Turn on the TV on any given Saturday, and you are likely to see all kinds of commercials for products that promote the idea that an actively managed, chemically treated (through fertilizers) lawn is a good thing. In fact, it seems to almost be our right to have the greenest lawn out there.
What is interesting, though, is the assumption that has been made by the lawn care industry that supports their marketing efforts—namely, that a conventional lawn treated with pesticides, herbicides and fertilizers that get frequently watered and mowed can be considered a carbon sink.
How much carbon can a lawn hold?
In 2008, a report was prepared by Dr. Ranajit Sahu in which he suggested that a “well managed” lawn absorbs more carbon than it releases and is therefore good for the environment.
Before going any further, it is important we look at the definition of terrestrial carbon sequestration, which the EPA defines as “the process through which carbon dioxide from the atmosphere is absorbed by trees, plants and crops through photosynthesis, and stored as carbon compounds in biomass (tree trunks, branches, foliage and roots) and as organic matter in soils.”
Okay, so to get back to the report by Dr. Sahu, which he conducted at the request of the Lawn Institute and the Outdoor Power Equipment Institute, he indicated that one acre of managed turfgrass will hold roughly 920 pounds of carbon in a year. He said a well-managed lawn that is mowed regularly and treated with chemicals must also be regularly watered to keep it growing vigorously.
The only kind of emission Dr. Sahu includes in his calculations is that from a lawn mower. He estimated that at about 160 pounds per acre, so he concluded that the net carbon storage of a well managed lawn at 760 pounds—hence, we have our carbon sink!
What the turf industry is not telling you
What about the CO2 emitted in the manufacture and application of lawn chemicals? Dr. Sahu acknowledged he did not evaluate “indirect carbon impacts,” but isn’t that an important thing to do?
A study by NASA’s Christine Milesi, which he does reference, indicates that carbon emissions resulting from fertilizer inputs range from 11-28 percent of a parcel of land’s total carbon sequestration potential. If we assume this at 20 percent, then emissions from chemical approach nearly 200 pounds per acre per year. Subtract this from Dr. Sahu’s total and we are down to 576 pounds.
Another really interesting point is that there are also carbon emissions that result from the process of obtaining clean water. In Portland, OR, city planners estimate their production of potable water emits 0.01 lb. of CO2 per gallon of water. For an average lawn, we are commonly advised to provide one inch of water each week, which amounts to 27,154 gallons of water.
Let’s say we irrigate our lawns just 6 times each year—we are now up to 163,000 gallons of water each year. If we multiply this amount of water by .01, we get 456 pounds of carbon emissions (1 pound of CO2 equals .28 pounds of carbon).
We are now down to 120 pounds of carbon storage per acre for “a well managed” lawn.
Why organic lawn care matters
An acre of established temperate forest holds anywhere from 2,000 to 6,000 or more pounds of carbon per year, depending on the age of the trees and other conditions. Mature grasslands hold up to 3,600 pounds per acre each year.
Organic lawn care is important, because it can take a parcel of land and leverage its built-in strengths and create beauty in a self-sustaining, responsible manner. There are options to create legitimate carbon sinks, such as wildflower meadows, pocket prairies, clover lawns, lawns made up of native grasses.
Lawns can be maintained organically and without chemicals—they just won’t be that unnatural bright green color you see in October. You won’t need to saturate them with hundreds of thousands of gallons of water each year and you also won’t need to worry about them during dry periods.
Ultimately, we all have a responsibility to the earth, our kids and the future, so next time you are tempted to grab that big bag of fertilizer from “unnamed big box store,” think about the true cost. Look beyond the numbers on the bag.
If you have questions, call Heidelberg Farms at (603) 501-9919. Together, we can make a difference.