Recently I received a message from a Peninsula resident who had been cleaning up a section of the Otago Harbour of plastic and other rubbish. Now as a keen fisherman and diver I found their efforts impressive, but it was also depressing at the amount of plastic they removed from around the harbours edge. The prevalence of plastic in the harbour that is washed up onto the tidal bays is quite significant and has become a chief villain in the conservation of wildlife and sea fish stocks. More attention has been brought to plastic entering our waterways in recent years, but it’s not actually a new problem. As early as 1977, Gregory R. Murray from the University of Auckland found microplastics in almost all the coastal areas he surveyed.
The problem with plastic waste when it enters the harbour ecosystem is that it fragments due to tide, waves and sunlight into microplastics that are often less than 1 mm in size. That small size enters the marine food chain in krill, crabs and shellfish and eventually makes its way into fish, birds, marine mammals and even humans. Sea birds are particularly vulnerable to eating plastic because they are largely surface feeders, diving down and scooping up pray along with plastic on the waters surface. This is particularly worrying for Dunedin and the Otago Peninsula whose populations of coastal sea birds include the Yellow-eyed Penguin, Blue Penguin, Red Billed Gull, Spotted Shag, White Fronted Tern, Southern Black Backed Gull, Sooty Shearwater, Fairy Prion, Black Shag and the iconic Royal Albatross. In a published 2021 study of marine rubbish by Ella van Gool the Otago region had the highest mean density and the highest mean weight of marine rubbish (AMD anthropomorphic marine debris) in New Zealand. The Ministry for the Environment also published a report on the impact of plastic on marine ecosystems in the Otago Harbour. Takiharuru (Pilots Beach) on the Otago Peninsula recorded 15 items of rubbish for every 100sqm of beach, of which 23% were hard plastics and 23% were food wrappers. Its incredible to think that in the heart of one the most important biodiversity areas on the Otago Peninsula that we should see such results.
We all must take collective responsibility for these results and must make real efforts to improve them. Local and national government including its agencies cannot continue to rely on the good will and feel good factor of community volunteers cleaning up our harbours and coastlines. The hard work of the local gentleman who contacted me recently on the Otago Peninsula should not be taken for granted. It needs more than just moral support, we actually need to have a plan to stop this issue growing any larger in Dunedin. The rising tide of waste and our ongoing consumption of plastic products needs to be seriously curtailed. Greater efforts in public rubbish collection, bin design & servicing along with stronger planning and statutory mechanisms need to be implemented to give the harbour and its biodiversity a chance. Given what we are seeing in the Otago Harbour a wider call from the community is needed to be more innovative and proactive in the control of waste entering its waters.