Carol Andrews, past national president, provides us with some facts related to causes of climate change. For example, each weekend, about 54 million Americans mow their lawns, use 800 million gallons of gas per year and produce tons of air pollutants. Clean air web site. Garden equipment engines, which have had unregulated emissions until very recently, emit high levels of carbon monoxide, volatile organic compounds and nitrogen oxides, producing up to 5% of the nation’s air pollution and a good deal more in metropolitan areas.
A conventional lawn mower pollutes as much in an hour as 40 late model cars (or as much air pollution as driving a car for 100 miles).
The key info here is the amount of petroleum consumed by the lawn mowers, although some of the other pollutants of traditional concern (VOCs, CO…) referred to also contribute to what is being referred to as global warming (reference Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2004 by EPA).
From the web site advertising “An Inconvenient Truth, “saving one gallon of gas eliminates 20 lbs of carbon dioxide emissions.” Just for fun, one can use that to calculate what the impact would be of a 50% reduction in lawns, assuming that would cut lawn care gas consumption at least by 1/2, then:
0.5 x 800 million gallons of gas x 20 lbs of CO2 emissions reduced per gallon of gas = 8 billion lbs of CO2 = 4 million tons of CO2 emissions prevented by mowing 50% less lawn based on their data and my calcs. If that lawn was converted to native plants, there would be additional reductions in energy use related to less need to pump water, install and maintain irrigation systems, etc. While the deep-rooted prairie plants are growing, they would absorb much more carbon than the lawn did, but once established we expect they would come into a carbon-neutral state (like rain forests and other in-tact ecosystems, whereas new-growth forests serve as a carbon sink).