Deforestation

Question 1

Name six effects deforestation has on the water cycle

Answer 1

• infiltration decreases
• soil erosion increases
• shorter lag time
• greater flood peaks
• greater bed load and suspension in rivers
• less annual rainfall

Question 2

Why does infiltration decrease?

Answer 2

Fewer pathways to the soil next to roots

Question 3

Why does soil erosion increase?

Answer 3

• tree roots hold soil together
• soil becomes dry so more vulnerable to wind erosion
• canopy blocks 80% of rainfall so the ground is more exposed as there is less obstruction

Question 4

What is lag time? Why is it shorter?

Answer 4

Time difference between peak rainfall and peak discharge in a river

No absorption or interseption by canopy

Question 5

Why are flood peaks greater?

Answer 5

No absorption from trees in drainage basin

Question 6

Why does rainfall decrease?

Answer 6

Less transpiration and so less moisture in the atmosphere to form cloud and rain

Question 7

Why would bed load and suspension increase?

Answer 7

No obstruction of material from the Forrest

Question 8

Name four impacts on soil health

Answer 8

• rapid soil erosion causes a loss of nutrients
• raindrop impact washes finer coats and humus away
• greater leaching causes mineral loss
• CO2 released from decaying woody material

Question 9

Name four impacts on the atmosphere

Answer 9

• turbulence is increased because the hotter ground induced convection currents
• oxygen content is reduced because there is less photosynthesis
• reduced evapotranspiration makes the air drier
• reduces shading increases direct sunlight on the ground

Question 10

Name one benefit and two disadvantages of afforestation

Answer 10

😊 carbon sequestration

😩 monoculture of commercial trees use more water and store less carbon + impacts on animals
😩 grassland conversion from temporate (here) to tropical (Savannah)

Question 11

Give seven disadvantages of temperate grassland conversion in the USA to grow biofuels

Answer 11

• initial removal releases CO2 as soil is disturbed
• annual ploughing enables soil bacteria to release CO2
• biofuel crops use carbon based nitrogen fertiliser which produces CO2 net emission
• reduces water table
• cultivated souls more susceptible to erosion
• natural habitats reduced
• absorbs less CO2 than grassland