A study, published in the journal Applied Ecology, shows that mowing your lawn too much is not good. Researchers found that urban lawns that are mowed continuously have adverse ecological effects, primarily on plant diversity and invertebrates. Weeds and pest species benefit from intense lawn mowing. The team combined data from Europe and North America using a meta-analysis to get their results.
Lead author of the study, Dr. Chris Watson, said:
Even a modest reduction in lawn mowing frequency can bring a host of environmental benefits: increased pollinators increased plant diversity and reduced greenhouse gas emissions. At the same time, a longer, healthier lawn makes it more resistant to pests, weeds, and drought events.
The problem with mowing lawns is they cut out the dandelions, clovers, and other essential plant species. If people mow their lawns less, it will allow plant diversity to increase, which will have a knock-on effect on thriving biodiversity with organisms such as pollinators and herbivores.
In seven datasets across three studies in Canada, the researchers found that intensive lawn mowing increased lawn pests and weeds. “These findings support a lot of research done by the turfgrass industry that shows that the more disturbance a lawn gets, the higher the likelihood of pest and weed invasion,” added Dr. Watson.
Intense lawn mowing also causes common ragweed to colonize disturbances, which isn’t a good thing since its one of the most allergenic plant species found in Europe and North America. The cost of ragweed-based allergy medicine is estimated to be up to CAD$155m per year in Quebec and €133m a year in Bavaria and Austria.
Dr. Watson explained:
Certain lawn invaders, such as ragweed, can be decreased simply by reducing lawn mowing frequency. This will decrease the pollen load in the air and reduce the severity of hayfever symptoms, the number of people affected, and medical costs.
The researchers used data on mowing contractor costs from a case study of Trois-Rivieres, Quebec, Canada, to further understand the economic costs. When mowing frequency was reduced from just 15 to 10 times per year, they estimated about 36% was cut from public maintenance costs.
Some people are concerned with long grass attracting rodents and ticks. However, Dr. Watson believes otherwise. “The presence of ticks is more strongly related to host populations, like deer, than the type of vegetation. With respect to small mammals, some species prefer longer grass’ whereas others do not. The next phase of our research aims to explore these negative perceptions in more detail,” Dr. Watson said.
The team plans to expand the research and begin improving lawns by applying their discoveries to them. “We plan to conduct some larger trials in partnership with the City of Trois-Rivieres that expand the suite of pests and weeks that mowing may impact. At the same time, we would like to investigate some of the negative perceptions of less-managed lawns and start working on some community outreach to promote low-intensity mowing for healthy lawns,” added Dr. Watson.
Other researchers involved in the study, “Ecological and economic benefits of low‐intensity urban lawn management,” include Léonie Carignan‐Guillemette, Vincent Maire, Caroline Turcotte, and Raphaël Proulx.