Loss of a Lagoon

In the 1970s, Southland’s Waituna Lagoon was the star of New Zealand wetlands.Today it’s bordering on a cesspool. Sue Maturin investigates how draining, dairying and development have brought this waterway to such a low ebb.

A few farmers in the catchment are using nitrogen inhibitors but they are not effective all year round, especially when it is cold and wet.

Environment Southland burst into a flurry of activity early this year, visiting farms with Fonterra and DairyNZ, with support from Federated Farmers, to identify areaswhere environmental improvements could be made.

More research has been commissioned, monitoring and compliance has been beefed up, and working groups have been set up in an Environment Southland-led process.
Work has begun on an interim plan change to the Water Plan to introduce a stronger regulatory approach.

Farm dairy effluent discharge consents have been called in for review.

Despite this, there is still a lot of buck passing between central government and Environment Southland, farmers and the dairy industry about who should pay, how to reduce
nutrient run-off and how much to reduce it by. Pockets of farmers deny the problems and are even fighting back, and the industry is procrastinating, calling for more science
and yet more evidence.

Allan Baird, the vice-chairman of Southland Federated Farmers dairy section, has accused the scientists of having vested interests. Intense farmer pressure on Environment Southland is threatening to weaken the council’s initial resolve for tough and immediate rules.

Gidday. I hope you are going to help us save Waituna Lagoon,” a Waituna farmer said, winding down his window as he stopped to watch me film the peaty water flowing into the polluted Waituna Lagoon.

He is one of the many Southlanders who have rallied behind urgent calls to fix the problems.
Waituna Lagoon, 40 kilometres south-east of Invercargill, was in 1976 New Zealand’s first wetland to be officially recognised as a wetland of international importance under the Ramsar Convention on Wetlands.

Now, after decades of wetland drainage and development, made worse by the recent rapid expansion in dairying and intensive farming, Waituna is so full of nutrients that it is at
risk of irreversible damage.

High levels of nitrogen and phosphorus in the sediments are threatening to “flip” the lagoon from being an ecosystem with clear water and healthy aquatic plants to one with murky, turbid water dominated by algae and slime.

The seagrass Ruppia, which is central to the lake’s health, has declined in recent years. The lake is filling up with sediment. According to the Lagoon Technical Group
(LTG), current expert opinion is that urgent intervention is needed to prevent a rapid “flip”.

To return the lagoon to a healthy state, LTG suggest there needs to be a 75 per cent catchment load reduction for nitrogen and a 50 per cent reduction for phosphorus.
Federated Farmers and DairyNZ say they are committed to helping protect the lagoon, but not everyone agrees on the goals or the methods to achieve them.

Waituna Lagoon is part of the Awarua wetlands complex, covering 19,500 hectares. The complex was an exceptional example of a largely unmodified coastal lake-type shallow lagoon within a largely intact coastal wetland system.

More than 80 bird species, including international and New Zealand migratory waders,
are known to visit the wetlands. Every summer thousands of migratory waders stop over. At least 10 threatened and seven at-risk endemic species can be regularly spotted,
though some, like the secretive bittern, require dedicated searching.

The wetlands are a hotspot for the giant kökopu and home to longfin eels, for which the lagoon is named, (wai = water, tuna = eel). The lagoon and its tributary
streams are traditional fishing areas for Mäori, and high numbers of waterfowl mean it is also popular with hunters.

Concerns about water quality and land intensification led to the establishment of the Waituna Landcare Group in 2001. Along with the Department of Conservation’s Arawai Käkäriki project initiated in 2007, they have been encouraging and supporting increased riparian fencing and planting.

Even so, not all the waterways are fenced. Further warnings about the need to improve catchment management in 2003 and more urgently in 2007 seem to have mostly gone unheeded.

Dairy conversion in the area has been rapid, going from five farms with 800 cows in 1990, to 28 farms in 2000 and now 41 farms, with more than 20,000 cows. More conversions are being considered.

There remain about 14 sheep and beef farms, some of which are also wintering dairy cows. Nearly 400ha of wetlands have been drained in the Waituna catchment since the late 1990s, and about 30ha of bush cleared. The lower catchment is made up of infertile and poorly drained soils requiring extensive drainage and fertiliser for farming.

Despite these constraints, dairy farms have been established. Some farms do not have enough storage for dairy shed effluent and so are often forced to spread effluent on watersodden soils.

But dairy shed effluent only accounts for about 10 per cent of nutrients lost from a dairy farm. Urine patches can contain up to 1000kg of nitrogen a hectare. In the meantime, some of the best farmers, such as Tony and Raewyn van Gool, are showing the way and have permanently fenced and planted waterways, constructed wetlands to filter the drain discharges and covenanted 4.6ha of remaining forest and red tussocks.

Others have also permanently fenced and planted waterways and created wider temporary fenced buffers, electric fenced swales, or wet hollows, and refrained from winter grazing
of crops planted in swales and gullies. According to James Ryan from DairyNZ, a few farms could do a lot to reduce nutrient and sediment run-off.

The trouble is that recent modelling shows that even the very best farm practices, including herd homes, are unlikely to be enough or brought in fast enough to save the lagoon. As well as requiring every farmer to implement best practice, rules are needed to bring about immediate changes in land management, such as reducing cow numbers to match soil capabilities, stopping wintering on fodder crops, no further wetland drainage or native
vegetation clearance and the use of rigorous nutrient management systems.

Relying on voluntary measures such as the 2003 Dairying and Clean Streams Accord has not worked. The parlous state of our lowland streams and lakes is well known. The era of lax national, regional and district policies and plans, where short-term profits have taken precedence over ecologically sustainable management, should be over.

Waituna is just the most recent high-profile wetland showing poor catchment management that will end up needing an expensive clean up. As with the Waikato River and lakes Rotorua and Taupö and the recently announced $12 million clean-up for Te Waihora (Lake Ellesmere), taxpayers and ratepayers will be expected to foot most of the bill.

Farmers have to take more responsibility and adopt farm practices that stop harmful nutrients and sediments reaching waterways. It’s time for industry, too, to demand
higher standards.

Sue Maturin is Forest & Bird’s South Island Advocate