Does farm pesticide use harm UK birds?
We recently funded research carried out by Professor Goulson and his team (Cannelle Tassin de Montaigu and Priyesha Vijendra) at University of Sussex into whether modern pesticide use (of which there are 300 different ‘active substances’ in use) is contributing to the ongoing decline of farmland birds.
Fig 1: Farmland birds decreased by 50% in last 50 year
Fig 2: Weight of pesticides decreased by 51% from 1990 - 2016, but the area treated increased by 63%
Pesticides could harm birds directly and indirectly..
Fig 3: Directly by poisoning birds
Fig 4: Indirectly via depleting food supplies (e.g. insects)
To ascertain the risk, the University analysed UK patterns of pesticide use since 1990 using data collected by Defra, and calculated changes in the ‘toxic load’ to birds (a measure of the total number of birds that could, in theory, be killed if all the pesticides used in farming were fed to them, using corn buntings as the reference species).
Overall toxic load due to insecticides, herbicides, fungicides and ‘other’ pesticides all decreased over time, partly due to EU bans and restrictions on organophosphates and some other pesticides.
Fig 5: 80% reduction in toxic load between 1990 and 2016
Organophosphates (which are no longer used) were very poisonous to birds, whereas the neonicotinoids are less toxic to birds, but much more toxic to insects.
Thus the risk of birds being directly poisoned may have dropped, but the risk that insect-eating birds might starve is likely to have gone up.
Although the data looks positive, new generations of active substances increased in weight used, including,
Fig 6: 109 pesticides increased in terms of the weight applied, and toxic load
Although they are not highly toxic to birds, weight for weight, they are used in large and steadily increasing quantities, and hence exposure to birds is likely to be high and growing.
Ethoprop was ranked highest in 2016 with a toxic load of 71 billion potential corn bunting kills, followed by chlormequat
Fig 7: Chlormequat had second highest toxic load
Fig 8: Ethoprop now banned in EU
The University team is now planning a second in the field phase of the study to investigate exactly which pesticides turn up in feather samples from wild birds, to understand what harm (if any) they might be doing.
To read more about this study, visit ‘PeerJ’ for open access: https://peerj.com/articles/9526/