Back to top
Credit: Paul Brown/Brown's Ranch

Food

Managed Grazing

Mob grazing on Brown’s Ranch in North Dakota.

Grazing animals create extraordinary environments—witness the Serengeti plains and tall grass prairies of the United States. Where original grasslands are still intact, they are abundant lands with carbon-rich soils. They benefit from the activity of migratory herds that cluster tightly for protection; munch grasses to the crown; disturb the soil with their hooves, intermixing their urine and feces; and then move on.

Managed grazing imitates these herbivores, addressing two key variables: how long livestock grazes a specific area and how long the land rests before animals return. There are three managed-grazing techniques that improve soil health, carbon sequestration, water retention, and forage productivity:

  1. Improved continuous grazing adjusts standard grazing practices and decreases the number of animals per acre.
  2. Rotational grazing moves livestock to fresh paddocks or pastures, allowing those already grazed to recover.
  3. Adaptive multi-paddock grazing shifts animals through smaller paddocks in quick succession, after which the land is given time to recover.

Improved grazing can be very good for the land and sequester from one-half to three tons of carbon per acre. However, it does not address the methane emissions generated by ruminants (cattle, sheep, goats, etc.), which ferment cellulose in their digestive systems and break it down with methane-emitting microbes.

References

André Voisin…theory of…managed grazing: Voisin, André. “Grazing Management in Northern France.” Grass and Forage Science 12, no. 3 (1957): 150-154; Voisin, André. Grass Productivity: An Introduction to Rational Grazing. Washington, D.C.: Island Press, 1988.

meta-analysis of…impacts of grazing: McSherry, Megan E., and Mark E. Ritchie. “Effects of Grazing on Grassland Soil Carbon: A Global Review.” Global Change Biology 19, no. 5 (2013): 1347-57.

carbon [sequestered] per acre: Tennigkeit, Timm, and Andreas Wilkes. “An Assessment of the Potential for Carbon Finance in Rangelands.” Working Paper No. 68. Nairobi, World Agroforestry Centre, 2008; Conant, Richard T. Challenges and Opportunities for Carbon Sequestration in Grassland Systems: A Technical Report on Grassland Management and Climate Change Mitigation. Rome: Food and Agriculture Organization of the United Nations, 2010.

pastures…70 percent of…agricultural land: Toensmeier, Eric. The Carbon Farming Solution. White River Junction, VT: Chelsea Green Publishing, 2016.

increasing [soil] carbon: Toensmeier, Solution; Flannery, Tim F. Now or Never: Why We Must Act Now to End Climate Change and Create a Sustainable Future. New York: Atlantic Monthly Press, 2009.

Will Harris…“heritage and responsibility”: McKenna, Maryn. “From Factory Farm to Organic Icon: Inside White Oak Pastures.” Modern Farmer. September 2013.

holistic and humane system: Byck, Peter. One Hundred Thousand Beating Hearts. 2016. http://www.carbonnationmovie.com/about/clips/244-one-hundred-thousand-beating-hearts-short-film

“how can I make this land better?”: Reece, Chuck. “The Dirt Underneath.” The Bitter Southerner. May 5, 2015.

organic matter…ten times higher: Reece, “Dirt.”

Gabe Brown…“going to help live”: Montgomery, David. Growing a Revolution. New York: W.W. Norton & Company, 2017.

view all book references

Errata

p. 74

Correction: Improved grazing typically sequesters a few hundred pounds of carbon per acre, but in some cases as much as three tons per acre.

Correction: Many who started at 1 percent organic matter are now at 6 to 8 percent, or more.

Correction: Brown has taken soil organic matter from 4 percent to 10 percent in six years.

view all errata

Technical Summary

Managed Grazing

Project Drawdown defines managed grazing as: a set of practices that sequester carbon in grassland soils by adjusting stocking rates, timing, and intensity of grazing. This solution replaces conventional grazing on grasslands, including both pastures and rangelands.

Livestock grazing covers over 3.3 billion hectares, or 25 percent of the world’s land area, making it humanity’s largest land use (Asner et al, 2004). Poor grazing practices have contributed to land degradation and loss of soil carbon. However, there are managed grazing practices that can enhance net carbon sequestration and other modes of soil and vegetation quality on grazing lands via: a) controlled intensity and timing of grazing; b) enclosure of grassland to encourage resting; and/or c) other kinds of planned and adaptive grazing.

Under managed grazing, emissions of the greenhouse gases methane and nitrous oxide continue, but are more than offset by sequestration, at least until soil carbon saturation is achieved. Drawdown takes the conservative assumption that emissions do not change with conversion from conventional to managed grazing.

Methodology

Total Land Area [1]

Total potential land for managed grazing is 1.3 billion hectares, consisting of non-degraded grassland. [2] Current adoption [3] of managed grazing is estimated at 79.2 million hectares. This figure was generated by using a regionally weighted adoption rate from a meta-analysis of 18 data points from 12 sources with data from 7 countries on 5 continents.

Adoption Scenarios [4]

Six custom adoption scenarios were developed based on the low, medium, and high regional linear adoption trends. The conservative adoption scenarios assume adoption through 2050, while some of the aggressive adoption scenarios consider an early peak adoption by 2030.

