John Roughan: This summer's beach warnings are over the top

Careers in environmental sciences probably thrive on public health warnings but let's not be ruled by them. Photo / Dean Purcell

Dr Megan Carbines, God bless her, is senior scientist at the Auckland Council. Last week she was quoted in the Herald saying city waste that gets into the sea after rain is quickly disinfected by salt water and sunlight and dispersed by the volume of water and exchange of tides.

She was quoted deep in a story about the threat human waste was said to be posing to marine life, not humans, but the implications for the ridiculous warnings appearing on Auckland beaches this summer were obvious.

Next day a marine scientist at the University of Auckland, Dr Andrew Jeffs, came down hard on Dr Carbines with a letter in the paper warning her statement was, "somewhat misleading and could lead to human health problems from people acting on the wrong impression she may have created."

I want to ask Dr Jeffs and all those behind the public health notices being posted on the beaches after the slightest rain, whether they are being just a little bit over the top. And if they think there is no harm in exaggerating the risk in a good cause, I'd suggest they come down from their puritanical perch and give more thought to what they are doing.

My grandchildren, born overseas, are enjoying their first summer in New Zealand. They live a short walk from a North Shore beach and they are loving the sea. One recent sunny evening we set out for a swim and arrived at the beach to find one of these cursed signs near the surf club advising against swimming. The reason, presumably, was that it rained the previous day. There was no sign of stormwater on the beach.

The kids were taken back home without a swim. Maybe Dr Jeffs feels fine about that. Maybe he even feels a surge of righteous responsibility. Maybe he is already reaching for his phone to send the Herald another letter saying the blame lies entirely with the Auckland Council that needs to fix its drains. But I haven't finished with his previous letter yet.

"Some bacteria and viruses found in sewage, including some that cause human health issues, " he wrote, "are surprisingly persistent in the marine environment..." Note the words "some" and "surprisingly" and wonder how serious this really is.

"Background level of mammalian faecal bacteria are common in most coastal waters around New Zealand," he continued, "especially in pastoral areas..... It is for these reasons we have extended closed periods for harvesting of shellfish and swimming...."

Then he comes to his real point: "The best way to protect the environment and human health is to stop the untreated sewage getting into the sea in the first place and not to rely on the sea 'disinfecting' sewage."

Old drains on the Auckland isthmus were a problem 40 years ago when I was reporting the council and apparently nothing effective has been done about them. Yet for at least 40 years we haven't needed these "extended closed periods", until now. Are they really necessary, especially in areas such as North Shore where the problem, I understand, is rarely sewage, it is stormwater from roads and roofs.

I won't mind paying the additional rate Phil Goff says he needs in order to upgrade the drainage and I don't need to be softened up by these overwrought warnings on the beaches and the council's new "Safeswim" website. I think we are being played.

The day the kids had to go home without a swim, I stayed and had a dip. I wasn't alone, quite a number of people had ignored the sign. It was two weeks ago now and I am fine, thanks. I thought I would be, for the reasons Dr Carbines later stated: the sea is a lot of water and tides quickly disperse everything. I didn't know nasties were disinfected by salt water and sunlight but it figures. Otherwise we'd be swimming in the excrement of fish.

Presumably bacteria from marine mammals are no problem, only the discharge of land mammals is a "surprisingly persistent" pollutant. But how convenient this sort of discovery is for the environmental joy-germs who we allow to govern so much of our lives these days.

They invoke the authority of science with a certainty that dispassionate science seldom claims. When they hear scepticism from non-scientists they worry we are "anti-science". We are not. We simply notice environmental science has a political agenda and, like social science, its selected data always point in the same direction. Real science is not like that, it's cautious, qualified, constantly disproving its hypotheses.

Careers in environmental sciences probably thrive on public health warnings but let's not be ruled by them. Take them with a grain of disinfecting salt. As Dr Carbines said, there's plenty in the sea.