Impacts of agricultural herbicide use on terrestrial wildlife in temperate landscapes: a review with special reference to North America

The existing literature was examined to assess the extent to which wildlife (plants, soil organisms, above-ground insects/arthropods, mammals, birds) living in terrestrial habitats has been affected by use of agricultural herbicides in temperate landscapes. Although North America was of special interest for regulatory reasons, the review was extended to western Europe because the most extensive and intensive work has been done there. The half-life of herbicides in the environment ranges from less than 1 month to more than 1 year. Wildlife within fields is most likely to be exposed to herbicides, particularly when fields are planted with crops (e.g. corn, soybean, wheat, cotton) which are routinely sprayed. Wildlife is also likely to be exposed in non-crop habitats adjoining croplands, primarily from direct overspray (especially during aerial application), and drift during and/or volatilisation after application. The most conclusive scientific evidence for direct effects of herbicides on arable weeds, and associated indirect effects on insects and birds exists in the United Kingdom. Evidence for similar effects in North America is primarily circumstantial at present. Little work has been done anywhere on impacts of herbicides on plants and their associated fauna in non-crop habitats adjoining treated fields. Chemical farming (in particular, the use of herbicides) has dramatically altered the habitat pattern of temperate landscapes in North America and western Europe. Strong evidence exists for adverse effects of changes in habitat pattern on beneficial insects and arthropods in the United Kingdom, and on birds in North America and western Europe. Toxicity testing guidelines for non-target plant protection need to be developed and enforced to support pesticide registration. In addition, research is needed to include more ecologically relevant plant species in laboratory tests, to develop multi-species tests (particularly in the field), to improve methods for risk assessment, and to develop options for mitigating risks. Large scale, long-term trans-disciplinary research of different farming systems is needed, particularly in North America, to integrate and better evaluate ecological, agronomic, and socio-economic costs and benefits of agricultural herbicide use in temperate landscapes.