BIO3082 Lecture Notes - Lecture 3: Atmospheric Methane, Sustainable Agriculture, Water Pollution
Lecture 3 – Agricultural Impacts
Agriculture is essential for Human Development
• Agriculture has fed the human population and driven economic and social
development
• Its importance will increase in a growing and warming world
• 28% of global population is directly or indirectly employed by agriculture
How Unsustainable Agricultural Contributes to Biodiversity Loss
• Triple threat to biota
1. Habitat Destruction
▪ Deforestation, land clearing and water withdrawal and soil
erosion
2. Greenhouse Gas Emissions
▪ Global methane and nitrous oxide emissions
3. Pollution and Eutrophication
▪ Fertilisers and run-off
• Sustainable solutions must balance needs
o Sustainable development depends on increasing food production to
accommodate growing population, whilst simultaneously reducing the
environmental footprint of agriculture
o Goals for 2050:
▪ Food distribution and access
▪ Resilience of food system
▪ Water pollution
▪ Unsustainable water withdrawals
Differentiate Agricultural Processes that Cause CH4 and N2O Emissions
▪ Sources and Sinks of atmospheric methane
o Naturally methane is produced and consumed
o Ruminants are a major source of methane
▪ Livestock ruminants
• 1.5 billion cattle, 1.1 billion sheep and 0.9 billion goats
• Produce fermentation → H2
• Up to 500 L of CH4 produced per day
▪ N2O Emissions
o Ruminants increase nitrogen loading in soils by
excreting large amounts of urea (urine) and organic
nitrogen (dung)
o Crop cultivation also drive emissions
o Ammonium based fertilisers
▪ 50% absorbed by plant, rest oxidised by
microbes: accumulates in soils or leaches into
water bodies
Metabolic Pathways that Consume and Produce CH4 and N2O
▪ CH4
o Cellulose is fermented by the ruminant microbiome
o Acetate, propionate and butyrate absorbed in
ruminant bloodstream
▪ Generates growth and gaseous molecules like CO2
find more resources at oneclass.com
find more resources at oneclass.com
