Heat goes on NZ wetlands
Wetlands on fire sounds like an oxymoron but it has become a reality for two significant ecosystems at opposite ends of Aotearoa.
One is now thought to have been burning underground for nearly a year and a new Department of Conservation (DOC) report suggests more of New Zealand’s last remaining wetlands could also be at risk of being ravaged by fires, as the climate continues to change.
While international leaders and diplomats gather in Egypt for COP27 – this year’s annual UN climate conference – DOC staff have also travelled to Geneva, Switzerland, for the Ramsar Convention on Wetlands of International Importance.
New Zealand signed the convention in 1976 and has seven wetlands with Ramsar status across the country – the Firth of Thames, Whangamarino and the Kopuatai peat dome in Waikato, the Manawatu¯ River Estuary, Wairarapa Moana, Farewell Spit in Golden Bay, and the AwaruaWaituna Wetland in Southland.
Together they make up nearly 68,000 hectares. All are home to a diverse array of wildlife and are important mahinga kai sites for local iwi. Since humans first arrived in Aotearoa, 90% of the country’s wetlands have been lost.
The report said despite a lot of work and new legislation to protect them, the overall state of New Zealand’s wetlands had continued to decline in recent years, due to pressures like land conversion, pollution and climate change.
DOC’s international policy manager, Danica Stent, said climate change was causing a unique issue to rear its head. ‘‘Last summer was a stark reminder of our wetlands’ vulnerability when the Awarua Wetland Ramsar site [in Southland] and Kaimaumau-Motutangi in Northland were both ravaged by fire.’’
The Southland fire, which is being treated as suspicious, started in April and burnt through 1370ha.
The fire at Waiharara, north of Kaita¯ ia, began in December last year and twice forced the evacuation of Kaimaumau. At its peak the fire engulfed 2800ha, and it has cost more than $9 million to battle the blaze.
Fire and Emergency said the fire still had not been formally declared out and while there were no active flames or smoke, it could still be burning away underground.
DOC’s freshwater ecosystems and threats manager, Nicki Atkinson, said it was ‘‘counterintuitive’’ to have fires in wetlands.
‘‘However, most wetlands exist in areas of deep peat soils, which are accumulations of decaying plant material. Once alight, the peat is a huge source of fuel for fires and can make them difficult to put out as they essentially burn underground.’’
Peat acted like a sponge, she said, so in winter it soaked up water and was wet. But in summer it dried out, making it relatively easy for it to catch fire. For this reason, droughts caused by climate change and the draining or diversion of water away from wetlands makes them more susceptible to fire.’’
The fires in both Awarua-Waituna wetland in Southland and Kaimaumau wetland in Northland burnt though significant areas of vegetation, and in some places also burnt the peat soils, she said.
‘‘It will take some years for those sites to recover fully, especially where the fire burnt down through the peat.’’ DOC was monitoring the sites for any impact on plant and animal species, and would take extra care managing weeds that tended to invade burnt areas.
But Atkinson said she thought more wetland sites could be at risk, as the climate continued to change.
Atkinson said the Ramsar sites were also susceptible to ongoing degradation through nutrient inputs, altered water inputs, and the loss of small, usually degraded wetlands in agricultural areas.
Wetlands, like lakes, accumulated nutrient and sediment run-off from both farms and urban land, so even if the amount of run-off coming from agricultural land dropped, they were still dealing with a legacy of built-up nutrients like nitrates.
‘‘This alters the way they function and can change which plant and animal species use wetlands for habitat.’’ Another major cause of wetland degradation was reducing the amount of water flowing into them, either though irrigation, by diverting water into surrounding land, or by increasing the amount of water that flowed out of them through drains.
‘‘Having less water in wetlands tends to promote weed and pest species, to degrade water quality, to release greenhouse gases into the atmosphere, and to reduce habitat for native and taonga species.’’
Atkinson said a nationwide stocktake of where our wetlands are, what state they are in and what specific pressures they are under would be a good first step to building a strategy for protection and restoration.
Stent said New Zealand could not afford to lose more wetlands, which could also play a part in our climate change solution. ‘‘We are also increasingly aware of the crucial role wetlands play in climate change mitigation – through storing carbon – and climate change adaptation, by buffering and absorbing severe weather such as flooding and sea surges.’’ But there had been significant changes in freshwater policy and investment in management, which were both slowing the rate of degradation, and created stronger policy tools to advocate for their protection and restoration.
‘‘Jobs for Nature funding includes over $400m to improve freshwater management, with many of the funded projects providing direct or indirect benefits to wetlands.’’
Some, like the Te WhanganuiA-Orotu (Ahuriri Estuary) restoration project in Hawke’s Bay and Lake Moawhitu in the Marlborough region, had wetland restoration as a main objective.
Robust targets in the National Policy Statement for Freshwater and Te Mana o Te Taiaio Biodiversity Strategy had been set to prevent further loss of wetlands, to restore them to a healthy, functioning state and to promote their role in carbon storage, she said.
‘‘We have also seen what strong partnerships can achieve. In 2020, Wairarapa Moana was granted Ramsar Wetland of International Importance status through Wairarapa iwi, community and local and central government collaboration. ‘‘Wairarapa Moana is home to critically endangered birds, and acknowledged by local Ma¯ori as a place of tremendous cultural and spiritual value.’’