Lawns and Your Carbon Footprint

Americans (and the rest of the world) are finally waking up to what may well be the largest environmental challenge humanity has ever faced: the fact that we have reached the carrying capacity of the planet to recycle our wastes. It is a challenge involving ecological, economic and sociopolitical issues and regardless of where blame for the burden on the environment is placed – whether a particular nation, or agricultural system, or natural variation itself – the problem remains nonetheless. It is observable and it is serious. We all need to reduce our "carbon footprint"  which is the amount of greenhouse gases like carbon dioxide our individual lifestyles are responsible for.

Faced with this, every one of us wonders what we can do slow down what seems an inexorable slide toward an unpleasant future for our descendents. The problem is so large, that whatever we can do seems insignificant. But NASA researcher Christine Milesi managed to put some hard numbers on to one personal solution we've been talking about here on safelawns.org : namely, how you take care of your lawn affects your own family's carbon footprint.

Here’s some of what she found out:

How much turf is there? According to the NASA analysis, there are 31,630,000 acres of turf in the USA (almost 50,000 square miles). That is larger than Pennsylvania, Ohio, Virginia, Tennessee, Kentucky, or Indiana, or equal to all the New England states put together (if you only include the southern half of Maine). In fact the state of Turfiana is the 32nd largest in the Union. All those yards and parks and golf courses add up!

How much water does it take? Irrigating all that lawn to an optimal state for growth would require about 200 gallons of water per person per day, depending on where you are and if you pay attention to the weather. Like gardens, lawns grow fastest with about an inch of water a week. If you subtract the amount contributed by rain and adjust that for the regional variations in humidity and evaporation, the average need is about 184 gallons per day per person. If you ignore the weather and just put on an automatic sprinkler, the figure rises to 238 gallons. That is a lot of water, especially in the arid parts of the country, which would fall at the top end of the spectrum.

Is Organic Better? Lawns, as it turns out, can be a boon in the fight against climate change and water pollution, but not all lawns are equal. Milesi found out that all that turf captures quite a bit of carbon from the atmosphere, a whopping 37 billion pounds per year if you mow high and leave the clippings on the surface (two key elements of organic lawn care). If you remove the clippings, that number drops by nearly two thirds, and if you send the clippings off to the landfill, then their decomposition actually makes climate change worse because it produces methane which is even worse than carbon dioxide.

What’s more, their study found that leaving the clippings in place made it possible to cut applications of synthetic fertilizers nearly in half, which means less runoff into streams and ponds, less groundwater pollution, and savings both in the energy needed to manufacture those fertilizers (also a climate change issue) and in the expense of cleaning up our water supplies.

To read the original article on Milesi’s work on the NASA website, visit http://earthobservatory.nasa.gov/Study/Lawn/printall.php

Notes & References

Milesi, C., S.W. Running, C.D. Elvidge, J.B. Dietz, B.T. Tuttle, R.R. Nemani. (2005) Mapping and modeling the biogeochemical cycling of turf grasses in the United States. Environmental Management 36(3), 426-438.