Conservation Note
Matt Shardlow on neonicotinoid insecticides
The chief executive of Buglife on a class of systemic insecticide, what it does beyond its target, and why invertebrate declines are so poorly monitored.
Matt Shardlow is chief executive of Buglife, the invertebrate conservation trust. This conversation was about neonicotinoid insecticides and the evidence then accumulating about their effects.
Neonicotinoids are systemic: applied as a seed treatment, the compound is taken up by the growing plant and distributed through its tissues, including pollen and nectar. That is what makes them effective, and it is also what makes their effects difficult to contain: the insecticide is present in the plant rather than on it, for the life of the crop, and reaches insects that were never the target.
The discussion covered what the compounds are, the evidence on pollinators and on aquatic invertebrates in watercourses receiving run-off, and the sub-lethal effects that a mortality-based assessment misses entirely. An insecticide that does not kill a bee outright but impairs its navigation removes it from the colony just as effectively, and a regulatory test that counts corpses will not detect that.
Underlying all of it is a monitoring problem. Invertebrate populations are poorly surveyed almost everywhere compared with birds or mammals, so declines are frequently established retrospectively, from the few long-running datasets that exist. A decline nobody was measuring is difficult to attribute and easy to dispute.
The scale of that gap is easier to feel with an example. Britain has around 250 species of bee, most of them solitary and most of them unrecorded by anyone who is not looking for them on purpose; the account of a common furrow bee is about one of the commonest, on ground most people walk over. Sub-lethal effects on a species like that would be invisible for years, not because the effects are subtle but because nobody counts the bee.
Buglife publishes current work on neonicotinoids and on invertebrate declines more broadly. The regulatory position in the UK and EU has moved substantially since this was recorded.