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Published: 2009-01-29 00:00:00

By Bala Tikkisetty, acting programme manager - coasts, land and wetlands.
Wetlands are like giant kidneys protecting the health of waterways – they help dilute and filter material that could otherwise harm our lakes and rivers.

With World Wetlands day occurring on 2 February, it is a good time to reflect on these and other benefits that wetlands provide.

Wetland is a generic term for the wet margins of lakes, ponds, rivers, streams, estuaries, lagoons, bogs and swamps.

Wetlands once covered large areas of the Waikato. Now they are some of our rarest and most at-risk ecosystems. They contain a diverse range of plants and animals and are home to many rare and threatened species.

Large areas of wetlands have disappeared with the development of farmland. It is estimated that about 90 per cent of New Zealand’s wetlands have been drained. This is one of the largest wetland losses anywhere in the world. Wetlands now occupy only about two per cent of the country’s total land area.

Conserving and restoring wetland habitats is worthwhile for many reasons.

Nitrogen and phosphorous enter waterways through ground water, surface runoff and effluent. Wetland vegetation uses these nutrients for growth. Wetlands remove up to 90 per cent of nitrates from ground water through a process called denitrification. Wetland plants trap sediment suspended in water, improving water quality. In riparian areas, their roots hold riverbank soil together, reducing erosion. Bacteria living in wetlands absorb and break down nitrogen from farm run-off and leaching thus improving water quality.

Wetlands regulate the flow of water by slowing water flow from land, soaking up excess floodwater and then slowly releasing water to maintain summer flows or recharge ground water.

Providing habitat for many different plants and animal life, including rare or threatened species, is another role for wetlands. Wetlands are also essential breeding areas for whitebait species and game fish as they provide a rich source of insects for fish, birds and amphibians.

Fishers, shooters, naturalists and other water-based recreationalists also make extensive use of wetlands. Wetlands’ importance to Maori, as mahinga kai (food gathering areas) - and as a source of plants for medicines and dyes - is well recognised.

On an international level, healthy peat wetlands are important in helping combat global warming as they soak up excess carbon.

Environment Waikato offer free advice to landowners on managing wetlands, including information on fencing, planting of suitable riparian margins and weed control.

Fencing keeps stock out, stops pugging of wetland margins and enrichment from animal wastes. Appropriate planting around the edges of the wetland reduces pollution from surrounding farmland, provides cover for wildlife, reduces bank erosion and reduces the temperature of water through shading.

Wetlands are worth caring for – the risk of failing to maintain their health is too great to ignore.