29th March, 2012, The Guardian
Pesticides linked to honeybee decline
The first study conducted in a natural environment has shown that systemic pesticides damage bees' ability to navigate
Common crop pesticides have been shown for the first time to seriously harm bees by damaging their renowned ability to navigate home.
The new research strongly links the pesticides to the serious decline in honey bee numbers in the US and UK – a drop of around 50 per cent in the last 25 years. The losses pose a threat to food supplies as bees pollinate a third of the food we eat such as tomatoes, beans, apples and strawberries.
Scientists found that bees consuming one pesticide suffered an 85 per cent loss in the number of queens their nests produced, while another study showed a doubling in "disappeared" bees – those that failed to return from food foraging trips. The significance of the new work, published Science, is that it is the first carried out in realistic, open-air conditions.
'People had found pretty trivial effects in lab and greenhouse experiments, but we have shown they can translate into really big effects in the field. This has transformed our understanding,'said Prof David Goulson, at the University of Stirling and leader of one of the research teams. 'If it's only one metre from where they forage in a lab to their nest, even an unwell bee can manage that.'
Prof Mickaël Henry, at INRA in Avignon, France, who led a separate research team, said: 'Under the effects we saw from the pesticides, the population size would decline disastrously, and make them even more sensitive to parasites or a lack of food.
Decline blamed on disease, loss of forage and pesticides
The reason for the huge decline in bee numbers has remained uncertain, but pesticides, the varroa mite and other parasites, and destruction of the flower-rich habitats in which bees feed are believed to be the key reasons. Pesticide manufacturers and the UK government deny a class of the chemicals called neonicotinoids cause significant problems for bees, but Germany, Italy and France have suspended key insecticides over such fears.
A spokesperson from Department for Environment, Food and Rural Affairs (Defra) said the new research did not change the government's position. 'The UK has a robust system for assessing risks from pesticides and all the evidence shows neonicotinoids do not pose an unacceptable risk to honeybees when products are used correctly. However, we will not hesitate to act if presented with any new evidence.'
Henry said the new research showed current approval processes for the pesticides are inadequate: 'We now have enough data to say authorisation processes must take into account not only the lethal effects, but also the effects of non-lethal doses.'
The pesticides investigated in the new studies - insect neurotoxins called neonicotinoids - are applied to seeds and flow through the plants' whole system. The environmental advantage of this is it reduces pesticide spraying but chemicals end up in the nectar and pollen on which bees feed. Goulson's group studied an extremely widely used type called imidacloprid, primarily manufactured by Bayer CropScience, and registered for use on over 140 crops in 120 countries.
Bumblebees were fed the toxin at the same level found in treated rape plants and found that these colonies were about 10 per cent smaller than those not exposed to the insecticide. Most strikingly, the exposed colonies lost almost all of their ability to produce queens, which are the only bee to survive the winter and establish new colonies. 'There was a staggering magnitude of effect,' said Goulson. 'This is likely to have a substantial population-level impact.'
The French team analysed the effect on honey bees of a new generation neonicotinoid, called thiamethoxam and manufactured by Syngenta. They fitted tiny electronic tags to over 650 bees and monitored their activity around the hive. Those exposed to "commonly encountered" levels of thiamethoxam suffered high mortality, with up to a third of the bees failing to return. 'They disappeared in much higher numbers than expected,' said Henry. Previous scientific work has shown insect neurotoxins may cause memory, learning, and navigation problems in bees.
A spokesman for Syngenta said: 'Although we take good research very seriously, over the last four years, independent authorities in France have closely monitored the use of Cruiser – the product containing thiamethoxam – on more than 1.9m hectares. When properly used no cases of bee mortality have been recorded.'
Julian Little, spokesman for Bayer Cropscience, criticised Goulson's study because the bees were exposed to imidacloprid in the labaratory, before being placed outside in a natural field environment to feed. 'All studies looking at the interaction of bees and pesticides must be done in a full field situation,' he said. 'This study does not demonstrate that current agricultural practices damage bee colonies.'
Goulson dismissed as "nonsense" Little's suggestion that the doses given to the bees were higher than in reality. Both Bayer and Defra suggested other field studies had shown no harmful effects to bees. Goulson said: 'If they have done these studies, where are they? They are not in the public domain and therefore cannot be scrutinised. That raises the question of just how good they are.' Damien Carrington, guardian head of environment
Abstract "A Common Pesticide Decreases Foraging Success and Survival in Honey Bees"
Nonlethal exposure of honey bees to thiamethoxam (neonicotinoid systemic pesticide) causes high mortality due to homing failure at levels that could put a colony at risk of collapse. Simulated exposure events on free-ranging foragers labeled with an RFID tag suggest that homing is impaired by thiamethoxam intoxication. These experiments offer new insights into the consequences of common neonicotinoid pesticides used worldwide.
statement Dr. Pettis
Jeffery Pettis, a bee expert at the United States Department of Agriculture, called Dr. Goulson’s study “alarming.” He said he suspected that other types of wild bees would be shown to suffer similar effects.
