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š¬ Think about it
Remember the falling dominoes? Push one and many fall. Nature works the same way. One small change can set off a long chain of effects. Let us see how a little pollution can reach a farmer's field.
How can pond pollution end up affecting farmers?
- Pollution makes many pond plants die.
- Fewer plants means less oxygen, so fish die.
- Fewer fish means more insects, which spread to farms.
- So farmers are forced to use pesticides, harming the environment.
One Change Leads to Another
Plants die
Pollution kills pond plants.
↓
Less oxygen
Fewer plants make less oxygen.
↓
Fish die
Less oxygen kills the fish.
↓
More insects
Fewer fish means insects increase.
↓
Pests damage crops on nearby farms
In this Activity, we will read about how exporting frog legs upset the balance of nature in India.
Materials needed
The frog figure (Fig. 12.14) and your notebook.
Procedure
1. Read that in the 1980s India exported many frog legs, especially of the Indian bullfrog.
2. Note that this large-scale harvesting reduced frog populations.
3. Recall that frogs eat insects.
4. Trace what happened to farm pests when frogs reduced.
2. Note that this large-scale harvesting reduced frog populations.
3. Recall that frogs eat insects.
4. Trace what happened to farm pests when frogs reduced.
Observation
With fewer frogs, agricultural pests rose. Farmers had to use more synthetic pesticides, harming soil, water and health.
Explanation
Frogs control pests. Removing them upset the balance. So the Government of India banned the export of frog legs to prevent more damage.
ā Summary
- Frog legs exported
- Frogs declined
- Pests increased
- Export was banned
Important Points
- One small change can trigger many other changes.
- These effects can reach far beyond the first habitat.
- Human actions can disturb the balance of nature.
ā Test Yourself
-
What happens when pond plants die from pollution?
View Answer
Less oxygen is made, so fish die, insects rise and pests spread to farms. -
Why did pests rise when frogs declined?
View Answer
Frogs eat insects, so fewer frogs meant more pest insects. -
What did farmers do because of more pests?
View Answer
They used more synthetic pesticides, which harmed soil, water and health. -
What did the Government of India do?
View Answer
It banned the export of frog legs to prevent further ecological damage. -
Can one change lead to others?
View Answer
Yes. One change can set off a long chain of effects in nature.
Important Definitions
- Cascading effect — one change setting off a chain of further changes in nature.
- Ecological damage — harm to the natural balance of an ecosystem.
