A cassowary's diet is dominated by fallen fruit, and it takes items that other rainforest animals simply cannot handle. Seeds pass through the gut largely undamaged and are deposited in a substantial pile of dung, complete with its own nutrient supply and often some distance from the parent tree.
Studies in Queensland's wet tropics have associated cassowaries with the dispersal of well over a hundred plant species, and movement records show seeds being carried hundreds of metres to several kilometres. Some large-fruited trees have no other surviving animal in Australia capable of swallowing them whole, which makes the bird's role hard to substitute. Ecologists describe such species as functionally dependent on a single disperser.
What is often garbled is the danger. Cassowaries have injured and, in rare documented cases, killed people, but attacks are strongly associated with birds habituated to human feeding rather than with unprovoked aggression in intact forest.