HUMAN IMPACT ON THE ENVIRONMENT
LIFE SCIENCES
STUDY GUIDES AND NOTES
GRADE 12

• The atmosphere and climate change
• Activity 1
• Activity 2
• Water quality and water availability
• Activity 3
• Activity 4
• Activity 5
• Food security
• Activity 6
• Loss of biodiversity
• Activity 7
• Solid-waste disposal
• Activity 8

CHAPTER 11:HUMAN IMPACT ON THE ENVIRONMENT

Organisms interact with other organisms and with the environment. When we, as humans, interact with the environment to satisfy our needs, we may have many negative impacts on the environment through our activities. We may pollute the land, the water and the atmosphere. We also make demands on the earth to ensure our food security. In doing all of this we may impact negatively on the biodiversity of our planet.

11.1 The atmosphere and climate change
Introduction

Climate refers to the long-term weather conditions of an area. The atmosphere is made up of nitrogen, oxygen and other gases, which include the greenhouse gases such as carbon dioxide and methane. Greenhouse gases absorb infrared (long wave radiation) long wave radiation emitted from the Earth and prevent it from escaping back into the atmosphere. This is known as the ‘greenhouse effect’.
The greenhouse effect is important in keeping the Earth warm so that it can sustain life. However, an increase in the concentration of greenhouse gases leads to the ‘enhanced greenhouse effect’. As a result, there may be a significant rise in the average temperature of the surface of the Earth over a period of time. This is known as ‘global warming’.
Increased concentration of carbon dioxide in the atmosphere is due mainly to:

• Burning of fossil fuels (for electricity, to power vehicles and for industrial processes): Combustion of carbon-rich fuels such as coal or plants (wood) releases carbon that was stored in them, as carbon dioxide.
• Deforestation: Cutting down trees and removing vegetation from the land decreases the amount of carbon dioxide taken up by plants during photosynthesis. This increases the amount of carbon dioxide available in the atmosphere.

Increased concentration of the methane in the atmosphere is due mainly to:

• The increased number of landfills: decaying organic matter in waterlogged soils such as landfills releases methane.
• The increased number of livestock: ruminants such as cows release methane gas through their digestive tracts.
• Mining of coal.

Increased temperatures may lead to:

• More evaporation of water which can lead to increased precipitation which eventually increases the potential for flooding.
• Rising sea levels caused by melting ice in the glaciers which can eventually increase the potential for flooding.
• Increased wildfires that increase the chances of soil erosion and eventually desertification.
• Increased loss of biodiversity, as species are unable to cope with rapidly rising temperatures, eventually leading to desertification.
• Increased droughts in some areas leading to desertification and food insecurity.

Carbon footprint
This is a measure of the total amount of carbon dioxide emissions of an individual, a defined population or a company per year.
Strategies to reduce the carbon footprint include the following:

• Reuse and recycle: less fossil fuels burnt in the production of some of the material.
• Drive less: by using public transport, walking, bicycles.
• Reduce the need for heating: insulating walls and building energy efficient homes.
• Carbon offsetting: by using alternative energy (solar and wind) and reforestation to act as a carbon reservoir.
• Technological developments: decrease the amount of energy needed for production/decreasing the dependency on carbon emitting fuels.

Destruction of the ozone layer
Ozone is a greenhouse gas that is found at low concentrations 15 - 50 km above the Earth’s surface. It absorbs the ultraviolet rays from the sun. The ultraviolet rays damage the DNA and cause skin cancer. Measurements in certain areas have shown a significant decrease in the amount of ozone layer. The damage to the ozone layer is caused mainly by chemicals called CFCs (chlorofluorocarbons), released by refrigerators, aerosol sprays and fast-food packaging.
If the measures to reduce the destruction of ozone layer fail:

• There will be a significant increase in the number of skin cancer cases.
• Ultraviolet rays reaching the Earth’s surface may cause permanent damage to our eyes.

Activity 1

Questions
1. Figure 11.1 below shows the averages of carbon dioxide concentration in the atmosphere since January 2009, as measured at the Mauna Loa Observatory in Hawaii.

