Editorial: Our rotting lakes must be restored

Pictures of lifeless fish washed up on the shores of dead lakes represent one of the most graphic indictments of the industrial despoliation of parts of Eastern Europe. Such a sight is simply unacceptable in a country keen to boast a clean, green image. Yet, as "Our Dying Lakes", the Herald's five-part series, revealed this week, we are uncomfortably close to an environmental calamity.

The average size of fish in once-magnificent lakes in the central North Island is dropping dramatically as the quality of their habitat deteriorates. Water once pristine now looks like pea soup and smells likes wet hay. In some instances, algal blooms are so bad that swimming is unsafe. The importance of tourism dictates that remedial action must start now. A worsening of an already bad situation cannot be contemplated.

Fortunately, the lakes identified as being sick enough to need action plans - Rotoiti, Rotorua, Rotoehu, Okareka and Okaro - are not yet beyond recovery. On the other hand, none will be fixed overnight. Such is the way of nature. Scientists have been warning since the 1980s of the threat posed by human activities and byproducts such as farming and sewage. The time necessary for repair will mirror the years taken for a minor problem to become a potential catastrophe.

The solution lies in reducing the amount of nitrogen and phosphorus entering the lakes from sources such as septic tanks, animal wastes and fertilisers. Some measures can be taken almost immediately, provided there is community support and adequate funding. The most obvious are retiring land, restricting stock numbers at the water's edge, and fencing to keep animals away from the lakes.

This singles out farmers, and places an immediate burden on them. Some will jib at this, as they will look askance at the idea of limiting stock numbers by placing a cap on nitrogen outputs from individual properties.

Nonetheless, farmers must accept that they have a large part to play, if only because, as in the case of Lake Taupo, it is estimated that 30 to 40 per cent of the nitrogen entering the water comes from sheep, cows and deer grazing in the catchment area. Protection work on farms is also the most cost-effective approach.

Farmers cannot bury their heads in the sand like those who oppose Fonterra's dairying and clean streams accord with central and local government. Adopting that attitude will not only stall the clean-up of the lakes, it will also mean that tough measures, such as a nitrogen cap, will eventually be required.

In the longer term, farmers can also contribute by converting pastoral land near lakes to forestry. Impressive work has already been done. At Rotoiti, 22,000 revegetation plants and 19ha of trees have gone in.

The other long-term answer lies in replacing septic tanks with reticulated sewerage schemes. But this will cost an estimated $36 million all up, and deliver less noticeable results than smaller sums spent on nutrient reduction from farms. If such schemes were to proceed, ratepayers would face a heavy financial burden. Inevitably, there would be calls for Government involvement.

Local authorities are achieving promising results by offering subsidies to farmers for environmental work. But the approach has been relatively piecemeal. The completion of plans for the five most troubled lakes must be the catalyst for a joint initiative between central and local government.

A partnership, also involving Tuwharetoa, has been formed to tackle Lake Taupo. There is no option but to extend this blueprint. Tourism will suffer a body-blow if some of our most popular lakes became out of bounds for fishing and swimming. An effective means of restoring them to their former glory must be found.