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What 30 Years of Study Tell Us About Grazing and Carbon Sequestration

By   /  November 13, 2017  /  16 Comments

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Please click here if you’d like to send us additional papers and data. This is Part 3 of an on
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About the author

Publisher, Editor and Author

Kathy worked with the Bureau of Land Management for 12 years before founding Livestock for Landscapes in 2004. Her twelve years at the agency allowed her to pursue her goal of helping communities find ways to live profitably AND sustainably in their environment. She has been researching and working with livestock as a land management tool for over a decade. When she's not helping farmers, ranchers and land managers on-site, she writes articles, and books, and edits videos to help others turn their livestock into landscape managers.

16 Comments

  1. Edmund Brown says:

    Thanks Kathy. I’ve been ruminating on the idea of carbon sequestration in grasslands. I’ve seen some interesting results of farms adopting some sort of managed grazing with relatively rapid (5 yrs or so) increase in SOM. My impression from those places is that their baseline is either arable land that was cropped (poorly?) for many years, or heavily set stocked pastures. Either of those management choices will depress the “natural” SOM level a peice of ground reaches at equilibrium.

    The papers I read in your biblio (I didn’t peruse all of them) here looked at more “mature” grasslands at or near equilibrium, and thus showed little or no CO2 sinking.

    This is the result I’d expect. There may be some management practices we could tinker with that could bump the SOM up a little higher in a perennial pasture of long standing, but chances are low it would make a big change.

  2. Tyler Carlson says:

    At the bottom of the green take-home box it states that “moderate grazing is better than no grazing at all”. If livestock exclusion and poor grazing management reduce potential carbon sequestration then it would seem counter to the concept that good grazing management DOES NOT enable more carbon to be sequestered. Grassland carbon sequestration it seems is driven by the primary productivity of the system… the potential of which is improved by sufficient or optimal moisture, nutrients, temps, cloud cover, etc. But to meet that potential, the photosynthesizing plant tissues need to have have an optimum balance between total mass or surface area and the productivity of each surface area unit (younger leaf tissue being better at photosynthesis than older leaves…correct?). As stated, under moderate grazing diversity remains highest and leaf litter is cycled while maintaining productive leaf area. It’s useful to frame how the system is working and to show that there’s nothing “magical” about grazing…as if the dunging by livestock and “trampling of litter into the soil”, as I have read or heard over and over in relation to mob grazing, is directly increasing soil carbon. Good grazing management optimizes the primary productivity potential of the sward…nothing has changed. Either the article is unnecessarily confusing on this or I am missing something. But it seems like years of inaccurate rhetoric and untested assumptions in the grazing community and a bit of semantics here is contributing to some of the confusion.

  3. Stefhan Gordon says:

    (Sorry for the double post- made some typos in the prior entry)

    The thing too with greater soil organic matter (that is soil carbon), there’s more water retention. So soil carbon increases moisture availability. Soil carbon and hydrology are interconnected. When you have more moisture, continuous cover, and no tilling, you also improve the soil ecosystem for methanotrophs that oxidize methane (Singh. JS. 2011) Some of those methanotrophs also become airborne, so these airborne methanotrophs also mitigate enteric methane (Santi Temkiv, T et al. 2013)

    The problem with so much of the science is that it’s reductive. It doesn’t look at how all the cycles are interconnected, and much of the older science doesn’t account for soil microbiology at all. The soil microbiology changes everything as Dr. David Johnson notes in this short video https://youtu.be/Fdh_j_KOmrY

    • Kathy Voth says:

      Let’s be careful not to confuse soil organic matter and soil carbon. You can check out part 2 in the series for a definition of the difference. Interestingly, the most recent research indicates that we may have over estimated water retention as a result of carbon increases. We’ll be exploring this in future articles as well. Finally, while David Johnson’s video is interesting, it doesn’t qualify as the type of peer reviewed research and literature we’re basing this series on.

  4. Stefhan Gordon says:

    Looking at your bibliography,it excludes all the recent research by Teague, Rowntree, Wang, Johnson and Chiavegato including this non-inclusive list of peer reviewed papers:

    Teague, R et al 2017 multi paddock grazing on rangelands why the perceptual dichotomy between research results and rancher experience

    (this paper notes some of the shortcoming the research as summarized in this recent article https://www.stuff.co.nz/business/farming/opinion/98855413/john-king-the-art-of-farming )

    Teague, r & barnes, m 2017 grazing management that regenerates ecosystem function and grazingland livelihoods

    Rowntree, jason e at al 2016 potential mitigation of midwest grass finished beef production emission

    Conant et al 2016 grassland management impacts on soil carbon stocks a new synthesis

    Wang, tong teague, richard et al 2015 ghg mitigation potential of different grazing strategies in thUnited States Southern Great Plains

    Teague, R et al 2016 the role of ruminants in reducing agriculture’s carbon footprint in North America

    (This last paper was co-authored by Rattan Lal, but she only cites older papers).

