Last week's Whanganui Science Forum gathering featured Massey Univeristy freshwater ecologist Professor Russell Death who had some dire warnings for our rivers. Frank Gibson heeds the call ...

Professor Russell Death was introduced to the audience as the hammer of water polluters and his talk was direct, to the point and did not pull punches.

The first slide was his answer to the question: "Do we care if our rivers die?". The slide showed one word" "NO".

His second slide compared the flood of rhetoric around water quality as reorganising the deckchairs on the Titanic. He feels that beyond talking about it there are very few people doing anything purposeful.

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A few facts - New Zealand has the highest percentage of endangered freshwater fish in the world; some of the most polluted rivers in the Western world; we are giving away water from our national parks for nothing; there is no monitoring of freshwater invertebrates (a valuable indicator of the health of a river); nitrate levels are increasing in all our waterways; and we have some of the highest levels of water-borne diseases in the world.

Perception is a big problem - polluted waterways conjure up images of Third World rivers covered in floating rubbish with dead fish and birds. When we see a New Zealand river that looks clear or brown with mud we think that is the natural state of things. It is not.

Many factors contribute to the health of rivers such as nutrients, oxygen content, algae and sediment content. Any one of these can throw out the whole balance of the ecosystem in the river.

Professor Death showed a plot of the concentrations of nitrate pollution in New Zealand. As a good teacher, he asked his audience to draw a conclusion but the correlation with dairy farming areas was too obvious to miss.

Anybody who has looked at Taranaki on Google Earth cannot fail to see circle of bush around his peak. The nitrate pollution starts immediately outside the fence that demarks the bush.

Several reports recently have dealt with water quality, and they all agree that water quality is declining. The causes are expansion of urbanisation, hydroelectric dams and dairy intensification, but this is a distorted truth.

Yes, the first two are a problem but the effect of dairy intensification reduces the other two almost to insignificance.

The scary thing about these reports is that they are backed up by at least 20 years of science investigation without significant action. A 2017 report that is an update of a 2014 report simply says that nothing has changed.

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These reports also lack depth - when considering the health of a waterway there are at least 13 factors to be considered, including fish, phosphorus, flood patterns and sediment content, and having any one of the factors wrong will affect the overall balance.
The reports consider the single factor of nitrogen content.

A criticism of the various reports is the lack of standardised criteria. Professor Death concluded that by changing the goalposts, the government had implied that while water standards had not improved from 2014 to 2017, at least they had not got worse.

Okay, so we have a problem, and the biggest cause is too many cows putting out too much urine which is too high in nitrates.

From 1990 to 2012, the dairy herd almost doubled from 3.4 million to 6.5 million; from 1993 to 2012 the land in dairy increased by 46 per cent.

One cow gives the same amount of waste as 14 humans, so having 6.5 million cows is equivalent to having a human population of 90 million.

Cow waste does not, for the most part, go through treatment plants as human waste does. Most of it goes as untreated, nitrate rich urine on to the paddock, sinks into the ground and finishes up in the waterways.

More cows means more cow poo which is leading to an increase in water-borne pathogens. The answer of many towns is to put chlorine into town water which may introduce health problems of its own.

Do you need to be a trained scientist to judge the quality of a river? It helps but there are some simple tests you can do.

Pick up a rock from under the water in a river and run your thumb nail along its surface. More than a thin layer of algae is too much and indicates excessive nutrient in the water.
Too much algae takes too much oxygen from the water which has a knock-on effect in the whole ecosystem of the river.

Is there anything living under the rock? If there are tiny creeping and crawling things, then the water is probably okay; if you find slimy wiggly things or small snails, the water is not good.

Put on gumboots and wade into the shallows, shuffling your feet among the rocks. Do you create a plume of sediment flowing downstream? If you do, there is too much sediment in the river filling the spaces under rocks where invertebrates live and fish use for winter hibernation.

If for no other reason, we need to reduce nitrate levels before they become toxic to humans. When that happens there will be definitely be no swimming in the river.

Professor Death was pessimistic about the likelihood of government doing anything useful and advocated that people should look at the waterways in their area.

We all have an implicit duty to learn about water care. To revive an old conservationist mantra: We must think globally and act locally.

*Frank Gibson is a semi-retired teacher of mathematics and physics who has lived in the Whanganui region since 1989.