Forests are storing vast amounts of carbon and every tree will at some point become part of the soil, if not harvested or washed into the sea. The degradation of trees is a long-term process as the structural compounds of wood are extremely difficult to break down. A complex community of invertebrates, fungi and micro-organisms is needed to decompose the wood and beetles that penetrate the bark are critical to the initiation of this process, also because they directly inoculate the wood with a characteristic community of fungi and bacteria. A particular type of wood decay are trunk cavities with wood mould in living trees. Saproxylic insects play an important role also in this process. In managed forests the majority of wood is harvested and very little is left to become dead wood and to finally be incorporated into the soil. The paucity of dead wood has important implications for forest biodiversity and for soil organic matter.