Figure 11.1: Average carbon dioxide concentration in the atmosphere since January 2009, at Mauna in Hawaii

1.1 Describe how deforestation could lead to an increase in the carbon dioxide concentration in the atmosphere.    (2)
1.2 Mention ONE human activity that might have led to the increase in carbon dioxide concentration as seen in the graph.  (1)
1.3 What was the carbon dioxide concentration in the atmosphere in July 2012?     (2)
1.4 What is the dependent variable in this investigation?         (1)
1.5 Explain how the excess carbon dioxide in the atmosphere could lead to climate change.    (4)
1.6 Mention ONE way in which humans can reduce the amount of carbon dioxide released into the atmosphere.    (1) [11]

Answers to activity 1
1.   
1.1 Cutting down of trees decreases the amount of carbon dioxide✔ taken up by the plants during photosynthesis✔    (2)
1.2 Burning of fossil fuels✔     (1)
1.3 393,5✔ ppm✔ (2)
1.4 Carbon dioxide concentration in ppm✔   (1)
Answers to activity 1 (continued)
1.5

• Carbon dioxide is a greenhouse gas✔
• which absorbs long wave radiation emitted from the Earth✔
• and prevents it from escaping back into the atmosphere✔.
• An increase in the concentration of carbon dioxide leads to an increase in the greenhouse effect✔,
• which may result in global warming✔. (any 4)

1.6

• Drive less✔/use public transport, walking, bicycle more
• Reduce the need for heating by insulating walls✔
• Building energy efficient homes✔
• Use alternative energy sources✔ (solar and wind)
• Reforestation✔to act as carbon reservoir
• Reuse and recycle✔ (any 1) [11]

Activity 2

Questions

1. An investigation to measure the ozone concentration and the chlorine levels has been done in Antarctica since 1950 and the results are shown in the graph below:

1.1 Give a caption for the graph.    (2)
1.2 What is the relationship between the levels of chlorine and the concentration of ozone?   (2)
1.3 Name the dependent variable(s) in the investigation.    (2)
1.4 In which 10-year period was the ozone depletion the greatest? (1)
1.5 In 1987 the Montreal Protocol was signed to lay down targets to reduce the use of CFCs by countries. Give TWO reasons why, despite a reduction in the use of CFCs, there was still a decline in the ozone layer.   (2)
1.6 Name ONE item that humans were using which contained CFCs.   (1)
1.7 Explain why the ozone layer is important for humans.      (2) [12]

Answers to activity 2

1.   
1.1 Changes in the levels of chlorine and ozone concentration✔ from 1950 to 1990✔  (2)
1.2 An increase in the level of chlorine ✔leads to a decrease in the ozone concentration✔   (2)
1.3

• Chlorine levels✔
• Ozone concentration✔ (2)

1.4 Between 1970 and 1980✔  (1)
1.5

• CFCs might persist for a long time in the atmosphere✔ 
• Other countries might have taken longer to implement the protocol✔
• Households were still using existing items with CFCs✔ (any)(2)

1.6

• Aerosols✔
• Refrigerators✔
• Food packaging✔   (any)(1)

1.7 The ozone layer provides protection against ultraviolet rays✔, thus reducing the chances of getting skin cancer✔         (2) [12]

11.2 Water quality and water availability

It is estimated that as many as 2 billion people won’t have sufficient access to clean water by 2050. This figure is expected to rise to 3.2 billion by 2080 — almost three times the number of people who now do without water. There are many efforts directed towards making good quality water available.

11.2.1 Availability of water
The availability of water may be influenced by the following factors:

Construction of Dams

• The construction of additional dams plays a major role in increasing the quantity of water stored and made available for later use by people and in agriculture.

Destruction of wetlands

• Wetlands should not be destroyed because they influence both the availability and quality of water.

Water wastage

• A large amount of water used for irrigation is lost due to poor farming practices. Open drain irrigation leads to loss of water by evaporation.  The use of water for irrigation further up a river decreases the availability of water for other users lower down the river.
• Availability is also affected by wastage of water through leaking taps and toilets and faulty pipelines.
• Wastage of water can be reduced by reducing the pressure in the pipes, by educating people to use water wisely and by maintaining all plumbing in good condition.

Cost of water

• The cost of water is influenced by costs involved in increasing the availability and quality of water.
• The cost per kilolitre (kl) of water increases with the increased use of water. This is meant to discourage over-use of water, thus allowing for its sustained use.
• A certain amount of water is available free to all citizens to ensure that water is available to the poorest.

Poor farming practices

• Contamination of water sources by fertilizers and pesticides has decreased the amount of clean water available, thus increasing the costs involved in purification.
• Over-grazing leads to soil erosion. On land that is eroded, water runs off rapidly rather than soaking into the ground, and is thus wasted.

