Lecture 3 - A World of Resources

Question 1

Define Land Degradation.

Answer 1

-Temporary/ permanent decline in productivity of land

Question 2

Define Soil Degradation.

Answer 2

-Decrease in soil quality, measured by changes in soil properties/ processes and consequent decline in immediate and future production

Question 3

Deifine Soil Erosion.

Answer 3

-Detachment and removal of soil/ rock by running water, wind, waves, ice flow and mass movement

Question 4

What are some Causes and Consequences of Soil Erosion?

Answer 4

Causes:-Deforestation
-Agriculture
-Construction
-Mining

Consequences: -Reservoir
sedimentation
-Decreased soil
productivity
-Pollution

Question 5

What are the 3 types of Soil Erosion by Water?

Answer 5

-Wash/sheet erosion
-Rill erosion
-Gully erosion

Question 6

Describe how Wash/sheet erosion works.

Answer 6

-Common in semi-arid areas
-Occurs when rainfall intensity exceeds infiltration capacity
-Water runs across the land in ‘sheets’ rather than channels, carrying the sediment downhill

Question 7

Describe how Rill erosion works.

Answer 7

-Forms when runoff concentrates
-Depth of flow in a rill is sufficient for turbulence so entrains larger particles than sheet erosion

Question 8

Describe how Gully erosion works.

Answer 8

-Consequence of rill erosion
-Deep channels due to increased runoff
-Caused by climatic changes
-Human causes include; changes in vegetation, increase in arable land and overgrazing

Question 9

What are the 3 main types of Soil Erosion by Wind?

Answer 9

-Creep (rolling along the ground, 25% of the load)
-Saltation (jumping along ground, 50-80% of the load)
-Suspension (particles in the air, <30% of the load)

Question 10

Give an example of Severe Soil Erosion

Answer 10

-Central Plains, USA (The Dust Bowl)
-Costs $44 billion per year to work against
-USA may lose all topsoil in 50 years
-It takes 500 years to build 1 inch of topsoil, and it is being eroded at 17X that rate in the USA

Question 11

What are some Major Causes of Land Degradation?

Answer 11

-Industrial pollution
-Inappropriate agricultural practices (loss of organic matter, reduction in vegetation cover, soil compaction and use of unsuitable land)
-Deforestation

Question 12

How does Deforestation relate to Soil Erosion?

Answer 12

-Canopy reduces raindrop erosion (the start point of all other forms of soil erosion)
-Humus absorbs raindrop impact and increases infiltration capacity
-Vegetation strengthens the soil

Question 13

How has Forest Cover changed over History?

Answer 13

-Deforestation by humans began in the Mesolithic
-Large areas of the UK were deforested before the 1st century BC
-Since pre-industrial times, 20% of the World’s forest has been lost
-Palm oil production caused 80% of deforestation between 1990 and 2000

Question 14

Give some examples of how Soil Erosion can be Prevented.

Answer 14

-Maintaining good soil structure
-Maintaining sufficient levels of organic matter
-Keeping soil moist
-Leaving weeds and grasses to grow between harvests (fallowing)
-Use windbreaks like hedges and trees

Question 15

Define Soil Conservation.

Answer 15

-Measures which control or prevent soil erosion or maintain soil fertility

Question 16

Define Desertification.

Answer 16

-Spread of desert-like conditions as a result of human actions

Question 17

What are some symptoms of Desertification?

Answer 17

-Reduction/ failure of crop yields
-Reduction of biomass
-Reduction of available water
-Encroachment of sand bodies
-Social disruption (migration)

Question 18

Why is Desertification a Problem?

Answer 18

-Threatens a quarter of the World’s total land area and a sixth of the population
-Population growth increases the likelihood as it results in; overcultivation, overgrazing, deforestation and salinisation