Waituna Lagoon is at high risk of irreversible damage because of intensification of land use in the surrounding catchment. The Lagoon is part of an internationally recognised wetland, and is also of great significance to Ngai Tahu.
Environment Southland is gearing up to lead an urgent inter-agency response to try and prevent the state of the lagoon deteriorating to the point where its natural character is lost forever. This work was identified as being of top priority at the Council’s strategic workshop over the weekend and was discussed again today.
Chairman Ali Timms said an effective response would require cooperation from landowners and government agencies including the Department of Conservation.
As a first step, Environment Southland will make an aerial inspection of all farms in the Waituna catchment to check they are complying with their consent conditions, following up with visits to properties if necessary.
Environment Southland’s scientists have been monitoring the lagoon and its catchment for several years, but the information has only recently been brought together and analysed as a whole as part of the new State of the Environment Report on fresh water that the Council is producing.
The monitoring results show that high levels of nitrogen and phosphorous in sediments are threatening to “flip” the lagoon from being an ecosystem with clear water and populated by aquatic plants (macrophytes) and a range of fish species to one with murky, turbid water dominated by algae. If that happens, it will be irreversible.
Ms Timms said that several agencies have been working to try and improve land management practices in the Waituna Catchment. These include Environment Southland, the Department of Conservation, the Waituna Landcare Group and Southland Fish and Game. “Collectively, these activities have not been enough to halt and reverse the decline in water quality, which now threatens the whole Lagoon and its ecosystem,” she said.
The Council agreed today that the regime for opening and closing the lagoon should be urgently reviewed in consultation with the community, while farmers will be recruited for a trial to test ways of minimising the amount of nutrients that are washed into tile drains.
Other possible actions will be discussed with landowners in the catchment, Ms Timms said. “Any effective action can only be undertaken in partnership with the community,” she said.