Geography and Environment

By the end of this unit, you must be able to determine the relationship between vegetation and human activities.

Unit objectives
By the end of this unit, you must be able to:
(a) identify different vegetation types on maps
(b) outline factors that influence the distribution of vegetation
(c) outline the importance of vegetation
(d) state the relationship between vegetation and human activities.

Vegetation

Do this in groups of four.
Take a walk in the area around your school.
Observe the vegetation growing around the school. Record the following in your exercise books.
• Type of vegetation
• Height of the vegetation
• Size of the leaves
(a) Discuss your observations in groups.
(b) Present your findings in class.

Vegetation refers to all the plant cover growing in a particular area. It also refers to the ground cover provided by plants.
Human beings, animals and insects all depend on vegetation. They purify the air that we breathe.

Classification of vegetation

Vegetation is classified into three main groups, namely:
(a) Natural vegetation
(b) Artificial vegetation
(c) Secondary vegetation

Natural vegetation
This is the vegetation that grows naturally in an area without any human aid. It grows under natural physical conditions and has not been interfered with by people or animals.
Types of natural vegetation include forests, grasslands, desert vegetation and swamp vegetation.

Forests
A forest is a large area of land covered by trees and other woody vegetation. The natural forests found in Rwanda are the natural forests of Nyungwe National Park, Volcanoes National Park and Gishwati and Mukura forest reserves. Most of the remaining natural forests in Rwanda are
protected as national parks or forest reserves.

       Fig. 9.1 Nyungwe Forest National Park.

Grasslands
Grasslands are areas where the main vegetation is grass. They grow naturally.
Examples of grasslands in Rwanda are the savannahs of Akagera National Park, Bugesera, Gisaka and Umutara.

        Fig. 9.2 Savannah at Akagera National Park.

Desert vegetation
A desert is an area of land with little or no vegetation. There is very little rainfall in these areas thus the conditions are unsuitable for plant and animal life. There are some plants adapted to growing in the desert. These are desert and semi-desert vegetation such as scrub and cactus.
However, there are no deserts in Rwanda.

Fig. 9.3 Desert vegetation.

   Swamp vegetation
A swamp is a wetland with woody vegetation.
Swamp vegetation can be found in salty or fresh water. The swamps in Rwanda are Mugesera, Rweru, Kagera, Nyabarongo, Mushaka and Kamiranzovu.      

                  Fig. 9.4 Rweru swamp.

Artificial vegetation
This is composed of the vegetation that has been planted by human beings.

            Fig. 9.5 Artificial forest in Rwanda

It is also known as planted vegetation.
Forests made up of exotic trees are examples of planted vegetation. Exotic trees that are planted include pine, cypress and eucalyptus.

                                                                     Fig 9.6

 1. Study the map shown above.

2. Using the key, identify the different types of world vegetation on the map.

3. Give examples of the vegetation types that are found in Rwanda. Locate the areas in which the vegetation are found on a map of Rwanda.
4. Present your findings in class.               

   Secondary vegetation
This is the vegetation that grows naturally in an area after being interfered with by people or animals. It is also known as derived vegetation. The vegetation is still in the process of development and will eventually acquire the characteristics of natural vegetation.       

A good example of secondary vegetation is the one that grows in an area after the previous vegetation cover is cleared or destroyed by an outbreak of fire. Do you know of any such vegetation in your country? 

Factors that influence the distribution of vegetation

                                      Fig 9.7

                        Fig 9.9

1. Identify the type of vegetation in all the pictures.
2. Suggest the factors that are suitable for the growth of the vegetation shown in each of the pictures.

3. Identify areas in Rwanda where each of the vegetation shown on the pictures are found.
4. How important are the vegetation to Rwanda as a country and to the people who live near them?

