Science shows there’s much amiss with Porirua harbour but Matauranga Māori is needed to get a measure of the mauri

The Porirua City Council – it seems – has no idea of how much mauri can be found in its harbour and waterways and how much more is needed before it can announce the mauri has been restored.

But it is using Western science to measure things that might contribute to the effort it is putting into restoring the mauri (or not).

It is working with Ngāti Toa on improving the health of the harbour and its contributing streams.

This work includes developing a Matauranga Māori programme “which assists in determining overall mauri of the harbour.”

The question about measurement – to assure us the mauri has been restored when the job is done – was raised by a pamphlet circulated by the council to advise landowners of the funds available for streamside plants.

The pamphlet refers to “Restoring the mauri of Te Awarua-o-Porirua Harbour”.

It describes “mauri” as a life force or essence.

Because mauri is a spiritual concept, one recipient of the pamphlet inquired, how is it measured by council staff and how much mauri (not enough, obviously) does the harbour now have?

The council was further asked if ratepayers’ money was being used for this programme, or is it central government money from taxpayers?

The answer is a mix of both.

The response came from  Lindi Eloff, Riparian Operations Manager.

She is described on Linkedin as an experienced Ecologist with a demonstrated history of working in the government administration industry. Skilled in Wildlife, Sustainability, Environmental Impact Assessment, and Environmental Awareness and Biosecurity with a Bachelor of Technology (B.Tech.) focused in Nature Conservation from University of South Africa/Universiteit van Suid-Afrika.

She told the inquirer:

To address your questions, I would like to refer you to some good information and publications regarding our harbour and what we are doing.

In 2012, concerns were raised about the poor state of the harbour. Evidence collected then on harbour health led to the development of the Porirua Harbour and Catchment Strategy and Action Plan. The document had three main objectives:

1) to reduce sediment rates

2) to reduce pollutant inputs

3) to restore ecological health.

As part of an overall programme of work to address these objectives, we are aiming to improve our streams which in turn improves our harbour.  Information on a number of those programmes can read about under the various headings within this website. In particular there is a lot of information under Harbour research and publications.

“This website” is headed “Healthy harbour”  It says the Porirua Harbour is the city’s greatest environmental taonga “and we [the council] are working hard to protect it. “

There is no mention of the harbour’s mauri content.  Or lack of it.

The second link took us to a page which apologised (“Oops, page not found”).  It explained that the council has had the biggest re-organisation of its website in 10 years, “and things are not where they used to be”.

Lindi Eloff went on to say in her email:

The streamside programme mentioned in the pamphlet Council circulated is one of a range of initiatives that Council and Greater Wellington are carrying out that aims to reduce sediment loss from source.  The others include ensuring sediment management on earthworks and building sites meets required standards.

A range of monitoring activities to determine stream and harbour health (including mauri) is carried out in streams and the harbour. For example, Greater Wellington Regional Council conducts sediment plate monitoring and bathymetry surveys in the harbour. Results of that monitoring can be found here.

This monitoring shows how much sediment deposition has been increasing. Water quality monitoring is also carried out – both formally at baseline sites by Greater Wellington and Citizen Science carried out by community groups. Information on monitoring and results can be explored here. The State of Environment report on water quality for our harbour can be found here. In this publication it clearly shows how the harbour health continues to decline and is at a critical state.

We are working with Ngāti Toa on improving the health of the harbour and its contributing streams, which included developing a Matauranga Māori programme – which assists in determining overall mauri of the harbour.

One of the three links took Point of Order to a page headed Te Awarua-o-Porirua Harbour Sediment Plate Monitoring 2020 Survey. Here we found plenty of mentions of measurable stuff:

The steady increase in sediment at the Onepoto intertidal sites is attributable largely to the deposition of coarse sediment on the Porirua Stream delta and the movement of sand across the tidally swept site near the Harbour entrance. During 2019, sediment deposition increased by an average of 4.6 mm and mean sediment mud content doubled across all Pāuatahanui intertidal sites.

Results also showed an increase in subtidal sedimentation of 7 mm/year in the Pāuatahanui Inlet and net subtidal erosion of 2.5 mm/year in the Onepoto Inlet over the past seven years.

