Mangrove spread concerns group
Whangamata¯ Harbour Care worried over expansion
ACoromandel conservation group has raised concerns about the state of Whangamata¯’s coastline and waterways. Whangamata¯ Harbour Care said it was especially worried about an expanding population of mangrove trees (ma¯ nawa) and stoats around the area.
Mangroves are woody trees or shrubs that are native to New Zealand. They are adapted to grow in environments that are too harsh for most other plants to survive.
The species has several benefits to the environment: organic matter produced by mangroves provides habitat and a rich source of food for species like snails, worms, shellfish, small fish and crabs, and they provide a buffer zone and protection from erosion of the coastline.
However, the extensive spread of mangroves can have negative impacts on the recreational, navigational and amenity values of estuaries.
Whangamata¯ Harbour Care chairman Ken Allen said there had been “a huge seedling” of mangroves around Whangamata¯ this year.
“We are trying to stop mangrove expansion.
“There are mangroves growing where they were not growing 60 to 70 years ago.”
Allen attributed the issue to farming and forestry practices over the decades.
“To be fair, local authorities are working with the farming sector and forestry is under pressure.”
The net result of farming and forestry had been the build-up of silt in the harbour, which fuels the growth of mangroves.
“If we let them, mangroves would take over our estuaries and harbour.”
Allen said the group was undertaking proactive steps to curb mangrove expansion, including drone mapping.
He said the group had four key concerns about the mangroves.
One concern was the cost-effective and better management of mangroves, but also sedimentation issues, impact on migratory wading birds and roosting sites, as well as the control of predator and pest animals to ensure a healthier habitat for harbour birds.
“By addressing these concerns, our future generation will also be able to enjoy the harbour as we do.”
Apart from mangroves, Allen said the group was concerned about stoats in and around the Whangamata¯ area, labelling them as “incredible and voracious killing machines”.
According to the Department of Conservation, stoats’ main prey are mice, rats, rabbits, and invertebrates such as weta, as well as birds, chicks and eggs.
Allen said stoats were skilled climbers, hunted day and night, and would often kill and store surplus food.
“They are a key target for Whangamata¯ Harbour Care pest control efforts, although they are more elusive than the rats often trapped.”
The group operates 20 traplines around the harbour and estuary edges, on the T¯ıtoki Golf Course and on private property.
The most recent trapline, managed by volunteers, was in the Wentworth Valley, which had been neglected for some time, he said.
Whangamata¯ Harbour Care pest control co-ordinator Roselle Gould takes care of locating the traps and resetting them.
“Primarily, they are located around the area of the Wentworth Valley motor camp,” Allen said.
“The results have been astonishing, as in the first two fortnightly checks of the trapline, a total of five stoats and 20 rats were caught. “This suggests a large population of pests in a valley Whangamata¯ residents cherish, and often take family, friends and visitors to also enjoy.
“The bushwalk and the waterfall are a great treat, but this level of pests will be taking a terrible toll on nesting birds, eggs and chicks. If we can reduce the pest numbers, the sound of bird calls may increasingly be heard in this beautiful valley.”
Gould said her role also involved co-ordinating a team of trapping volunteers to clear and monitor 20 traplines around the harbour and beyond.
“The trapping volunteers are the ones who go out and do the dirty work. They clear our traps of stoats, rats, hedgehogs and possums twice a month, sometimes more often.
“I’m always looking for more volunteers. I’m always interested in talking to the public about why it is so important to trap rats and other predators.”
Whangamata Harbour Care is a community-based volunteer group that was set up in 1997.
Since its inception, members have spent thousands of hours in the local harbour and estuaries, removing rubbish, planting native flora and controlling vermin and other predators, to protect the biodiversity found in the harbour.