Urban parks: a global warming downer?

Green is good — right? Not necessarily when it comes to lawns, according to a new study by University of California Irvine researchers. For the first time, scientists compared the amount of greenhouse gases absorbed by ornamental turfgrass to the amount emitted in the irrigation, fertilizing and mowing of the same plots.

In four parks near Irvine, they calculated that emissions were similar to or greater than the amount of carbon dioxide removed from the air through photosynthesis — a finding relevant to policymakers seeking to control the gases that trap heat in the atmosphere and contribute to climate change. “Green spaces may be good to have,” said geochemist AmyTownsend-Small, the lead researcher in the paper published in the journal Geophysical Research Letters. “But they shouldn’t be automatically counted as sequestering carbon.”

The paper is particularly timely, she added, because governments are calculating their carbon footprints, and discussing whether parkland could offset other sources of emissions, such as refineries, power plants and automobiles. Turfgrass covers about 1.9% of the U.S. and is the most commonly irrigated crop. It is increasingly in demand in urban areas.

Townsend-Small and colleague Claudia Czimczik measured the carbon content of the parks’ soil, and compared that with emissions from producing fertilizer, from mowing with gasoline-powered equipment and from pumping water to irrigate the plots. The pumped water was recycled — but if it were fresh water transported from distant rivers, as is much of Southern California water, emissions would be higher, said Townsend-Small. They also factored in the nitrous oxide released from soil after fertilization. Nitrous oxide is a greenhouse gas 300 times more powerful than carbon dioxide, which is released by fossil fuel combustion.

 

California has no regulations to control turfgrass, but the study “shows the importance of full life-cycle analysis for greenhouse gases,” said Mary D. Nichols, head of the California Air Resources Board, which is charged with reducing the state’s carbon footprint. Research is underway, she noted, to develop varieties of grass that need less mowing and use less water.

What about the heat island effect, the vaunted benefit of plants as a way to cool cities? “Irrigating trees in urban Southern California reduces the heat island effect,” said Stephanie Pincetl, author of “Transforming California: A Political History of Land Use and Development.” “But lawns have no such benefits, and also contribute to water pollution because they are heavily fertilized.”

Townsend-Small said that turf emissions vary according to region. Studies would need to be done in wetter northern climates. There, she said, grass might not need irrigation, but it would also absorb less carbon during cold winter months.

Using rakes rather than leaf-blowers, and hand mowers rather than gasoline-powered equipment, would improve lawns' carbon footprint.

 “About 40% of the drinking water we import at great financial and environmental expense is used for outdoor irrigation,” said Paula Daniels, an L.A. Department of Public Works commissioner. “This study hopefully will motivate more of us to make changes in our landscapes.”

--Margot Roosevelt

 Photo: Students from Los Angeles County School of Arts performed a dance during a news conference several years ago to promote the use of electric lawn mowers. Electric models produce far fewer greenhouse gases than gasoline-powered motors. Credit: Carlos Chavez/ Los Angeles Times

Comments

[Daniel]

I would rather sleep in an outhouse than spend the night in Irvine

[andrew nelson]

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo780.html

This Letter presented projections of future sea-level rise based on simulations of the past 22,000 years of sea-level history using a simple, empirical model linking sea-level rise to global mean-temperature anomalies. One of the main conclusions of the Letter was that the model results supported the projections of sea-level rise during the twenty-first century that are reported in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Unfortunately, we have since found that our projections were affected by two oversights in our model approach. First, we tested the sensitivity of our results to the length of the time step used in the integration of the model for the period of deglaciation, which we found to be robust. However, we overlooked that the simulations of the twentieth and twenty-first centuries are sensitive to this time step, which led to an overestimation of the sea-level response to warming in the simulations for these centuries. Second, we did not include the effect of the uncertainty in the temperature reconstructions since the Medieval Climate Anomaly in our uncertainty estimates for the twenty-first-century projections. This led to an inconsistency between the twentieth-century simulation used to test the predictive capability of the model and the twenty-first-century simulation, owing to a provisional allowance for warming since the Little Ice Age in the twentieth-century simulations. Thus we no longer have confidence in our projections for the twentieth and twenty-first centuries, and for this reason the authors retract the results pertaining to sea-level rise after 1900.