Erosion, however, is largely an artefact of the baseline monitoring commencing shortly after a significant deposition event in the Onepoto Inlet in 2013. Since then, there has been an average increase in subtidal mud content of 66% in the Pāuatahanui Inlet, and 69% in the Onepoto Inlet.

Mud content was highest in deeper settlement basin areas, with four of the five muddiest subtidal sites in the harbour located in Pāuatahanui. Throughout the Harbour, soft mud has extended shoreward by between 10 m and 305 m, with a corresponding large increase in the shallow subtidal area covered by mud-dominated sediments.

Changes may be associated with episodic inputs of sediment from catchment sources. Recent rates of deposition greatly exceed the recommended ANZECC Default Guideline Value of 2 mm/year, indicating an increased likelihood of significant environmental damage.

There was no mention of the mauri content or lack of it.

The second document explained the council’s Streamside Planting Programme 2021 – 2041

Our vision is that the mauri (life force) of Te Awarua-o-Porirua is restored and its waters are healthy, so that all those who live in the region, including Ngāti Toa and our manuhiri (visitors), can enjoy, live and play in our environment and future generations are sustained, physically and culturally

There is no description of the mauri that is to be restored or how it is being measured.

The third link steered us to a report which provides a snapshot of the health of the Porirua Harbour and streams which addressed a key question: So what does “healthy” look like?

The answer:

Healthy harbours and streams have a range of insects, varied habitats for different wildlife, and a mix of both sea and land plants. These things work together to keep our streams and harbour clean and available for us to use.

The document then explains the range of indicators on which the council is reporting. Some indicators are measured and given a measurement result and others are measured and given a grade.

Recreational water quality monitoring is a measurement of the number of enterococci in coastal water and faecal coliforms in freshwater. These two bacteria are counted and then used to assess the likelihood of disease-causing bacteria, viruses and pathogens in fresh and coastal water.

Macroalgae species are a building block of life in the harbour. They provide food, shelter and nursery habitat for aquatic animals and remove excess nutrients. Too many nutrients in the water can lead to huge growth of macroalgae called algal blooms. The blooms smother habitat and other species, reduce oxygen and smell when they die.

Periphyton is the algae or slime coating on rocks, gravel or tree roots in streams. Periphyton are the primary food producers in streams just as plants are for life on land. Too many nutrients in streams can lead to large amounts of periphyton growth.

The blooms can reduce the amount of oxygen in streams and smother freshwater insect habitat.

Zinc and copper can have long term toxic effects on reproduction and growth rates of aquatic life in streams and the harbour. The amount of zinc and copper can be used to indicate how many other metals like cadmiuim, chromium, detergents and hydrocarbons may be in the water. Increases in zinc and copper are likely to show a decline in the overall health of the harbour.

Saltmarsh and sea grass. The harbour is the largest estuary in the lower North Island and the only one with any significant seagrass cover. Seagrass provides habitat important to feeding, spawning, and as a nursery for invertebrates, fish and birds. Both seagrass cover and saltmarsh extent have been dramatically reduced from their historical extent.

Macroinvertebrate community. Freshwater invertebrates (eg snails, worms and insects) are a vital part of the freshwater ecosystem – they feed on algae and are an important source of food for fish and birds. The MCI is a score based on the presence or absence of a range of invertebrates with different tolerances for pollution. A high score means a relatively unpolluted stream with good habitat for diverse and sensitive macroinvertebrates; a low score means polluted water and poor or limited habitat, with few pollution-sensitive species.

Freshwater fish. We have 35 native freshwater fish species in New Zealand, 31 of these are found only here. Only we can protect these species unique to our country. Freshwater fish are affected by water quality, habitat loss and degradation, barriers and modification of streams, and introduced fish that compete for food and habitat.

That covers the science.  But again, there is no mention of the mauri in the harbour or the streams.

On the funding question, the council official’s response was:

Our overall streamside programme is funded through by both local and central government.

This leave us waiting patiently for the day the council triumphantly tells us – as an article of faith  – that the mauri has been restored and our money has been well spent.