The Mammalian Methane Emissions Menace

AT the website of the University of New Mexico we read Research Suggests Large Mammals Influenced Global Climate. Here are some excerpts, with bold added by us:

More than 13,000 years ago, millions of large mammals such as mammoths, mastodon, shrub-ox, bison, ground sloths and camels roamed the Americas and may have had profound influences on the environment according to research in a paper titled, “Methane Emissions from Extinct Megafauna” released in the publication Nature Geosciences Sunday.

Here’s the abstract: Methane emissions from extinct megafauna. Let’s read on:

The extinction of these large herbivores, which also include horses, llamas and stag moose in addition to the giant wooly mammoth, probably led to an abrupt decrease in methane emissions and atmospheric concentrations of the gas with potential implications for climate change says Dr. Felisa Smith, Associate Professor of Biology at the University of New Mexico.

[…]

Approximately 13,400 years ago, the Americas supported a mammal fauna that was richer than that of Africa today explained Smith. “Around 11,500 years ago and within 1,000 years of the arrival of humans in the New World, 80 percent of these large-bodied mammals were extinct,” said Smith in the paper.

Humans — you can’t let ‘em loose anywhere! We continue:

“This is arguably the first detectable influence of humans on the environment going back 13,400 years to when humans first got to the continent,” said Smith. “I think that it’s intriguing because there are a lot of ramifications. Potentially, if the decrease in methane, which is synchronous with this ice spell, was actually the cause, then humans contributed to the Younger Dryas cold episode.

We hope you’re paying attention. The Younger Dryas, according to Wikipedia, “also referred to as the Big Freeze, was a geologically brief (1,300 ± 70 years) cold climate period between approximately 12,800 and 11,500 years ago” This implies that the extinction of those large herbivores could have brought an end to what was then a period of global warming.

Here’s more from the University of New Mexico news item:

Herbivores produce methane as a by-product of cellulolytic-microbial fermentation during the digestive process. Enteric emission occurs when methane (CH4) is produced in the rumen as microbial fermentation takes place; most of this is released as burps. Past studies have shown that domestic livestock are an important contributor to greenhouse gas concentrations and can represent ~20 percent of annual emissions.

Burps? Well, those too. Moving along:

The researchers looked at 114 different herbivorous species that were extirpated from the Americas at the end of the Pleistocene epoch. Using ice cores to determine the amount of methane during the onset of the Younger Dryas cooling period, they found the extinction of megafauna closely coincides with an abrupt drop in atmospheric methane concentration.

No burps, no methane. And methane is a greenhouse gas. Are you starting to see where this is going? Another excerpt:

Armed with that information, the researchers then decided to try and determine how much methane was produced by these species. They came up with an estimate of the number of animals and then an estimate of how much methane those animals actually produced. Other animals such as elephant, giraffes and hippos have been studied by putting a gas mask type of apparatus on them to determine how much methane they produce in a day.

Consider, dear reader, that if things had worked out differently in your life, you might have become a master of mammalian methane measurement. While you’re pondering that, here’s one final excerpt from the article:

“We were able to come up with an estimate, which turns out to be about 10 teragrams. This is really pretty enormous,” said Smith. “When you bracket it, at the very minimum, the demise of all these animals explains 12 percent of the decrease in methane seen at this time. At the maximum, it explains the entire decrease. This suggests that the extinction of megafauna by humans caused a detectable impact on the environment long before the development of agriculture and the industrial age.”

[…]

The calculations suggest that decreased methane emissions caused by the extinction of New World megafauna could have played a role in the Younger Dryas cooling event.

The lesson is clear. To halt the progress of global warming we must exterminate all remaining mammalian herbivores. Hurry, before it’s too late!

Copyright © 2010. The Sensuous Curmudgeon. All rights reserved.

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26 responses to “The Mammalian Methane Emissions Menace

  1. Curm, you are making fun of something without really considering it fully.

    Aside from the unwarranted claim that humans were the primary reason for the mega-fauna die off, is it possible that there is something to this?

