Why do humans affect the
environment?
• Large populations in many areas of the world.
• Humans in industrial countries: – Utilize a lot of energy.
– Consume a lot of food.
– Use a lot of material to maintain a luxurious lifestyle.
Over-population
• United nations predict the world population to reach 7 000 000 000 in the end of October 2011.
Global warming
• Green house gases (e.g. CO2, methane, nitrous oxide) are released into the air.
Methane
• Potent green house gas.
Effects of global warming
• Melting of polar ice
• Flooding of costal areas.
• Climate change – more extreme weather like storms and hurricanes.
The natural green house effect
• We need the natural level of the green house effect, the problem is the increased green
house effect.
• If the natural green house effect did not exist the avereage temperature on Earth would be minus 18 °C.
Water vapour and clouds
• Water is the most important natural green house gas.
• Water does not affect the increased green house
Oil spills
• Marine habitats are destroyed by oil spills
• Birds, fish, crustaceans, plankton. More or less all organism are affected.
• Organisms get poisined by the oil.
Famous oil spills
• Exxon Valdez: 1989, Oil-tanker ran aground on the coast of Alaska. (40 000 ton).
• Kuwait war: 1991, On purpose by Saddam Hussein’s troops (20 million ton, the largest oil spill ever).
• Deepwater horizon: 2010, Explosion of an oil rig in the Mexican gulf. (780 000 ton, largest unintentional oil
Toxins in organisms
• Many toxic substances are not water soluble and stay in the fat tissue of the organisms.
• Bioaccumulation: Toxins will accumulate
during the life time of an individual.
= Older organisms have higher concentrations.
• Biomagnification: Toxins will be transferred and magnified along the food chain. = Top predators will have the highest concentrations.
Environmental toxins
• Clorinated organic molecules – DDT: Effective pesticide.
– PCB: Electric isolator and plastic softener.
– Both were banned in the 1970’s but still
remain in the environment and damage the nervous system and interferes with the hormonal system.
• Heavy metals
– Lead: Damage the nervous system, blood and brain disorders.
Destruction of tropical rainforest
Why should we save the
tropical rainforest?
• Holds almost half of the species on Earth.
• Many substances found in the rainforest are active ingredients in medicines.
Acidification
• Sulphur dioxide and nitrous oxides are emmited when fossil fuels are used.
• When dissolved in moisture in the air, sulphuric acid and nitric acid are formed.
• The acids come
down with the rain and the soil, lakes and rivers get
What happens in acidic lakes?
• First crustaceans, mollusks and small fish die (pH 6).
• External skeleton of crayfish soften, leading to fungal attack (pH 5.6)
• Some species of larger fish die (pH 5)
• Aluminum is released into the water and clogs the gills of the fish,
obstructing the breathing (pH 4.2).
Ocean acidification – A new problem
• The oceans have before been thought of as ”immune” to acidification.
• But recently it was discovered that the high levels of carbon dioxide in the air makes more dissolve in the ocean as
Eutrophication
• Fertilizers like nitrates and phosphates leak out into lakes or to the sea.
Eutrophication – oxygen depletion
• The algal bloom prevents the light to reach down, plants and larger algae die.
• Later on when the mass of single-cell algae die
there will be large amount of dead material at the bottom.
• Decomposing bacteria use all the oxygen
in the water - the lake or ocean
The ozone layer
• At 10-50 km altitude.
• Protects organisms from UV-B radiation.
• Ozone molecules consist of 3 oxygen atoms, O3
• Is broken down by CFC (chloro- fluorocarbon) used in aerosol cans and refrigerators.
Depletion of the ozone layer
• The ozone layer has become thinner since the 1970’s.
• In springtime the layer gets particularly thin in the polar regions – “ozone hole”.
• Most use of CFC forbidden but the molecules can stay in the atmosphere for 100
Tropospheric ozone (ground level)
• Ozone at the ground level (0-1 km) does not protect from UV-B radiation.
• Damage plants and animals, including humans.
• Photosynthesis affected, airway problems in humans.
The different roles of ozone
• Good ozone is high up in the stratosphere.
Sustainable development
• To meet the needs of the people living in the world at the moment in a way that will make it possible to also fulfill the need of the generations to come.
• For this to be possible we have to limit our use of energy and material.
• If all people in developing countries rise their material standard of living to our level the Earth will run out of
