Generated Summary
This document is a primer from Project Drawdown, focusing on the role of agriculture and land use in addressing climate change. It explores how changes in land use, agricultural practices, and food systems offer opportunities to reduce greenhouse gas emissions, sequester atmospheric carbon, and help address climate change. The study uses a multi-faceted approach, examining the impacts of food, agriculture, and land use, strategies for reducing greenhouse gas emissions from agriculture, and the potential for creating carbon sinks on working lands. The research emphasizes the significant contribution of agriculture and land use to climate change, highlighting the need for both emissions reductions and carbon sequestration to achieve meaningful progress. The document also covers the limitations and challenges associated with carbon sequestration, particularly in the context of agricultural lands, and underscores the importance of addressing methane emissions from livestock. It also analyzes the importance of sustainable agriculture and dietary choices to mitigate climate change and highlights the potential of various farming practices to sequester carbon.
Key Findings & Statistics
- Agriculture and land use contribute to about 24% of the world’s greenhouse gas emissions.
- Roughly 24% of greenhouse gas emissions stem from food, land use, and agricultural practices.
- Fossil fuels account for about 62% of today’s climate warming, while the remaining 38% comes from other sources.
- The food, agriculture, and land use sector ties electricity generation (at ~24% and ~25% of total emissions) as the top two contributors to climate change.
- Methane (CH4) emissions from agriculture and industry contribute to about 10% of greenhouse gases.
- Nitrous oxide (N2O) from agriculture and industry contributes to about 6% of greenhouse gases.
- Deforestation and land use contribute about 11% of greenhouse gases.
- The largest single source of greenhouse gases from land use and agriculture is tropical deforestation and other land use (~9%).
- Methane (CH4) emissions are the second largest source of greenhouse gases from land use & agriculture.
- Methane is a powerful greenhouse gas, trapping nearly 28 times the heat of CO2 on a molecule-for-molecule basis, averaged over 100 years.
- Livestock production, including land use change, is the source of ~14-15% of all anthropogenic greenhouse gas emissions, while producing only 10% of the world’s food.
- The use of fertilizers and animal manures has doubled or tripled the flows of nitrogen and phosphorus across the Earth’s surface.
- About 35% of the world’s ice-free land is used for croplands and pastures.
- Roughly 70% of the world’s water withdrawals are devoted to irrigation and other agricultural uses.
- Agriculture is responsible for about 85% of global water use.
- The residence time of methane in the atmosphere is a little over a decade.
- Nitrous oxide is approximately 300 times more powerful than CO2 in trapping heat in the atmosphere on a molecule-for-molecule basis, and lasts in the atmosphere for several centuries.
- Livestock production is responsible for a large portion of the world’s agricultural emissions; about a third of all crops are grown for livestock feed.
- Enteric fermentation from livestock currently emits ~2.1 Gt CO2-eq of methane per year and is projected to rise to ~3.4 by 2050.
- Overall, the potential of enteric fermentation reduction has been estimated to be ~0.4-1.2 Gt CO2-eq / yr — a ~12–35% reduction of 2050 levels.
- Manure emits ~0.88 Gt CO2-eq/yr today and is projected to increase to ~1.5 Gt by 2050.
- The potential for reducing methane and nitrous oxide emissions from manure is limited, ranging from 0.01-0.26 Gt CO2-eq/yr.
- Emissions from overuse and inappropriate use of synthetic fertilizers are a major source of nitrous oxide. Approaches to reducing emissions include better management of synthetic fertilizers and use of alternative nitrogen sources. Estimates of the potential of these solutions range from 0.03-1.07 Gt CO2-eq/yr.
- Current emissions from other sources is 0.67 Gt CO2-eq, projected to rise to 1.09 by 2050. Emissions reduction potential is estimated at 1.6-3.3 Gt CO2-eq.
- For every billion metric tons of CO2 that is sequestered, 25 million metric tons of nitrogen is required.
