OPINION: It’s the Sounds Jim but not as we knew them

OPINION:

You know that your environmental management has hit rock-bottom when it comes to the attention of legendary Stuff cartoonist Tom Scott.

William Shatner, aka Captain James T. Kirk, is depicted floating in space, lamenting the state of the Marlborough Sounds on his recent trip into orbit.

The cartoon followed a scientific report to Marlborough District Council on why Pelorus Sound/Te Hoiere is swimming in mud as a recent satellite image shows.

Marlborough Mayor, John Leggett, was recently quoted in Stuff as saying: “There’s nothing really new here. It’s what we’re going to do about it that’s important”.

READ MORE:
* Erosion, farming and forestry identified as Sounds mud sources
* Doing nothing in our oceans is a major way to do something about climate change
* ‘World-leading’ salmon farming standards needed for forestry in Marlborough Sounds

Let’s channel Mr Spock, and ask whether there is something new in the report? In fact there is.

The NIWA study is a remarkable forensic investigation that “fingerprints” the different sources of sediment. It reveals a startling picture of new and old sediments.

Something old

Most sediment sloshing around in Pelorus Sound are the legacy of 150 years – washed down from gold mining, deforestation, farming, and road slips, and eroded as far back as the 1860s.

It carries a marine carbon signature, indicating it has been on the seabed. But why is it still moving?

Decades of scallop dredging and flatfish bottom-trawling have disturbed the stability of the seafloor, and frequently re-suspended these old “legacy” sediments into the water column.

Powerful incoming tidal currents of 20-30,000 m3 per second along the main channels blast this suspended material, until it settles out in the slower moving waters of the side bays of the Sound.

It doesn’t stay in place permanently though, as dredging and trawling also occurs in many of these places, and storms and waves can also break the cohesion of the settling sediments.

Not only is the seafloor frequently disrupted, naturally occurring shellfish beds, tubeworm towers and sponge gardens cannot re-establish. These living habitats provide juvenile fish refuges and feeding grounds, and they also capture and store carbon.

The loss of this hidden infrastructure has been devastating to biodiversity and fisheries in the Sounds, and inimical to climate mitigation too.

Something new

The study shows that the sediment tap has not been turned off though – in fact, it is flowing at similar, if not greater, unsustainable rates to the past.

Pine clearfelling on steep slopes, and dairy cows moving along and across streams, continue to erode away the valuable topsoil at alarming rates.

The council has been working with dairy farmers over the last 20 years to reduce an estimated annual 3 million cow movements over 149 water crossings, to only 13 unmanaged crossings in 2018.

Less successful has been its management of forestry. Why is that important?

The NIWA report states: “Our finding that topsoil from harvested pine contributes 190 x more sediment than native forest/indigenous forest also demonstrates the importance of harvested hillslopes as a source” (p87). And, “The results suggest that sediment accumulating in the Mahau Sound…are disproportionately sourced from harvested pine areas (p97).

Subsoil erosion from slips and land-clearance is also very high – but the sources are not able to be finger-printed accurately. What the NIWA report suggests is that pine clearfelling is one likely cause.

The council has known about forestry effects on the Sounds waterways for decades, but has done little about it, even in its recent Marlborough Environment Plan.

There are no harvesting rules on steep slopes. Harvesting by heavy machinery is allowed in wet winter months when erosion potential is highest. Topsoil runs freely from ridge top to seashore as there are no restrictions on the size of clear-cuts. Replanting is able to occur on steep faces, incised gullies, and highly erodible slopes – thereby locking in the cycle of environmental damage.

There is little resilience to climate change, as photographs of clear fell forest after rainfall show.

Council are fully aware of these issues, as the mayor says. So what gives? Let’s look at Council’s environmental governance, and ask what needs to happen in future.

Governance

An analysis of the council’s meeting agenda papers and minutes reveals that there is no report-back mechanism for decisions. There is also no register of numbered decisions for tracking progress.

This means that environmental issues that the Mayor and councillors think are being resolved, may not get resolved or get actioned effectively. As I saw from my time there, there is little monitoring or evaluation of outcomes from decisions, and therefore the wheels keep spinning on some issues.

Two examples illustrate this. In 2014, Council allocated $200,000 to the Marlborough Marine Futures community-led forum that sought to improve environmental management in the Sounds. In 2018, it decided to explore a Sustainable Land Transition Fund initiative to retire forestry from erosion-prone areas. Both initiatives sunk due to lack of support from staff, and inadequate governance oversight.

The Pelorus/Te Hoiere catchment project is the latest attempt, but risks going the same way as it depends on voluntary measures without the necessary accompanying changes to land-use rules.

Councillors have also now delegated decision-making power to staff to resolve appeals on the Environment Plan after Environment Court mediation.

These decisions set environmental rules for the future, so need to be transparent and made at arms-length from council staff involved, even peripherally, in the mediation and in the plan development.

This is because the council is defending a plan that enables excessive erosion from forestry and ongoing disturbance of the seafloor. This is contrary to its own expert internal science advice.

Independent and contestable policy advice should also be sought, to ensure that councillors are presented with a range of options that are fully evaluated, to begin the restoration of the Sounds.

It is beyond time for Marlborough District Council to put ecologically appropriate rules on land use and marine activities to reverse the shocking environmental decline of the Marlborough Sounds.

The Minister for the Environment may need to seriously consider investigating the council’s performance, as the Sounds deserve 21st century leadership and a shift to bicultural governance.

The Sounds may not be as we knew them. The question is: how do we want to know them in future?

Dr Steve Urlich is a senior lecturer in the Department of Environmental Management, Lincoln University. He was Marlborough District Council’s coastal scientist from 2013-2018.

Marlborough District Council response:

The Marlborough District Council recently commissioned NIWA to study sediment sources in Te Hoiere/Pelorus Sound using the latest scientific techniques.

The study improves our understanding of how human-induced and natural erosion sources have contributed to sediment composition and accumulation, and identifies the sources of sediment deposited in the river and in Mahau Sound.

Seventy per cent of material deposited in the Sound over the last century is “legacy sediment”. Goldmining, native forest clearance, pastoral farming and more recent agricultural and forestry activities have left their legacy in the Marlborough Sounds.

Thirty per cent of the deposited sediment comes from contemporary land uses over the past century.

Subsoils are the largest contributor, followed by stream-bank erosion. Native forest and harvested pine forest (after 1979/80) account for similar and small proportions of the sediment. Contributions from kanuka, scrub and pasture make up the remainder. The proportions vary according to location.

The effects of increased soil erosion and sedimentation have ranged in scale, from localised impacts on cockle beds due to early Māori activities in Mahau Sound to extensive catchment-wide soil erosion and sedimentation since European settlement.

For further information go to www.marlborough.govt.nz/environment/coastal/sedimentation

The NIWA report is called ‘Sources of fine sediment and contribution to sedimentation in the inner Pelorus Sound Te Hoiere’ and is accompanied by a short summary document called ‘Tracing the sediment in Pelorus Sound’.