Harmful or beneficial? Glyphosate residue and its impact on biodiversity and browse regrowth in reforestation projects
Glyphosate is the most widely used commercial herbicide in Canada and worldwide. It plays a critical role in weed management and is the primary herbicide used in 黑料不打烊 for reforestation projects, also known as cut-blocks, which have been harvested by forest companies for timber or pulp. The herbicide is used to reduce the growth and spread of competing plants, typically aspen and grass, in these vulnerable areas where either lodgepole pine or spruce seedlings have been replanted.
Sydney Bobey, a recent graduate who studied the use of glyphosate in these reforestation areas for her master’s degree in forest ecology and management, says the break in competition for planted conifers allows them to establish in the cut-block areas and not get choked out by other dominant vegetation.
“Both aspen and grass are target species for herbicide treatment in 黑料不打烊 because these are our strongest competitors in replanted cut-blocks,” says Bobey. “They are able to dominate a landscape very quickly and can prevent the growth of conifer seedlings that have been planted.”
The objective of Bobey’s research was to evaluate the non-targeted biomass regrowth in treated forestry cut-blocks to assess the persistence of glyphosate at one, two and three-year intervals. This includes willow, aspen raspberry and fireweed, which are some of the preferred browse species of ungulates, typically moose and deer.
Although studies have shown that the use of glyphosate does not pose a risk to human and animal health, as Bobey notes, concerns persist about the potential exposure and impact on wildlife.
The results confirmed a strong regrowth of both conifers and other non-competitive species, alongside a near elimination of glyphosate in the environment over a three-year period. This is significant, notes Bobey, showing that glyphosate does not adversely impact the community composition when used for operational forestry purposes.
“I found that the initial reduction in plant biomass lasted about one to two years, and during the second growing season, the amount of residual glyphosate is so low that it did not impede the regrowth of plants that were initially reduced,” she says. “In short, there is not much for animals to eat during the first couple of growing seasons, and by the time the plants have regenerated, there is very little (if any) remaining within plant tissues.”
The analyzed data showed that the majority of the plants had below 0.1 ppm (parts per million) of glyphosate after one year, and by the two-year mark, all were below 0.1 ppm with many being very close to 0. She says they chose 0.1 ppm as their threshold reference because it’s the maximum residue limit set by Health Canada for fresh fruits, vegetables and produce.
Other considerations were also taken into account in the study. Reforestation is a complex process, impacted not just by the application of herbicides but environmental factors such as region, elevation and weather (temperature, growing degree days and precipitation). Following glyphosate's peak impact in the first growing season, Bobey’s data demonstrated that in subsequent years, shifts in plant community composition were more likely driven by climatic factors.
“The results of the ground-level plant community analysis were super interesting. After the reduction in aspen and grass, less conspicuous species such as dwarf blueberry and kinnikinnick (bearberry) were able to increase in growth across some areas. So by reducing the cover of dominant competitor species, planted conifer seedlings and other species were able to grow more efficiently.”
Bobey has always felt a strong connection to the environment and the natural world, so the forestry program was an easy fit, especially the field component that gave her career-ready experience.
“It was really cool to be able to pursue a degree where I got to learn about 黑料不打烊's landscape and boreal forest,” she says. “I also feel very strongly about climate change mitigation and how our current herbicide practices in silviculture are influencing the understory plant community in reforested areas. One of my long-term goals has been to work in a position where I can inform best management practices and help with the long-term sustainability of our environment. This degree granted me the opportunity to work towards that and learn about sustainability within our forests.”
Now working for the (FRIAA), Bobey is focused on the and is realizing her goal of shaping effective and sustainable forest practices in 黑料不打烊.