Threats to wetlands

Since European settlement in Western Australia, human activities have degraded many wetland environments. Impacts include:

Alteration of natural water regimes

This can be caused by activities such as artificial drainage, the extraction of groundwater, the construction of dams and weirs and the loss of vegetation. Plants and animals that inhabit wetlands are often dependent on a particular water regime, and may be affected by changes in water levels and inundation.

Loss of vegetation

The vegetation that occurs around wetlands is an important component of the ecosystem. The vegetation assists in maintaining regular wetland water regimes, provides habitat and food for fauna, protects against salinity and erosion, provides soil stability, filters pollutants and provides natural beauty while helping to maintain a healthy wetland. Loss of vegetation will result in the loss of these values.

Salinisation and excessive inundation

Effect of Salinity on wetlands (note the intrusion of samphire into the wetland as a result of clearing), photo taken by Melissa Rogers

Salinisation and excessive inundation are widespread issues in agricultural areas and are generally caused by the replacement of perennial deep rooted native vegetation with shallow rooted introduced annual crops and pasture. Because annual crop and pasture species use less water than native vegetation, this can result in a rise in the water table bringing with it dissolved salts that have accumulated in the surface layers of the soil. The effects of salinity and excessive inundation on wetlands include a reduction in water quality.  Aquatic invertebrate communities can be affected and permanently altered because some invertebrates have a lower threshold of tolerance of salinity.  Wetland plants that cannot tolerate high levels of salt in the soil or the extended period of inundation can die as a result of these factors. Impacts from mining activity, such as brine discharge, is also a factor that can cause salinisation in wetlands.

Introduction of invasive species

Weed Typha orientalis (Bulrush) invasion of wetland, photo taken by Melissa Rogers

This includes the introduction of weeds and feral animals (such as carp, mosquito fish, Salvinia, grasses, donkeys, goats and camels) into the wetland environment. Weeds invade and compete with native plant species for resources. Feral animals are known for their destructive impact on wetland areas and can disrupt the intricate food chains that exist within the ecosystem.

Water pollution

Contamination of a water body can be caused by various activities, including the use of chemicals (such as fertilisers and pesticides) in the catchment of wetlands, the drainage of pollutants and toxic materials into wetlands, and accidental chemical/oil spills. Some contaminating substances can be harmful to wildlife and can greatly reduce the water quality of the wetland. The use of fertilisers in the wetlands catchment can cause nutrient enrichment in the wetland. This has the potential to cause algal blooms in the water body. These blooms in turn may be toxic to some fauna, particularly fish and waterbirds, and result in events such as fish kills.

Natural processes

Fire, floods, cyclones and drought are all naturally-occurring processes that have the potential to damage wetland environments. Fire can remove or change habitat available for wildlife around wetlands. Floods, cyclones and drought can impact the natural water regime of the water body and the vegetation surrounding the wetlands.