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.

What are the Environmental Consequences of Using Silviculturally Effective Forest Vegetation Management Treatments?

“…The use of treated sites by moose and deer generally remained unchanged or even increased during the first growing season after treatment, but after eight years browse was three to seven times more abundant in herbicide-treated sites (depending on herbicide chemistry, formulation, and rate). The short-term effects of herbicide application on browse and cover may indirectly reduce populations of moose and deer, but in the long term, treated sites may have more browse and bedding available (Sullivan and Sullivan 2003). Few, if any, long-term deleterious effects on large mammals are attributed to forest herbicide applications Sullivan 2002, NCASI 2009).…”

Are chemical or mechanical treatments more sustainable for forest vegetation management in the context of the TRIAD?

“…This phenomenon is normally very favourable for tree seedling growth, but in certain cases the new vegetation composition enhanced competition (Horseley 1988, Groninger et al 2004). However, in most situations herbicide application has a greater impact on relative species dominance than on species composition or diversity (Boyd et al 1995, Miller et al 1999, Sullivan and Sullivan 2003. In other words, community structure is the main parameter affected by a chemical treatment.…”

“…In other words, community structure is the main parameter affected by a chemical treatment. Sometimes, species richness and diversity of vascular plants can be increased, particularly herbaceous species, after a glyphosate treatment (Sullivan and Sullivan 2003). On the other hand, chemical control of woody plant for several years can decrease species richness over time despite the initial enhancement of herbaceous diversity (Miller et al (2003).However, repeated treatment has less influence on herbaceous species richness than woody plants (Balandier et al 2006).…”

Plant Community Diversity and Tree Growth Following Single and Repeated Glyphosate Herbicide Applications to a White Spruce Plantation

“…While short-term reductions in total vegetation cover are typically observed following herbicide treatments, several studies show that a single application of glyphosate in boreal spruce plantations can either increase or have no effect on plant community diversity [8][9][10][11][12][13]. However, these studies generally report decreases in woody cover and increases in herbaceous cover following herbicide treatments.…”