Pulpavore

Pulparoves were large, flying insects. They were the natural gardeners of a former forest planet whose only surviving giant tree supported all life on the planet. For years they stayed away from the villagers, tending the remote farmsteads. In a quest for more material to turn to compost they moved closer to the main settlement. At first the colonists believed them threat but after The Doctor explained their role in the ecosystem, the colonists began talks with the Pulpavores for an agreement that saw the planet given the chance to be re-seeded. (DWAM: The Evergreen Death)