4.3 human impact on the cycles

Question 1

what are the three human effects from land use ?

Answer 1

• forrestry
• farming
• urbanisation

Question 2

urbanisation effect on the water cycle

Answer 2

**Artificial impermeable surface (e.g tarmac) **
- reduces infiltration rates with little water being able go to free flow as throughflow
- increased run- off
- little water storage capacity
- Quicker water travels to streams = rise in discharge - more risk of flooding

Sewage systems / drains/gutters
Removes water from area rapidly
Flows quickly to streams and rivers (lag time reduces significantly)

Houses on flood plains - takes away natural buffer → so water unable to be naturally stored

Question 3

urbanisation effects on the carbon cycle

Answer 3

• More CO2 released by humans domestically
• As their are more in an area the fossil fuels will ^ releasing more CO2 into the atmosphere

Question 4

Farming effects on the water cycle

Answer 4

Farming - ploughing furrows down slope
- Accelerated run off
- ^ soil erosion
- Tractors compacting soil → harder water to infiltrate ^ run off
- ^ trees → ^ interception → may counterbalance some of the increased lag time → but converting land to crops reduces evaporation

Water irrigation
- Diverts water from stores (e.g from ground water = lots of water on surface = ^ evaporation rates)

• Most water lost through soil drainage and evaporation

Question 5

farming effects on the carbon cycle

Answer 5

**Ploughing **
- Allows soil to have more oxygen → ^ fungi / decomposers as are able to respire (break down material more/ releases co2 to the atmosphere)

• Soil carbon storage is reduced by ploughing
• Harvesting of crops only small amounts of organic matter is returned to the soil
  Changes to the carbon cycle are less apparent on pasture land / where farming replaces natural grasslands
• Carbon exchanges through photosynthesis often lower than in other systems → due to a lack of biodiversity + growth of crops to only ⅘ mths

Question 6

forestry effect on the water cycle

Answer 6

Plantations - high density of conifer trees
- Higher interception capacity

• Evergreen don’t lose leaves - intercept all year round
• Made of needles → ^ surface area so able to trap water better (bigger lag time)
• ^ evaporation ^ transpiration rates ( as leaves all year)

**Plant factors **
Evergreens with needles

• High density = high interception rates = longer lag times near plantations = lower peak flow → near plantations may be less water for urban / human use