Hauraki Plains wetlands

• Category: Inland Aquatic Biomes.
• Geographic Location: New Zealand.
• Summary: The Hauraki Plains wetlands have been significantly reduced through transformation to agriculture.

Wetlands were once widespread features of the Hauraki Plains landscape on New Zealand's North Island. Less than 20 percent of the original freshwater wetlands remain today because of intensive drainage for agriculture and development over the past century. National efforts are aimed at restoring and protecting wetlands in the Hauraki Plains, and two locations here are recognized internationally for their global conservation value.

River movements and volcanic activity over thousands of years created the current Hauraki Plains landscape. About 20,000 years ago, volcanic material washed into the Waikato River and caused the floodplain to build up; the river to meander; and ash, pumice, and other sediments to be deposited across the plains. After the Waikato River shifted toward the west coast, the Waihou (formerly Thames) and Piako rivers were formed, flowing north to the sea at the Firth of Thames, a large bay. Bounded by these rivers, the Hauraki Plains filled in with estuarine deposits, river mud, and peat. Key features of the wetland area today are the Kopuatai peat dome and the tidal flats at the Firth of Thames.

At close to 24,711 acres (10,000 hectares), the Kopuatai peat dome is New Zealand's largest unaltered raised bog, as well as the largest freshwater wetland on the North Island. There are two main wetland types included in the site: peatland and mineralized wetland. The peatland is acidic, low in nutrients, and dominated by rainfall. By contrast, the mineralized areas surrounding the bog are nutrient-rich and sometimes flooded by the Piako and Waitoa rivers. The physical features of the peat dome and mineralized swamps play an important role in flood control and protection; they provide storage for floodwater from the river catchments. Managed by the Department of Conservation, Kopuatai is also a lifeline for many endangered and protected plant, bird, and fish species.

Biota

Important plant species found in the Hauraki Plains wetlands include the kahikatea tree (Dacrycarpus dacrydiodes). These endemic (found nowhere else on Earth) conifers can grow to a height of 180 feet (55 meters); they were used for building boats, thanks to the long, straight boards produced from the trunks. Other notable plants in the Hauraki Plains wetlands include the manuka or manuka myrtle (Leptospermum scoparium), a shrub-like tree that often returns first in cleared areas. Flax and bulrush are also common plants found in the wetlands.

The wetlands are a popular feeding and nesting site for approximately 54 bird species. Ducks and white-faced herons are two characteristic wetlands birds found here. Other birds include the beautifully plumed pukeko bird or purple swamphen (Porphyrio porphyrio). Easily recognized by its indigo plumage and red beak and legs, the pukeko is noted for walking or running, rather than flying, from danger. Various eels are also plentiful in the wetlands area.

The shallow tidal flats of the Firth of Thames cover approximately 21,004 acres (8,500 hectares) and lie within the Crown-administered Coastal Marine Area. This zone includes shallow estuarine water and mudflats, shell banks, grass flats, mangrove forest, salt marsh, and limited freshwater swamp margins. One of New Zealand's three most important coastal stretches for shorebirds, the area is used by more than 25,000 waterfowl and wader species, including many migratory birds. Aside from offering food and habitat for waterfowl, the Firth of Thames provides an important fishery of local significance.

Threats and Protection

The Haruaki Plains wetlands face many threats, including drainage for agriculture and housing, logging and its associated erosion, pollution from farm runoff, grazing, burning, and decreasing water levels due to the accumulation of sediment. Dairy farming is the main local industry, using two-thirds of the total area of the plains, although cattle and sheep farming also contribute to the regional economy, along with tourism. While these industries provide financial stability for the inhabits of the region, they create dangerous pollution and habitat destruction.

Displacement of native plants by invasive species like willow, gorse, and blackberry; and the spread of exotic fish such as mosquito fish and koi carp have further disrupted the ecology of waterways and make wetland restoration more difficult. Potential climate change threats for this area may come from rising sea levels, which can change the nature of the wetlands, producing salt incursion and coastal area erosion. Extreme weather events produced by climactic changes may also result in flooding beyond capacity of the local hydrological system to contain, again harming habitat niches.

In 1976, New Zealand became a party to the Convention on Wetlands of International Importance, the Ramsar Convention. This intergovernmental treaty provides the framework for national action and international cooperation for the conservation and wise use of wetlands. Two of the six Ramsar sites in New Zealand—the Kopuatai peat dome and the Firth of Thames—are in the Hauraki Plains region and were listed in 1990 for their extraordinary ecological significance.

The Hauraki Gulf Marine Park Act of 2000 further protects the waters of the gulf and the Firth of Thames; it established the Hauraki Gulf Forum to manage use, development, and conservation within the park. Soon after, the Waipa Peat Lakes and Wetlands Accord was signed in 2002. This ratified a commitment by multiple government agencies and conservation organizations to work together to promote the sustainable use and conservation of lake and wetland resources in the Hauraki Plains. In a 2022 meeting, members of the Hauraki Gulf Forum voted to update and strengthen the Hauraki Gulf Marine Park Act.

Additional strategies to address wetland conservation in the public and private sector come from the National Wetland Trust, established to increase the appreciation of wetlands and their values within the country; the Environmental Initiatives Fund of the Waikato Regional Council, which provides funding for restoration projects; and open-space covenants among landowners to protect their wetlands in perpetuity. Through efforts that recognize wetlands as a vital cultural and ecological resource, the Hauraki Plains remain a stronghold for wetlands in New Zealand.

Bibliography

Cromarty, Pam and Derek A. Scott. A Directory of Wetlands in New Zealand. Wellington: New Zealand Department of Conservation, 1995.

Peters, Monica and Beverley Clarkson, eds. Wetland Restoration: A Handbook for New Zealand Freshwater Systems. Canterbury, New Zealand: Manaaki Whenua Press, 2010.

Young, Alexander Douglas. "Wastelands 'which might doubtless easily be drained': A Contextual Study of the Drainage of the Hauraki Plains." New Zealand Journal of Environmental Law, vol. 24, pp. 247-78, 1 Jan. 2020, www.nzlii.org/nz/journals/NZJlEnvLaw/2020/10.pdf. Accessed 12 Nov. 2024.