1. He polluted forests. (This is habitual. His habit was to pollute areas of land covered with trees. It might imply that he did not pollute streams, lakes, cities or rivers.)
He polluted the forests. (He polluted certain specific land areas that were forested. This is a one-time event in the past.) 2. He watched news. (This is not the way we w
In general, when you use the with a plural you are assuming that your listener knows which ones you are talking about. You have some particular ones in mind. There may also be the implication "all of them".