World Wetlands Day, marked annually on February 2, highlights the importance of wetlands across the globe as water storage and filtering sites, as well as habitats for an extraordinary array of flora and fauna.
There are 171 countries as signatories to the Ramsar Convention, with 2414 wetlands covering more than 250million hectares designated as sites of international importance. New Zealand became a signatory in 1976.
The convention encourages the "wise use’’ of wetlands, so they can be sustained economically, socially, and environmentally.
Otago Regional Council freshwater scientist Dr Sami Khan said wetlands had historical, cultural, economic and ecological significance, were reservoirs for knowledge and food and provided significant habitats for plants, fish, birds, reptiles, insects and micro-organisms. They also contained culturally important medicinal plants for Māori.
Wetlands also perform important ecosystem functions by storing water, filtering sediment, nutrients, bacteria and toxic compounds, accumulating carbon and buffering major flooding events.
Dr Khan said New Zealand had lost 90% of its wetlands in the past 150 years, most destroyed to develop farmland, and those surviving were under threat from land modification and other human activities.
Despite the introduction of the Resource Management Act in 1991, which legislates for wetland protection, nearly 5500ha of wetlands have been destroyed, and the condition of wetlands has continued to degrade.
The Otago region contained many diverse and distinctive wetlands, from lowland coastal areas to Alpine areas, including several nationally significant wetland systems, Dr Khan said.
Of the nine broad wetland hydrosystems recognised nationally, eight occur in Otago.
"The number, variety, and types of wetlands in Otago are a major natural asset for the region,’’ he said.
In greater Dunedin and coastal Otago, wetlands were mainly associated with estuaries and the lower reaches of rivers and streams, and experienced varying degrees of coastal, tidal and salt water influence, Dr Khan said.
Lowland stream valleys feature mainly freshwater marshes and swamps, including Tokomairaro River Swamp, Akatore Creek, Lower Coutts Gully Swamp and Whareakeake Marsh.
Stream-mouth lagoons, infrequently open to the sea and with brackish water, include Lower Otokia Creek behind Brighton, Kaikorai Lagoon and Tomahawk Lagoon.
Larger tidal and saline wetlands are found around Otago Peninsula and Otago Harbour, including Hoopers Inlet swamp, Allans Beach, Papanui Inlet saltmarsh and Aramoana saltmarsh.
There were seven wetland sites of international significance in New Zealand — the closest to Dunedin being Awarua Waituna Lagoon in Southland.
