Science

Published on August 5th, 2009 | by Steve Savage

5

Earthworms: Do They Help or Hurt in Terms of Climate Change?

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Every once in a while I come across something in the scientific literature that really surprises me.  Because there isn’t much oxygen in a worm gut, it creates the ideal conditions for these particular microbes (“de-nitrifiers”) to turn nitrate (NO3) into nitrogen gas and also generate some nitrous oxide in the process.

Nitrous Oxide

Ok, some background. Nitrous oxide (N2O) is a very potent greenhouse gas with 310 times the global warming potential of carbon dioxide. Its really an Achilles heel for agricultural sustainability because around 80% of the human-generated emissions of this gas come from farms. If even a small amount of the farmer’s nitrogen fertilizer gets converted to N2O it becomes a major part of the total carbon footprint of that field

As the Worm Turns

We generally think of earthworms as a sign of a good, healthy soil because they are beneficial in creating channels in the soil for air and water to move.  One good thing about the very sustainable form of farming called no-till is that when it is practiced, earthworm populations increase.  But what about this N2O issue?  One scientists calls worms a “mobile anoxic microzone” and another estimates that one third of the N2O released from a soil is generated inside of worms.

Not to Worry

So I scanned the scientific literature about nitrous oxide from no-till and conventionally tilled farm soils.  I was relieved to find that the emissions are no higher and often lower with no-till except on very poorly aerated soils.  So it seems that earthworms are both part of the problem and part of the solution when it comes to climate change.

So if you find earthworms out in your garden or compost pile, don’t hurt them.  They are probably still good on the whole.

Earthworm photo from schizoform. via Flickr under Creative Commons License



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About the Author

Born in Denver, now living near San Diego. Agricultural scientist for 30+ years with a Ph.D. in Plant Pathology. Have worked for Colorado State University, DuPont and Mycogen and for the last 13 years consulting for all sorts or companies, universities and grower groups. Experience in biological control, natural products, synthetic chemicals, genetics, GMOs and agronomic practices. Have given multiple invited talks on the interaction between agriculture and climate change (both ways)



  • http://www.yahoo.com Bobby B.

    The fact that N2O (nitrous oxide) without any C (carbon) somehow affects a farm’s carbon footprint has me questioning everything I learned in my chemistry and thermodynamics classes. Why the heck did I spend all that money and time studying to be an engineer when all that science would be disproven by a single sentence from an internet blogger?

    BTW, earthworms also serve as great fish bait. ;-)

  • http://appliedmythology.blogspot.com Steve Savage

    Bobby,
    Sorry for the confusion. Nitrous oxide is just one of several “greenhouse gases.” The term “carbon footprint” is based on the fact that the biggest human contribution to the greenhouse effect comes from the carbon dioxide in fossil fuels. The other greenhouse gases that we put into the atmosphere are talked about in “carbon equivalents” just so the total effect can be quantified.

    I may seem like just another “internet blogger” spouting off. I understand that concern because I also see a lot of disinformation coming out, but in this case I’m a Ph.D. biologist that has spent a great deal of time learning about this for the last 2+ years.

  • http://www.Greenertrends.com Kate

    I like earth worms so I am happy to hear that their not so bad for the environment.

  • http://www.yahoo.com Bobby B.

    Not so much confusion, as clarification. I did not mean to imply that I was questioning your credentials, however, disinformation is easily digested when put into print. Words matter, and using them accurately is important when one chooses to attach his name to articles containing scientific jargon.

    You are correct that there exists much disinformation on both sides of the global warming, climate change, maybe mini-ice age debate. Unfortunately, a good bit of the misinformation is generated by organizations with agendas; governments, research grant applicants, international councils, corporate enterprises, etc. To compound the matter, climate change science has allowed itself to be corrupted by money and politics. In a more bizarre twist, the acceptance of the “science” from either side of the debate now requires a nearly cult-like religious faith. Although most people cannot differentiate between kilo, mega, giga, terra, milli and micro, do you ever wonder why there is so much fuss about three greenhouse gases which account for 0.03325% of all atmospheric gases (C = 0.033, CH4 = 0.0002, N2O = 0.00005)? Do you ever ask why water vapor and dust – the main components of clouds – are excluded from the accepted global warming computer models when it is known that their presence lowers temperatures? Do you ever wonder why the IPCC forced the famous hockey stick graph and continues to get caught manipulating the data, or why NASA and the EPA suppress information that does not fit the accepted models? Why did the United States House of Representative recently pass a bill that if it becomes law will subject every homeowner, landlord and tenant to home inspections, to fines, and to eviction from the premises without warrant or provocation (HR2454 – Section 201)? Why is unsettled science being used to alter what has long been considered the foundation of any free society; property rights?

    But back to the earthworms. In the 1970’s, NOx (nitrous oxides) and SOx (sulfur oxides) were blamed for acid rain. Why is acid rain out of vogue and why does it fail to make the news much these days? Hhhmmmm? Anyway, I honestly do not know how much impact the earthworm population might have on climate change, and you have obviously looked at the topic with a discerning, unbiased eye. For that, I congratulate you. However, be mindful that some might misuse your findings to initiate some kooky legislation to enforce earthworm family planning, to increase taxes on earthworm farmers, or to force anglers to purchase carbon credits from Al Gore for using live bait.

    Keep up the good work!

  • Deborah Murray

    I had at least ten live earthworms in my office yesterday on the carpet…never happened before, yes a lot of rain..could this have anything to do with a close earth change>??

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