Consequences of human activity

• Deforestation (Madagascar):

  • Minining for nickel + lots of rainforest clearing. Over 35 years, 2/3 of rainforest lost
• Deforestation (Madagascar):

  • Less trees = weaker sink. Soil becomes saturated = soil erosion. Less vegetation = less nutrients in soil
• Deforestation (Madagascar):

  • Soil erosion: 400 tonnes per hectare / year in some regions.
• Deforestation (Madagascar):

  • Reducated evaporation + evapotranspiration. Less rainfall. Positive feedback. Smaller lag time = increased surface runoff
• Conversion of grassland to farming (US prairies):

  • Farmers encouraged to grow soya + corn. Therefore can increase ethanol in petrol. Boost rural economies + reduce OPEC influence
• Conversion of grassland to farming (US prairies):

  • Ethanol in petrol can reduce emissions by roughly 2%
• Conversion of grassland to farming (US prairies):

  • Farms are not a greater carbon sink that grasslands
• Conversion of grassland to farming (US prairies):

  • Fertilisers required which can infiltrate into water sources
• Conversion of grassland to farming (US prairies):

  • Heavy irrigation. Aquifers drained - Ogallala Aquifer dropped 5 feet in peak extraction
• Afforestation (Africa's Great Green Wall):

  • Aims to restore 100m hectares of degraded land
• Afforestation (Africa's Great Green Wall):

  • Aims to create 10m jobs, and will sequester 250m tons of CO2
• Afforestation (Africa's Great Green Wall):

  • Soil binded by roots - less erosion. Greater nutrients
• Afforestation (Africa's Great Green Wall):

  • Increased interception and greater groundwater storage. Less GHG