    Is it possible that methane, as a GHG, could have an effect on climate? Is there physical evidence that methane dropped around the same time period? Did the temperature drop?

    Granted, correlation is not causation, but since the press release is not the paper, I would have to see how they made the connection before I believed one way or the other. If their paper is nonsense, we will hear about it from other scientists, probably from within the climatology group. Until then, I’m not going to jump the gun by hopping on the bandwagon, or by making fun of them.

    Remember, one reason the scientific process was developed was to counter act ‘common sense’ errors.

  2. Once again, Tundra Boy, relax. I couldn’t resist the opportunity to post about methane.

  3. I’m still trying to figure out if I should give a rat’s ass.

    How many rat’s asses would it take to methane-o-lize me? I know my wife’s dog tries awfully hard and I’m pretty kind to the mangy little bastard, all things considered.

    So, when I’m grillin’ burgers this evening I’m saving the planet, right? We’ll except for the 5 pounds of propane I’ll burn up. Probably evens out.

  4. longshadow

    Does this mean I have to purchase a carbon methane indulgence from AlGore™ for “Williard,” my pet Woolly Mammoth?

  5. Longie, the methane indulgence you’ll need for “Willard” is a pittance compared to what you need for yourself.

  6. longshadow

    I defer to your Curmudgeonly expertise, as you are widely regarded as a flatulence factotum.
    ;-)

  7. “Other animals such as elephant, giraffes and hippos have been studied by putting a gas mask type of apparatus on them to determine how much methane they produce in a day.”

    Great. We won’t die by fire and armageddon (as the Revelations predicted), we’ll die of super-farts.

    *giggle*

  8. LRA says: “*giggle*”

    It’s not funny! A true environmentalist would be deeply concerned with this methane issue.

  9. Gabriel Hanna

    A true environmentalist would be deeply concerned with this methane issue.

    From the fringe wackos at EPA, who are utterly unlike serious environmentalists:

    http://www.epa.gov/rlep/faq.html

    Ruminant animals, such as cattle, sheep, buffalo, and goats, are unique. Because of their special digestive systems, they can convert otherwise unusable plant materials into nutritious food and fiber. This same helpful digestive system, however, produces methane, a potent greenhouse gas that can contribute to global climate change. Livestock production systems can also emit other greenhouse gases such as nitrous oxide and carbon dioxide.
    1. How much methane is produced by livestock?

    Globally, ruminant livestock produce about 80 million metric tons of methane annually, accounting for about 28% of global methane emissions from human-related activities. An adult cow may be a very small source by itself, emitting only 80-110 kgs of methane, but with about 100 million cattle in the U.S. and 1.2 billion large ruminants in the world, ruminants are one of the largest methane sources. In the U.S., cattle emit about 5.5 million metric tons of methane per year into the atmosphere, accounting for 20% of U.S. methane emissions.

    For a specific break-down of US methane sources, from livestock to other sources visit the Methane Sources & Emissions Web page.
    2. How will global climate change affect agriculture?

    The potential effects of climate change on agriculture are uncertain, and could be positive in some respects and negative in others. At the regional level, changes in precipitation and temperature patterns could jeopardize current agricultural practices. The frequency of extreme weather events such as floods, droughts, and severe storms may increase. Sea levels could rise, threatening vulnerable coastlines around the world, and tropical diseases and pests that affect plants and animals could increase their range.

  10. Snap! I suppose super-farts is a serious matter after all!!

  11. Gabriel Hanna

    @LRA:

    The obvious solution is to tax meat so people will eat less of it. And some environmental groups advocate that.

    Not any of the serious ones, of course.

    http://www.prospect.org/cs/articles?article=are_cows_worse_than_cars

  12. Gabriel, as a Texan, I wish I could say that not eating meat would be the easiest way to reduce my carbon footprint… but I can’t.

    *sigh* If only my will was as strong as my convictions. Meat is yummy. (If if makes you feel better I eat more chicken and fish than beef.)

