The Wet Tropics is home to a range of wetlands, from towering paperbark (melaleuca) swamps and scrubby whipstick melaleuca swamps to wet sedgelands and grasslands. The different wetland vegetation types are often found as complex mosaic mixed with some drier vegetation types on coastal swales or poor soils.
Melaleuca forests range from tall open forests to sparse shrublands. Melaleucas are the dominant tree species in poorly drained lowland coastal areas where the water table is near or above ground level for most of the year. They usually occur as components of vegetation mosaics reflecting specific habitats. These include Melaleuca leucodendra and Melaleuca dealbata complexes in freshwater and brackish swales in old beach ridge systems, Melaleuca quinquenervia forests in freshwater swamps, and Melaleuca viridiflora on low nutrient soils with impeded drainage and seasonally waterlogged. Drainage and clearing of coastal swamps, often for sugar cane, has threatened some melaleuca communities (see Melaleuca viridiflora communities listed as threatened).
The most extensive remaining forests are on poorly drained alluvial flats on the coastal plain south of Cardwell. Swamp forests formed by alliances of Melaleuca quinquenervia, Melaleuca cajuputi, Melaleuca leucadendra and Melaleuca dealbata are relatively extensive on the very wet portions of the coastal plain from Ingham northwards to Cape Tribulation. A rare highland example of Melaleuca quinquenervia swampland is also found in the Koombooloomba area.
Depending on soils, drainage, fire regimes and water flows, sedges and grasses may dominate wetland areas. Sedgelands are found on coastal lowlands between Gordonvale and Cardwell.