Toxicity, transport, and fate of forest herbicides

Abstract

Public opposition to use of herbicides in forests typically centers around concerns over potential toxicity to wildlife. Characterization of the risk of silvicultural herbicides to wildlife requires an understanding of herbicide toxicity and environmental fate and transport. The fate and chemistry of herbicides and adjuvants within environmental media determine how and which organisms may be exposed and duration of those exposures. The nature of the toxicity of herbicides, adjuvants, and their decomposition products, and levels at which those toxic responses may be observed, determine which organisms or life stages may be most susceptible to any toxic effects and which exposure concentrations and durations can be considered safe. In general, herbicides most commonly used for vegetation management in forestry (glyphosate, triclopyr, imazapyr, sulfometuron, metsulfuron methyl, hexazinone) degrade quickly once they enter the environment and thus are neither persistent nor bioaccumulative. Because modern herbicides have been designed to target biochemical processes unique to plants, they exhibit a low level of direct toxicity to animals. When used according to label instructions, modern silvicultural herbicides pose little risk to wildlife.

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

“…However, herbicides such as hexazinone and glyphosate are strongly adsorbed onto soil or organic particles in the upper organic layer, minimizing their opportunity to enter water either as runoff water or through subsurface flow (Roy et al 1989a,b;Tatum 2004 …”

Understanding First Nations rights and perspectives on the use of herbicides in forestry: A case study from northeastern Ontario

“…In addition, government agencies rely on the abundance of science suggesting that concerns about negative impacts on human health and the environment are largely unwarranted when registered herbicides are used according to label instructions (Thompson et al 1991, Lautenschlager and Sullivan 2002, Tatum 2004, Swift and Bell 2011. However, from the First Nations viewpoint, this reasoning appears to be dismissive, disrespecting First Nations rights, experiences, and views, and is simply interpreted as a defensive measure to justify herbicide use because it is the most efficient (i.e., least cost) to control competing vegetation.…”

“…These reactions restricting herbicide use in forestry have persisted despite efforts to mitigate the aerial application of herbicides (Thompson et al 2010(Thompson et al , 2012, and an abundance of science suggesting that concerns about negative impacts on human health and the environment are largely unwarranted when registered herbicides are used according to label instructions (Thompson et al 1991, Lautenschlager and Sullivan 2002, Tatum 2004, Swift and Bell 2011.…”

Weeds in Forestry and Possibilities of Their Control

“…In general, herbicides most commonly used for vegetation management in forestry (glyphosate, triclopyr, imazapyr, sulfometuron and etc.) degrade quickly once they enter the environment and thus are neither persistent nor bioaccumulative (Tatum, 2004). Forest herbicides persist short term in the environment, and have few toxic effects when operationally applied following herbicide labels (Guynn et al, 2004).…”