Glyphosate-based herbicides (GBH) are commonly applied to many outdoor environments and are widely used in agriculture and forestry. Scientists have now suggested that these herbicides can linger in plants and may have deleterious impacts on their health. The work, which was reported in Frontiers in Plant Sciences, showed that a year after GBH was applied, there were deformities in reproductive parts of a plant called prickly rose (Rosa acicularis).
In this study, the researchers gathered GBH-treated samples of prickly rose from both greenhouse-grown wild plants and 'cutblocks' from natural areas where these plants compete with conifers growing in commercial harvesting operations, as well as untreated prickly rose from different places.
The work showed that one year after the applications of GBH, the pollen viability of glyphosate-treated plants went down 66 percent on average compared to untreated controls. Over 30 percent of a part of the plant that contains pollen, called the anthers, did not open up, and these flowers became functionally infertile. There were also color changes that may disrupt their interactions with pollinating insects. There were still traces of GBH on these plants two years after the initial application.
"The changes to plants have been documented in the past, in agricultural plants, so it is not surprising to find them in forests," said Dr. Lisa J. Wood, an assistant professor in the Department of Ecosystem Science and Management at UNBC. "What is important is the timeline. To continue to find these effects one to two years after herbicide applications, in new parts of growing plants, is noteworthy."
Honeybees are attracted to prickly rose plants, so they may be impacted by GBH traces. Glyphosate has been in use since the 1970s but concern is growing about its safety, and the carcinogenic impacts it might have on humans.
The researchers are planning to continue this work; they want to know whether GBH-induced color changes in the plants actually do reduce the interest pollinators have in them. They also want to determine whether insects and hummingbirds carry glyphosate residues.
"This will tell us if pollinators are taking up residues from the plants they feed on," Wood explained. "We will also research other plants to see if the changes we observed in the wild rose are also found in other flowers."
Research has suggested that glyphosate isn't acutely toxic to most organisms at levels that are typically used in Canada, but we still don't know much about what the long-term effects of glyphosate use may be, or how it alters the natural environment.
"The more we learn the better, and research can always be used to better inform management," Wood noted. "Herbicide practices may change if the research shows that this is in the public's best interest."