12   agriculture and climate
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  • 1. Climate Change and Agriculture
    • Effects of agriculture on climate change
    • Effects of climate change on agriculture
  • 2.
    • Most of the effects of agriculture on climate change revolve around greenhouse gases.
    • - CO 2
    • - CH 4
    • - N 2 O
    • There are also albedo effects.
    Climate Change and Agriculture C O O O N N C H H H H
  • 3.
    • Land clearing is the leading source of agricultural CO 2 .
    Agriculture and CO 2
  • 4.
    • Forests are much more efficient carbon sinks than farmland.
    • Farms waste “carbon space” vertically and horizontally.
    Agriculture and CO 2
  • 5.
    • Agriculture also creates soil disturbance and increased rates of organic decomposition – both result in CO 2 release.
    Agriculture and CO 2
  • 6.
    • Soil erosion resulting from agriculture further reduces the land’s ability to uptake carbon.
    Agriculture and CO 2
  • 7. Agriculture and CO 2
    • Forest area in the United States between 1620 and 1920 AD.
  • 8. Agriculture and CO 2
  • 9. Agriculture and CO 2
    • Brazil contains 30% of the world’s rainforest.
    • That is almost 13 Long Islands a year!
  • 10. Agriculture and CO 2
  • 11.
    • Borneo losing 5000 square miles a year (3.6 Long Islands).
    • Why? …
    Agriculture and CO 2
  • 12.
    • China - high demand for wood (housing, flooring, furniture).
    • Forest is replaced with Palm plantations (palm oil a key ingredient in detergent, soaps, cosmetics, foods, etc. ).
    Agriculture and CO 2
  • 13.
    • “ Slash and burn” agriculture creates CO 2 as part of the deforestation process.
    Agriculture and CO 2
  • 14.
    • Methane is a byproduct of many agricultural activities.
    • Current concentration in the atmosphere is 1700 parts per billion – preindustrial concentration was less than half of that (700 ppb).
    • 21 times more effective greenhouse gas than CO 2 .
    Agriculture and CH 4
  • 15. Agriculture and CH 4
    • Main agricultural sources are rice paddies, livestock, and termite mounds.
    • Landfills, swamps, biomass burning also significant sources.
  • 16.
    • Bacteria need oxygen just like we do. In environments where O 2 is not available, bacterial will use CO 2 as an oxygen source (CO 2 in, CH 4 out) - anaerobic respiration.
    • Standing water with lots of organic matter will quickly turn anaerobic.
    Agriculture and CH 4
  • 17.
    • Typical rice paddy is submerged at least 4 months a year.
    Agriculture and CH 4
    • Rice agriculture contributes 50-100 million tons of CH 4 per year to the atmosphere – this is the largest anthropogenic source.
  • 18.
    • What to do about it?
    • Experimenting with varieties that don’t require as much water, and denser-growing varieties (more rice per paddy).
    • Using specific fertilizers can also make a difference.
    Agriculture and CH 4
  • 19. Agriculture and CH 4
    • Livestock (cows in particular) are the next major agricultural source of methane.
    • 100 million tons per year.
    • Comes from bacteria living in the animals’ stomachs and intestines.
  • 20. Agriculture and CH 4
  • 21. Agriculture and CH 4
    • Decomposition of cow and chicken manure accounts for another 25 million tons of methane.
    • Some of this gets collected in slurry tanks (“biogas”) and is used as fuel.
  • 22. Agriculture and CH 4
    • Deforestation in the tropics leaves a lot of dead wood that is quickly colonized by termites.
  • 23. Agriculture and CH 4
    • Natural methane sources:
  • 24. Agriculture and CH 4
    • Anthropogenic methane sources:
    • Energy- and ruminant-related methane dominate.
  • 25. Agriculture and N 2 O
    • Nitrous oxide – “laughing gas.”
    • Relatively low concentrations (300 ppb now , 275 ppb pre-industrial).
    • 310 times more effective greenhouse has than CO 2 .
    • Similar to anaerobic methane production, bacteria in low/zero-oxygen environments convert nitrite (NO 3 ) to nitrogen gas (N 2 ) and nitrous oxide (N 2 O).
  • 26. Agriculture and N 2 O
    • The use of man-made fertilizers rich in nitrogen compounds contributes to N 2 O production in soils.
    • 2-4 million tons of N 2 O from this source per year.
    • Widespread use of animal manure as fertilizer can release substantial amounts.
  • 27. Agriculture and Climate
    • But when did all of this really start?
  • 28. Agriculture and Climate
    • Recently been speculated that humans may have been influencing climate for much longer than previously thought.
  • 29. Agriculture and Climate
  • 30. Agriculture and Climate
    • When human population decreased, CO 2 levels decreased.