Droughts and floods

• During periods of drought, water availability decreases. Water used from dams during the drought periods cannot be easily replaced.
• Natural vegetation can hold back water from floods. If the natural vegetation is removed, flood waters are lost.

Boreholes and their effect on aquifers

• Boreholes have been used to increase water availability in areas that do not have direct access to other sources of water.
• Constant use of boreholes eventually leads to the drying up of aquifers (the source of borehole water) thus decreasing water availability in the future.

Water recycling

• The availability of water can be increased if existing water is used for more than one purpose. For example, some water used in the household can be used for the garden. Sewage water can be treated and used again.

Exotic plantations and the depletion of the water table

• Some exotic plants use a large quantity of water from the ground. As a result, this decreases the level of the water table, making less water available to other vegetation in the area.

11.2.2 Quality of water
The quality of water may be influenced by the following factors:
Eutrophication and algal bloom

• Water used for agriculture may contain pesticides, herbicides and fertilizers which pollute the water in rivers, dams and lakes, causing eutrophication. The added nutrients lead to an increase in algal growth (algal bloom). These algae over-use and thus deplete the oxygen in the water, thus reducing the potential for life in such        water.

Thermal pollution

• Thermal pollution refers to the heating of water caused by the use of water for cooling in power-stations and industries.
• The quality of water is affected because heated water has a lower oxygen content, making it difficult to support life.

Pollution of water through domestic, agricultural and industrial use

• After water is used for domestic purposes it may contain detergents (such as from washing) and pathogenic bacteria (such as in sewage). This polluted water has to be treated before it can be used again.
• After water is used for industrial purposes it may contain many heavy metals, oil, heat and fertilizers. This adversely affects the quality of  the water and all life that depends on it.
• Fertilisers and pesticides may run off into rivers, ponds and dams and pollute the water.

Mining

• Water returned to the environment from mines is generally acidic and toxic. This water is hot and thus also contributes to thermal pollution.

Alien Plants

• Alien invasive water plants block the waterways, reducing light to other aquatic plants. These plants eventually die and decompose.
  Bacteria that decompose these plants eventually deplete the oxygen supply in the water.

Water purification

• The quality of water is improved through purification methods.
  Undrinkable water can be made drinkable.

Activity 3

Questions
1.  A group of learners conducted an investigation to determine the average amount of water used by a household for different purposes. They collected data on water-use from 5 families in their neighbourhood. The results are shown below.

1.1 Identify the:
a)  Dependent variable   (1)
b)  Independent variable (1)
1.2 State TWO ways in which the reliability of the results can be improved.      (2)
1.3 Draw a pie-chart to represent the data in the table. Show all calculations.   (7)
1.4 Describe ONE advantage of making the results of the survey available to the various households that participated.  (2) [13]

Answers to activity 3

1.1
a)  Average amount of water used✔   (1)
b)  Purpose for which water is used✔  (1)
1.2

• Repeat the investigation✔
• Select the households randomly✔
• Increase the number of households involved in the investigation✔  (any 2)

1.3 Calculations for proportions of slices in the pie-chart

Average amount of water used by a household for different purposes

(7)
1.4 Owners can identify the areas of greatest water use✔ to  allow them to then develop strategies to reduce water use in that area✔ (2) [13]

Activity 4

Questions
1.  Describe how alien plants may reduce both the availability and quality of water.  (4)
2.  Describe how poor farming practices may reduce both the availability and quality of water.   (4) [8]

Answers to activity 4

1.                            
   • Alien invasive plants may use water excessively✔ and thus reduce the amount of water available for the natural vegetation✔ of an area (2)
   • Alien invasive water plants block the waterways, reducing light to other aquatic plants✔. These plants eventually die and decompose✔. Bacteria that decompose these plants eventually deplete the oxygen supply in the water✔. (any) (2)
2.                                    
   • Over-grazing leads to soil erosion✔. On land that is eroded, water runs off rapidly rather than soaking into the ground✔, and is thus wasted. (2)
   • The use of fertilizers and pesticides may pollute nearby dams, ponds and rivers✔ thus reducing the quality of water available✔ (2) [8]

Related Items

Activity 5

Questions
1.  Read the article below entitled ‘Durban to Recycle Sewage water into Drinking Water’.

