Why our estuaries matter

Our estuaries are important ecosystems that support many species, including fish, shellfish and birds. Estuarine habitats such as seagrass beds are important nursery habitats for some species, including commercially important species such as snapper. Fringing wetlands, such as saltmarsh and mangroves, act as filters that trap sediment and pollutants, improving water quality in coastal waters. Estuarine wetlands also act as buffer zones that protect shorelines from erosion and inundation.

New Zealanders value their estuaries for social, economic, spiritual and cultural reasons. Estuaries provide for recreational activities, such as swimming, paddleboarding and fishing, and attract tourists from overseas as well as from New Zealand. Estuaries have always been important to Māori. Settlements were often established near estuaries, which are important sources of kai moana, rongoā and other resources, and estuaries often contain wāhi tapu. Today, many towns and cities are located on or near estuaries, and industries such as aquaculture and fishing rely on estuaries and harbours.

Human activities that take place within an estuary and its catchment have the potential to impact on the health of an estuary. These include:

• urban development
• agriculture
• forestry
• aquaculture
• fishing
• recreational activities.

Estuaries are the downstream receiving environment of freshwater ecosystems, and so anything that influences freshwater eventually influences an estuary.  

Major pressures on estuaries in New Zealand are high inputs of sediment and nutrients caused by land use change and intensification. Increased sediment loads smother estuarine plants and animals, altering habitats and reducing biodiversity. Increased nutrient loads contribute to eutrophication symptoms in estuaries, such as algae blooms, which also have detrimental effects on estuarine plants and animals. These impacts adversely affect the ecological functioning of our estuaries, and their value to people.