Wetlands are areas that are permanently, seasonally or intermittently waterlogged or inundated with water that may be fresh, saline, flowing or static. Some wetlands occur naturally in the environment, and others are artificially made to provide a certain function. It is difficult to give a single definition of what a wetland is because there are so many types, ranging from those that are permanently wet to those that are wet every ten to fifteen years. In WA, the term 'wetlands' commonly refers to basin or flat wetlands and the term 'waterways' is applied to channel wetlands (eg. rivers). For example, lakes are permanently inundated basins, sumplands are seasonally inundated basins, damplands are basins with seasonally waterlogged soils and seasonally waterlogged flats are known as palusplains.

At least 80 per cent of all of the natural wetlands that were once present on the Swan Coastal Plain prior to European settlement have either been cleared, filled or developed. An estimated 15 per cent have retained high ecological values (ie Conservation Category Wetlands).

In Australia, the driest inhabited continent, wetland diversity is among the greatest in the world and Australia has a large number of the world’s internationally recognised wetlands. Nearly 20 per cent of Australia’s bird species depend on wetlands and many birds rely on different wetlands for different parts of their life cycle. Australian wetlands are also critical for the survival of birds that migrate across the globe each season and Australia has international treaty responsibilities for these species.

As well as birdlife, wetlands support many different types of plants and provide a home for animals such as fish, frogs, tortoises and invertebrates. Many are great spots for recreation and people enjoy camping, swimming, boating, fishing, bushwalking and birdwatching around wetlands. They help in reducing the severity of floods and can help keep water clean and healthy by filtering out pollutants.

Seasonal wetlands, particularly seasonally waterlogged wetlands, often have a higher plant and animal species richness than permanent wetlands. Seasonally waterlogged wetlands, however, are being lost at a faster rate than other wetland types due to their less obvious boundaries and the traditional land development approach.

Like many other ecosystems, wetlands are constantly under threat by human activities. Many of Australia's wetlands have been badly degraded by activities such as land clearing, farming, mining, and urban and industrial development. It is important to manage wetlands wisely to ensure that their important values are maintained in the long term, and the Department of Environment and Conservation plays a valuable role in helping to conserve wetlands in Western Australia.