1.1 List FIVE different strategies referred to in the article intended to increase the availability of clean drinking water.  (5)
1.2 Describe THREE arguments used in the article to convince the reader about the safety of recycled sewage water.    (6)
1.3 List THREE processes that will be used to ensure that the recycled sewage water will be fit for human consumption.   (3) [14]

Answers to activity 5

1.1

• Recycling sewage water✔
• Purifying sea water✔
• Replacing old, leaky pipes✔
• Reducing water pressure✔
• Building new dams✔ (5)

1.2

• No outbreak of water-borne diseases✔ in Windhoek for 42 years✔
• 3 safety barriers✔ to ensure the quality✔ of treated effluent
• Stored for at least 12 hours✔ allowing sufficient time for repeated testing✔ (6)

1.3

• Pumped at high pressure through ultra-filtration membranes✔  to remove suspended and dissolved solids and bacteria
• Filtration through tiny pores✔
• Ultra-violet disinfection✔ (3) [14]

11.3 Food security

Food security refers to the access, by all people at all times, to adequate, safe and nutritious food for a healthy and productive life. Food security may be influenced by the following factors:

Exponential growth of the human population

• The world’s population is growing at an exponential rate (very rapidly) and as a result some countries cannot produce enough food to feed their growing population. Food production needs to increase as rapidly as the world population; otherwise many countries will experience food insecurity.

Droughts and floods

• Climate change has led to more frequent and severe droughts and floods. Droughts result in crop losses and livestock death which reduce the food available in an area. Floods cause extensive damage in a short period of time and decrease the amount of farmland available to grow crops. People also usually lose their homes,  possessions and economic security during floods, further impacting on food security.

Poor farming practices - monoculture, pest control, loss of topsoil and the need for fertilizers

• Monoculture is the growing of one type of crop over large areas of land year after year. Monoculture depletes nutrients and water supplies and therefore impacts negatively on the quality of the topsoil.
• Pest control involves the use of pesticides (chemicals) to kill pests that compete with humans for food. Pesticides may kill or get into the tissues of healthy plants. This may reduce crop production and, since pesticides are expensive, increase the cost of food and thus reduce access to poor consumers. Many farmers now use biological control, which uses a natural predator/parasite to get rid of the pest instead of using expensive pesticides.
• Topsoil is the top 1.5 metres of soil that contain the nutrients that plants require for growth. The tilling of the soil between plantings and heavy rainfall cause much of the topsoil to be lost, leading to the loss of valuable nutrients over time, reducing crop yields.
• The use of fertilizers, both inorganic (chemical) and organic (compost and manure) can increase the nutrients in the soil and keep soil fertile. This replaces nutrients in the soil that are lost when crop plants absorb them. Fertilizers can be expensive, contributing to the high cost of food, thus reducing access to poor consumers.

Alien plants and reduction of agricultural land

• Alien plants deplete the topsoil of water and nutrients. These alien plants out-compete indigenous plants because they have no natural predators, grow rapidly and invade land that could be used to grow crops.

The loss of wild varieties and the impact on gene pools

• Crop plants have replaced wild varieties. The preservation of wild varieties is important because, if changing environmental conditions destroy the present crop plants, then wild varieties could be used as alternative sources of food. If wild varieties are wiped out, it will reduce the genetic diversity and thus the gene pool.

Genetically engineered food

• Genetically engineered food is produced from genetically modified organisms (GMOs). Genetic engineering involves the inserting of a gene (with a desired characteristic) from one organism into another organism to increase the yield. For example, a gene for drought resistance could be inserted into a crop plant that grows in areas where water is scarce.

Food wastage

• Wastage could occur during the storage, production and processing of food. Wastage includes food thrown away and food not eaten. Wastage increases the prices of food to consumers and could reduce food security in a country.

Activity 6

Questions
1.  Study the table below and answer the questions that follow.

