Shift in Herbaceous Biomass on Global Rangelands Projected To Affect Meat and Milk Production in Low-Income Countries

Cattle production is a global industry that provides protein and income to regions around the world as well as a nutritional and financial safety net for low-income populations. In many places, cattle graze on rangelands, which contain grasses and grass-like plants, shrubs, and even trees. In the coming decades, rising temperatures and shifting rainfall patterns associated with climate change may affect the growth of rangeland forage for livestock, which in turn could affect the production of meat and milk in some of the lowest income regions of the world. 

To understand how climate change might alter cattle production globally and regionally, researchers from USDA’s Economic Research Service modeled the effects of temperature and rainfall changes through 2050 on rangeland herbaceous biomass, which consists of nonwoody plants such as grasses that livestock consume as forage. They looked at scenarios that simulated high concentrations of greenhouse gas associated with climate change and found the total amount of herbaceous biomass on rangelands globally would decline by 4 percent in the next quarter century. The researchers then estimated how such a shift in livestock forage would potentially affect meat and milk production and found these changes were forecast to be small. Global meat production would stay about the same and milk production is expected to decline by 1 percent. However, the results varied regionally, with the most vulnerable populations expected to suffer the largest losses in biomass, meat, and milk production. 

Shifts in Herbaceous Biomass To Vary by Region

Livestock production contributes about 40 percent of the global value of agricultural output in developed countries and 20 percent in developing countries. Because of geographical differences in climate and latitude, the distribution and abundance of grazeable rangeland for livestock also varies. In some regions, rangeland vegetation is the primary source of nutrition, and in others, ranchers supplement it with other types of feed, such as grain.  

Researchers found the estimated effects of climate change on herbaceous biomass grown on rangelands varied by region. In general, researchers estimated that areas near more northern latitudes and those at higher elevations, both of which tend to have cooler climates, would fare better if temperatures warmed up than regions that are already relatively hot. Some of the regions affected the most were in Africa, where rangeland dominates the landscape. For instance, shifts in temperature and rainfall were projected to result in the depletion up to 34 percent of western Africa’s herbaceous biomass by 2050. Mexico and Central America also were expected to see reductions. Other regions were projected to see an increase in biomass concentrations, with the largest gain in northern Europe at 37 percent. North America, which has more biomass than most European regions, was estimated to gain 15 percent by 2050. Within North America, the gains for Canadian rangelands were estimated at 45 percent, higher than the projected 3 percent gains in the United States. Most U.S. rangeland is in the western half of the country, which showed a mix of gains and losses that averaged out to a small overall gain. 

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Changes in Potential Beef and Milk Production Follow Regional Shifts in Forage

After determining the potential effect of climate change on rangeland and livestock forage, researchers used that information to estimate the consequence for meat and milk production. They found that shifts in meat and milk production generally followed the results of the herbaceous biomass. 

 Some areas of the world that had large increases in herbaceous biomass (particularly North America) had highly productive livestock sectors, meaning that cattle in these regions can gain more weight on average for a given quantity of feed than in other regions. Thus, the potential increases in herbaceous biomass translated to very large increases in beef and milk production in these areas. This is, in part, why global losses to meat and milk production are smaller than global losses in herbaceous biomass. Model results indicate North America is expected to gain 11 percent in meat and milk production after a 15-percent estimated gain in herbaceous biomass. In some of the northern and currently colder latitudes of North America, where projected vegetation growth was highest, cattle are not grazed, so those areas were not included in the meat and milk estimates. As with the biomass results, projected gains in beef and milk production were higher for Canada than for the United States (almost 50 percent compared with 2 percent).

Other regions such as in Africa and Mexico and Central America were expected to lose meat and milk production after climate change-related decreases in herbaceous biomass.  

Greatest Losses in Meat and Milk Production Would Occur in Areas With Higher Cattle Densities 

Areas with higher densities of cattle are projected to lose more herbaceous biomass on average than those with lower densities of cattle and thus would suffer greater losses in meat and milk production because of climate change. When considering areas that have at least 10 cattle per 55-by-55-kilometer grid square, global meat and milk production were estimated to decline by about 1 percent and 3 percent, respectively. By contrast, areas that have at least 500 cattle per grid square were estimated to lose nearly 6 percent meat production and 8 percent milk production. In some areas where higher temperatures and lower rainfall were expected to boost forage volume, such as in high northern latitudes in Canada, there are fewer cattle per square kilometer, so areas of losses tended to be concentrated in areas of higher cattle densities.

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Lower Economic Development Associated with Greater Losses in Meat and Milk Production

Climate change was estimated to have more profound effects on some regions than others, with production losses in milk and meat in hot regions with low levels of economic development. The least-developed countries of the world, mostly in Africa and Asia, were expected to lose about 14 percent of their meat and milk production collectively. Previous research also has shown that livestock in hot climates would be particularly vulnerable to heat stress exacerbated by climate change.

By contrast, developed countries in the Group of Seven economic group (Canada, France, Germany, Italy, Japan, the United Kingdom, and the United States) could collectively see a 10-percent increase in meat and milk production. Emerging economies in Brazil, Russia, India, and China (known as the BRIC countries) also were estimated to experience net gains, while most other regions are forecast to experience net losses. 

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Researchers also looked at a scenario in which increased rates of carbon dioxide in the atmosphere, a process known as carbon fertilization, would help plants grow. In carbon fertilization, increased carbon dioxide concentrations promote growth in some plants by increasing the rate of photosynthesis. Especially for plants that currently are in areas of lower temperatures and earlier growing seasons (including temperate grasses, as well as wheat, rice, and soybeans), carbon fertilization could offset the negative effects of temperature and precipitation changes, leading to growth in herbaceous biomass, milk, and meat production. Under this scenario, results still varied widely by region, with losses in production in some of the world’s most vulnerable areas.