Man’s Impact on the Environment Topic

Must-Know Effects of Deforestation

This science revision note aims to help your child

– identify the concepts associated with the plants.

– Explain how the plants help in minimising soil erosion.

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Dana wanted to set up an experiment to simulate the negative effects of deforestation. She planted identical plants into two trays of soil – Tray A had three plants while Tray B only had one plant. She placed the trays on identical ramps. She placed a container at the bottom end of each tray, then poured 500ml of water onto the leaves of the plants. She then waited for the water to be collected in the containers.

Dana noticed that one of the setups (A or B) had less soil collected in the container than the other. Which setup was it? Explain your answer.

STEP 1

Identify the factor that affects the amount of soil collected in the container. What is the changed variable?

The only changed variable is the number of plants, so this must be the factor that affects the amount of soil collected.

STEP 2

How does the number of plants affect the amount of soil collected in the container? Let’s consider how soil gets collected in the container in the first place.

When water is poured onto the soil, it washes the soil into the container.

STEP 3

So how do the numbers of plants affect how much soil is washed into the container?

Firstly, let’s take a closer look at the parts of the plant to see which part(s) possibly affects the soil being washed into the container. Looking at the diagrams, two main parts of the plant depicted are the leaves and the roots.

Secondly, the amount of soil being washed into the container is affected by two main aspects:

The impact of water hitting the soil – the greater the impact, the looser the soil gets, making it easier to flow down into the container
How anchored the soil is – the more anchored the soil is, the harder it is for it to flow down into the container

Now let’s try to connect the plant parts with the two mentioned aspects:

Leaves – the leaves do not come into contact with the soil, hence they do not affect how anchored the soil is. However, they can affect the impact of water that reaches the soil because the leaves provide cover, slowing down the flow of water. More leaves provide more cover against the falling water, slowing down the flow of water into the soil, thus reducing the impact of the water onto the soil.
Roots – the roots are inside the soil, so they have no effect on the impact of water that reaches the soil. However, they affect how anchored the soil is because the roots hold on to the soil. There are roots that hold onto the soil more strongly.

With more leaves and roots, less soil gets washed into the container. Hence, Setup A, which has more plants, had less soil collected in the container.

FINALLY, put your answer together

Question: Dana noticed that one of the setups (A or B) had less soil collected in the container than the other. Which setup was it? Explain your answer.

Answer: Setup A had less soil collected in the container because it has more plants than Setup B. With more plants, there are more leaves to reduce the impact of the water hitting the soil. Also, there are more roots to hold on to the soil more strongly / firmly. Thus, less soil erosion had taken place in setup A than in B.

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