A new method of clearing mechanically mulched mangroves has been trialled by Bay of Plenty Regional Council after calls for action by local Forest and Bird members to address "dead zones".
The council's trial in the Waikareao estuary on Friday was the first step to investigate different ways to manage or
remove the mulch as part of a wider removal project in selected sites around Tauranga Harbour.
Council chairman John Cronin said the trial was "timely" as concerns had been raised that mangrove mulch was not being flushed from areas as quickly as hoped.
Forest and Bird members spoke out in the Bay of Plenty Times this month for the council to halt the mechanical removal of the remaining 30ha of mangroves in its programme, over fears it was creating "dead zones" or oxygen-depleted areas, where many different species such as titiko mud snails and crabs could not live.
The concerns were earlier raised by the National Institute of Water and Atmosphere, which has been monitoring mangrove removal in the estuary as well as at Matua, Waikaraka, Te Puna and Omokoroa.
The council has acknowledged some areas where there was limited tidal flow and a higher density of mangroves, these combined conditions had hampered the flushing of the mulch.
Mr Cronin said he was pleased Friday's trial went ahead, adding it was "important to alleviate any concerns that the mulch is causing a smothering effect".
"We hope that by removing mulched material, the estuary bed will revert to open mudflats quicker."
The trial involved the purpose-built mechanical mangrove mulcher being followed by a beach groomer. The groomer has been used to remove sea lettuce from Mount Maunganui beach and other areas around the harbour.
The mulch will be taken off site as green waste to be composted.
Data collected would be analysed over the next week to test the efficiency of recovering the mulch.
"This has been, as expected, a good learning experience. We should be able to improve a couple of equipment issues which will help in the long term," Mr Cronin said.
The results of the trial will be considered by the council and, if successful, will continue in other areas where mangroves will be removed this year, under consent.
