The Wet Tropics

In the wet tropics, it is warm or hot throughout the year. Rain falls most of the year round, and there is a short dry season of just one or two months. In some mountainous regions, such as in the highlands of Papua New Guinea and elsewhere in south-east Asia, rain can occur throughout the year and the total annual rainfall can be over 10 000 mm (10 metres)! All that water has to go somewhere, and the wet tropics can boast spectacular wetland complexes, from the highlands to the coast.

Tropical rainforests support an incredible diversity of animals, insects and plants, and tropical wetlands are equally productive ecosystems. Wetlands of the wet tropics include peat swamps and peat forests; mountain streams and rivers; flooded forests and plains; mangroves, tidal flats and coral reefs.

The Wet-dry Tropics

About one quarter of the world’s tropical landmass 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 three months of the year. In Australia, the wet-dry tropics extend across the north of the continent and south-east along part of the Great Dividing Range (see map of Australia).

The wet season is spectacular, with dramatic lightning displays, monsoon rains 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, the black soil floodplains become dry and cracked and many waterholes disappear. During this time, permanent creeks, rivers and billabongs become important refuges for great numbers of crocodiles, fish, birds and other animals. Fires occur in the woodland, and later on floodplains and along creeklines as they dry out. By the end of the dry season, the weather grows hotter and more humid and the entire landscape seems to bask in the sun, waiting for the first rains.