  13. retiredsciguy

    What am I missing here? Isn’t the methane emitted by mammals (from either end) just recirculating carbon that was originally in the atmosphere anyway? How can that contribute to global warming? Y’know, the old carbon cycle we learned in 4th or 5th grade — plants take carbon dioxide out of the air, using the sun’s energy to combine it with water to form carbohydrates, which are then eaten by us animals who exhale it as CO2 or burp and fart it back out again as methane. And even if methane is a more potent greenhouse gas than CO2, isn’t it oxidized pretty quickly back to CO2?

    I can understand the concern about burning fossil fuels. That rapidly puts carbon back into the atmosphere that’s been sequestered for many millions of years, increasing the CO2 levels in the atmosphere. But I just don’t understand the concerns about ruminant animals, unless it’s just a red herring being promoted by PETA.

    Speaking of which, Curmy, when you wrote “To halt the progress of global warming we must exterminate all remaining mammalian herbivores”, did you have them in mind?

  14. Gabriel Hanna

    Isn’t the methane emitted by mammals (from either end) just recirculating carbon that was originally in the atmosphere anyway? How can that contribute to global warming?

    Methane is CH4, right? And carbon dioxide is CO2. Methane absorbs more strongly (about 80 times), so the carbon atom in the carbon dioxide responsible for less warming than the same carbon atom in the methane.

  15. retiredsciguy says:

    Curmy, when you wrote “To halt the progress of global warming we must exterminate all remaining mammalian herbivores”, did you have them [PETA] in mind?

    Not specifically, but a good principle should have wide and even unforeseen applications.

  16. Gabriel Hanna

    LRA, I am not interested in making you consume less meat, or making you change your lifestyle in any way. Just giving you a heads up on what the environmental movement has in store for you. Just as the government is now talking about regulating salt in food; it would have been dismissed as absurd a few years ago, but here we are. (Does no one bake anymore? Salt in baked goods is not optional.)

  17. Gabriel– I get what you are saying. Believe it or not , I have to watch my red meat consumption anyway as I have familial hypercholesterolemia. I’d give it up altogether, but the occasional steak is such a treat! Anyhow, I like chicken and fish just fine. Heck, I could eat sushi every day if I could afford it!

    LOL!

  18. retiredsciguy

    Gabriel Hanna: “Methane is CH4, right? And carbon dioxide is CO2. Methane absorbs more strongly (about 80 times), so the carbon atom in the carbon dioxide responsible for less warming than the same carbon atom in the methane.”

    Gabe, you’re a much better researcher of these matters than I could ever hope to be. Do you know if there are any studies of the rate of oxidation of CH4 to CO2 in the atmosphere?

    Since a lot of methane is released to the atmosphere from the earth, but there’s not all that much methane in the air, it would seem that it must oxidize fairly rapidly.

  19. For a retiredsciguy, with access to the internet, seems rather lazy. Wikipedia ( http://en.wikipedia.org/wiki/Methane ) says methane has a half-lif of 7 years and “The abundance of methane in the Earth’s atmosphere in 1998 was 1745 parts per billion (ppb), up from 700 ppb in 1750.”

  20. retiredsciguy

    Thanks, RogerE. Yes, I am a bit lazy, but I also have other things I enjoy in life besides sitting in front of a computer solving all the world’s problems. A 7-year half-life seems short, doesn’t it? I’ll check out the wiki article in a moment, but do you recall if it mentioned how we were able to sample what the atmosphere contained in 1750? If the samples were air bubbles contained in ice cores, it would seem that with a half-life of 7 years, there wouldn’t be much methane left.

    What I’m saying is, how much confidence can we place in that 700ppb CH4 in 1750?

  21. Gabriel Hanna

    @retiredscienceguy:

    Methane is a stable chemical. In the atmosphere, it will eventually run into something that will destroy it; maybe a fire or cosmic radiation or something. Hence the half-life of seven years. But trapped in an ice bubble, it will last indefinitely. So, you can place a great deal of confidence in the ice-core samples for carbon dioxide and methane. For water vapor, I’d guess you couldn’t.

