A little effort makes a huge difference.

Given below are the names of some environmentalists who strived for a sustainable earth for everyone. Find out more details about them and complete the table.

| Sl. No | Name of the Environmentalist | Their Contribution |
|--------|------------------------------|---------------------|
| 1 | Sunderlal Bahuguna | |
| 2 | Saalumarada Thimmakka | |
| 3 | Tulsi Gowda | |

What is the biggest challenge faced by our world today?