Published on May 17th, 2018 | by Nexus Media0
Mowing Your Lawn? Skip One Week, But Not Two
May 17th, 2018 by Nexus Media
Originally published on Nexus Media.
By Marlene Cimons
Ecologist Susannah B. Lerman believes most homeowners fall into one of three groups when it comes to lawn care. Group #1 includes “lawn people,” who covet the perfect lawn and “spend thousands of dollars each year to have a lush, green, weed-free lawn,” she said. Group #2 is made up of “neighbors of lawn people,” who are clueless, but watch what their neighbors do with their lawns, and follow their lead. “They figure that they, too, should irrigate, fertilize and mow,” she said. Group #3 are those who just don’t care, and “do the minimum to keep the lawn alive,” she said.
Which group are you in?
If you picked #3, or feel like you fit somewhere between #2 and #3, then give yourself a pat on the back. Believe it or not, by not doing much, you’re doing a lot. Mowing every two weeks — instead of weekly — and not dousing grass with chemical herbicides and fertilizers, helps the environment and supports the health of bees, which are among the world’s most important pollinators.
“Group #3 can feel vindicated, and can let their neighbors know that they don’t mow frequently, because it’s for the bees,” said Lerman, a scientist with the U.S. Forest Service and adjunct professor at the University of Massachusetts Amherst, who conducted a study to see which lawn-mowing schedule was best suited for bees. The research recently appeared in the journal Biological Conservation.
“I don’t think households in group #1 will change too much, but I do think the research provides a nudge for folks in group #2 — and I think this includes a significant number of Americans, but I don’t have any data to back my hunches — yet,” she said. “The beauty of the study is that we can do something for conservation by doing less.”
Furthermore, unless you’re one of the few who still uses a manual mower, you’re also fighting climate change by saving energy, and curbing emissions of carbon dioxide, a potent greenhouse gas that contributes to global warming. The early results of another Lerman study currently underway suggest that “lawns mowed every three weeks emit significantly less CO2 [than lawns mowed more frequently], so this can be part of the ‘package’ or message to mow less,” Lerman said.
Pollinators such as birds, bees, butterflies, moths, flies, wasps, beetles and bats are critical for agriculture and food production because they transfer pollen between seed plants, affecting a vast number of the world’s crops. Moreover, they have a role in maintaining biodiversity by helping to keep ecosystems in balance.
But climate change has been disrupting the work of pollinators in recent years, especially troubling as bee habitats and populations also are continuing to decline. Bees are important pollinators and they have been suffering under a warming planet. Rising temperatures have threatened any number of bee species, including bumblebees. Shoring up bee habitats could slow this decline, and that’s where lawns come in.
While pollinators typically are found in more wild settings than lawns, Lerman’s research demonstrates “that areas previously dismissed as ‘non-habitat’ — and the loss of habitat due to urban development has huge implications for bee declines — actually support a surprising number of bees.” She added, “Lawns, when not fertilized or sprayed with herbicides, have the potential to provide habitat.” That could provide a lot of bee habitat. In the United States, lawns cover an estimated 63,000 square miles, roughly the area of the state of Florida, according to the study.
Lerman and her colleagues — including Joan Milam, also of UMass, Alix Contosta at the University of New Hampshire and Christofer Bang of Arizona State University — recruited 16 homeowners in Springfield, Massachusetts, and in 2013 and 2014 assigned each yard one of three mowing schedules: weekly, every two weeks or every three weeks. They then examined the bees’ response. The lawns were not watered or fertilized or had herbicides applied during the course of the study.
The scientists counted yard flowers — decorative flowers that homeowners avoid when mowing— and lawn flowers — weedy plants that are the target of lawnmowers. Researchers also measured average grass height and counted and identified bees. Lawns mowed every three weeks had more than twice as many weedy flowers as those mowed more frequently. Lawns mowed every two weeks, on the other hand, had the greatest number of bees, but less diversity among bee species than the other two intervals.
This finding surprised scientists, who had assumed that the longer time between mowing, the better it would be for bees. They speculate that bees have a tougher time reaching the flowers when the grass is very high. “We thought that the number of bees would match with the number of flowers,” she said. “However, the three-week yards had a lot more flowers, but also taller grass. For some of the really small bees — about the size of a grain of rice — it might have been too much effort to get to the flowers. And these small bees really dominated our study.”
Allowing dandelions, clover and other “weeds” to bloom — and not poisoning or whacking them — provides a source of pollen and nectar, two things bees need to survive, she said. “We refer to these ‘weeds’ as the unsung heroes for bee conservation,” Lerman said. “One thing we hope to do in future work is to start measuring the quality of these flowers and see how they compare to other types of flowers people plant in pollinator gardens. This will allow us to assess whether the dandelions and clover are ‘junk food.’ Other research has shown that the clover provides important food sources for bees, so perhaps the weedy flowers are ‘good enough.’”
The homeowners, for the most part, loved being in the study “but mostly, I think they loved the free lawn mowing we provided for the entire two years,” Lerman said. “The homeowners who received weekly mowing enjoyed the constant attention to their lawns, though when we arrived to mow, there were some weeks that the lawn didn’t really look like it needed a cut.” They mowed anyway to stick to the study protocol.
“The two-week yards usually looked ready for a mow and the homeowners from this group were also happy to see us,” she said. “When we arrived at the three-week yards, we had to convince ourselves that the lawns didn’t look that bad, but they did look messy. These homeowners…told us that their neighbors kept asking when the lawn was going to get mowed, or even offered to come over and mow the lawn for them, or at least dig up the dandelions. The householders resisted, proudly stated that the yard was part of a science project…All yards had lawn signs that explained the study but also — I hoped — let the neighbors know that, particularly for the three-week yards, that the ‘messiness’ was intentional.”
Lerman thinks people are obsessed with their lawns because “a lawn is considered an extension of the home and a status symbol,” she said. “The lawn or yard is a way for self-expression and how you present yourself to your neighbors.” Some spray and fertilize and mow weekly “because they think it’s expected of them to be accepted by their neighbors, and not always because that is what they really want to do.”
For these and other reasons, it may take a lot of persuasion to get them to change, she said. “But I think the bee issue is a hot topic, and really relevant, so letting society know that they can help bees might be a good message. I think stressing that they don’t have to do anything, but rather less of what they are already doing, might resonate with many.”
It certainly resonates with Lerman. “My time is precious and although I’ve dedicated my career to studying how birds and bees and other wildlife respond to the way we take care of our yards, I do the very minimum in my yard,” she said. “I don’t have time to plant a pollinator garden. And I know, for many folks, they might not have the time, the money or a green thumb for pollinator gardens. Hence the ‘lazy lawnmower’ message really speaks to me — and many others.”
Marlene Cimons writes for Nexus Media, a syndicated newswire covering climate, energy, policy, art and culture.