Deforestation Lab: What a Hillside Loses with Its Trees
See a forest as infrastructure: roots and leaf litter let rain soak in and hold soil, trees recycle moisture into rain and store carbon; remove them and floods, erosion and drought follow.
Before you try
What if a whole hill range were cleared? Where would the monsoon rain go?
Try it out
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What happened?
Move a control to see what changes and why.
Rounded per-hectare rates for run-off, soil loss and infiltration; real figures depend on soil, species and farming.
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Try these ideas
- Press Clear the hill and watch the river. Then press Replant.
- Set rainfall to 3,000 mm and find the cover needed to keep soil loss under 5 t/ha.
- Compare a 10° and a 40° slope at the same cover.
Why it works
On a forested slope, rain is slowed by the canopy, soaks through leaf litter and is held by a mat of roots, so most of it enters the ground and feeds springs and wells for months. Strip the trees and rain hits bare soil, runs off in sheets and carries the topsoil with it: the river turns brown and floods fast, then runs dry sooner because less water reached the ground. Soil that took centuries to form is gone in a few monsoons.
Forests also make rain: much of the moisture over a large forest was released by the forest itself, so clearing it dries the region downwind. And each hectare of standing forest holds around 120 tonnes of carbon, released as carbon dioxide when it is burnt. In this lab you set the forest cover, rainfall and slope, clear or replant the hill, and read run-off, soil loss, infiltration and carbon.
Check your understanding
Question 1 of 4
Forests reduce flooding because
After a hill is cleared, its river
Cutting and burning a forest releases
Soil erosion is worst on
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Pour water on a tray of bare soil and a tray with grass and compare the run-off colour.
- Ask: why do hill towns lose their springs after logging?
- Find out what the Chipko movement was protecting.