Well, I have just watered the
garden as it has been so dry lately, The cherry tree is covered in blossom and,
normally, would be literally be buzzing - covered in honey bees and bumbles.
Last year, we had hardly any cherries as the strong winds quickly
blew
away all the blossom and the bees had virtually no time to do their job
hence - practically no fruit! This year the winds are soft at present,
the blossom is out, the sun
is shining and over the last couple of hours I have seen one fat bumble
and one
small bee on the whole tree, and at the moment, NONE!
A EU ban on the neonicotinoid pesticides thought to harm bees is good news, despite British reluctance, says biologist Dave Goulson a biologist at the University of Sussex in Brighton, UK. His new book on bumblebees, A Sting in the Tale, has just been published.
“Yesterday the European
Commission decided to impose a ban on the use of neonicotinoid pesticides in
the European Union. These chemicals will now be banned for two years for crops
that attract bees. All EU nations, even the UK and the others that voted
against this move this week, must impose the ban by December this year.
I was very sceptical when I was
first asked to support such a ban. The idea is that neonicotinoids – a family
of pesticides designed to kill crop pests such as aphids – are responsible for
the worrying decline
in bee numbers over the last decade or so.
Having previously been asked to
sign up for campaigns claiming that the bee problem was due to mobile phones,
genetically modified crops, overhead power lines, and various other eccentric
or implausible notions, I suspected that the neonicotinoid hypothesis was just
the latest on the list. However, a review of the science suggested that there
was something worth investigating.
The issue has focused largely on
harm the neonicotinoid chemicals clothianidin, imidacloprid and thiamethoxam
might be doing to bees, both domestic honeybees and wild pollinators such as bumblebees.
Neonicotinoids are widely
applied as a seed dressing to crops such as oilseed rape, and being systemic
they spread through the plant into the nectar and pollen. They are highly toxic
to insects: for example the "LD50" – the dose that kills half of test
subjects – in honeybees is about 4 billionths of a gram.
To put that in context, 1 gram –
little more than the weight of a sachet of salt – would provide an LD50 to 250
million honeybees, or roughly 25 metric tonnes of bee. They are neurotoxins,
binding to neural receptors in the brain and causing swift paralysis and death.
Until recently, there had been
few studies of the effects
of neonicotinoids on my own specialism, bumblebees. All were small scale
and nearly all performed in cages or glasshouses. Taken together, they seemed
to suggest that exposure to very low levels, such as might occur when a bee fed
on a treated oilseed rape crop, was not sufficient to kill many bees, but it
seemed to affect their behaviour, particularly their ability to learn, gather
food and navigate.
None of the safety tests on
which pesticides are judged fit for use assess these abilities. What is more,
they are likely to be much more important in the field than in small-scale test
environments: in the open, bees perform astonishing feats of navigation and
learning when gathering food from flowers. It seemed to me, and to other
researchers around the world, that there was a need to study what these
sublethal effects might be doing to bee colonies in natural situations.
We carried out our
investigations in 2011 and published
them last year (Science,
DOI: 10.1126/science.1215025). We exposed bumblebee nests to the
concentrations of neonicotinoids found in the pollen and nectar of oilseed rape
for two weeks, and then placed the nests out in the field to see how they fared
compared with control nests. Over the next six weeks the treated nests grew
more slowly, and ultimately produced 15 per cent as many new queens.
Since our study, work from other
labs has confirmed that field-realistic
doses greatly reduce pollen collection in bumblebee workers, potentially
explaining why our treated nests performed poorly. It has also been found that
concentrations of neonicotinoids as low as 1 part per billion in their
food cause a drop in egg-laying in bumblebees of 30 per cent. Considerably
higher concentrations than this have been found in the pollen of treated crops.
For bumblebees, the evidence so
far is convincing and coherent: exposure to levels of neonicotinoids commonly
found in crops profoundly damages colony success. The only study that appears
to contradict this was recently placed online by the British government's
Department for Environment, Food and Rural Affairs. It describes a study
the department conducted last year in which it attempted to repeat our work
but with the pesticide exposure phase of the experiment occurring in the field.
The researchers placed bumblebee
nests next to the only untreated field of oilseed rape they could find, and
next to two other fields treated with two different neonicotinoid pesticides,
and followed the colonies over time.
However, the experiment had
shortcomings that make the conclusions unreliable. There was only one example
of each condition – the untreated field and the two treated fields – and,
disastrously but interestingly, the control nests all became contaminated with
the pesticides. The summary of this report claims the study shows no clear
effect of neonicotinoids on bumblebee colonies: that is hardly surprising,
given the absence of any controls, and it is hardly the sort of evidence one
would wish a government to base its policies upon.
Perhaps the most valuable lesson
to be learned from this work is that bumblebee nests placed in the landscape
become contaminated with multiple types of these chemicals, even on farms where
none is used. Many of the nests had concentrations of neonicotinoids higher
than 1 part per billion, and most had detectable levels of at least two
different types.
While the debate so far has focused
on bees, there are broader issues to consider. These chemicals last in soils
for a long time, and evidence has recently emerged that they accumulate over
time (PLoS
One, 10.1371/journal.pone.0029268). This is likely to be enough to
affect soil life profoundly.
It has also emerged that the
chemicals get into vegetation around fields and into streams and ponds (Bulletin
of Environmental Contamination and Toxicology, DOI:
10.1007/s00128-011-0515-5). A concentration of just 6 parts per 10 billion
is enough to kill mayfly nymphs. It may be that we have missed the bigger
picture of harm that is being caused.
A common argument in favour of
neonicotinoids is that they provide economic benefits, and that alternative
pest-control methods are worse. But studies from US, for example, show that
yields of soya bean do not benefit at all from dressing seed with
neonicotinoids, despite this being standard practice (Journal of Economic
Entomology, DOI: 10.1603/ec11429). Sadly, similar experiments in the UK
have not been conducted. Given that farmers get most of their technical advice
from pesticide companies, it is reasonable to suppose that a good proportion of
UK pesticide use may be unnecessary.
The European Food Safety Agency
spent six months evaluating the evidence and concluded that current use of
neonicotinoids poses unacceptable risks. The British parliament's Environmental
Audit Committee agreed. Numerous non-governmental organisations, including the
Royal Society for the Protection of Birds, which is normally very cautious,
followed suit. What was once a radical stance is now where the vast majority of
informed opinion lies; but the British government stands apart.
However, after yesterday's
European Commission decision the British government will have to implement the
moratorium nevertheless. Perhaps this imposed mass field trial will finally
provide the evidence to convince it and other doubters to accept the growing
signs that neonicotinoids are at least partly to blame for the decline of our
most vital pollinators.”
Correction: When this article was first published, a different
study concerning neonicotinoid persistence in soils was mentioned.
