Termites are important in two ways. They are destructive when they feed upon, and often destroy, wooden structures or vegetable matter valuable to humans. Introduced species, because they are not so well equipped as native species to adapt to changes in their new environments, tend to seek shelter in protected, man-made environments such as buildings and thus are likely to become the most serious pests, causing significant damage to houses and wooden furnishings. Some termites feed on living plant materials and can become serious crop pests. Termites are also extremely beneficial in that they help to convert plant cellulose into substances that can be recycled into the ecosystem to support new growth.

Source: Britannica