There are four main factors that influence the distribution of vegetation over the earth’s surface.
• Climatic factors
• Edaphic factors
• Topographic factors
• Biotic factors

Climatic factors

1. Look at the vegetation surrounding your school
2. Identify some of the factors that have influenced their growth and presence in the area.
3. Classify them according to the factors identified in (2) above.
4. Note down your findings.
5. Discuss them in a class presentation.

Climate is the weather condition in an area over a long period of time. The main elements of climate that influence vegetation include precipitation, temperature, sunlight and wind.

(a) Precipitation
Precipitation is the deposit of water in liquid or solid form on the earth’s surface from the atmosphere.
The type and amount of precipitation influences the type and distribution of vegetation. Different plants have different moisture requirements.

Areas that receive heavy and well distributed rainfall throughout the year have forests composed of many tree species.
Areas with moderate and seasonal rainfall are dominated by grasslands.
Areas with low rainfall are dominated by desert and semi-desert vegetation.

                   Fig. 9.10 Natural rainforest.

(b) Temperature

Temperature plays an important role in the growth of vegetation. It determines plant processes such as germination, rate of plant growth, flowering, ripening of fruits and shedding of leaves.
Warm conditions encourage rapid growth of plants. Cold conditions slow down the rate of plant growth.

(c) Sunlight
Sunlight is important to plants for photosynthesis. Long hours of sunlight encourage the growth of many varieties of plants. Areas with fewer hours of sunlight have fewer plants.

(d) Wind
The moisture content and strength of the winds influences plant growth. Warm moist winds contain sufficient moisture. This helps in the formation of rainfall necessary for plant growth.

Hot dry winds cause wilting of plants since it accelerates water loss from the plants. Strong winds cause the trees to bend.

Edaphic factors
This refers to soil particularly with respect to its influence on organisms. Deep well drained soils support a variety of large trees.
Soils that are shallow in depth support the growth of shallow rooted plants such as grass.
The pH of the soil also determines the type of plants found in a region. Soils with nutrients and humus support the growth of plants. Soils with few nutrients support very little plant growth.

Topographic factors
Topography defines the physical features in a place. The topographic factors include relief, slope and aspect. These factors affect vegetation through soil formation processes, climate, soil moisture and soil nutrients.

(i) Relief
Relief refers to the difference in elevation between any two points on the earth’s surface. The height of the land determines temperature and rainfall. There is an increase in vegetation with an increase in altitude. This is distinct on mountains. The vegetation ranges from grass to forests,
bamboo, heath and moorland.

(ii) Slope
Steep slopes experience high rates of soil erosion leading to the development of thin and shallow soils. This results in poor plant growth. Gentle slopes have deep and welldrained soils resulting in the growth of thick vegetation and a wide variety of plants. Flat areas are easily waterlogged resulting in the growth of swamp vegetation.

(iii) Aspect
Aspect is the direction of the slope with regards to sunshine and rainfall. Slopes that are exposed to the sun are warm. They support plant growth. The slopes which are not exposed to the sun have fewer vegetation.

Biotic factors
These are the living organisms which have an effect on the growth of vegetation.
These include human beings, animals, bacteria, burrowing animals and insects.
Human activities such as deforestation, mining and overgrazing destroy vegetation. Other activities such as agroforestry, reforestation, afforestation and creation of forest reserves result in the development of vegetation.
Some insects aid in plant pollination. Animals and birds aid in seed dispersal leading to growth and distribution of vegetation.
Burrowing animals and earthworms aerate the soil resulting in suitable conditions for plant growth.

Task 9.1
1. Describe how each of the following factors influences the growth of vegetation.
(a) Climate factors
(b) Edaphic factors
(c) Topographic factors

2. Explain how human activities have influenced the distribution of
vegetation. Use specific examples from Rwanda.

Importance of vegetation

Work in groups of four.
1. Go outside your classroom
2. Look at the vegetation surrounding your school.
3. Find out the importance of the vegetation to the people who live near  them and to the country.
4. Write your findings down.
5. Discuss them in a class presentation.