Adapted from CUP Biology: Jones and Jones, 2010
1.1 For Sub-Saharan Africa, calculate the food wastage by consumers as a percentage of the total food waste. (3)
1.2 Suggest a reason for this low percentage calculated in QUESTION 1.1 above. (2)
1.3 Explain the differences in the pattern of food wastage in developed and developing regions. (4)
1.4 State TWO possible ways of preventing the high levels of food waste that are found in the developed countries. (2) [11]
2. The following questions relate to the factors that threaten food security in a country.
2.1 Give ONE reason why there has been an increase in the demand for food over the years. (1)
2.2 State one way in which the use of each of the following helps to increase food productivity:
a) Pesticides (1)
b) Fertilizers (1)
2.3 Describe how the use of pesticides could destroy food chains. (2)
2.4 Explain why GMOs may be considered a threat to food security. (3) [8]

Answers to activity 6

1.
1.1 Food Wastage in Sub-Saharan Africa
5/160✔ × 100✔ = 3.1%✔ (3)
1.2 Access to food is scarce and the food that is available is either provided by international aid agencies or subsistence farming✔. Very little food is bought and even less is bought from supermarkets.✔ There is no food left over to waste.✔ (any 2)
1.3 In developed regions: buy food from markets, shops and supermarkets, often in excess of their requirements and will throw unused food away.✔ The markets, shops and
supermarkets will also throw away unsold food.✔
In developing regions: people will depend more on small, local sources of food,✔ have less food security and will not have food in excess of their needs.✔ (4)
1.4 Possible ways to reduce food waste include:

• Prevention - prevent consumers from throwing away food or stop them from producing/buying more food than they need✔
• Plan what you need before you shop and reduce impulse and spontaneous buying✔
• Understand how to store and preserve food✔
• Ensure that unused food is used in some way - e.g. give to the poor, animal feed, compost heaps.✔
• Education✔ (any 2) [11]

2. 2.1 There has been a rapid increase in the human population✔ (1)
2.2
a) Pesticides kill the pests which destroy the crops✔ (1)
b) Fertilizers increase nutrient content in the soil✔ (1)
2.3 Secondary consumers e.g. birds can eat the pests with the poison✔, which can kill the birds3 thereby decreasing the population size of birds✔
OR
The pest can become extinct✔, and the population size of the secondary consumer feeding on the pest will also decrease✔ (any 1 × 2) (2)
2.4

• Loss of flora and fauna biodiversity by inbreeding of GMOs✔
• Entire species could be wiped out✔ if exposed to diseases✔ (no variation in the population)/GMOs will have no resistance to the diseases (3) [8]

11.4 Loss of biodiversity

Biodiversity refers to the variety of plant and animal species on Earth. Biodiversity ensures that we have food, fresh water, medicines and fuel that we obtain from our environment. It also ensures that the climate is regulated, floods are controlled (wetlands), diseases are kept in check (predators eat the sick animals) and water is purified (filtering by wetlands).
Biodiversity ensures that seeds are dispersed, nutrients are cycled (e.g. nitrogen and phosphorus) and oxygen and soil continue to form. It also helps improve our quality of life by providing us with forms of recreation and ecotourism. As biodiversity declines, these things do not occur as they should and the survival of humans becomes threatened.

11.4.1 Factors that reduce our biodiversity
Habitat destruction through:
Farming methods
Monoculture: Monoculture is the growing of one type of crop over large areas of land year after year. Monoculture replaces indigenous plants and reduces biodiversity. Insects that specialise in feeding on one type of crop spread rapidly because there are no natural enemies or barriers to stop them. This means the farmer needs to use more pesticides to kill them. Intensive use of agrochemicals such as fertilisers and pesticides often end up in rivers, streams and groundwater, poisoning species in the area and
causing eutrophication. This results in a large loss of biodiversity.
Overgrazing: It occurs when livestock such as sheep or cattle are kept in an area for too long; the vegetation is grazed to a point where it will not grow back. It causes soil erosion by removing the plants that bind the soil together with their roots. Topsoil is lost during rainstorms. This can lead to the extensive destruction of land through desertification which results in loss of biodiversity. Sometimes overgrazed land becomes subject to alien plant invaders which destroy habitats by taking over the land.

Golf Estates
Developments such as golf estates are a form of monoculture that requires large amounts of water, pesticides and fertilisers which may runoff and poison aquatic ecosystems. Housing associated with golf developments replaces large areas of natural vegetation.

Mining
Mining alters the environment and can negatively affect the biodiversity in an area. Pollutants in the form of dust and smoke may be released into the air while vegetation is removed and replaced with rock and waste dumps. Underground water may be poisoned because of sulphates and heavy metals released into them.

Urbanisation
The growth of large cities   (urbanisation) also negatively impacts on biodiversity. Surfaces are covered with concrete, and natural habitats are destroyed to build houses and businesses. Habitat fragmentation causes the loss of biodiversity, as natural plants are replaced by exotic trees and plants.

