Researchers at the University of Manitoba have published two articles outlining potential benefit to native butterflies and birds to be reaped from modification of existing mowing and herbecide regimens in utility corridors.
The articles, derived from a field observations of 48 Manitoba Hydro right-of-ways in and around Winnipeg from 2007-2009, were published last January and August in Landscape and Urban Planning and Avian Conservation and Ecology, respectively.
Right-of-ways below transmission lines are generally maintained by Manitoba Hydro through frequent mowing, spraying of herbicides, vegetation and debris clearing in order to control vegetation height, for aesthetic appeal, and as a safety measure.
The lead scientist, Lionel Leston, who currently resides in Alberta, was a Ph.D. student at the time of the study.
Leston and his research assistant, U of M professor Nicola Koper, conducted population counts of native bird and butterfly species present, while noting factors such as the presence of native plant species.
“I was interested in how the mowing regime along transmission lines and surrounding land uses – like the amount of urban land – how they interacted to influence the diversity and abundance of species along transmission lines, and whether or not urban transmission lines might be managed as habitat for different species,” Leston said.
The article focused on birds is thought to be the first urban bird study to evaluate different effects of urban landscapes on bird species that looks beyond traffic and noise as potential factors.
There has been a general decline of grassland bird species populations in North America. The authors of the study note that long-term changes in land use, including increases in land devoted to agriculture and urbanization, are all probable causes of grassland bird decrease linked to destruction of habitat.
“We’ve been really concerned about the loss of tallgrass prairie habitat across Manitoba,” Koper said. “Manitoba has lost more than 99 per cent of the tallgrass prairie that was here before.”
The studies suggests that managing urban grassy areas such as those below transmission lines could help alleviate this decline.
“[Professor Leston] found that if you reduce mowing from twice a year to once a year, we got quite an improvement in the diversity of a range of different species,” Koper added.
“And so that’s something that could be done that would save Hydro money but could still accomplish their goals: you could keep the woody vegetation down with mowing once a year.”
For birds, counting was done three times every summer from 2007 to 2009 to measure populations.
The study suggests that efforts to increase grassland bird populations in urban areas should be concentrated on areas with little adjacency to shrubland and forests, on which the mowing regimens can be adjusted.
The study further notes that mowing on the selected lands should be adjusted to suit grassland birds.
Speaking to the potential societal benefits of implementing the study’s findings, Leston said they extend beyond simply cost-saving measures.
“There’s the potential environmental benefits of reduced noise pollution,” he said, “because you’re not mowing so much, reduced chemical pollution because you’re not spending as much money spraying as much herbicide or using as much fuel in mowing and spraying.”
