Survey supports mangrove management for birdlife

BY JULIA WADE

A recent scientific study focusing on the aftermath following the removal of Mangawhai’s mangroves, has revealed several valuable environmental enhancements since the plants were pulled, including many benefits for endangered native birds.

Ecology consultancy company, Bioresearches, was commissioned by Mangawhai Harbour Restoration Society (MHRS) to determine any impact the organisation’s planned mangrove management program may have on the surrounding bird life.

Conducted throughout 2018, the study surveyed the mangrove-cleared area known as ‘Sand Island’ – located within the harbour in front of the Mangawhai Tavern – as well as the Insley Street estuary, and found no adverse effects on the environment following the removal of the controversial marine plants. Instead the research showed significant ecological benefits within the restored tidal and shoreline areas, including providing nesting areas and wetlands for birdlife, and restoration of vital coastal habitats.

MHRS received the completed compiled report late 2019 and chair Doug Lloyd says the society’s volunteers are thrilled with the results.

“We are very pleased with the scientific findings, that mangrove removal has created benefits for native birdlife and will over time, enable the restoration of highly valuable environments such as seagrass, salt march and inter-tidal areas,” he says.

“I hope this will provide great comfort to the Mangawhai community, that sustainable environmental practices being undertaken by MHRS in our harbour estuary system are scientifically proven to be successful, and ongoing broader environmental development initiatives should be enabled and completed, ensuring the wellness of our estuary ecosystems going into the future.”

Led by Biosearches senior ecology consultant Graham Don, who has 40 years of experience in the field and specialises in marine ecology, the report states ‘expert scientific advice has confirmed mangrove removal at Sand Island has been unequivocally beneficial for coastal birds’.

The surveys back-up former long-term research, which stated how mangrove extraction had increased biodiversity in the harbour, and shows removal of the plants provides an increased habitat for birds to feed and rest. In particular, four threatened species and six at-risk species including fairy terns, banded dotterel, caspian tern, lesser knot, eastern bar-tailed godwit, red-billed gull, royal spoonbill and South Island pied oystercatcher as well as various other oystercatchers, were recorded using Sand Island.

Furthermore, due to the increased numbers of NZ dotterel frequenting the cleared area, Sand Island is now known as a ‘Wetland of International Importance’ under the ‘Ramsar Convention’ which states is ‘an area that supports more than 1 per cent of the individuals in a population of one species of waterbirds’. The average numbers of birds using the Insley Street cleared habitat also remains steady. ‘Clearly the mangrove-cleared area is habitat that is attractive to a typical diversity of harbour birds’.

A rare Northland estuarine coastal habitat, ‘saltmarsh’, of which ‘less than 15 per cent of the original environs remains’ due to the ‘dominant ecological monoculture of mangroves’, is still being dominated within the harbour and estuary by the spread of the plants the report says, with only 10 hectares of saltmarsh left in Mangawhai. However, where mangroves have been removed in other locations, ’dramatic improvement in saltmarsh vegetation has occurred’.

Removal of mangroves from Mangawhai Harbour began in 2004, with three environmentally successful extraction projects being undertaken in the following years. More than 2000 locals and residents signed a petition in 2016 asking Northland District Council (NRC) to allow further removal in an attempt to return the harbour back to its clear 1946 state, prior to the building of the causeways which reduce tidal flow and result in the promotion of mangrove growth.

Although often a contentious issue, with some people maintaining the plants are important to wildlife, MHRS receive ‘overwhelmingly positive’ feedback from the community Lloyd says.

“We are delighted with the support as maintenance and continuing restoration is vital to the sustainable management of the Mangawhai

Harbour, both ecologically and for the community,” he says. “The MHRS look forward to working with the regional and district councils as well as other stakeholders in the continuation of the harbour’s restoration.”

¢ MHRS is a voluntary charitable society established for the purpose of the restoration, maintenance and enhancement of the Mangawhai Harbour and surrounding features, and represents the interests of Mangawhai community and environs. For further information please contact MHRS chair Doug Lloyd, doug.lloyd3@gmail.com

Mangawhai Harbour Restoration Society chair Doug Lloyd and members are delighted with the results of a recent report which revealed their mangrove extraction efforts are benefiting wildlife, saying ‘clearly the mangrove-cleared area is attractive habitat to a typical diversity of harbour birds’. PHOTO/JULIA WADE

“We are very pleased with the scientific findings, that mangrove removal has created benefits for native birdlife.”