As much as agriculture and forestry are affected by climate change, they are also promoters of climate change, being responsible for 13.5% and 17.4% of global anthropogenic greenhouse gas emissions, respectively. Dumortier et al. (2012) decided to assess the leakage effect that will occur as U.S. cattle production declines. The authors used a combination of a global agricultural production and trade model and a greenhouse gas model to project global leakage of carbon dioxide-equivalent pollutants as a result of declining U.S. cattle production. The leakage effect occurs when countries increase their agricultural production in order to maintain the demand after another nation decreases their production. They found a net increase of 37–85 kg CO2-equivalent per kg of beef globally. The authors attributed this change to inelastic domestic demand and land-intensive cattle production systems that are used internationally. —Anthony Li
Dumortier J., Hayes D. J., Carriquiry M., Dong F., Du X., Elobeid A., Fabiosa J. F., Martin P. A., Mulik K. 2012. The effects of potential changes in United States beef production on global grazing systems and greenhouse gas emissions. Environmental Research Letters 7, 024023
The authors used an agricultural production and trade model along with a greenhouse gas model to project CO2–equivalent pollutants released. The production model projects crop and livestock production, commodity prices, utilization, and crop area based on U.S. beef production decline. Once these projections were made, the authors were able to apply the greenhouse gas model to it. The greenhouse gas model is designed to calculate emissions associated with land-use change and agricultural production. The land-use change component contains emissions as a result of biomass and soil carbon. The agricultural production component accounts for emissions from enteric fermentation, manure management, and agricultural soil management, which all release methane and nitrous oxide. The researchers also accounted for a country’s stocking rate, which is the number of animals allotted to an area for a given length of time. They provided “a sensitivity analysis for major livestock producing countries to identify the carbon savings that could potentially be achieved between the baseline and the scenario by allowing for intensification” of stocking rate. For all countries, they held stocking rates constant except for Brazil, where they allowed it to increase based on historical stocking rate increases.
The findings of this paper were split based on source of emission. For agricultural production, the results based on a U.S. beef production drop of 17.06% showed an increase of emissions by 10.94 Mt CO2-e from enteric fermentation and 13.83 Mt CO2-e from manure management in Brazil and the rest of the world. Overall, emissions from livestock increased slightly by 3.22 Mt CO2-e. For land-use change, results show pasture area in Brazil increasing by 6.85 million ha after a decrease in U.S. pasture of 33.90 million ha. On a global scale, almost 10 million fewer ha of pasture are used. Despite the amount of land saved, the models predict a significant release of carbon in Brazil, projecting that 1961 and 3641 Mt CO2–e is emitted from land-use change in croplands and pastures, respectively. The results show that a decrease in production in one country results in an increase in production in other countries, and subsequent land-use change varies between countries based on stocking rates.
The results show a mixed future for agricultural systems if regulations decrease cattle production. For agricultural production, there is a difference in meat production per head in the US compared to other countries, as the U.S. generally has lower emissions of methane per unit of meat due to the high energy diet the livestock receive and the cattle’s shorter lifetime. Brazil’s cattle’s higher methane per unit of meat is the reason why emissions from enteric fermentation and manure management will increase as U.S. cattle production lowers and foreign production increases. Generally, emissions in the US.. will decline as a result of reduced livestock population, but emissions in other countries will increase because of expanded herd size. The expansion of herd size largely depends on the country’s stocking rate. Countries with lower stocking rates will have to expand their farm area more to compensate for demand for cattle. Subsequently, this causes land-use change and its associated emissions to vary widely from country to country. Emissions also depend on the type of production system that is being decreased and increased. Feedlot production systems are generally more energy and CO2 intensive than pastoral production systems. Although this study did not take into account energy and CO2 associated with production systems, it cited previous studies on this topic.
Adoption of greenhouse gas policies in the agricultural sector may not have its intended consequences. The results of this study generally show that an increasing number of greenhouse gas policy adopting countries will be matched by an increasing amount of emissions by leakage in other countries. This leakage is widely dependent on which countries assume which role in this situation. From this paper, we should note how climate change is a global issue, and policies that address this must take into account its repercussions on a global scale.