Vegetation management and ecosystem disturbance: impact of glyphosate herbicide on plant and animal diversity in terrestrial systems

Abstract

The conservation of biological diversity (biodiversity) is becoming an integral part of the sustainable management of forest- and agro-ecosystems. A vital part of these systems is weed control, or vegetation management, to enhance crop production. Because of its widespread use and environmental compatibility, this review was designed to evaluate glyphosate herbicide in terms of: (i) its role as a disturbance agent and (ii) a measure of its impact on species diversity of terrestrial plants and animals. Our analyses were based on 60 published studies of terrestrial plants and animals in temperate zone forest- and agro-ecosystems. Species richness and diversity of vascular plants was either unaffected or increased, particularly herbaceous species, in response to glyphosate. Responses of plant species in forest ecosystems differ from those in agro-ecosystems where glyphosate is used to repeatedly reduce non-crop vegetation in most situations. Richness and diversity of songbirds appeared little affected by glyphosate-induced habitat alteration. In studies on small mammal communities and glyphosate use, none found significant reductions in species richness or diversity. As for avian responses, some small mammal species declined temporarily whereas others increased in abundance. The impact of glyphosate on large mammalian herbivores was measured by abundance of animals and food plants and by habitat use. Hares (Lepus spp. L.) and deer (Odocoileus spp. Rafinesque and Capreolus capreolus L.) were little affected, whereas reductions in plant biomass and related moose (Alces alces L.) forage and habitat use generally occur for 1–5 years after treatment. Studies on terrestrial invertebrates covered a wide range of taxa with variable responses in abundance to glyphosate treatments. The magnitude of observed changes in mean species richness and diversity of vascular plants, birds, and small mammals, from the effects of herbicide treatment, were within the mean values of natural fluctuations of these variables. The biological significance of this impact is limited to shifts in species composition based on changes in floral composition and structure of habitats. Management for a mosaic of habitats within forest and agricultural landscapes, which provide a range of conditions for plant and animal species, should help ameliorate the short-term changes in species composition accompanying vegetation management with glyphosate.Key words: agro-ecosystems, forests, glyphosate, plants and animals, species richness and diversity, vegetation management.