  22. retiredsciguy

    The Wikipedia article that Roger E directed me to ( http://en.wikipedia.org/wiki/Methane ) did not state how it was determined that the methane content of the atmosphere was 700 ppb in 1750. We know it was measured directly in 1750 because methane wasn’t even known until 1776 or 1778 (same article).

    So let’s assume the methane level in 1750 was derived by studying bubbles in ice cores. Methane has a molecular weight of 16, while the molecular weights of nitrogen and oxygen are 28 and 32 respectively. That being the case, wouldn’t most of the methane rise to the upper parts of the atmosphere, where it would be less likely to be trapped in air bubbles in glaciers?

    What I’m saying is, I don’t think we have a good handle on what the concentration of methane was in 1750. Furthermore, the wiki article said that a citation was needed for the claim that the half-life of methane in the atmosphere is 7 years. IOW, says who the half-life’s 7 years?

    At any rate, the fact that CH4 is so much lighter than air would result in it causing the upper atmosphere to heat up from its greenhouse effect. That could cause the air column to be more stable, resulting in less rain and thus leading to drought. Maybe.

  23. Gabriel Hanna

    So let’s assume the methane level in 1750 was derived by studying bubbles in ice cores. Methane has a molecular weight of 16, while the molecular weights of nitrogen and oxygen are 28 and 32 respectively. That being the case, wouldn’t most of the methane rise to the upper parts of the atmosphere, where it would be less likely to be trapped in air bubbles in glaciers?

    The atmosphere mixes pretty evenly, I understand. We don’t find all the argon and nitrogen and oxygen stratified, do we? You’ll find more methane higher, perhaps, but it’s a small effect.

    What I’m saying is, I don’t think we have a good handle on what the concentration of methane was in 1750.

    Right, but you didn’t actually study this or read any papers or anything, so how do you know what is known and what isn’t?

    At any rate, the fact that CH4 is so much lighter than air would result in it causing the upper atmosphere to heat up from its greenhouse effect. That could cause the air column to be more stable, resulting in less rain and thus leading to drought. Maybe.

    It’s a nonlinear system, with both positive and negative feedbacks. You can’t reason it out like that. You have to simulate it. That’s what the climate models are there to do. Fortunately they’ve been working on it for decades and you could find that have already answered many of your questions, if you took the time to read the papers.

  24. retiredsciguy

    “…and you could find that have already answered many of your questions, if you took the time to read the papers.”

    Geez, Gabe, if I did that, when would I have time to read the Curmudgeon? Or sleep?

  25. Gabriel Hanna

    Yeah, I don’t have a lot of time to read papers outside my field either.

    Anyway, wikipedia on ice cores is a good place to start. Turns out you can even get water vapor concentrations–I didn’t think you could, but shows how much I know.

  26. Gabriel Hanna

    When I was a kid, we had a song in our Sunday School book about how Jesus looks like to the children around the world who worshipped him. James Taylor covered it:

    Some children see Him lily white,
    The baby Jesus born this night.
    Some children see Him lily white,
    With tresses soft and fair.
    Some children see Him bronzed and brown,
    The Lord of heav’n to earth come down.
    Some children see Him bronzed and brown,
    With dark and heavy hair.

    Some children see Him almond-eyed,
    This Savior whom we kneel beside.
    Some children see Him almond-eyed,
    With skin of yellow hue.
    Some children see Him dark as they,
    Sweet Mary’s Son to whom we pray.
    Some children see him dark as they,
    And, ah! they love Him, too!

    The children in each different place
    Will see the baby Jesus’ face
    Like theirs, but bright with heavenly grace,
    And filled with holy light.
    O lay aside each earthly thing
    And with thy heart as offering,
    Come worship now the infant King.
    ‘Tis love that’s born tonight!

    I don’t get too annoyed by depictions of Jesus as white, anymore than I get annoyed by depictions of Biblical figures as fifteenth-century Italians.