Max Finlayson & Abbie Spiers,
Environmental Research Institute of the Supervising Scientist, June 1998
About the note
About one quarter of the world's tropical land mass is classified as wet-dry. The wet-dry tropics are characterised by two broad seasons-a cool/warm dry season and a warm, humid wet season. The climate is strongly seasonal and most rainfall occurs over just 3 months of the year. Australia's wet-dry tropics extend across the north of the continent and south-east along part of the Great Dividing Range. The wet seasons are spectacular, with dramatic lightning displays, extensive flooding and lush vegetation growth. There is a high risk of cyclones along the coast at this time of year. It is a time for many animals to breed, including crocodiles, fish, water birds and frogs. In the dry season that follows, many floodplains and waterholes dry up and annual burning begins in the savanna woodlands. The few permanent creeks, rivers and billabongs become important refuge areas for many animals in these warm, dry months.
Rivers, billabongs, seasonally-flowing streams and floodplains are wetlands. So are mangrove forests, coastal salt flats and man-made dams or sewage ponds. The Ramsar Convention for Internationally Important Wetlands defines wetlands as 'areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, brackish or salt, including areas of marine water the depth of which does not exceed six metres'. With such a broad definition the wet-dry tropics are literally awash with wetlands!
eriss includes this broad spectrum of wetland habitats in its research program. In this program we aim to provide information that can be used to protect and manage wetlands on a catchment basis.
Wetland habitats in the wet-dry tropics include: escarpment streams,· flood basins and plains, waterfalls and plunge pools, estuaries and seagrass beds, lowland permanent or seasonally-flowing streams, tidal reaches of streams, permanent billabongs or lagoons, mangroves and salt flats.