the researchers compared crops that are  cultivated almost 
exclusively in tropical regions, they found no difference  between the success of 
insect-pollinated crops — such as oil palm, cocoa and the  Brazil nut — and those 
crops that need only the breeze to spread their pollen.  
Underplayed, overplayed
The results, published in Current Biology_1_ 
(http://www.nature.com/news/2008/081016/full/news.2008.1175.html#B1) , are surprising because several previous 
studies  have found very large impacts at local scales. Taylor Ricketts, head 
of  conservation group WWF's conservation science programme, and his 
colleagues,  reported in 2004 that pollinators increased coffee yields by 20% on 
plants  growing a kilometre or less from forests in Costa Rica_2_ 
(http://www.nature.com/news/2008/081016/full/news.2008.1175.html#B2) .  
In 2005, a team led by Jacobus Biesmeijer of the  University of Leeds, UK, 
found evidence of a drop-off in bee diversity in the  United Kingdom and the 
Netherlands_3_ 
(http://www.nature.com/news/2008/081016/full/news.2008.1175.html#B3) . This coincided with a decline in outcrossing  plant species relative to 
other sorts of plants.  
And worries about a pollination crisis have found their  way into 
international politics, most prominently with the establishment of the  International 
Initiative for the Conservation and Sustainable Use of Pollinators  (IPI) at a 
United Nations meeting in 2000. 
But some scientists think that the pollinator crisis is  overplayed. Jaboury 
Ghazoul, a plant ecologist at ETH Zurich, Switzerland, has  argued that it is 
driven mainly by reported declines of crop-pollinating  honeybees in North 
America and bumblebees and butterflies in Europe_4_ 
(http://www.nature.com/news/2008/081016/full/news.2008.1175.html#B4) . 
Other data show that native pollinator communities  elsewhere exhibit mixed 
responses to environmental change, and Ghazoul says that  few staple food crops 
depend on insect pollinators.  
"When the IPI was established, there was some  disagreement about how much 
pollinators are declining," says Linda Collette, a  senior officer on crop 
associated biodiversity at the FAO, which oversees the  IPI programme.  
Hidden threat
Klein says her findings do not necessarily negate that  idea that the world 
is in the throes of a pollination crisis. The data might  hide how farmers have 
adapted to the problem, she suggests. 
For example, in almond pollination, many growers move  honeybees into their 
orchards and use pheromones to stimulate foraging activity,  she says. Some 
even place compatible pollen in the bees' hives so that they  transport it to the 
desired variety of almond. And many passion-fruit growers in  Brazil now 
pollinate crops by hand.  
For the FAO, the increasing reliance on farmworkers  rather than insects may 
not represent a crisis. "At the end of the day, what's  important to the FAO 
is crop production," says Collette. "There may be labour  costs involved in 
pollinating crops but there could also be market benefits — if  the fruits are 
better from that, for instance." 
However, Klein points out that a sudden drop in crop  yields could be just 
around the corner. "There could be a more widespread  threshold effect coming," 
she says, "especially if the honeybee problems get  worse in places like 
California." 
This may be more likely as farmers all over the planet  start to fill ever 
more hectares with pollinator-dependent crops, which  contributed 8.4% of total 
agricultural production in the developed world in 1961  but 14.7% in 2006. "We 
assume that the trend will continue as many biofuels  crops, such as canola, 
oil palm and jatropha, are pollinator-dependent plants,"  says Klein. 
    *   References
    1.  Aizen M. A., Garibaldi, L. A., Cunningham, S. A. &  Klein, A. M. 
Curr. Biol.  doi:10.1016/j.cub.2008.08.066 (2008).  
    2.  Ricketts, T. H. , Daily, G. C. , Ehrlich, P. R. & Michener, C. D. 
Proc. Natl Acad. Sci. USA 101, 12579–12582 (2004).  
    3.  Biesmeijer, J. C. et al. Science 313, 351–354 (2008).  
    4.  Ghazoul, J. Trends Ecol. Evol. 20, 367–373 (2005). 

Laurie Davies Adams
Executive  Director
Pollinator Partnership 
423 Washington Street, 5th  floor
San Francisco, CA  94111
415-362-1137
LDA at pollinator.org

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