- The world’s current greenhouse gas emissions are equivalent to roughly 52 Gt-CO2-eq per year. These lifetime estimates for carbon uptake on agricultural lands range between 1.3 to 8.5 times higher.
Other Important Findings
- Conserving and restoring tropical forests is essential to reduce greenhouse gas emissions.
- New methods of animal agriculture, including feed additives and improved grazing techniques, can help lower methane emissions.
- More prudent use of nitrogen fertilizers and manure in farming can reduce nitrous oxide (N2O) emissions.
- Reducing food waste and adopting plant-rich diets can significantly lower the environmental impact of agriculture.
- The potential for enteric fermentation reduction has been estimated to be ~0.4-1.2 Gt CO2-eq / yr — a ~12–35% reduction of 2050 levels.
- High-quality feeds like grains produce less methane in the ruminant digestive system.
- The potential for reducing methane and nitrous oxide emissions from manure is limited, ranging from 0.01-0.26 Gt CO2-eq/yr.
- Manure management can be improved by cooling manure, covering during storage, separating liquids and solids, aeration, and applying chemical additives and nitrification inhibitors.
- The potential of peatland restoration range from 0.51-2.00 Gt CO2-eq/yr.
- Managed grazing can also increase soil carbon.
- In order to stop climate change, we must ultimately achieve “net zero” emissions of greenhouse gases.
- By deploying different agricultural practices – usually referred to as “regenerative agriculture” – it is possible to create new carbon sinks.
- The build-up of soil organic carbon can potentially offset these methane emissions for a time, but if the build-up of soil carbon eventually slows down, as scientists believe it inevitably almost always will, it will become challenging to continue to offset the cattle methane emissions.
Limitations Noted in the Document
- The document acknowledges that the potential for carbon sequestration on working lands is still subject to many open questions.
- The build-up of soil organic carbon can potentially offset methane emissions for a time, but this will not last.
- The document emphasizes that the sequestration rates decrease as biomass and soils asymptotically reach a “slowdown,” and a dynamic equilibrium between carbon inputs and losses, and estimates of agricultural carbon sinks must take this into account.
- The document highlights that the practices that sequestered carbon are discontinued, the carbon that was gained can be quickly emitted back to the atmosphere – especially carbon that is not bound to mineral particles.
- The text also recognizes that the capacity of soil methane sinks is limited compared to the overall emissions from agriculture.
- Estimates for the area of grassland amenable to carbon sequestration through improved grazing and pasture management are based on more conservative figures.
- The document also notes that there are many complexities that affect sequestration in grazing systems, including the mix of warm- versus cool-season grasses, rainfall, and soil texture, and grazing intensity.
- The document recognizes that emissions from agriculture can be reduced through regenerative practices but that carbon stored in soils and biomass can be lost because of climate change and other disturbances
Conclusion
The core message is that the world’s food system, agricultural practices, and land use play a critical role in climate change. The document strongly advocates for immediate emissions reductions and long-term investments in regenerative agriculture. The analysis underscores that agriculture and land use are significant contributors to climate change, primarily due to deforestation, methane emissions from livestock, and nitrous oxide emissions from fertilizers. The solution involves a two-pronged approach: reducing emissions from agricultural practices and enhancing carbon sinks. It emphasizes the potential of regenerative agriculture, including practices like agroforestry and managed grazing, to create new carbon sinks and improve soil health. The text also highlights the significance of addressing methane emissions from livestock, while simultaneously acknowledging the challenges in achieving that. The document does emphasize the need for a diverse approach that includes reducing food waste, promoting healthier diets, and addressing the overuse of fertilizers. The document concludes with a call to action, urging a multi-sectoral approach involving agriculture, land use, and other sectors to achieve a comprehensive climate solution. It is the need to manage carbon sinks well into the future to avoid releasing carbon back into the atmosphere, and recognize the risks associated with the lack of permanence in agricultural carbon stocks. The document highlights that the challenges in making agricultural changes involve policy, practice, capital, and behavior. It suggests that the various solution sets could generate incredible economic and social co-benefits. The goal is to combine these, and the main question is: will we?