Colony Collapse Disorder” (CCD) refers to the seemingly spontaneous abandonment of their hives by honeybees.
Bees have been abandoning their hives for centuries, but the rate at which such collapses have been observed started to increase more drastically in the 1970s, reaching alarming proportions around 2006. While numerous causes for the phenomenon have been floated, from pathogens and parasites to electromagnetic radiation and a proliferation of genetically-modified crops, new research from the Harvard School of Public Health bolsters the case that a certain class of insecticides seem to be to blame.
Working with the Worcester County Beekeepers Association in Massachusetts, the researchers exposed 12 colonies across three locations to a “sub-lethal exposure of neonicotinoids, imidacloprid or clothianidin.” Neonicotinoids are popular insecticides that are chemically similar to nicotine. The scientists also observed six untreated control colonies at the same locations. The study found that all the bee colonies went about their business normally through the summer and fall, but by the end of winter six of the twelve hives exposed to the insecticide had been abandoned. One of the six control colonies was also lost due to an infestation by a fungus.(1)
Research in the UK by T.D. Breeze, A.P. Bailey, K.G. Balcombe and S.G. Potts entitled ‘Pollination services in the UK: How important are honeybees?’ makes for interesting reading.
They found that honeybee populations have nose-dived so dramatically in recent years that they can only do half as much pollination as they did in the early 1980s.
Where honeybees used to provide around 70 per cent of the UK’s pollination needs they now only pollinate a third. At worst, that figure could well be more like 10 to 15 per cent.
Paradoxically over the last 20 years, the proportion of UK crops that rely on insects for pollination has risen from just under 8 per cent in the early 1980s to 20 per cent in 2007. And over the same period, yields of insect-pollinated crops, which include oil seed rape and field bean, have gone up by 54 per cent.
This means that honeybees can’t be solely responsible, or aren’t the only important pollinator.
So if honeybees aren’t pollinating the crops, the question arises what is? The researchers think that other important pollinating insects, such as bumblebees, hoverflies and solitary bees must be making up the shortfall.
‘Our finding suggests that wild insect pollinators make a much bigger contribution to UK crop pollination than previously thought,’ says Tom Breeze from the University of Reading, lead author of the study
Insect pollination is estimated to be worth around £400 million per year to UK crop agriculture. And until now, people have widely assumed that honeybees are the most important pollinators, with a figure of around 90 per cent of pollination services coming from honeybees bandied around.
‘We had an inclination that this wasn’t an accurate figure at all,’ says Breeze. ‘Honeybees have been in decline for years, so it didn’t make sense.’
Indeed, there is a complete absence of large scale research that backs up the assumption that honeybees are the main pollinators.
So Breeze and colleagues from the University of Reading set out to learn how important insect-pollinated crops are to UK agriculture and – using data from an earlier study – to figure out the real contribution from honeybees.
This is the first time anyone has looked at the contribution from both honeybees and other pollinators on such a grand scale.
‘Bumblebees, hoverflies and red mason bees are key wild pollinators, but there are at least 250 bee species alone in the UK, which we thought almost certainly contribute more than honeybees do,’ Breeze says.
Although Breeze and his colleagues found that honeybees don’t provide the same level of service that other species do, they point out that it’s not one pollinator or the other that’s important; both types are crucial.
‘There was a seminal study in 2006 which found that you get the best pollination, best yields and best fruit when you have both wild pollinators and honeybees,’ says Breeze.
‘This study challenges the long held beliefs surrounding the importance of honeybees as the major pollinators and could potentially result in a paradigm shift in people’s thinking,’ says Science and Innovation Manager Dr Andrew Impey from the Natural Environment Research Council.
Furthering this research Professor Simon Potts from the Department of Agriculture, examined how important insect-pollinated crops are to UK agriculture and how much of this work is done by honeybees.
There has recently been mounting evidence that honeybee hive numbers are in a long-term state of decline in many developed nations. Analysis of hive numbers indicates that current UK populations are only capable of supplying 34% of our pollination needs, falling from 70% in 1984.”
In spite of this decline, insect-pollinated crop yields have risen by an average of 54% since 1984, casting doubt on long-held beliefs that honeybees provide the majority of pollination services.
Professor Potts said: “In the early 1980s honeybees provided most of our pollination services, however, following severe declines in hive numbers over the last 30 years, there are no longer enough honeybees to do the job and it is now our wild insects, such as bumblebees and hoverflies, that have filled the void to ensure that our crops are pollinated and our food production is secure.”
Many of the UK’s most valuable crops, including apples, strawberries, runner beans, and, increasingly oilseed rape, are pollinated by other insects. Tom Breeze, who conducted analysis for the study, said: “The total monetary value of pollinators to crop production in the UK is estimated at £430 million per year. This research suggests that the majority of this value is derived from wild pollinators and not honeybees.”
Stuart Roberts, Chairman of the Bees, Wasps and Ants Recording Society, said: “We welcome this research from the University of Reading. Though many beekeepers still believe that honeybees are the most important pollinators, they can only pollinate a third of crops at most, and in reality they probably only contribute to 10-15% of the work. Wild bees are the unsung heroes for our food security and so it is these species on which we need to focus our conservation efforts.”
As insect-pollinated crops are likely to become increasingly important to UK agriculture in the immediate future, the study will help direct new developments in effective pollination management at a field and landscape scale.