Care
Mangrove management
Mangrove management
Image: BOPRC
Care > Mangrove Management
If there is one plant in the Ōhiwa Harbour that is able to become the subject of heated debates, surely it is the mangrove, or manawa, a native plant that has arrived in New Zealand relatively recently – about 14,000 years ago. The increasing spread of this highly adaptive estuarine plant probably results from the increase in sediment in the harbour in recent times. It has worried some people in the Ōhiwa community for many years. Among their concerns were the impact on shellfish beds and fish breeding, the obstruction to natural drainage and the reduced access to the harbour for boating and swimming.
As a result, the Ōhiwa Harbour Strategy partners started supporting the management of mangroves in 2008. In 2009 they developed an approach to management that included both dealing with the sediment flowing into the harbour from the land and controlling the mangroves themselves. The removal areas were carefully selected. It was well understood that mangroves, as a native plant, do have their place and provide habitat for other species, in particular the uncommon banded rail. In order not to disturb wildlife and considering dense mangrove stands act as coastal buffer zones, a removal boundary was drawn, as shown on the map
Section of the Ōhiwa Harbour mangrove removal map. Mangroves near the shore inside the blue line are protected
In 2011 Te Upokorehe, as one of the partners of the Ōhiwa Harbour Strategy partnership, was granted resource consent to control mangroves outside the mapped boundary. Te Upokorehe Resource Management Team and a small number of other local residents did the bulk of the hard work. With logistical support from the Strategy partners, each summer about ten working bees were held around the harbour.
Considering the value of mangroves the focus has been on the removal of seedlings and outlying plants from the outer fringe of established mangrove “forests”. Mangroves were cut with hand-held loppers into small pieces which are removed by the tide. At the end of 2020, volunteers completed a first “round” of the harbour. This means, since the start in 2011, outlying mangroves were removed from right around the harbour where access permitted the work. This included some fringes of Uretara, Ohakana and Hokianga islands.
In 2020 the resource consent expired, however, new rules in the new Regional Coastal Environment Plan allowed areas previously managed to continue to be controlled without a consent. In 2021 seedling removal continued in these areas.
A High Court decision in late November 2021 stopped this work. What had happened? The National Environmental Standards for Freshwater (NESF) 2020 provide very stringent protection for natural wetlands and do not allow any modification of them. Up to now it had been assumed that these new rules did not apply to saltwater wetlands (such as areas of mangroves). The Bay of Plenty Coastal Environment Plan previously allowed the Ōhiwa volunteers to do the work Upokorehe have been doing and this approach was supported by the Environment Court.
However, the Minister of Conservation and Forest and Bird appealed to the High Court. The judge had a different view from the Environment Court and declared any saltwater wetland (including mangroves) are subject to the National Environment Standards for Freshwater since they are natural wetlands. This decision over-rides the Environment Court and the Regional Coastal Environment Plan. In short, as a result of the High Court decision, mangrove removal in the Ōhiwa Harbour came to an end.