Humans and Their Effects on the Environment

Question 1

What are the reasons for deforestation?

Answer 1

• to provide more timber as building material

- to clear land for farming: provides more food, from gross from which biofuels based on ethanol can be produced

Question 2

What are the consequences of global warming/

Answer 2

• rise in sea levels: low-lying places may be flooded as sea expands when warm and ice also melts
• climate change: more extreme weather e.g. longer droughts, more hurricanes
• changes in migration patterns: birds may migrate further north as it gets warmer
• change in distribution of animals and plants species: may become more widely distributed or less
• less biodiversity: animals may become extinct if they are unable to survive a change in the climate

Question 3

Why does destroying peat bogs add more CO2 to the atmosphere?

Answer 3

• bogs are areas of land that are acidic and waterlogged. plants don’t fully decay because there is not enough oxygen. this forms peat
• carbon is stored in the peat instead being released
• peat bogs are often drained to be used as farmland, cut up as fuel, or sold as compost
• peats start to decompose when they are drained so CO2 is released, more CO2 released, adding to greenhouse effect

Question 4

What natural stores can carbon dioxide be sequestered (locked up) in?

Answer 4

• oceans, lakes and ponds
• green plants: remove CO2 during photosynthesis
• peat bogs

Question 5

How does eutrophication cause serious damage to rivers and lakes?

Answer 5

1. mineral ions (nitrates and phosphates) from fertilisers or sewage enter the water
2. increased concentration of these ions in the water cause algae and/or plants to grow fast
3. eventually water is so fall of algae and plants that some organisms can’t get enough light to photosynthesise and die
4. with more food available, microorganisms that fed on dead organisms increase in number
5. the respiration of the microorganisms depletes all the oxygen in the water
6. aerobic organisms (e.g. fish) die because of reduced oxygen concentration

Question 6

What are the four main problems of deforestation?

Answer 6

• more methane in the atmosphere: - rice is grown in warm, waterlogged conditions, ideal for decomposers, which produce methane, meaning more is released into the atmosphere. - cattle produce methane and rearing them means more methane
• more CO2 in the atmosphere: CO2 released when trees are burnt to clear land and microorganism feed on bits of dead wood and release CO2 from respiration
• less CO2 taken in: cutting loads of trees means photosynthesis is reduced
• less biodiversity (variety of different species in a habitat): many species become extinct and there are lost opportunities as new plants and animals are source of new foods, new fibres for clothing and medicines

Question 7

What may waste pollute?

Answer 7

• water: with sewage, fertiliser, toxic chemicals
• air: with smoke, gases such as sulphur dioxide, contributing to acid rain
• land: toxic chemicals such as pesticides and herbicides
• sewage and fertilisers: may cause eutrophication

Question 8

What is eutrophication?

Answer 8

• when fertilisers and sewage such as nitrates and phosphates leach into the water

Question 9

What human activities reduce land for plants and other animals?

Answer 9

• building
• farming
• dumping waste
• quarrying for metal ores

Question 10

What is deforestation?

Answer 10

• the cutting down of forests