Wild bee declines have been ascribed in part to neonicotinoid insecticides. While short-term laboratory studies on commercially bred species (principally honeybees and bumblebees) have identified sub-lethal effects, there is no strong evidence linking these insecticides to losses of the majority of wild bee species. We relate 18 years of UK national wild bee distribution data for 62 species to amounts of neonicotinoid use in oilseed rape. Using a multi-species dynamic Bayesian occupancy analysis, we find evidence of increased population extinction rates in response to neonicotinoid seed treatment use on oilseed rape. Species foraging on oilseed rape benefit from the cover of this crop, but were on average three times more negatively affected by exposure to neonicotinoids than non-crop foragers. Our results suggest that sub-lethal effects of neonicotinoids could scale up to cause losses of bee biodiversity. Restrictions on neonicotinoid use may reduce population declines.

Chronic exposure to neonicotinoid insecticides has been linked to reduced survival of pollinating insects at both the individual and colony level, but so far only experimentally. Analyses of large-scale datasets to investigate the real-world links between the use of neonicotinoids and pollinator mortality are lacking. Moreover, the impacts of neonicotinoid seed coatings in reducing subsequent applications of foliar insecticide sprays and increasing crop yield are not known, despite the supposed benefits of this practice driving widespread use. Here, we combine large-scale pesticide usage and yield observations from oilseed rape with those detailing honey bee colony losses over an 11 year period, and reveal a correlation between honey bee colony losses and national-scale imidacloprid (a neonicotinoid) usage patterns across England and Wales. We also provide the first evidence that farmers who use neonicotinoid seed coatings reduce the number of subsequent applications of foliar insecticide sprays and may derive an economic return. Our results inform the societal discussion on the pollinator costs and farming benefits of prophylactic neonicotinoid usage on a mass flowering crop.

Summary1. In response to reported increases in badger numbers and associated agricultural damage, a questionnaire survey of 3600 land owner/occupiers was conducted in 1997 to determine the extent and signi®cance of badger damage in England and Wales. We assess the signi®cance of badger-induced damage and highlight problem regions, farm types and speci®c crops to allow targeting of future research eorts at amelioration. (This survey investigated alleged badger damage to agriculture but did not address the role of badgers in the transmission of bovine tuberculosis.) 2. The return rate of the questionnaire was 55´1% (n = 1982) and 150 of the responses were ground-truthed. 3. Almost 30% of those land owner/occupiers who responded reported that badger damage had occurred in the previous 12 months, and 57% reported an increase in damage during the past 5 years. 4. Badger damage was widespread, but its incidence was highly dependent on region and farm type. The most frequently reported damage (25´5%) resulted from badgers' burrowing activities (especially those causing damage to fences). Crop damage was also frequently reported (21´2%), with wheat, forage maize and vines being damaged most frequently. 5. Ground-truthing showed that incorrect attribution to badgers of damage was negligible and that the majority of respondents had assessed correctly the extent and cost of badger damage, except for predation on livestock where most`evidence' was circumstantial. 6. Most reported damage was of little economic consequence to individual land owners/occupiers; however, approximately 5% estimated that they had incurred costs of over £1000. 7. Assuming that the questionnaires returned were a random subset of those distributed, the mean estimated national cost was £41´5 million per annum (62% of which was due to burrowing activity). Assuming that all the non-respondents had no damage, the estimate was £21´5 million per annum. 8. Future research into management options for damage limitation should be targeted at the areas and situations of most signi®cant damage. These are primarily burrowing damage and direct crop damage to wheat, maize, vines, fruit and vegetables. The region suering the most intense damage was the south-west of England. The highly seasonal nature of the damage to some crops will allow preventative action to be taken at the most appropriate times. Predation by badgers on livestock is considered a small-scale and unproven problem.

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