Theory:

     Grandfather wasn’t content with growing trees in our compound. During the rains, he would walk into the jungle beyond the river-bed armed with cuttings and saplings which he would plant in the forest.
 
     ‘But no one ever comes here!’ I had protested, the first time we did this. ‘Who’s going to see them?’
 
     ‘See, we’re not planting them simply to improve the view,’ replied Grandfather. ‘We’re planting them for the forest and for the animals and birds who live here and need more food and shelter.’
 
     ‘Of course, men need trees too,’ he added, ‘To keep the desert away, to attract rain, to prevent the banks of rivers from being washed away, for fruit and flowers, leaf and seed. Yes, for timber too. But men are cutting down trees without replacing them and if we don’t plant a few trees ourselves, a time will come when the world will be one great desert.’ 
Explanation:
 
Grandfather had a compound full of trees, but he was not satisfied. During the rainy reason, he would go into the jungle which was located beyond the river-bed. He would take pieces of plants and young trees for growing more trees in the jungle.
 
The first time when the author had accompanied him, he opposed. He asked him why he had to do this, as no one ever came to the jungle, and nobody is going to see them.
 
The wise grandfather replied that they were not planting the trees for good views but for the following reasons:
  • Planting for the forest.
  • For the animals and birds that live there and require more food and shelter
Grandfather further added that humans also needed trees for the following reasons:
  • To keep the land fertile and not dry like a desert.
  • To bring more rain.
  • To prevent the soil from getting eroded.
  • To get more flowers, fruits, leaves and seeds.
  • To get more wood.
He finally said that people are cutting down trees without replacing them. If we cut a tree for any reason, we should make sure we replace by planting more number of trees. If we don't plant a few trees for ourselves, the whole world will become a desert soon, without any vegetation, rain or life.
 
Meanings of difficult words:
 
No.
Words
Meanings
1
contentsatisfied, peaceful
2
protestedopposed, disagreed
3
river-bed
the channel in which a river flows
4
armedequipped with all items required
5
cuttingsa piece cut from a plant for propagation
6
saplingsa young tree used to grow a new tree
Reference:
State Council of Educational Research and Training (2019). Term-1 English Standard-6. When the Trees Walked - Ruskin Bond (pp. 107-122). Published by the Tamil Nadu Textbook and Educational Services Corporation.