By Elizabeth Sellors, Master Gardener
North American’s love affair with lawns is a recent development in the human history of altering our environment. Lawns became the hallmark of homeownership in the 1800’s when North American home owners began to copy the 18th century idea of landscaping with vast swaths of green turf commonly associated with English country estates. North Americans’ dream was to attain a patch of perfectly manicured bright green, lush grass attached to their homes. And, not just any grass but a singular type of grass, weed-free, not a hair over one-and-a-half inches tall and neatly edged. Lawns came to represent shared ideals, collective responsibility and conformity.
The ubiquitous North American lawn is attained at significant expense. The volume of resources required to maintain lawns is staggering. They require more equipment, labour, fuel, water and use more agricultural toxins than industrial farming. It is estimated that collectively North American home owners invest some $60 billion a year in the turf grass industry through lawn care products and contracted lawn care services. Maintaining lawns is incredibly time consuming. An estimated 54 million U.S. homeowners mow their lawns every weekend. That equates to approximately 22 times each year, spending more than three million hours pushing or riding their lawnmowers. One might assume that this devotion is a labour of love, were it not for a survey conducted on lawn care practices that found 58% of US home owners dislike mowing their lawns.
Doug Tallamy, professor of Entomology and Wildlife Ecology at the University of Delaware, has condemned lawns, calling them a status symbol that has gone on too long. Tallamy notes that the total area of lawn in the US today equals the size of New England. If you include home properties, parks, greenways and golf courses that equals 2% of the continental US. Lawns are such a major component of North American culture that in controlled neighbourhoods, homeowner associations dictate lawn care with fines being levied if lawns are not maintained to strict guidelines.
Turf grass is the largest irrigated crop in the US, something environmental scientists have declared unsustainable. Doug Tallamy has proposed a partial solution to help home owners transition to more sustainable properties. He suggests cutting existing lawns in half, devoting half to grass and the other half to native plants, shrubs and fruit trees as a way of reducing pollution, improving human health and providing habitat for wildlife. An added bonus: freeing-up time devoted to mowing grass.
The principal piece of equipment necessary to maintain a lawn is the lawn mower. It was invented in the 1800’s by English engineer Edwin Budding. The first versions were pulled by animals. Next came steam powered mowers. Today, there are four types: gasoline, electric, reel and robotic. The preference of most home owners is the gas-powered mower. They tend to be more durable and can go a long distance on a tank of gas, a bonus if you have a large yard. But, gas powered mowers are, to quote writer James Fallow: “Vastly non-fuel-efficient because, by their design, they slosh together a mixture of gasoline and oil in the combustion chamber and then spew out as much as one-third of that fuel as an unburned aerosol.”
Statistics indicate that gas lawn mowers contribute 5% of all air pollution in the U.S. American home owners use 800 million gallons of gas annually to cut their lawns. Operating a typical four-stroke, four-horsepower gasoline lawn mower for an hour is estimated to produce the equivalent emissions of hydrocarbons to that of driving a newer mid-sized car 93 miles. Older two-stroke gas lawn mowers are worse, with about 30% of engine fuel failing to undergo complete combustion, resulting in higher levels of pollutants. Volatile organic compound emissions from 2-stroke engines are about 124 times higher than from cars and pick-up trucks. In addition to creating considerable pollution during use, their proximity to people means potential health risks. Compared to electric lawn mowers, four-stroke gas powered mowers emit eight times more nitrous oxide (N2O), 3,300 times more hydrocarbons, 5,000 times more carbon monoxide (CO) and more than twice the carbon dioxide (CO2) per hour. Estimates indicate that the average US home owner uses their lawn mower a total of 25 hours a year. For a gas mower, that would be the equivalent pollution to driving a car 2,400 miles. Conclusion: Gasoline lawn mowers are an ecological catastrophe to both the environment and human health.
One of the most serious environmental issues associated with gas mowers occurs while filling the mower. It is estimated that 17 million gallons of gasoline are spilled annually in the U.S. while filling lawn mowers. This wasted fossil fuel was extremely expensive to extract, refine and transport, and resulted in polluting soil and ground water, creating greenhouse gases and contributing to climate change.
But, electric mowers are no saints when it comes to maintaining a healthy planet. They are available in two forms: corded and battery-powered. Batteries for electric mowers are either sealed-lead acid or lithium-ion. Lead is a heavy metal with dangerous health impacts. The mining process to collect materials used to produce mower batteries contributes to dangerous lead emissions. Eighty-five (85%) of the world’s lead consumption is in lead-acid batteries. Lead batteries are 99% recyclable, if handled correctly, but if landfilled, can pollute vast areas of ground. Lithium-ion batteries have negative environmental and health impacts. During lithium processing chemicals can leach, spill or become air-borne emissions, and with only 5% recyclability, lithium-ion batteries are not yet cost effective to strip for parts and are typically landfilled Resource-depletion, global warming, ecological toxicity and harmful impacts to human health have been associated with lithium-ion batteries. Corded electric lawn mowers do not rely on batteries, but are only ecologically safe if the electricity is produced cleanly. If it is powered by coal, the pollution occurs out-of-sight. Fortunately, according to Manitoba Hydro 97% of electricity used in Manitoba is hydroelectric power.
Reel mowers produce no emissions, and have excellent cutting ability. They mulch by dispersing clippings in a fine spray that decomposes quickly and because the cylinder rotates in a forward motion, not horizontally like gas and electric mowers its cuts are clean. This allows the wounds on the grass blades to seal, holding moisture in and disease organisms out.
Another option, the robot solar powered lawn mower, has the benefits of free energy, produces no emissions and operates at just 65 decibels (dB), unlike gas mowers that operate at 90 – 105 dB. It is sad but true, that the louder the gas mowers, the better the cutting efficiency.
Once mowing is complete, yard waste has to be dealt with. Yard waste has serious consequences if landfilled. While grass clippings have been banned from most North American landfills, it still makes up to 20% to 50% of the annual waste stream. Yard waste breaks down anaerobically in landfills, producing methane gas which is 21 times more harmful than carbon dioxide as a contributor to climate change.
Doug Tallamy has warned that unless we replace lawns with native plants, the future of biodiversity in North America is dim. While it is unlikely that lawns are going away any time soon, there is evidence that North Americans are beginning to rethink their home landscapes. As climate change becomes more of a concern, homeowners are considering naturescaping. An interest in naturalizing lawns supports an entomological ecology in which native plants, birds and other animals, fungi and bacteria (and a myriad of other soil organisms can co-exist without the use of pesticides and herbicides and dependence on city water supplies. Slowly, homeowners are learning to embrace native plants as a way to engage with wildlife and attract beneficial insects, birds and other creatures to their gardens.
Yale Climate Connections – Doug Tallamy on Lawns
Greenwich Sentinel – Tallamy Urges a Green Revamping of our Status Front Lawns
Forbes – Robert Rapier: Environmental Implications of Lead-acid and Lithium-ion Batteries
Government of Canada – Lawn Maintenance
EPA – National Emissions from Lawn and Garden Equipment
(EPA is an independent executive agency of the United States federal government tasked with environmental protection matters)