Dr. Pettis is also convinced that neonicotinoids in low doses make bees more vulnerable to disease. He and other researchers have recently published experiments showing that neonicotinoids make honeybees more vulnerable to infections from parasitic fungi.
“Three or four years ago, I was much more cautious about how much pesticides were contributing to the problem,” Dr. Pettis said. “Now more and more evidence points to pesticides being a consistent part of the problem.”
New pesticides linked to bee population collapse
Two studies confirm dangers of 'nerve agents' used on one-third of all British cropland
Worldwide declines in bee colonies, threatening much of global agriculture, may be caused by a new generation of nerve-agent pesticides, two new scientific studies strongly suggest. The findings place a massive question mark over the increasingly controversial compounds, now the fastest growing family of insecticides in the world.
Bee declines represent a serious threat to agriculture because bees are the pollinators of a large percentage of crops. Both honey bees and wild bumble bees are seriously harmed by exposure to neonicotinoid insecticides, even by tiny doses not sufficient to kill them outright, the studies by British and French scientists report today.
The British study, carried out by scientists from the University of Stirling, concludes that "there is an urgent need to develop alternatives to the widespread use of neonicotinoid pesticides on flowering crops wherever possible".
About 30 per cent of British cropland – 3.14 million acres – was being treated with the chemicals in 2010, while in the US the figures for neonicotinoid use are enormous: in 2010, 88 million acres of maize, 77 million acres of soy and 53 million acres of wheat were treated with them. The compounds, which attack insects' central nervous systems, have been increasingly implicated in the widespread decline of honey bees and wild bees over the past decade, which have culminated in the mysterious colony collapse disorder in the US – a phenomenon in which the whole population of a beehive suddenly vanishes.
The value of bees' pollination services has been estimated at £200m per year just in Britain. The global annual value of pollination has been estimated at £128bn annually.
Many beekeepers have become convinced that the new pesticides are behind the declines, and in France, Italy and other countries they have been banned. But in Britain and the US their use continues.
Last year The Independent revealed that the American government's own chief bee researcher, Dr Jeffrey Pettis of the US Department of Agriculture, had conducted a study showing that bees exposed to microscopic doses of neonicotinoids were much more vulnerable to disease – but his study had not been published nearly two years after it was completed. Dr Pettis's findings were eventually published two months ago and were described by The Economist as "a plausible hypothesis for the cause of colony collapse disorder".
The findings of the two new studies, published simultaneously in the journal Science, are explosive.
The British study, led by Stirling's Professor David Goulson, showed that growth of colonies of the common buff-tailed bumble bee, Bombus terrestris, slowed after the insects were exposed to "field-realistic levels" of imidacloprid, a common neonicotinoid insecticide. The production of queens, essential for colonies to continue, declined by a massive 85 per cent in comparison with unexposed colonies used as controls.
"Given the scale of use of neonicotinoids, we suggest that they may be having a considerable negative impact on wild bumble bee populations across the developed world," the Stirling team says.
The French study, led by Mikaël Henry from France's National Institute for Agronomic Research in Avignon, looked at honey bees exposed to another neonicotinoid product, thiamethoxam.
The study found that even though the dose was sub-lethal, the exposure seriously affected the bees' homing abilities to the extent that they proved to be two to three times more likely to die while away from their nests than untreated bees. "Non-lethal exposure... causes high mortality due to homing failure, at levels that could put a colony at risk of collapse," the researchers say.
"These new studies put beyond all reasonable doubt the capacity for neonicotinoids to cause environmental destruction," said Matt Shardlow, director of Buglife, the invertebrate conservation trust. "Our Government must take the precautionary step of banning their use." The Government has twice been formally asked to suspend neonicotinoids; on both occasions the requests were ignored.
The problem posed by neonicotinoids is that they are "systemic" pesticides, which means that they do not just sit on the surface of the plant, but are taken up into every part of it, including the pollen and the nectar; and so even if bees are not the target species, they ingest the chemicals through the pollen and nectar when they are foraging.
Force of nature: The life of bees
Bumble bees are distinctive for their large, furry appearance. They are hugely important as natural crop pollinators. The queen is the only individual that can survive the winter, hibernating underground and emerging in spring to build a nest.
She lays eggs which hatch as worker bees. The workers fly from flower to flower gathering nectar and spreading pollen as they go. Bumble bees pollinate a great variety of plants – both wild and agricultural.
Honey bees have a different life cycle, with all the bees surviving the winter inside the hive. Honey bees are much better than bumble bees at producing honey, made from the nectar and sweet deposits of trees and plants brought back to the hive. It is these bees that are bred by beekeepers all over the world.
Both honey bee and bumble bee populations have dramatically declined in recent decades. In Britain, bumble bees have been vanishing since the 1950s. A UN report last year said that a phenomenon known as Colony Collapse Disorder that had seen the number of honey bee colonies in Europe and the USA plummet since the 1960s, had become a global problem, with beekeepers in Japan and Egypt all reporting losses of their colonies.