This is my first review as a member of the WAR group, so please bear with me.
Let me preface this by telling you that as a vocation, for many years I was a Reclamation Forester, focused on planting trees on disturbed land. With that said, here we go.
Things I liked:
First I liked that you were taking the time to educate young people about trees. You brought up quite a few good points. When I write or speak to children in the age group you are targeting I try not to give them all the answers but to get them thinking, get them questioning, get them searching for answers on their ow. We need to be there to help them along their way but I would much rather they form their own opinions based on the facts they've discovered than having them parrot mine. They have brains, let's get them exercising them.
It is a wide educational range that you are targeting. There are some words that will be unfamiliar to 8 year olds and some of the writing may be to simple for 15 year olds. That is a tough one to handle but overall i think you did it quite well.
Things I would change:
1st paragraph, 2nd sentence: insert a comma between trees and like and also between Banyon and bear.
2nd paragraph: I would rewrite as follows:
Trees are Nature’s wonders and a provide many benefits to mankind as well as to all other living things. The uses of trees are many and varied. They provide shelter and homes for wildlife which use them for protection,food and places to raise their young. Humans have used almost any and every tree to their benefit. These benefits include shelter, warmth from burning and even medicines.
3rd paragraph: realise should be realize.
2.1 Usefulness of trees:
I would only add that trees also help prevent pollution and provide a good bit of the oxygen that we breathe
2.2 Examples of usefulness of trees:
4th paragraph: Remove the a between have and cleaner in the last sentence.
3.1 What are forests?
I would add here that most forested land is in private ownership, not the government, at least here in my part of the world. Forests are not necessarily dense but that is how we think of them. Here would be a good place to introduce the words ecoystem, niche or habitat.
3.2 Environment and forests:
I have to be careful when reading this because I tend to put my interpretation and philosophies in the forefront of my review. I am trying to be as unbiased as possible. As a writer you should endeavor to do the same.
For example, there is a school of people out there that would tell you that the felling of the trees is not irresponsible but rather it is being done for two reasons: Forst Management and because of the demand for the product - timber. There are instnaces, especially near the equator where forests are destroyed, not harvested, for the sake of agricultural. This would, in my opinion, fall into to the irresonsible catagory. Since you are presenting this information to 8 to 15 year olds it is a good idea to present the facts objectively and I think you do a fairly good job of that for the most part, but keep in mind, that when it comes to the world we live in and the environment, nothing is quite as simple as we would believe or are led to believe. I'll get off my soapbox now.
3.3 Greenhouse effect and global warming:
A very nicely written section and a very good explanation of global warming.I only refer you to my previous comments in the section above.
3.4 Soil conservation:
Again, nicely stated. Easily understood, short and to the point sentences. Nothing to comment on here other than I would add the word help between thereby and reduce. They can't do it on their own.
Given everything you mentioned in your previous sections, this section seems a bit light. You need to expnad upon it. Your reasons all refer to us but don't forget we are not alone. I think I would add something on forest management. With good management technigues we can still have all the benefits that trees provide us. It almost sounds like you're saying if we cut down one tree, that's bad and that isn't so. Give it some more thought.