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Summary Human impact
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Summary and notes needed for grade 12, Relative to both IEB and NSC
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- Earth’s atmosphere = 78% Nitrogen, 21% Oxygen, Rest = water vapour, - Definition → the amount of CO2 added to the atmosphere by humanArgon, CO2 and Ozone (O3). activities. (can have a heavy / light footprint)
- Greenhouse gases = water vapour, methane, ozone, CO2 & nitrous oxide - Heavy carbon footprint = large emissions = damage to the environment.
- An ↑ in GHG’s = ↑ average temperature on Earth (global warming → - Certain activities release a set amount of CO2 → “emission factor”
leads to climate change) - Eg. petrol’s emission factor = 2,68 CO2 per litre
- Climate change = rapid, no time for organisms to adapt
- CO2 = colourless & odourless
- Term was first used by Svante Arrhenius, Swedish scientist.
- Release of CO2 = decomposition of dead organic material, product of
- In a greenhouse, heat from the sun enters & warms the plants.
cellular respiration, power stations burn fossil fuels to produce electricity
- The plants then give off heat & cannot pass back out through the glass →
(demand ↑ ∴ ↑ need for burning); transport of people by cars (burn
trapped.
gasoline)
- This effect maintains life on Earth.
- SA = largest emitter of CO2 in Africa!
- Earth’s atmosphere lets short wavelengths of sunlight (that have lots of
- As population grows, there is ↑ demand to transport goods & people.
energy) pass through.
- When sunlight strikes & warms Earth’s surface, it loses some energy.
4
- Heat energy goes back into the atmosphere & some escapes into space,
but most of it is absorbed by GHG’s ∴ heat is trapped → global warming! - Anaerobic respiration in mammals
- Decaying organic wastes in land-fill sites
- Treatment of waste water
- Agricultural activities
- Mining (methane is trapped in lower levels of the earth)
- Ice melts (methane is trapped in crystal structure)
- Combustion of fossil fuels
, - Via Nitrogen-rich fertilizers - Definition → thinning of the ozone layer
- Ozone in upper atmosphere reduces dangerous UV radiation that
reaches Earth.
- Causes of ozone depletion = chlorofluorocarbons (CFCs) which are used
- Definition → the process of changing land use from forestry to a non- in fridges & aerosols
forest use (agriculture, mining, housing) - How it ↑ CO2 = more UV light reaches earth, then plants die or can no
- Reforestation → replanting trees to get forests back longer photosynthesise at the same rate ∴ lots of the CO2 remains in the
- Afforestation → grow trees to sell for commercial use atmosphere
- Forests act as carbon “sinks” → use up CO2 - Other effects = causes skin cancer; affects human immune system
- Reasons for deforestation = fuel, wood & paper products, grazing space, - Solutions to ozone depletion = international action has been taken to
roads, mining, replaced by plantations (eg. palm oil plantations) & limit CFC’s → Montreal Protocol
agriculture → bring in money. - Montreal Protocol = 160 nations agreed to phase out CFCs.
- How it leads to an increase in GHG’s: - Other ways to reduce ozone depletion = monitoring skin cancer, increase
> amount of CO2 used by those plants is reduced public awareness, Investigate new ozone-friendly propellants
> Cows, sheep, goats replace trees which produce methane
> Production of wood & paper products use energy & release
SECTORS THAT PRODUCE THE MOST GHG’s:
CO2
> ↑ no. of dead tree trunks = ↑ in termite population (produce ▪ Power stations (25, 9%), Industry (19,4%), Forestry (17,4%),
methane) Agriculture (13,5%)
> Less transpiration = less water vapour = less rainfall
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