Harbour history and care passed to younger generations
BY JULIA WADE
Sand mining concerns, mangrove controversy and adverse effects from past environmental events were all hot topics in a presentation given to local schoolchildren recently, to educate and highlight the current health and history of Mangawhai’s harbour.
Mangawhai Beach School (MBS) intermediate students were treated to the expertise and experiences from coastal consultants and ocean engineers, Andre and Robin La Bonte on May 20. The couple have had a close relationship with Mangawhai’s coastline and waters for nearly 30 years, working in consultation with Mangwhai Harbour Restoration Society (MHRS) on projects designed to protect and enhance the harbour.
“Mangawhai's identity, to a great degree, is centred around the beautiful Harbour,” Andre says. “We think it’s important for future and present generations to know the history of the restoration of our harbour so that work done by MHRS, sandspit revegetation and stabilisation, pest control, river channel maintenance, bird nesting and foraging, and mangrove management, will continue.”
Beginning with the historical events of 1991’s civil rebellion, the ‘Big Dig’, Andre explained the timeline and link between sand mining in the waters adjacent to the spit and the detrimental impact on the coastline, stating that if mining had been allowed to continue Mangawhai’s iconic sandspit could have been lost.
“Luckily the sand mining was stopped… however now they are taking it south of Mangawhai and proposing to take a lot of sand, the equivalent of the Sandspit itself. When sand is taken from the coastline’s natural restorative system it erodes the dunes,” he says. “Unfortunately New Zealand is the last country in the developed world to allow nearshore mining.”
Andre also discussed mangroves and says that although the plants have been in New Zealand long enough to be considered a native, they are ‘out of balance’ due to human-induced changes such as causeways, intensive farming and storm water flows.
Describing how the protection of the plants came about due to ‘junk science’, a decision based on foreign mangrove behaviour not on NZ mangroves, Andre explained some of the differences between the native variety and their overseas tropical cousins.
“In Florida 80 per cent of fish need mangroves to grow, an ‘obligatory relationship’, but there is no evidence of marine dependency on NZ mangroves,” he says. “Mangroves have only been in New Zealand for 14,000 years… so therefore all of the marine organisms haven’t evolved with mangroves… snapper, birds and different fish didn’t know mangroves, they grew without them.”
The La Bonte’s also presented research including a seven year long study conducted along Molesworth Drive which showed that the ‘number and type of critters’ living in the area was the highest where the mangroves had been systematically removed.
Questions were asked about the best way to clear the dense mangroves forests. Andre says the removal process with consents, helicopters, diggers and chippers is not cheap.
“It’s costly and time consuming… although scythes are one of the best tools,” he says. “It is a concern that if they’re left to spread it will become more expensive to keep the harbour clear.”
Students also heard how their former predecessors from ‘a few’ decades ago could swim in the waters that lap the school’s grounds before mangrove forests took hold.
MBS principal Aaron Kemp, who also attended the presentation, posed the idea that if the causeway was opened up, producing an increase in water flow, there is a possibility the school could eventually get their beach back, suggesting ‘perhaps Mangawhai Beach School pulling out baby mangroves is not a bad thing then?’
“Not at all, it’s helping resist the spread of the plants and keeping those areas open for wading birds and seabirds to use,” Andre replied.
“Mangwhai harbour is unique in the sense that it’s located far from another source of seedlings. If we were permitted to remove the mangroves, it would be just a minor amount of plucking the new juveniles that came up, and we could see the harbour returned to a pre-1940’s condition.”
Andre and Robyn La Bonte pass on their years of knowledge and experience to future generations, ensuring the care and protection of Mangawhai’s harbour lives on. PHOTO/JULIA WADE
“Mangawhai's identity, to a great degree, is centred around the beautiful Harbour.”
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