2/20/2010 6:58 PM
Beautiful green lawns provide numerous environmental benefits and their ability to store carbon is one of them; but when a recently published research study regarding the ability of grass to store carbon reached the opposite conclusion of previous studies, more than a few scientists were scratching their heads.
A study by Amy Townsend-Small, Earth system science post-doctoral researcher at University of California, Irvine received extensive media coverage because of the negative conclusions she presented regarding growing grass lawns. Her study suggested that the carbon-storing benefits of lawns were counteracted by fuel consumption.
Focusing on four parks and lawns in Southern California, the Townsend-Small study found that greenhouse gas emissions from fertilizer production, mowing, leaf blowing and other lawn management practices were four times greater than the amount of carbon stored by grass in parks and lawns. Now this is totally opposite of previous research findings regarding carbon sequestration in lawns and the amount of carbon resulting from the care and maintenance of lawns.
You might have seen assorted headlines that read:
· "Urban Green Space May Aid Global Warming"
· "Green Spaces (Lawns) Are Not So Green"
· "Urban Lawns Contribute to Climate Change"
· "The Grass Isn't Always Greener"
· “Lawn Care = Bad for the Environment?”
· “City Parks May Be Bad For The Environment”
· “Study Fumes Over City Park Grass”
· “New CO2 Threat to the Planet”
There is a problem with that conclusion: The authors of the Amy Townsend-Small research report acknowledge their study contained errors and miscalculations! OOPS!
So how did the errors in the study come to light? Dr. Thomas Rufty, Bayer Distinguished Professor, Environmental Plant Biology, North Carolina State University questioned the findings based on previous research models and proceeded to point out several discrepancies in the Townsend-Small research report:
Rufty commented, "Regarding carbon sequestration and greenhouse gas emissions in urban turf' by Townsend-Small and Czimczik, we suspected an error in calculations because their numbers were so different from the models we are developing.” Rufty was challenged to find out why there was a discrepancy. He reported that two of his Ph.D. students took apart all of the assumptions and calculations in the Townsend-Small paper and found mistakes. When asked to provide a complete analysis of the situation … they immediately presented their findings. Rufty reviewed their findings and confirmed they were right and that errors had been made. DOH!
Rufty then emailed the authors and they confirmed there was a mistake in their spreadsheet that no one had caught during the writing or peer review. The authors said 'someone' had informed them of the mistake and a correction was posted. Their corrected calculations showed that CO2 generation was 122 g m-2 yr-1 rather than 1238 g m-2 yr-1 as stated in their research paper.
"This is important, because it makes the situation with 'ornamental lawns' carbon neutral to positive, depending on some of their other assumptions about fertilization. The students also are arguing that the authors made another mistake regarding lawn equipment that will result in decreasing the estimated CO2 even further!
So continue to enjoy your lawns since they still are good for the environment.