Impacts of increased adoption of managed grazing from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.

  • Plausible Scenario: Adoption of managed grazing in this scenario is estimated to be 447.8 million hectares.
  • Drawdown Scenario: Adoption of managed grazing in this scenario is estimated to be 576.8 million hectares.
  • Optimum Scenario: Adoption of managed grazing in this scenario is estimated to be 705.9 million hectares.

Despite high availability of the total allocated grassland area, the adoption of managed grazing reaches only 54 percent even under the most aggressive adoption scenarios because of low historical adoption rates.

Emissions, Sequestration, and Yield Model

Sequestration rates are set at 0.63 tons of carbon per hectare per year. This is the result of meta-analysis of 49 data points from 25 sources. It is assumed that there is no change in methane and nitrous oxide emissions on conversion from conventional to managed grazing.

Yield gains compared to business as usual annual grazing were set at 10.2 percent based on meta-analysis of 5 data points from 2 sources.

Financial Model

First costs of managed grazing are estimated at US$136.95 per hectare. [5] For all Drawdown agricultural solutions, it is assumed that there is no comparison first cost as conventional grazing (in this case) is already in place on the land. Results are based on meta-analysis of 5 data points from 4 sources. Net profit per hectare is US$254.08 per year (5 data points from 3 sources), compared to US$145.97 per year for the conventional practice (10 data points from 8 sources).

Integration [6]

Drawdown’s Agro-Ecological Zone model allocates current and projected adoption of solutions to the planet’s forest, grassland, rainfed cropland, and irrigated cropland areas. Adoption of managed grazing was limited to non-degraded grassland, and was the second-highest priority there after silvopasture.

Results

Total adoption in the Plausible Scenario is 447.8 million hectares in 2050, representing 34.3 percent of the total suitable land. Of this, 368.6 million hectares are adopted from 2020-2050. The impact of this scenario is 16.3 gigatons of carbon dioxide-equivalent greenhouse gas emissions reduced by 2050. Net cost is US$50.5 billion. Net savings is US$735.3 billion. Increase in global livestock yield is 3.5 million metric tons between 2015-2050.

Total adoption in the Drawdown Scenario is 576.8 million hectares in 2050, representing 44.2 percent of the total suitable land. Of this, 497.6 million hectares are adopted from 2020-2050. The impact of this scenario is 22.0 gigatons of carbon dioxide-equivalent by 2050.

Total adoption in the Optimum Scenario is 705.9 million hectares in 2050, representing 54.1 percent of the total suitable land. Of this, 626.7 million hectares are adopted from 2020-2050. The impact of this scenario is 27.6 gigatons of carbon dioxide-equivalent by 2050.

Discussion

Benchmarks

Projected impacts for this are within Intergovernmental Panel on Climate Change (IPCC) benchmarks for managed grazing. The IPCC estimates an impact of 0.1-0.8 gigatons of carbon dioxide-equivalent per year by 2030 (Smith, 2007), while the Drawdown model shows 0.6-0.8 gigatons of carbon dioxide-equivalent per year in 2030.

Limitations

A key limitation was the lack of information on current adoption. More robust adoption data would improve the model results. Financial data is also rarely reported and is largely limited to Organization for Economic Cooperation and Development (OECD) countries. Financial results would benefit from robust data from other regions. Yield gain data is also very limited in this study.

Conclusions

Managed grazing is a solution that addresses the world's most widespread land use. It represents a net-sequestration system for producing livestock products. Even the most aggressive plant-based diet scenarios show significant need for livestock products in 2050. Thus, managed grazing is an essential supply-side food solution in any mitigation program.


[1] To learn more about the Total Land Area for the Food Sector, click the Sector Summary: Food link below.

[2] Determining the total available land for a solution is a two-part process. The technical potential is based on the suitability of climate, soils, and slopes, and on degraded or non-degraded status. In the second stage, land is allocated using the Drawdown Agro-Ecological Zone model, based on priorities for each class of land. The total land allocated for each solution is capped at the solution’s maximum adoption in the Optimum Scenario. Thus, in most cases the total available land is less than the technical potential.

[3] Current adoption is defined as the amount of functional demand supplied by the solution in the base year of study. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.

[4] To learn more about Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Land Use Sector-specific scenarios, click the Sector Summary: Food link.

[5] All monetary values are presented in US2014$.

[6] For more on Project Drawdown’s Food Sector integration model, click the Sector Summary: Food link below.

Full models and technical reports coming in late 2017.

Research Inquiry Form

Want more information on Project Drawdown’s research methodology and models? Complete this form to contact the Drawdown Research team.

Which Drawdown solution sector most interests you? * (choose one)
Do you have a copy of Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming? *
What would you like to know about Drawdown’s research methodology and models? * Please note that, due to time and resource constraints, we may not be able to provide extensive information or data.
Other questions, comments, or suggestions:
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
6 + 11 =
Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.
Back to top

Join Us

We would like to stay in touch with you. Please sign up for updates to discover ways you can participate in the work of Drawdown.


Contact

Click to expand
Please send me more information about ways that I can participate as: (check all that apply)
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.