Cool Farming: Climate Impacts Of Agriculture And Mitigation Potential

Generated Summary

This document, titled “Cool Farming: Climate impacts of agriculture and mitigation potential,” presents a comprehensive analysis of the environmental impacts of agriculture, with a specific focus on greenhouse gas (GHG) emissions and potential mitigation strategies. The study, conducted by Greenpeace, examines the contributions of agriculture to global GHG emissions, the various sources of these emissions, and the potential for reducing agriculture’s climate impact. The research approach involves an overview of data from the IPCC and other sources to examine the link between agricultural practices and climate change, exploring how different farming methods and dietary choices affect emissions. The study provides data on various farming practices, including cropland management, livestock management, and fertiliser use. The research also explores the potential of changing dietary patterns as a means of reducing agricultural emissions, particularly through the reduction of meat consumption. The scope includes the examination of the global contribution of agriculture to GHG emissions, and it assesses mitigation options that could change the role of agriculture from a major emitter to a carbon sink. The methodology includes an overview of the main sources of greenhouse gas emissions in agriculture and the potential for their mitigation.

Key Findings & Statistics

• Agriculture contributes significantly to greenhouse gas emissions (GHG), with the total global contribution ranging between 8.5-16.5 Pg CO2-eq, representing 17-32% of all global human-induced GHG emissions.
• Agricultural lands occupy about 40-50% of the Earth’s surface, accounting for an estimated emission of 5.1 to 6.1 Pg CO2-eq yr-¹ in 2005.
• Methane (CH4) contributes 3.3 Pg CO2-eq yr-¹ and nitrous oxide (N2O) 2.8 Pg CO2-eq yr-¹ of global anthropogenic emissions.
• Agriculture accounts for about 60% of N2O and about 50% of CH4 of global anthropogenic emissions in 2005.
• Nitrous oxide emissions from soils and CH4 from enteric fermentation of cattle constitute the largest sources, 38% and 32% of total non-CO2 emissions from agriculture in 2005, respectively.
• Globally, agricultural CH4 and N2O emissions increased by nearly 17% from 1990 to 2005, with an average annual emission increase of about 0.06 Pg CO2-eq yr-¹.
• The Middle East and North Africa, and Sub-Saharan Africa have the highest projected growth in emissions, with a combined 95% increase in the period 1990 to 2020.
• East Asia is projected to show large increases in GHG emissions from animal sources.
• Total global agricultural GHG emissions will be the sum of agricultural emissions (5.1 – 6.1 Pg, 10 – 12% of total global emissions), land use change (5.9 ± 2.9 Pg; 6 – 17% of total global emissions), agrochemical production/distribution (0.3 -0.7 Pg, 0.6-1.4% of total global emissions) and farm operations (including irrigation) (0.1 – 0.9 Pg, 0.2 – 1.8% of total global emissions).
• The production of fertilisers is energy intensive, and adds a noticeable amount, between 300 and 600 million tonnes (0.3 – 0.6 Pg) CO2-eq yr-¹, representing between 0.6 – 1.2% of the world’s total GHGs.
• The greatest source of GHG emissions from fertiliser production is the energy required, which emits carbon dioxide, although nitrate production generates even more CO2-eq in the form of nitrous oxide.
• Animal farming has a wide range of different impacts, ranging from the direct emissions of livestock, manure management, use of agrochemicals and land use change to fossil fuel use.
• Enteric fermentation contributes about 60%, the largest amount, to global methane emissions.
• Beef meat has the highest climate impact of all types of meat, with a global warming potential of 17 kg CO2-eq per kg of meat, while pig and poultry have less than half of that.
• The overall potential for mitigation in agriculture emissions is up to 6 Pg CO2-eq yr-¹, but with economic potentials of around 4 Pg CO2-eq yr-¹ at carbon prices up to 100 US$ t CO2-eq¯¹.
• A person with an average US diet for example, could save 385 kcal (equating to 95 – 126 g CO2) of fossil fuel per day by replacing 5% of meat in the diet with vegetarian products.
• The area of rice grown globally is forecast to increase by 4.5% to 2030, so methane emissions from rice production would not be expected to increase substantially.

Other Important Findings

• The study identifies that agricultural practices have changed dramatically since the advent of agriculture, with more recent changes including the use of synthetic fertilizers, mechanization, and large-scale farming systems.
• Intensive agriculture relies on high external inputs, particularly of fertilisers, pesticides, herbicides, irrigation and fossil fuels.
• The solution to the environmental problems caused by today’s agricultural methods lies in a shift to farming practices which could provide large-scale carbon sinks.
• A reduction of meat consumption could greatly reduce agricultural GHG emissions.
• The expansion of croplands is thought to be over, though expansion into tropical forests continues to be a major problem.
• Global woodland areas are projected to decrease at an annual rate of ~43,000 km², but developed countries are projected to increase their woodland area by 7,400 km² per year.
• The study examines the potential for the mitigation of greenhouse gas emissions from agriculture, with a global technical mitigation potential by 2030 of each agricultural management practice.
• The conversion of arable cropland to grassland or forest typically acts as a carbon sink.
• The conversion of drained croplands back to wetlands can result in an even greater carbon sink.
• Smallholder farms may often store more carbon than commercial arable agriculture due to more trees.
• Organic farmers usually apply practices that promote carbon sequestration in the soil and could favour GHG savings from organic cropping.

Limitations Noted in the Document

• The document notes that a quantified separation of intensive and extensive agriculture is difficult due to complex interactions between practices, the lack of readily available statistics, and the presence of both types of practices on the same farm.
• The study also acknowledges that the actual contribution of land use change has a high uncertainty.
• The document also mentions that, in industrial farming settings, the increase in reliance on herbicides and machinery may offset benefits.
• The study also indicates the economic potential for mitigation is a maximum of 4.3 Pg CO2-eq yr¹ at a carbon price of 100 US$ t CO2-eq.
• The document suggests that the values given in Table 8 should be considered with caution because forest projects are less standardized in regard to baselines and actual costs.

Conclusion

The study’s key finding is that agriculture has a significant mitigation potential, which could change its position from a major GHG emitter to a much smaller source or even a net carbon sink. This can be achieved through various strategies, including improved cropland management, grazing-land management, and the restoration of organic soils as carbon sinks. The research emphasizes that a shift to farming practices that provide large-scale carbon sinks is crucial for mitigating climate change. A particularly impactful change, as noted by the study, is the reduction of meat consumption. The study also provides an important recognition of the role of diet in reducing GHG emissions. Adopting a vegetarian diet, or at least reducing the quantity of meat products in the diet, would have beneficial GHG impacts. Considering the large contribution of agriculture to overall emissions, the potential impact of mitigation efforts is substantial. The study suggests that by taking appropriate steps, agriculture could transform from a significant source of emissions to one that is less impactful, or even a net carbon sink. The document emphasizes that the most effective approach is to improve cropland management, grazing-land management, and the restoration of organic soils as carbon sinks, which together could change the position of agriculture from one of the largest greenhouse gas emitters to a much smaller GHG source or even a net carbon sink. The options for mitigating emissions, the study notes, require a multi-faceted approach. Several of the mitigation strategies are related to changes in land use, as the authors write, “the reversion of cropland to another land cover, typically one similar to the native vegetation is one of the most effective methods of reducing emissions / increasing carbon sinks.”