The review, funded by the Department of the Environment (DoE) and English Nature, was carried out by a consortium including Oxford University, the Institute of Terrestrial Ecology, Plantlife and the Royal Society for the Protection of Birds (RSPB). Their report, a summary of which was released in May,1 will shortly be published in full by the Joint Nature Conservation Committee.
The researchers studied population trends over the past 20-30 years for some 40 bird species which breed on farmland. 24 species were found to have declined. Worst affected were the tree sparrow, grey partridge, turtle dove, bullfinch, song thrush and spotted flycatcher, each of which have declined in abundance by more than 70%. Lapwing, skylark, linnet and reed bunting each declined by over 50%.
The report reveals the steadily increasing intensity of pesticide use. In 1975, only a tiny proportion of the total area of cereal crops was sprayed with insecticides, but this rose to 90% by 1990. Herbicides were used on about 140% of crops in 1975, but this rose to 250% by 1975 - implying that each crop was sprayed on average 2.5 times. Over the same period, the use of fungicides rose even more dramatically from 20% to 300%.
The report attempts to link the date at which declines in each bird species began with trends in pesticide use. For 11 of the 12 species for which data are available, it concludes that there is an association or possible association with increased pesticide applications.
Although this is far from evidence of a causal relationship, the findings were supported by detailed studies on the impact of pesticides on bird numbers and food species. One study found that reductions in species of food insects were associated with intensive pesticide use. Another found that skylarks were more abundant and produced more young on organic farms than on conventional ones. Long-term studies of grey partridge in Sussex have also found that the survival of young birds is reduced by the impact of insecticides and herbicides on food species.
In the case of the grey partridge, the report concludes that the indirect effects of pesticides are "a major factor in population declines." For the other 11 species, it concludes that pesticides "cannot be ruled out" as a major factor on the basis of the birds' diet and ecology, and because of the timing of the declines.
To encourage bird populations, the report recommends minimising pesticide use through integrated crop management and greater use of pest-specific products which have less impact on non-target species. It also supports a switch to organic farming methods or the less intensive methods used several decades ago.
The RSPB used the launch of the report to call for tougher controls on pesticides and a change in agricultural policy to support farming methods which encourage wildlife. "We want to see pesticide products that are more specific to pests and a move away from broad-spectrum products," the RSPB's agricultural policy officer, Jonathan Curtoys, told ENDS. To promote this, the RSPB suggests taxing pesticides according to their environmental impacts - increasing the price of older, broad spectrum products which tend to be relatively cheap.
The RSPB also wants to see more of the £3.6 billion given to farmers in support payments channelled into environmental farming schemes, which presently attract only 3% of funding. And it has proposed a target to convert 5% of UK agricultural land to organic farming within five years, compared with 0.3% today.
In common with the report, the RSPB did not recommend the application of "comparative assessment" - a principle incorporated in the draft EC Directive on biocides (ENDS Report 257, pp 39-41 ). Using this principle, products would be withdrawn from sale if other products, or alternative methods of pest control, were available which presented lower risks to the environment.
A spokesman for the DoE said that it was unable to comment on the prospect for new controls on pesticides in view of the change of Government and a likely review of many policy issues.