Forests are complex terrain, and the easiest and cheapest way to monitor them is, of course, with a UAV. With a UAV you can conduct drone surveillance around the clock or at any time convenient for you. If your forest is large, Culver Aviation's automated aerial surveillance UAV network can help. Check out the features of their Menatir system , which is used for a variety of tasks, and I'm sure you'll make the right choice.