People asked some useful questions in the comments below the essay I shared on Wednesday. I'll try to answer them here. If you don't like grammar, don't read number 1 below!
1) When writing about our planet, should we write: Earth, earth, the Earth or the earth?
To be honest, this confuses native speakers and you'll see it written in different ways. I wrote "life on Earth" and "the Earth's climate", and I've found plenty of examples of both phrases written in this way, in publications such as National Geographic. However, I've also found both phrases written with the lower case "e" (earth). If you read the grammar rules on a website like this one, you'll probably be even more confused. Either way, you won't lose any marks in the IELTS test, so don't worry too much about this.
Note: After reading about the grammar rules myself, I'll probably follow the convention of writing "Earth" without "the" when I'm using it as a proper noun (name). Following this rule, I would write "Earth's climate" instead of "the Earth's climate".
2) Does "Try to limit the contribution" mean "make every effort" or "make little effort"?
It means "make every effort to limit the contribution".
3) Should we write "represents a threat" or "presents a threat"?
Both are possible, but "represents a threat" is a very common collocation, and has more results on Google.
4) Is it possible to completely agree/disagree without mentioning the other side?
Yes. I chose to completely agree, and I mentioned the negatives of the other view. However, you don't have to mention the other side at all. You can simply support your opinion in both main paragraphs.
5) Do we write "life on Earth" or "the life on Earth"?
It's normal in English to write "life on Earth". It's best to learn this as a fixed phrase; don't worry about why we don't say "the life".