Invasive algae bill put at $285 million

The invasive algae didymo, confirmed in yet another southern river last week, could cost the lower South Island as much as $54 million by 2012, says a report commissioned for Biosecurity New Zealand.

All up, Didymoshenia geminata could cost New Zealand up to $285 million if it flourished and persisted in high and medium risk rivers, and if its spread could not be controlled, says the Institute of Economic Research.

In the worst of three scenarios, didymo would spread to almost all the most at-risk rivers in Otago and Southland and its impacts, first felt when it was discovered in Southland two years ago, would be acute by 2008-2009.

The algae would spread to the central South Island by this year - it was found in the Ahuriri River in February - and, if the South Island controlled area failed, the North Island by 2007-2008.

Costs would mount as the algae killed-off native species, reduced recreation values, and what tourists spent, increased the cost of irrigation and drinking water, and imposed new costs on hydro electricity generation.

Under the scenario, the loss of native species would cost $54 million, tourism expenditure would be hit by more than $63 million, and the overall reduction of recreational values would cost more than $88 million.

The report, prepared under "considerable uncertainty" as to the spread and effects of didymo, found the algae would have the most acute effects in the North Island and central South Island.

The lower South Island had the most high-risk environments, but the rest of the country had "substantially higher populations to suffer reduced recreation and existence values," the report said.

Otago Fish and Game councillor and fishing guide Ian Cole said that "northern-centric" aspect of the report sent "all the wrong messages" to the worst affected areas of New Zealand.

A 1999 study found the fresh-water fishing industry was worth about $700 million, and an overall reduction on tourism income less than 10 per cent of that total seemed "strange" even if "there isn't much chance of things falling over completely".

The report was "bureaucratic nonsense", and the money would have been better spent ensuring overseas visitors knew the risk of spreading didymo, Mr Cole said.

North Otago Federated Farmers president Bruce McNab said worst-case impact on agricultural, municipal, and industrial water intakes - about $26 million - would be a huge burden for rural communities.

The voracity of the algae, its spread, and its potential impact on expensive spray-irrigators had been "a terrible surprise".

The report simply confirmed the farming sector's worst fears.

- OTAGO DAILY TIMES