[nels]

The research showed that maintaining lawns and turf with fertilizer and machinery results in higher emissions and does not say that "parks" are contributing to global warming. You should really change this entirely misleading headline. Parks come in many forms, including forests, meadows, etc. And besides that, it is not the lawns themselves, it is the way they are maintained.

On top of this, the real issue here is not the amount of public lawns, its the amount of private lawns in this country's urban areas. A very small percentage of lawns are in urban parks, and in fact, it is urban parks that allow people to go without yards and use them efficiently in common spaces.

I'm not really what purpose this research is serving. Whatever it actually found has been distorted by the messaging.

[Turfdoctor]

It should be known that this study had a serious flaw in it's initial findings. They overestimated carbon emissions generated by fuel consumption by a factor of 2X and also as Theresa points out seriously skewed fertilizer applicaitons to the high side. No proffesional turf mamager (like a golf couse superintendent or sports turf manager) would fertilize at such levels or the growth would require more mowing than you want to deal with. Whether this was all an honest mistake or agenda driven intentional miscalculation we will never know as this was not caught in their "peer review" process, but uncovered by a group of turfgrass scientists at North Carolina State University who spotted the error after the misinfomration had been published on the internet and brodcast on cable news.

[Weatherbot]

As far as carbon footprints go human contributions to CO2 emmissions are miniscule. Consider that natural sources for CO2 emmissions account for 150 gigatons a year while humans produce 6 gigatons. It is highly unlikely that any efforts by humans to reduce CO2 emmissions will have much effect. Also, statistical data I've collected thus far do not support a larger trend of warming (see weatherbot.blogspot.com).

[cigarbat]

This is dishonest.

In nearly every park there are trees shrubs and other plants. It is a distortion and a lie (normal for most colleges these days) to only measure what you want to promote your own beliefs.

Try measuring the entire park, you'll find the results massively different. Parks are a net reducer of carbon footprint.

[bnolteus]

We the people deserve green lawns and white picket fences. We the people are greedy and ignorant of all the choices we make that affect the environment later. The climate summit is a bunch of crap to make the common person feel like society is trying to make a change. Change needs to come from every individual. Change needs to be in the form of eliminating useless pieces of society and replacing them. In this case if every green grass yard in america was converted to a garden which produced vegetables for the people, didn't need to be mowed and needs less water(depending on size)...in any case the return of gardening saves all the gas and emissions used to ship produce worldwide.

We the poeple are stupid because we continue to build on the mistakes made by humans for thousands of years...Mansions built upon faulty foundations will surely crumble...Compounding social mistakes are like our compounding population each just gets bigger and more and more difficult to fix as we continue to rely on the same models that have furthered technology and information but are killing the world we live on.

bnolteus...
bend...OR

[dhwj]

Why in the world would comments to the LAT require the consent of the author of the article. Is this so there can be no or limited dissent???

[dhwj]

Since we now know that the earth has been COOLING for over 10 years, that Jones and Mann are frauds, that man made global warming is B*, we can stop worrying about whether lawns absorb or emit carbon dioxide [which in any case helps plants grow and thus food production].

[Theresa]

"In addition to understanding the generated numbers, it is also important to keep in mind the type of input or level of maintenance that is written into the model or equation. For example, the model may assume that all lawns are irrigated, when in actual fact they are not. The model may also assume that all lawns are fertilized four times per year and clippings removed, when in fact that is not the case. As determined by Scott's consumer studies, there are 80 million single family homes in the USA. 50% of those lawns get no fertilizer applied at all, 37.5% are fertilized 1.8 times per year, and only 12.5% are fertilized 3 or more times per year(2). Additionally, it is important to note that that much of the research is suggesting that "healthy" lawns receiving inputs from fertilizer, returned clippings and irrigation are actually showing an increase in carbon sequestration(3). This would make sense, seeing as the root system, turnover of roots, and litter biomass in a healthy turfgrass system is significant(4). "

http://buckeyeturf.osu.edu/component/option,com_LandscapeNotes/Itemid,86/noteid,2453