By Alister Doyle
OSLO (Reuters) - Pesticides used in farming are also killing worker bumblebees and damaging their ability to gather food, meaning colonies that are vital for plant pollination are more likely to fail when they are used, a study showed on Sunday.
The United Nations has estimated that a third of all plant-based foods eaten by people depend on bee pollination and scientists have been baffled by plummeting numbers of bees, mainly in North America and Europe, in recent years.
British scientists said they exposed colonies of 40 bumblebees, which are bigger than the more common honeybee, to the pesticides neonicotinoid and pyrethroid over four weeks at levels similar to those in fields.
Neonicotinoids are nicotine-like chemicals used to protect various crops from locusts, aphids and other pests.
"Chronic exposure ... impairs natural foraging behavior and increases worker mortality, leading to significant reductions in brood development and colony success," the scientists wrote in the report in the journal Nature on Sunday.
Exposure to a combination of the two pesticides "increases the propensity of colonies to fail", according to the researchers at Royal Holloway, University of London.
A 2011 U.N. report estimated that bees and other pollinators such as butterflies, beetles or birds do work worth 153 billion euros ($200 billion) a year to the human economy and are in decline in many nations.
The findings underscored the importance of wider testing of pesticides to ensure they do not also target bees, it said.
France banned a neonicotinoid pesticide made by Swiss agrochemicals group Syngenta in June, citing evidence of a threat to the country's bees. A report last month, however, said that the original research was flawed.
"My guess is that the decline of bees is like a jigsaw -there are probably a lot of pieces to put into place. This is probably a very important piece of that jigsaw," lead author Richard Gill told Reuters of the findings about pesticides.
In a separate commentary in Nature, Juliet Osborne of the University of Exeter in England said the study underscored the need to understand all factors that may contribute to harm bees and to "Colony Collapse Disorder".
"For example, we have as yet no convincing demonstration of the relative effects of pesticides on bee colonies compared to the effects of parasites, pathogens and foraging resources," she wrote.
Gill endorsed recommendations by the European Food Safety Authority for longer testing on adult bees and larvae, new ways of assessing cumulative exposure to toxins and separate assessments for different bee species.
He said previous studies had mostly examined the impact of pesticides on individual bees, rather than colonies. Bumblebees form colonies of a few dozen bees, while honeybees can number up to tens of thousands.
"Effects at the individual level can have a major knock-on effect at the colony level. That's the novelty of the study," he said.
The average number of bees lost in the experiment - both dead in the nesting box and failing to return - was about two-thirds of the total for bees exposed to a combination of the two pesticides against a third for a control, exposed to neither.
Bumblebees exposed to a combination of pesticides were about half as successful at gathering pollen, used as food, compared to a control. They also devoted more workers to collecting food, meaning fewer were raising larvae.
Other experts said more research was needed. "It certainly wouldn't be fair to say that this research spells doom for wild bees," said James Cresswell of the University of Exeter.
(Editing by Alison Williams)
Also on HuffPost:
<a href="http://www.ciat.cgiar.org/Newsroom/Documents/ghana_ivory_coast_climate_change_and_cocoa.pdf" target="_hplink">A report released by the International Center For Tropical Agriculture </a>warns chocolate could become a luxury item if farmers don't adapt to rising temperatures in Ghana and the Ivory Coast, where a majority of the world's cocoa is grown.
Coffee lovers may want to get that caffeine fix before the treasured drink becomes an extinct export. Starbucks raised the issue last year when the company's director of sustainability told <em>The Guardian</em> <a href="http://www.huffingtonpost.com/2011/10/16/starbucks-climate-change_n_1011222.html" target="_hplink">climate change is shortening the supply chain of Arabica coffee bean</a>.
Famed for producing some of the world's best beer, <a href="http://www.nature.com/news/2008/080502/full/news.2008.799.html" target="_hplink">Germany could suffer from a drop in production due to climate change induced water shortages</a>. Barley and hops can only be grown with water and using cheaper alternatives like corn isn't possible in Germany because of strict regulations about what you can make beer with.
Thanks to a failing peanut crop due to last summer's scorching hot weather, <a href="http://www.huffingtonpost.com/2011/10/10/peanut-butter-price-jump_n_1003732.html" target="_hplink">there's a shortage of peanuts in supply</a>. If temperatures continue to rise, a jump in peanut butter prices is just the prelude to what's in store for the beloved American spread.
Scientists at the British Meteorological Office warn that Italy may soon be forced to<a href="http://www.theaustralian.com.au/news/world/climate-threat-to-italys-pasta/story-e6frg6so-1225797946930" target="_hplink"> import the basic ingredients to make pasta because climate change will make it impossible to grow durum wheat domestically</a>. The crop could almost disappear from the country later this century, say scientists.
<a href="http://www.treehugger.com/green-food/goodbye-maple-syrup-climate-change-pushing-sugar-maple-out-of-northeast-us.html" target="_hplink">A warming climate could make maple syrup history.</a> Shorter cycles of below freezing weather mean sugar maples aren't producing enough sap, which is later boiled down to make maple syrup.
<a href="http://usda01.library.cornell.edu/usda/current/Hone/Hone-03-30-2012.pdf" target="_hplink">It's no secret that bee populations are dropping nationwide</a>. Wetter winters and rainy summers make it harder for bees to get out and about to collect, leaving them to starve or become malnourished and more prone to other diseases. This doesn't just mean a decline in honey. We rely on bees to pollinate crops. When bees disappear many food crops could also die off.
<a href="http://www.spiegel.de/international/europe/best-served-chilled-top-french-wines-at-risk-from-climate-change-a-748139.html" target="_hplink">France is losing its enviable climate for grape growing</a> thanks to a shifting climate. Because a wine's taste is a result of the balance of sugar and acidity in the grapes it is made from, the right growing temperature is essential. Grapes grown in cold are unlikely to develop fruity flavors, giving an acidic taste. Warm weather produces too much sugar, leaving a "jammy" and heavy taste.
Also On The Huffington Post...
This trailer for "Carbon Nation", documentary movie about climate change SOLUTIONS, will impact you even if you doubt the severity of the impact of climate change or just don't buy it at all.