On World Wetlands Day (Friday 2 February), Forest & Bird has issued a warning that New Zealand’s unique wetlands are in crisis, and will continue to degrade unless more is done to protect them.
“Ninety percent of New Zealand’s original wetlands have been destroyed by agricultural and urban development”, says Forest & Bird’s Freshwater Advocate Annabeth Cohen. “And we aren’t doing a very good job of protecting what’s left.”
Forest & Bird has released maps that show the extent of wetland loss, comparing the situation before human settlement, and the few remnants that are left.
Ms Cohen says wetlands play a vital ecological role – as well as providing unique habitat for threatened plants, birds, and fish, they also improve water quality, and reduce flood risks to nearby communities.
Healthy peat bogs lock up large amounts of carbon, making them essential for managing climate change.
A fifth of native bird species use wetlands as their primary habitat, relying on a linked series of wetlands for resting and feeding.
“The trouble is, our original wetlands have been drained for agriculture, and the now rare remnants can’t cope with the huge amounts of nutrient and sediment-loaded runoff, which degrades the quality of the water, making it very difficult for whitebait, eels, and other native freshwater species to survive there.”
“Wetlands can occur in many places, from estuaries to mountaintops, but very few of these special ecosystems remain. Those that do remain are often isolated and don’t provide the connection that wildlife need.”
“In Southland alone, the regional council estimates that 10% of their wetlands have disappeared since 2007,” says Ms Cohen.
“While in the Hawke’s Bay, it took the Supreme Court to save a rare oxbow wetland from the Ruataniwha water storage dam.”
Wetland ecosystems has been recognised internationally by the Ramsar Convention, and six New Zealand wetlands have been recognised under this covenant due to their environmental significance.
The Department of Conservation is responsible for managing our Ramsar sites, but in cases like the vast Whangamarino wetland in the Waikato, their efforts are hampered by poor management from regional council.
“If an internationally recognised Ramsar wetland like Whangamarino is in such bad shape - what hope do our other wetlands have?”
“Regional councils must do more to protect wetlands, and that means better management of surrounding agriculture, enforcing rules to prevent illegal vegetation clearance and wetland drainage, and working with community, iwi, and DOC to restore wetlands that have become degraded.”
- Nelson has the lost the greatest proportion of its wetlands = 99.2%
- Southland has lost the largest area of wetlands in hectares (404,000 ) followed by Waikato (328,290)
- Otago has lost the least proportion of wetlands in NZ – only 76%, but has still lost nearly 84,000 hectares of wetland.
- Canterbury has lost nearly 167,000 hectares of wetland.
- Auckland has lost 55,000 hectares of wetland.
- Overall, New Zealand has lost 2,221,304 hectares of wetland, and only 249,776 remain.
Auckland / Northland
- Before human occupation, the Auckland region had 57,851 hectares of wetland ecosystem.
- Only 2639 hectares remain, or 5% of the original wetland area.
Freshwater wetlands once comprised about 25 per cent of the region’s land cover, they now comprise less than 0.5 per cent.
The low-lying western suburbs in Auckland City were once full of cabbage trees and flax, and formed habitat for weka, banded rail, bittern and pūkeko. On the Auckland isthmus, swamps developed behind beach deposits at the mouths of streams, along streams restricted by lava flows, in ponds in volcanic craters and on the surface of lava flows. Swamp forests with kahikatea, pukatea, swamp maire, raupō, cabbage trees and harakeke (flax) would have once covered large expanses of the low lying areas of the Kaipara and Franklin districts and also parts of Rodney.
Te Henga is the largest remaining wetland in Auckland and home to a wide range of native animals including bittern, fern bird and spotless crake and pāteke (brown teal). Forest & Bird’s Waitakere Branch is controlling predators in the area and restoring it with plantings, helping to protect these species and return this valuable habitat to its natural state.
- Before human occupation, the Waikato had 356,516 hectares of wetland ecosystem.
- Only 28,226 hectares remain, or 8% of the original wetland area.
The Whangamarino wetland, between Auckland and Hamilton is one of the largest in the country, at over 7000 hectares. It is one of six Ramsar wetlands, contains many rare wetland plants and is a notable bird habitat. The wetland is in a very degraded state. Water drains into it from one of the country's most polluted lakes, Lake Waikare, and last summer the wetland became anoxic (oxygen depleted), causing thousands of fish to die.
The regional council manages the wetland for flood protection, meaning the water levels rise and drop many meters in a short time and overload the wetland with nutrients and sediment. This makes it hard for plants and wildlife to thrive. This special site needs to be managed for its environmental values, not used as a drain.
Manawatu and Horowhenua
- Before human occupation the Manawatu-Wanganui region had 264,511 hectares of wetland ecosystem.