  5. Chad Grantham says:

    Maybe the answer is not increased carbon sequestration or SOM due to grazing alone per se, which is one of the theories by successful graziers. However, these people manage in a way that promotes ground cover, keeps plants in a vegetative state, and overall land health. Those are the reasons for the carbon sequestration and SOM increase because it allows for water infiltration and limits the effects of drought due to this proper management and their grazing management is the driver behind this.

    My thoughts are yes the grazing does do what successful graziers are saying, but the science doesn’t back it up. The studies, according to this article, show that spring precipitation is the reason for the CO2 uptake due to increased biomass and less bare ground which is exactly what good graziers manage for. Compare those two characteristics, biomass and ground cover between properly managed land and poorly managed land during a drought and you will see that grazing management does indeed have a large influence on CO2 sequestration.

    • Kathy Voth says:

      Chad, I’m not sure I understand what you mean to say. So to clarify, the research we reviewed shows that good grazing does not have an impact on CO2 sequestration. Bad grazing management, like grazing too early in the season before plants put on enough growth, or grazing that leaves bare ground, can increase respiration of CO2 during the dormant season. Hopefully that helps. Thanks!

      • Chad Grantham says:

        Thanks Kathy, what I was trying to say is that the science doesn’t support that grazing has an impact but what mob grazing and HHDPG does is what helps contribute to carbon sequestration, increased biomass and ground cover through the proper management of such systems.

        It may be spring precipitation or timely moisture that the research is stating that contributes to the sequestration, but if those areas are poorly managed and bare, then the moisture doesn’t do anything significant. In a round about way, grazing properly more or less causes and is responsible for sequestering carbon because of the improvement of the land and vegetative condition that then sequesters the carbon once timely moisture occurs. Hope that is easier to understand. Thanks again…

        • Kathy Voth says:

          Hi Chad,

          Thanks for the clarification. Actually, the areas studied were all well managed, and were on areas that had historically been managed well. So again, grazing was not responsible for sequestering carbon. It was just the precipitation that caused increased biomass. In arid regions scientists have found that in drought times, well managed areas will maintain better, but in wet times, everyone looks good. We’ve seen this over and over. But just because grazing may not increase soil carbon sequestration does not mean it has no role in the system. Managing litter and grazing for wildlife habitat are two important ways grazing contributes to the system. There are others as well that we’ll explore in future articles in this series.

  6. Paul Sharpe says:

    If moisture availability might be important, there will be some farms in hilly country that could direct runoff to ponds or dams, which is very common in Australia. Some of this could be used for irrigation in a dry spring. Selecting some early-maturing and some late-maturing forage varieties might help keep up green growth earlier in spring and later in fall.

  7. Chip Hines says:

    The research was probably done in a protocol to eliminate variables. I would suggest testing soils in a real world environment with a known first rate grazier that makes changes throughout the growing season according to natural fluctuations of rainfall.

    • Kathy Voth says:

      Scientific study, by its very nature, strives to reduce variables to provide conclusive answers. When you read the articles, you’ll see that because these scientists were working in real world situations, they modified their grazing plans to adjust for natural fluctuations in forage growth and precipitation. In each case they noted the changes they made, how those changes coincide with best grazing practices, and how the changes affected results.

  8. John Marble says:

    I suspect you will get some rotten tomatoes for this work. Just duck. I am reminded of my favorite Winston Churchill quotation:

    “However beautiful the strategy, you should occasionally look at the results.”

    The thoughtful graziers I know are trying to do their best to improve things on the ground, and the concept of carbon sequestration is a pretty seductive story. I look forward to more analysis in you coming articles.

    Finally, I was heartened by your final paragraph reminding us of all the other good reasons for managing our plants, animals and soils.

  9. Gene Schriefer says:

    Did these studies also review changes in soil organic matter?

    While perhaps not a permanent part of the soil carbon, higher SOM helps the system function better. . . healthier soil, more water storage.

    another tool worth consideration is the addition of biochar to lower quality soils as a soil amendment, which is more stable than SOM.

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