The dune system
The dunes at Mason Bay have high conservation value and are some of New Zealand’s largest remaining unmodified dune systems.
Flocks of New Zealand dotterels feed and nest here and kiwi sign is common. Large populations of Ficinia spiralis (pingao (declining) still remain within the dunes, with isolated patches of the threatened plants Gunnera hamiltonii (nationally threatened) and Euphorbia glauca ((sea spurge) declining).
The dune system extends up to 3 km inland and is easily accessible from the Great Walk tramping hut at Mason Bay.
The threat of marram grass
Marram was planted at Mason Bay as part of efforts to farm the area in the 1930s and1960s.
Mike Hilton of Otago University’s Geography Department calculated that if marram wasn’t controlled at Masons Bay it would occupy all available habitat in the dune system by the year 2030. Marram would displace pingao, sea spurge, Gunnera hamiltonii and other native plant species found throughout the dunes.
DOC Stewart Island has been controlling marram at Masons Bay for over 15 years. In a joint venture with Otago University students and staff monitor the impact of removal of marram on the dune system, undertake herbicide trials to ensure that the most appropriate method and herbicide is used and look at dune morphology.
Marram grass control
Phred Dobbins in Stewart Island manages the project which can be challenging logistically due to the remoteness of the location. Control is by use of 'Gallant' a herbicide specific to grasses (pingao is a sedge) and an ‘Argo’ – an 8-wheeled vehicle, complete with a 250-litre spray tank and two long hoses under pressure from a petrol pump. Large areas of marram are now controlled by helicopter.
Results are impressive and the choking cloak of sage-green marram is being gradually drawn back to reveal creamy white dunes topped with a crest of golden pingao. However the team need to keep controlling the plants to prevent reinvasion into cleared areas.