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 more than 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. Project Drawdown takes the conservative assumption that emissions do not change with conversion from conventional to managed grazing.
Total Land Area
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 nondegraded status. In the second stage, land is allocated using the Project 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.
Total potential land for managed grazing is 1.2 billion hectares, consisting of nondegraded grassland. Current adoption of managed grazing (defined as the amount of functional demand supplied in 2014) is estimated at 71.6 million hectares. This figure is the mean in million hectares of: 1) total reported adoption from the two leading holistic grazing nongovernmental organizations (NGOs), 2) the total certified organic grazing land as reported by two leading NGOs, 3) the total of data points from five studies representing South America, Canada, the US, Australia, and China, which collectively account for 54 percent of global grazing land (FAOStat 2019).
Ten custom adoption scenarios were developed based on the low, medium, and high regional and country level estimates available in the literature and gathered through personal communication. 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 to 2050 were generated based on two growth scenarios. These were assessed in comparison with a Reference Scenario, in which the solution’s market share was fixed at the current levels.
- Scenario 1: Adoption of managed grazing in this scenario is estimated to be 502.1 million hectares.
- Scenario 2: Adoption of managed grazing in this scenario is estimated to be 749.02 million hectares.
Emissions, Sequestration, and Yield Model
Sequestration rates are 0.67, 0.48, 0.64, and 0.63 tons of carbon per hectare per year for tropical-humid, temperate/boreal-humid, tropical semi-arid, and temperate/boreal semi-arid areas, respectively. This is the result of meta-analysis of 55 data points from 22 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 21.4 percent based on meta-analysis of 14 data points from 11 sources.
All monetary values are presented in 2014 US$.
First costs of managed grazing are estimated at US$75.01 per hectare. For all Project Drawdown grazing 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 15 data points from five sources. Net profit per hectare is calculated at US$342.2 per year for the solution (based on meta-analysis of 18 data points from 12 sources), compared with US$154.12 per year for the conventional practice (based on 20 data points from 15 sources). Annual operational cost per hectare is calculated at US$626.43 for the solution (based on meta-analysis of 15 data points from 10 sources), compared with US$672.41 for the conventional practice (based on 11 data points from eight sources).
Tropical staple trees are not as labor-efficient as annual crops, in a mechanized context. However, 175 million hectares of the world’s farms are smallholders with little mechanization. The net profit per hectare figure shows that these crops are economically viable despite higher labor costs.
Project 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 nondegraded grassland, and was the second-highest priority there after silvopasture.
Total adoption in Scenario 1 is 502.1 million hectares in 2050, representing 43 percent of the total suitable land. Of this, 430.51 million hectares are adopted from 2020 to 2050. The impact of this scenario is 16.4 gigatons of carbon dioxide-equivalent greenhouse gas emissions reduced by 2050. Net cost is US$33.6 billion. Net savings in profit is US$2.1trillion and in operational cost is US$640.8 billion. Increase in global livestock yield is 4.26 million metric tons from 2020 to 2050.
Total adoption in Scenario 2 is 749.02 million hectares in 2050, representing 65 percent of the total suitable land. Of this, 677.39 million hectares are adopted from 2020 to 2050. The impact of this scenario is 26.0 gigatons of carbon dioxide-equivalent by 2050. Net cost is US$52.9 billion. Net savings in profit is US$3.4 trillion and in operational cost is US$1010.8 billion. Increase in global livestock yield is 6.74 million metric tons from 2020 to 2050.
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), and IPCC (2019) ranks managed grazing as having a “moderate” climate impact, a category for which the range is 0.3–3.0 gigatons of carbon dioxide-equivalent greenhouse gas emissions per year in 2030, while the Project Drawdown model shows 0.4–0.7 gigatons of carbon dioxide-equivalent per year in 2030. The Project Drawdown model’s calculations are thus in line with the available benchmarks.
A key limitation was the lack of information on current adoption. More robust adoption data would improve the model results. Financial data are also rarely reported and are 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.
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.