> > Published online 16 October 2008 | Nature | doi:10.1038/news.2008.1175 > > > Agriculture unaffected by pollinator declines > > > > Global crop yields have not suffered even though key insect populations > have shrunk. > > Anna Petherick > bee > 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< > http://www.nature.com/news/2008/081016/full/news.2008.1175.html#B1>1, 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< > http://www.nature.com/news/2008/081016/full/news.2008.1175.html#B2>2. > > 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< > http://www.nature.com/news/2008/081016/full/news.2008.1175.html#B3>3. 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< > http://www.nature.com/news/2008/081016/full/news.2008.1175.html#B4>4. > > 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 > > > > * Aizen M. A., Garibaldi, L. A., Cunningham, S. A. & Klein, A. M. Curr. > Biol. doi:10.1016/j.cub.2008.08.066 (2008). > * Ricketts, T. H., Daily, G. C., Ehrlich, P. R. & Michener, C. D. Proc. > Natl Acad. Sci. USA 101, 12579–12582 (2004). > * Biesmeijer, J. C. et al. Science 313, 351–354 (2008). > * Ghazoul, J. Trends Ecol. Evol. 20, 367–373 (2005) > > > -- > "Love is like a beautiful flower which I may not touch, but whose fragrance > makes the garden a place of delight just the same". > Helen Keller >
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