Deforestation
Deforestation is the permanent destruction of indigenous forest and woodland areas. Deforestation is caused by human activities such as agriculture, logging, and using trees as firewood. Deforestation leads to the destruction of the habitats of other organisms, like frogs and insects, and this leads to the loss of biodiversity.

Loss of wetlands and grasslands
Grasslands and wetlands have unique plant and wildlife and provide many ecological services to humans. Destruction of these habitats will lead to the loss of species.

Poaching
Poaching refers to the illegal hunting of animals, either for food or because certain body parts can be sold for money. ‘Poaching’ may also be applied to plants that are removed and sold for profit e.g. medicinal plants. Some wild animals are hunted for food (‘bush meat’) and are on the verge of extinction. Elephants are poached for their tusks to make carvings and jewellery and rhinos are hunted for their horns which are used in the Far East for medicinal reasons.

Alien plant invasions
These plants are species that have been introduced into an area and which compete with the natural plants in the area. They can outcompete indigenous plants, thus reducing the biodiversity.

11.4.2 Ways in which our biodiversity can be maintained
Control of alien plant invasions
Alien invasive species may be controlled by mechanical, chemical and biological methods. Mechanical methods involve chopping down plants or physically removing them by hand and is very time consuming. Chemical control involves spraying herbicides onto the plants; this can pollute the environment and is expensive. Biological methods involve introducing a natural enemy from the alien plant’s environment and allowing it to reproduce and feed on the invasive plant.

Sustainable use of the environment
Sustainable use of the environment means using resources without harming the ability of future generations to use that resource. Substances from indigenous plants such as the African potato, Hoodia, rooibos and Devil’s claw all have economic and medicinal value. These indigenous plants can be used sustainably by encouraging traditional healers to grow their own plants and through improving education of the women who generally gather the plants in the wild. Encouraging traditional healers to be part of formal medical programmes would encourage training to be on- going and help establish sustainable use of medicinal plants. Legislation should be passed to limit the numbers of plants that can be harvested at one time and seeds of medicinal plants could be collected and distributed to increase plant numbers.

Activity 7

Questions
1.  Study the following table showing a summary of the rhino poaching incidents in South Africa from 2006 - 2010.

1.1 How many rhinos were illegally hunted in 2009?    (1)
1.2 Suggest THREE ways in which the poaching of rhinos can be stopped.    (3)
1.3 Describe the general trend observed in the table.   (2)
1.4 By what percentage did the poaching of rhino incidents increase in North West from 2008 to 2010? Show all working. (3)
1.5 Use the data in the table and draw a bar graph to show the number of rhinos poached each year from 2006 to 2010 in South Africa.  (7) [16]
2.  Read the following passage on Rooibos (Aspalanthus linearis) and answer the questions that follow.

2.1 Describe TWO ways in which over-exploitation of plants, such as Rooibos, impacts on other life forms and the environment. (2)
2.2 Describe THREE strategies that could be used to prevent the over-exploitation of plants such as Rooibos.  (3) [5]

Answers to activity 7

1.
1.1 122 ✔ (1)
1.2

• Rhino horns must be sawn off ✔
• Implant a ‘Pro Tag Device’ to monitor movement of the rhino ✔
• Institute heavy penalties like imprisonment instead of fines ✔ (3)

1.3 Rhino poaching ✔ has increased ✔ from 2008 to 2010 (2)
1.4 44✔  × 110 ✔ = 628,53% ✔  (3)
       7 ✔      1   ✔

1.5 

2.
2.1

• Plants can become extinct ✔/leads to loss of biodiversity
• Food chains/webs can be destroyed✔
• Could lead to degradation of the environment ✔
• Erosion of ground surface if too many plants are removed ✔
• Increase run-off of water ✔
• Alien plant invasion ✔in the habitats from which the plants are removed
• Upset the balance of oxygen and carbon dioxide ✔/global warming if too many plants are removed (any 2)

2.2

• Sustainable harvesting ✔
• Impose quotas ✔/limit numbers
• Limit area✔where plants are harvested
• Limit size of plants harvested ✔
• Limit time/seasons of collection ✔
• Research done to look at reproductive cycle✔/alternative source of active ingredient/cloning
• Legislation to control harvesting ✔
• Permits to control harvesting ✔
• Monitoring of harvest ✔
• Penalties ✔for breaking legislation
• Education ✔/campaign on the impact and consequences of over-exploitation
• Establish nurseries ✔/seed banks - to replace plants harvested
• Establish more nature reserves ✔ to conserve indigenous plants  (any 3) (5)

