1. Intro

• Agriculture → CO2 emissions, but also majority of CH4 and NO2 emissions
• Overall, agriculture/land use & electricity generation → equal global impact on climate change
• Can work to reduce emissions, and also offers potential as carbon sinks (regenerative agriculture)— note, carbon sinks are important, but slower effect & themselves threatened by changing environmental conditions

2. Climate impacts of food, agriculture, and land use (FALU)

• Clearing land & habitats → single biggest driver of biodiversity loss
• Dominant driver of water use (85% global water use)
• In order, climate change contributions from FALU = tropical land deforestation, methane emissions, nitrous oxide emissions
• Livestock production is main responsibility: land use for pasture, emissions from cattle, growth of crops for feed

3. Reducing greenhouse emissions from agriculture

• Conserving and restoring tropical rainforests
• New methods of animal agriculture
  • Reduce methane emissions from ruminant livestock by: increasing food digestibility, feed additives, breeding & management, improved forage quality, tree fodder
  • Manure management from all livestock
• New methods of rice cultivation (currently produce lots of methane)
• More prudent fertiliser use
  • Nutrient management of synthetic fertilizers, compost/manure/nitrogen-fixing plants as nitrogen sources, crop-livestock integration
• Indirect strategies that lower demand: reduce food waste, promote plant-rich diets, intensify agriculture to be more productive/efficient

4. Creating carbon sinks on working land

• ~55% of our CO2 emissions already absorbed by forests and oceans
• Three main carbon pools: biomass carbon (above ground, like wood*, and below ground, like roots) detritus carbon, soil organic carbon (can influence by balance of input by farmers and losses by microbial degradation via farming practices)
  • vast majority of all biomass carbon
  • Rate of carbon sequestration by landscapes slows down (approaches saturation) on scale of 20-100 years
• Practices to promote sequestration: restoring forests and planting large areas of trees, using regenerative techniques to help crop & grazing lands accumulate more carbon, perennialize agriculture
  • Agroforestry = key example
• Size of carbon sinks constrained by availability of other nutrients, water
• Overcoming methane emissions from cattle is still a challenge— limited capacity of land as "methane sink"
• New initiatives to also address increasing soil inorganic carbon (rocks and such)

5. How much carbon can we sequester and for how long?

• How much land can we use?
  • Should not convert natural ecosystems to agricultural land to sequester carbon— the former are almost always more effective
• How much carbon can each hectare of land sequester?
  • Ultimately, no one knows— need to be careful with how you estimate
• How long can agricultural landscapes hold carbon?
  • In biomass, mainly limited by lifetime of trees
  • For soil organic carbon, depends on practices being maintained → must be mindful of this!

6. Conclusion: We must change agriculture to help address climate change.