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Summary Human Impact on the Environment
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Highly recommend, Literally everything that is required to know about human impact on the environment (according to the official life sciences guidelines issued by the department) is included. Highly recommend as it will save you a lot!
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CHAPTER TWELVEHUMAN IMPACT ON THE
ENVIRONMENT
THE ATMOSPHERE AND CLIMATE CHANGE
The atmosphere is made up of: 78,08 Nitrogen, 20,95% Oxygen and 1% of
Greenhouse gasses.
WEATHER: Everyday forecast. Is it sunny or rainy today? Short term.
GLOBAL WARMING: The rise in the average temperature on Earth. Brought about by
the increase of greenhouse gasses.
CLIMATE CHANGE: The Earth’s weather pattern. Long term. Ie it is warm and
rainy in summer seasons.
HOW THE ‘GREENHOUSE’ EFFECT IS BROUGHT ABOUT AND HOW IT CAUSES GLOBAL
WARMING
WHAT IS THE GREENHOUSE EFFECT
● Svante Arrhemius termed the ‘Greenhouse Effect’ in 1896
● He related the Earth’s atmosphere to a greenhouse
● It is clear, allowing the sun’s radiation into the house or onto the
earth, but thick enough to trap some of the heat inside to keep the
house or earth warm
● The GHGs in the atmosphere lead to the thickening of the Carbon Dioxide
blanket in the atmosphere
● The
greenhouse effect
is natural and
essential. Without
it the world would
be turned cold and
we would be living
in an ‘Ice Age’
, CAUSES
Table showing the contributions and sources made by GHGs to the ‘greenhouse
effect’
GREENHOUSE GAS CONTRIBUTION SOURCE OF GAS
Carbon Dioxide 53% Respiration, decomposition, burning fossil fuels, forest
fires
Methane 17% Cows, sheeps, swamps, rice paddy fields, natural gas
leakage, rubbish dumps, landfills, water treatment works
Nitrous Oxide 5% Breakdown of organic matter in soils by microbes,
nitrogen fertilizers, burning of wood and fossil fuels
Ozone 13% Natural in atmosphere, formed as a reaction of certain
substances in sunlight
CFC’s 12% Fridges, foams, aerosol sprays, solvents
WHY THERE IS AN INCREASE IN GHG EMISSIONS
INCREASE IN CARBON DIOXIDE EMISSIONS
● Carbon dioxide is the second most important gasses when bringing about
climate change, next to water vapour
● The two main contributors to carbon dioxide emissions are from burning
of fossil fuels for electricity and burning of petrol and diesel for
transport
● These emissions have increased seven times from 1950 to 2008
● South Africa is the 13th largest carbon dioxide emitting country on
Africa
● As the population increases, so does the amount of emissions
● A carbon footprint is made by a person or business depending on the
amount of carbon dioxide emissions that they make. A heavy carbon
footprint is one which releases a large amount of carbon dioxide and
causes a large amount of damage. A light footprint is the opposite
● We can work out the amount of carbon dioxide released into the
atmosphere by each one of us by multiplying the amount of energy source
used per month by the emission factor for that energy source
, INCREASE IN METHANE EMISSIONS
● Just behind carbon dioxide in terms of importance of a greenhouse gas
● One of the fastest growing GHGs
● Although there is less methane than carbon dioxide, its impact on global
warming is 21 times that of carbon dioxide
● The South African National Greenhouse Gas Inventory estimated that SA
released about 21 000 tons of methane from wastewater treatment and
about 721 000 tons from waste disposal
INCREASE IN NITROUS OXIDE EMISSIONS
● Manure has been replaced by chemical fertilizers
● The nitrogen-rich fertilizers release nitrous oxides with 300 times more
heat trapping capacity per unit of volume than carbon dioxide
DEFORESTATION AND INCREASE IN GHGs
● Deforestation is the process of changing land use from forestry to a
non-forest use such as agriculture, housing or mining
● Forests are important as plants use up carbon dioxide during
photosynthesis
● Deforestation occurs because:
○ Trees are cut down to make fuel, wood and paper products
○ Trees are cleared for grazing space or to create roads
○ Forests are cleared for mining development
○ Indigenous forests are cleared to be replaced by plantations and
agricultural crops as they bring in more money
● Four ways deforestation leads to increase in GHG levels
1. Less carbon dioxide is captured due to there being less plants
2. The cattle which replace the trees produce methane
3. The production of wood and paper products uses energy and releases
carbon dioxide
4. The increase in dead tree trunks and branches leads to increased
termite populations, which produce methane
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