Question

forests are called ' lungs of the Earth ;

Answer 1

Yes forests are called lungs of the earth as they absorbs carbon dioxide and give out oxygen. They also provides us all the necessary things that are essential for a living. They also provides medicine..

Answer 2

heya, 
forests are called as "lungs of the earth" because, the forest is full of trees.trees take carbon dioxide out of the air and replace it with oxygen. but now a days peoples are cutting trees thats why the forest are looking incomplete. if the peoples still cut all the trees then one day there is no tree and if there is no tree then we will not get . oxygen, if we will not get oxygen then we can breath and we will die.. 
by growing more trees
>>  we will get oxygen to live.
>> we will get fruits and vegetables.
>> trees will absorb carbon dioxide and will change carbon dioxide in the oxygen.
>> by a large tree, it can supply a day supply of oxygen for about 4 peoples.

our earth is covered with trees about 50% but day by day peoples are cutting trees and the rate of trees are decreasing. we all help each other and its paid but the plants are helping us in free of cost.

this is why forests are called as 'lungs of the Earth'. 
grow more trees, be eco-friendly.

thank you. i hope this will helps you......