- Only 6983 hectares remain, or less than 3% of the original wetland area.
- The Manawatu estuary near Foxton is one of six New Zealand Wetlands of International Importance under the Ramsar Convention.
The Manawatu Estuary, at the mouth of the Manawatu the largest estuary in the lower North Island of New Zealand, an important site in the lifecycle of many indigenous and migratory bird and fish species, and a significant recreational resource. The Manawatu river is currently listed by MfE as having the worst catagory of water quality. Agriculture exists right up to boundary of estuary.
Lake Horowhenua also known as Punahau, lies west of Levin and 5 kilometres from the coast. It is a shallow lake, only 2 metres deep, and flows into Hokio stream. The lake was once surrounded by forest as the centre of a rich wetland ecosystem. Today the trees are gone and the wetland has been substantially drained. Local iwi, with the help of the Horowhenua Lake Trust, are attempting to restore the wetland system to its former state as a conservation area.
- Before human occupation the Hawkes Bay region had 113,362 hectares of wetland ecosystem.
- Only 2458 hectares remain, or 2% of the original wetland area.
The Ruataniwha scheme would have destroyed a rare oxbow wetland, which provides habitat to native fernbirds, fish, and other threatened species.
Waitangi wetland provides a variety of wetland and coastal habitats that support a significant population of bird species. It connects with the nearby Tukituki Estuary. The construction of the Heretaunga Plains Flood Control Scheme in the 1960 and 70s significantly altered the wetlands. Numerous stopbanks and pump stations were constructed along these rivers and Muddy Creek south to the Tukituki River to provide flood protection and drainage to extensive areas of land between Napier and Hastings.
- Before human occupation the Wellington region had 122804 hectares of wetland ecosystem.
- Only 2774 hectares remain, or just over 2% of the original wetland area.
The Hutt Valley was once marshlands and swamp forest. At the time of European arrival, swampy marshlands extended several kilometres up the valley from the river mouth. Wetland species such as raupo, flax and toetoe dominated. Beyond this, kahikatea, matai, puketea and rimu forest grew extensively on the valley floor. Most of the valley floor has been cleared of the original forest cover with only a few small remnant stands and trees remaining.
Significant remaining wetlands in the Wellington region include Pencarrow lakes, Waikanae estuary, and Pauatahanui inlet. Forest & Bird’s Kapiti-Mana branch has put a lot of work into restoring the Pauatahanui Wildlife Reserve at Pauatahanui inlet.
- Before human occupation, the Canterbury region had 187,115 hectares of wetland ecosystem.
- Only 19,851 hectares remain, or 11% of the original wetland area.
Although the Upper Rangitata Valley and Mackenzie Basin had experienced the largest examples of wetland reduction, of the Orari and Opihi zones, only about 522 hectares of the historic wetland areas remained, about 9 per cent of the original historic area.
Besides having New Zealand’s best inter-montane wetland system, Canterbury is also known for having Te Waihora/Lake Ellesmere as the most important wetland habitat of its type in New Zealand. A 1990 National Water Conservation Order declared it as an outstanding wildlife habitat. Extensive wetlands around the lake margins act as a filter and played an important role in maintaining water quality, but these have been largely drained. Due to direct pressures in this over allocated and intensively developed catchment like conversion to pasture, irrigation and heavy grazing, Te Waihora regularly experiences water quality issues like toxic algal blooms which are hazardous to human and animal health.
- Before human occupation the Otago region had 110,804 hectares of wetland ecosystem.
- Only 27,050 hectares remain, or 24% of the original wetland area.
- The Waipori-Waihola wetland covers 2000 ha, and is one of the largest and most significant remaining freshwater wetlands in New Zealand.
Lake Waihola is currently classified as the worst water quality “very poor” or supertrophic particularly because of sewage, stormwater, dairy shed and farm runoff. Drainage schemes have drained the majority of the original wetlands although the Sinclair Wetlands between the two lakes has survived and is protected under a QE II covenant.
- Before human occupation the Southland region had 450,984 hectares of wetland ecosystem.
- Only 47231 hectares remain, or 10% of the original wetland area.
- The Awarua-Waituna Wetland is one of six New Zealand Wetlands of International Importance under the Ramsar Convention.
- Southland’s wetland continue to disappear. According to a regional council report, Southland has lost 10% of its remaining wetlands since 2007, mostly to agriculture (40% to dairying).
Awarua-Waituna Wetland is a large wetland site of 20,000 ha. It is an estuarine wetland, frequented by migrating and wading bird species, as well as threatened plants and insects including sub-alpine species. Intensive land use and the conversion of surrounding catchments to dairying land are the primary threats to its water quality. This lake is currently listed by the Ministry for the Environment as having the second worst (intermittent) water quality.