Vegetation is a major component of the ecosystem. It is important because of the following reasons.

1. Food – Some vegetation are a source of food for human beings and animals.
Some insects also feed on vegetation.

2. Habitat for wild animals – Forests and other vegetation provide a home for wild animals. Wild animals attract tourists. They earn the country foreign exchange that aids in economic development. Therefore, we should not destroy our vegetation.

Fig. 9.11 Vegetation provides habitats for wild animals.

3. Sources of medicine – Some types of vegetation such as barks, roots and leaves of trees are used as medicine. They are used in curing different diseases in both animals and in humans too.

4. Prevent soil erosion – Vegetation holds soil together. This prevents erosion by water and wind. Vegetation also reduces the speed of water when it is raining. Roots of vegetation hold soil particles together. This helps to reduce soil erosion and conserve soil.

5. Purify the air – Vegetation purify the air that we breathe. They utilise carbon (IV) oxide in the atmosphere and release oxygen.

6. Improve soil fertility – Plant materials that fall from different vegetation decompose into humus. This improves the fertility of the soil. The decaying material increases the organic matter
content in the soil.

7. Source of timber – Trees are a source of timber. This is used in making furniture and building. Trees are also a source of fuel. However, trees should not be cut carelessly. Whenever one tree is cut, two more trees should be planted.

8. Source of raw materials – Vegetation are also a source of raw materials for industries. For example, trees are used in the manufacture of paper, plywood and rubber.

9. Windbreaks – Vegetation such as trees act as windbreaks. They help in reducing the speed of wind. This reduces the effects of wind such as blowing away roof tops or soil erosion.

10. Conserve soil and water – The roots of vegetation help in conserving soil and water. They hold the soils together and conserve moisture in the soil.

Task 9.2
1. Explain the importance of vegetation to the economy of Rwanda.
2. Give five uses of trees.

Relationship between vegetation and human activities

Work in groups of four.
1. Find out how the presence of the vegetation around your school has influenced the activities that take place in the area.
2. Use the Internet, textbooks and topographic maps to find out how vegetation influences human activities in different areas of the world.
3. Write down your findings.
4. Present them in class.

1. Vegetation type and distribution have a great influence on human activities and occupation over the earth’s surface. For example, availability of grass has led to livestock keeping due to availability of pasture.
2. Overdependence on vegetation by human beings for their needs has had a negative impact on vegetation.
It has lead to a reduction in the area under natural vegetation. Such human activities include overstocking leading to overgrazing, pollution and deforestation.

                     Fig. 9.12 Deforestation.

3. The human population is growing. There is need for land for settlement. Human beings are destroying vegetation to create more land for settlement. This has had an effect on the distribution of vegetation.
4. Human activities such as pollution lead to climate change. This leads to global warming and causes a decrease in vegetation.

Work in groups of four.
1. Find out how the human activities that take place have affected the vegetation in the area surrounding your school.
2. Use the Internet, textbooks and topographic maps to find out human activities have affected vegetation in different areas of the world.
3. Write down your findings.
4. Present them in class.

Did you know?
• The forest at Nyungwe is one of Africa’s true rainforests with more than 200 types of trees and numerous flowering plants.
• Much of Rwanda’s natural rainforest has been cut down to make way for its growing population.
• The bamboo is a natural vegetation.
• Some plants like the Venus flytrap are carnivorous.
• There are over 200,000 plant species.

1. Define vegetation.
2. List and describe the different types of vegetation.
3. Discuss four factors that influence the distribution of vegetation.
4. Assess the importance of vegetation to Rwanda.
5. Describe how natural vegetation has influenced the following human activities.
(a) Tourism
(b) Livestock keeping
(c) Building and construction
(d) Medicine
6. Describe how the following human activities have influenced the distribution of vegetation.
(a) Overstocking
(b) Mining
(c) Pollution
(d) Urbanisation.