One way that they are economically valuable is that it is mostly made up of the stuff that we have and need now like papers, tables, money, houses, etc. Wood is very very important in the human society and the place to get them is the forests.
A way that it is ecologically valuable is that the trees create habitats for the animals that live in the forests for protection from storms, other animals, etc. The trees in the forest can also be a source of food for some animals because those animal can feed on the leaves.
