Authors of a new study are critical of government use of herbicides on federal lands in North America, finding that over 201 tonnes of herbicide were sprayed on federal wildlands in the United States in 2010, which covered an area of over half a million hectares.
“The numbers are much less than those for croplands, but they are astonishing,” says Viktoria Wagner from the University of Montana’s Department of Ecosystem and Conservation Sciences. “Imagine: the wildland area sprayed by herbicides in that year is comparable to 930,630 football fields, and the amount of herbicides used equals the weight of 13 school buses.”
Commonly used to control the spread of invasive non-native plant species on public wildlands (non-crop oriented and non-urban areas such as forests, wetlands, roadsides and power line corridors), herbicides have now become the go-to approach for public land management. In comparison to mechanical or biological methods, herbicides are easy to apply and come relatively cheap, and while modern chemical herbicides have been vetted for safety by government agencies, their ongoing impacts on ecological systems -including their effects on human populations- are less understood, according to the study’s authors.
Which makes the current lack of available information on their widespread use in Canada all the more distressing.
While the research team, hailing from the University of Montana, Algoma University in Sault Ste. Marie, Ontario, and the Ontario Ministry of Natural Resources and Forestry, aimed at tracking the use of herbicides on federal lands across Canada, the U.S. and Mexico they quickly ran into the problem that very few government agencies in the three regions regularly keep records on herbicide use, quantities used, their efficacy as well as their financial costs. Five out of seven agencies in the United States were able to provide the researchers with data, but none in Canada, where numbers are kept on cropland herbicide use but not for use on wildland regions, say the researchers, with the blame falling on the lack of proper coordination at the national level.
“According to our survey, herbicide usage data have not been tracked for Canada, at either the provincial or national level,” say the study’s authors. “This finding likely reflects the fact that Canada currently lacks a single comprehensive legislative framework on invasive species management.”
The authors see access to this type of information as crucial for a wide range of stakeholders, ranging from land managers, public groups, scientists and pesticide manufacturers. “By archiving and sharing usage, monitoring and financial cost data in a standardized way, agencies would allow scientists, land managers and stakeholders to assess herbicide efficacy and impacts and make inferences about its suitability as a management tool, as well as to share information.”
In Canada, publicly owned lands account for 89 per cent of the country’s area, with 323 million hectares of it covered in forests. An estimated 60 per cent of Mexico is federally owned while 30 per cent of the United States is public land.
The new study appears in the Journal of Applied Ecology.