Human land and water impacts

Question 1

Desertification

Answer 1

Desertification is a process whereby productive land is transformed into desert.

Question 2

Desertification characteristics

Answer 2

dramatic loss of vegetation

loss of roots binding soil

soil erosion - loss of topsoil by wind and water

soil degradation - soil quality declines (nutrients and water holding capacity)

Carbon held by the soil is released into the atmosphere

Question 3

Desertification causes

Answer 3

Causes
Desertification both causes and is caused by climate change. Desertification is also caused more directly by humans when land is poorly managed.

Climate change:

changing rainfall pattern

higher temperatures

Poor land management:

over/under-grazing

over cultivation

inappropriate irrigation

deforestation

Question 4

Desertification effects

Answer 4

loss of vegetation

loss of biodiversity

reduced productivity of land

loss of soils and increased soil erosion

Increased carbon dioxide released from soils

poverty, political instability and violence

Question 5

Deforestation

Answer 5

Deforestation is the permanent destruction of natural, indigenous trees and bushes by felling and burning in order to clear the land for other purposes.

Question 6

Deforestation characteristics

Answer 6

Once over 10%, tropical rain forests now only cover 2% of the land surface yet contain over 50% of all terrestrial species.

Over 50% of the remaining forests will be lost and up to 10% of all species will lost directly due to deforestation by 2050.

Question 7

Deforestation causes

Answer 7

Agriculture e.g. palm oil and cattle farming

Timber

Urbanisation

Wood for fuel

Mineral mining

Politics

Traditional medicines

Question 8

Deforestation effects

Answer 8

Effects
soil degradation and soil erosion

floods

loss of biodiversity

disrupted water cycle - both atmosphere and ground water

Increased carbon dioxide in the atmosphere

Question 9

Solutions

Answer 9

Recycle e.g. paper and support use of recycled products

Refuse products with palm oil

Promote forest protection and combat illegal logging

Replace cut down trees by planting

Question 10

Water scarcity

Answer 10

the lack of fresh water resources to meet the standard water demand. Two factors are important in determining water scarcity: water availability and water quality

Question 11

Water availability

Answer 11

the amount of fresh water available for human use

Question 12

Water quality

Answer 12

the condition of the water that makes it suitable for a particular purpose, like drinking

Question 13

Factors affecting water scarcity include:

Answer 13

Mean annual precipitation and climate change

Dams

Wetland destruction

Poor farming practices

Droughts and floods

Alien plants

Boreholes

Water wastage

Question 14

Mean annual precipitation

Answer 14

Rain does not fall evenly across the earth. Some regions receive more rainfall than others. Where there is more rainfall, there is more fresh water available.

Question 15

Dams

Answer 15

Dams are barriers constructed to hold back water and raise its level, resulting in a reservoir of water. Water is thus able to be collected in rainy seasons. Dams can also be used to control the flow of water to downstream locations. Dams supply of water for domestic & industrial purposes, are used for flood control, a source of hydroelectricity and water for irrigation.

Question 16

Negative impacts of large dam construction:

Answer 16

Habitat loss as they are flooded

Local human communities must be relocated

Downstream banks dry out and soil erosion increases

Downstream species die out as natural flood cycles disrupted

Question 17

Ways to reduce dam impacts

Answer 17

Manage water discharge to mimic nature more closely

Plant water-wise crops that are able to cope with the natural rainfall patterns of the area

Recycling of waste water

Question 18

Wetland destruction

Answer 18

Wetlands are areas with waterlogged soil, a high water table and many aquatic plants. Wetlands increase biodiversity, purify water, store water, act as a natural flood control and replenish the water table. The destruction of wetlands reduces their function and affects both water availability and water quality.

Question 19

Poor farming practices

Answer 19

Poor farming practices that affect water scarcity include mismanaged grazing and poor irrigation methods

Question 20

Droughts and floods

Answer 20

Climate change means dry areas are getting drier, while wet areas are getting wetter. Extreme weather events are also more likely. Both mean there is less water available

Question 21

Alien plants

Answer 21

An alien plant is a plant that has been introduced to an area from outside its native range, either purposefully or accidentally

Question 22

Water wastage

Answer 22

Although water is a limited resource for South Africa and demand often exceeds supply, water is still wasted by domestic, industrial and agricultural users.

Question 23

Pollution

Answer 23

Domestic pollution includes sewage and grey water carrying pathogens and excess nutrients from human waste as well as detergent wastes. For example, washing powders are very rich in phosphates that lead to eutrophication in water bodies.

Question 24

Heavy metals

Answer 24

f heavy metals are present in water, they accumulate into the bodies of small organisms, which is called bioaccumulation. Small fish are eaten by larger fish, who then accumulate all the heavy metals from their food. This means that larger predators get larger doses of the heavy metals. This is called biomagnification.

Question 25

Eutrophication

Answer 25

Fertilisers used get washed off soil & plants. They get washed into water bodies. This causes algal bloom (excessive growth). This blocks light for deeper plants, and prevents gaseous exchange across the water surface. Water plants die and their decomposition increases the CO2 levels in the water. Fish & other aquatic organisms die from insufficient O2. Water is contaminated by decomposing organisms.