Download - 12 agriculture and climate
Climate Change and Agriculture
• Effects of agriculture on climate change
• Effects of climate change on agriculture
• Most of the effects of agriculture on climate change revolve around greenhouse gases.
- CO2
- CH4
- N2O
• There are also albedo effects.
Climate Change and Agriculture
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• Land clearing is the leading source of agricultural CO2.
Agriculture and CO2
• Forests are much more efficient carbon sinks than farmland.
• Farms waste “carbon space” vertically and horizontally.
Agriculture and CO2
• Agriculture also creates soil disturbance and increased rates of organic decomposition – both result in CO2 release.
Agriculture and CO2
• Soil erosion resulting from agriculture further reduces the land’s ability to uptake carbon.
Agriculture and CO2
Agriculture and CO2
• Forest area in the United States between 1620 and 1920 AD.
Agriculture and CO2
Agriculture and CO2
• Brazil contains 30% of the world’s rainforest.
• That is almost 13 Long Islands a year!
Agriculture and CO2
• Borneo losing 5000 square miles a year (3.6 Long Islands).
• Why? …
Agriculture and CO2
• 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 CO2
• “Slash and burn” agriculture creates CO2 as part of the deforestation process.
Agriculture and CO2
• 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 CO2.
Agriculture and CH4
Agriculture and CH4
• Main agricultural sources are rice paddies, livestock, and termite mounds.
• Landfills, swamps, biomass burning also significant sources.
• Bacteria need oxygen just like we do. In environments where O2 is not available, bacterial will use CO2 as an oxygen source (CO2 in, CH4 out) - anaerobic respiration.
• Standing water with lots of organic matter will quickly turn anaerobic.
Agriculture and CH4
• Typical rice paddy is submerged at least 4 months a year.
Agriculture and CH4
• Rice agriculture contributes 50-100 million tons of CH4 per year to the atmosphere – this is the largest anthropogenic source.
• 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 CH4
Agriculture and CH4
• 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.
Agriculture and CH4
Agriculture and CH4
• 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.
Agriculture and CH4
• Deforestation in the tropics leaves a lot of dead wood that is quickly colonized by termites.
Agriculture and CH4
• Natural methane sources:
Agriculture and CH4
• Anthropogenic methane sources:
• Energy- and ruminant-related methane dominate.
Agriculture and N2O
• Nitrous oxide – “laughing gas.”
• Relatively low concentrations (300 ppb now, 275 ppb pre-industrial).
• 310 times more effective greenhouse has than CO2.
• Similar to anaerobic methane production, bacteria in low/zero-oxygen environments convert nitrite (NO3) to nitrogen gas (N2) and nitrous oxide (N2O).
Agriculture and N2O
• The use of man-made fertilizers rich in nitrogen compounds contributes to N2O production in soils.
• 2-4 million tons of N2O from this source per year.
• Widespread use of animal manure as fertilizer can release substantial amounts.
Agriculture and Climate
• But when did all of this really start?
Agriculture and Climate
• Recently been speculated that humans may have been influencing climate for much longer than previously thought.
Agriculture and Climate
Agriculture and Climate
• When human population decreased, CO2 levels decreased.