14-1190b-innovation-managing-risk-evidence

CASE STUDY
NEONICOTINOID INSECTICIDES AND INSECT POLLINATORS
Charles Godfray and Angela McLean (University of Oxford)
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Neonicotinoids were introduced in the 1990s
and now make up about 30% by value of the
global market in insecticides. They can be
used in different ways, but most commonly they are
applied as seed treatments, with the insecticide being
taken up systemically by the growing plant. Because
the compound is present in all plant tissues, it is
potentially very effective in reducing the damage done
to crops by insect pests. However, the presence of the
insecticide in pollen and nectar raises the possibility
that neonicotinoids may harm populations of beneficial
insects such as bees and other pollinators. This is
a particular concern, because there is evidence
that pollinator populations have declined in
Europe over recent decades.
A series of studies 1 which found
that bees suffered harmful, sublethal
effects after foraging on
treated flowering plants prompted
the European Commission to
ban the use of neonicotinoid seed
treatments for flowering crops
for an initial period of two years starting in
December 2013. But there is controversy over
whether this ban is justified by the
strength of the underlying evidence
base.
The debate over
neonicotinoids
highlights a number
of issues concerned with
making decisions in the face of
uncertainty, particularly concerning
environmental questions.
1. Policymakers need to know whether this
type of insecticide reduces pollinator densities
in real agricultural landscapes. But the answer to
this question requires large and expensive field
experiments, at spatial scales that reflect agricultural
practice and bee foraging distances. Carrying out
such experiments is not currently required for
insecticide registration, and as a consequence
few have been conducted.
2. In the absence of these large-scale field
trials, data on the toxicity of different
compounds chiefly comes from laboratory
experiments and so-called semi-field
studies, which typically involve administering known
doses of the insecticide to pollinators in the field.
Experiments with neonicotinoids clearly show they
can harm individual pollinators, but the most severe
sub-lethal effects occur when insects are exposed
to concentrations higher than they are likely to
receive as a result of routine agricultural practice.
Less severe effects can be observed at more realistic
concentrations, but whether these are bad enough to
affect pollinator population densities is much less clear.
3. Because the evidence base is limited,
different policy conclusions can be drawn
depending on the importance given to
avoiding any potential negative effects of
low-dose exposure to different
compounds or combination of
compounds.
4. It is unclear what farmers
will do without recourse to
neonicotinoids, and how this
might affect pollinators. Will they use less
insecticide overall, or switch to potentially
more harmful chemicals? Might they grow
fewer crops that benefit pollinators? How
should these behavioural and economic factors
be included in policy formulation?
5. Recently, a new area of debate has opened up.
A number of non-governmental organizations have
argued that the evidence base for neonicotinoid
effectiveness is small and dominated by industryfunded
studies, and that farmers are subject to
intense marketing to buy insecticides. Industry
responds that there is no other source of funding
for this type of study, their experiments are of high
quality, and that farmers are sophisticated customers
for different agrichemical products. Would all sides
gain from greater openness in the way industry
studies are set up and reported?
6. Finally, neonicotinoids are only one of
several potential explanations for the loss of
pollinators, chief among them being habitat
loss. Could there be a danger that the policy
focus on one threat might lead to reduced
attention being paid to more important
factors?