11.5 Solid-waste disposal

Solid waste is any solid material that is of no use to humans and which needs to be disposed of in a safe and environmentally friendly way.
Managing dumpsites for rehabilitation and prevention of soil and water pollution The simplest and most cost effective way of disposing of solid waste is to bury it in landfill sites. A landfill site is a hole where solid waste is dumped and then covered by soil. However, this way of disposing of solid waste contributes to soil and groundwater pollution because rain seeps through the waste to produce a toxic substance called leachate. To prevent the toxic leachate from reaching the groundwater, a plastic liner is placed
under the dumpsite area.
Rehabilitation of landfill sites occurs before they are closed down. This involves the covering of the old landfill site with clay soil, which is impermeable to water, and then it is covered with topsoil. Grass or other vegetation is then planted on the old landfill site. The growth of the plants stabilises the area and the old landfill site may be used as a recreational area such as a park or a golf course.

The need for recycling
Various methods may be used to manage solid waste, they include the reduction of waste, re-using waste and recycling of waste.

• Re-using waste products includes re-using plastic shopping bags, re-using glass and plastic containers - this helps to reduce the waste produced.
• Recycling is a process whereby used materials/waste products are recycled to make new products, for example plastic, glass, tin and paper. The advantage of recycling is that it provides employment, reduces the use of raw materials and energy, and reduces air, ground and water pollution.

Using methane from dumpsites for domestic use: heating and lighting
Methane is a gas produced as a result of the decomposition of organic waste. The methane gas can be used as a fuel. Methane can be collected from landfill sites and used to generate electricity for domestic use - heat for cooking and electricity for lighting.

Safe disposal of nuclear waste
South Africa also uses radioactive material such as uranium to power its nuclear power station at Koeberg in the Western Cape. Unfortunately, a by-product of using uranium is nuclear waste that is still radioactive and therefore dangerous to living organisms. The nuclear waste is stored in thick steel drums and buried in trenches at special protected sites.

Activity 8

Questions
1.  State FOUR strategies you would use to manage solid waste if you were appointed as the head of the waste disposal division of your town.  (4)
2.  The following table shows the total amount of solid waste and the amount of recyclable material dumped in a South African city landfill site over a number of years.

2.1 Describe the general trend in the total amount of waste produced and the amount of recyclable materials dumped from 2003 to 2006.    (2)
2.2 Explain TWO advantages of recycling.   (4)
3.  The graph below shows the percentages of various types of waste found on the grounds of a school.
3.1 Draw a table to illustrate the percentages of waste shown in the graph above. (5)
3.2 The school wants to manage the large amount of wastegenerated on a daily basis. They decide to recycle the waste.
3.2.1 Define ‘recycling’. (2)
3.2.2 Give TWO reasons why the recycling of waste is advantageous. (2) [19]

Answers to activity 8

1.

• Investigate methods to collect and utilise methane gas as a fuel ✔
• Encourage citizens of the city to sort their waste ✔ into different waste containers
• Partner with recycling companies for improved collection of different wastes ✔
• Institute fines ✔ for people that do not separate the waste into different bins
• Educate people to use organic waste ✔ for example to make compost
• Encourage recycling ✔of items such as papers, tins, glass 
• Encourage citizens to reuse ✔ items such as glass
• Penalties/charge people extra if they generate more waste ✔ (any 4)

2. 2.1 Both ✔ the total amount of waste produced and the amount of recyclable material increased ✔ from 2003 to 2006 (2)
2.2

• People collect and sell waste at buy-back centres ✔ and therefore benefit economically ✔/create own jobs
• People who collect waste and take it to recycling depots✔ contribute to sustainable use of materials ✔
• Recycling saves energy ✔ and therefore reduces the amount of energy used to make new products ✔ (any 2 × 2) [4]

3.
3.1 Percentages/amount of each type of waste on the school grounds

3.2
3.2.1 The process by which waste materials✔are treated in such a way that they can be used again✔/ reused (2)
3.2.2

• To avoid over-exploitation of the limited natural resources✔
• To save/raise money✔/(create jobs)
• To reduce the amount of waste material✔/cleaner environment
• Less energy✔used/Reduce carbon footprint
• Fewer landfill sites✔ (any 2) (2) [19]