Ngāi Te Rangi Settlement Trust chairman Charlie Tawhiao. Photo / File
Generations of Robin Rimmer's family have lived beside the Welcome Bay estuary over the past 100 years.
He believes pollutants have caused "unacceptable" harm to the ecosystem in his lifetime but feels he has made little headway raising this with local government.
While Rimmer welcomes the prospect of change, he believes it has come "years too late" and that most residents don't understand the importance of estuaries and "the true state" of the Tauranga Harbour.
"It looks beautiful ... But if you live beside it and have to spend dozens of hours - as I do every year - for 40 years, just to keep the shoreline and the mudflats clean of rubbish, and if you go out after every major weather event or storm and you see the sediment, the clay, the dirt and the debris, it's a completely different world."
He says the influx of sediment in Welcome Bay has meant mangrove populations have "exploded" and replaced habitats needed for other species - the salt meadows that act as nurseries for īnanga whitebait and snapper, the sand flats where beds of cockles and macroinvertebrates thrive, and the marshes that white-fronted terns, fernbirds and oystercatchers and even godwits call home.
Rimmer's not alone in his concerns.
Saltwater fly fisherman and guide Lucas Allen has noticed eelgrass beds "decreasing at a dramatic rate" as a result of heavy amounts of silt going into the estuary, and invasive pest bird species such as black swans and Canadian geese that eat the grass.
"They also eat small crabs and flounder, a massive part of the juvenile and older fishes' diets."
He says the problems "need to be addressed urgently".
"The eelgrass is said to be the barometer of harbour health as it supports so many organisms and baitfish."
The condition of Te Awanui, Tauranga Harbour was one of five case studies featured in the Parliamentary Commissioner for the Environment's 220-page "Managing our Estuaries" report released last week..
It described "a tangle of overlapping jurisdictions and responsibilities, ever-changing policies, and inadequate enforcement and compliance".
Commissioner Simon Upton said climate change would make today's problems even worse, with warming seas, ocean acidification, sea-level rise and increased storm surges.
Seventy-three freshwater bodies feed into the harbour and the catchment covers 1300sq km from the Kaimai Range to Pāpāmoa.
Because estuaries in the harbour are transitional zones where freshwater meets saltwater, they act as a nursery for many animals.
But they also act as waste traps for pollution.
Upton's report noted that decades of population growth, forest clearance, intensive farming and industrial business had increased pollution from stormwater, sewerage, sediments and nutrient-runoff in New Zealand's estuaries.
The amount of nitrogen entering Tauranga Harbour was 3.9 times higher than before humans arrived, he said.
He wrote that during heavy rain in the Tauranga area, zinc and copper pollutants are exceeding water quality guidelines for the harbour.
Upton also noted sources of bacteria in the harbour were "related to seepage from septic tanks, with an additional agricultural component in drains adjacent to fields with stock".
He said community members had formed 11 estuary care groups around the harbour but "these activities occur in isolated pockets, and most of the coastal margins are unattended".
One of Upton's recommendations a robust monitoring system to help local government and community decision-making, that included mātauranga Māori.
In Tauranga, he noted iwi members felt "excluded from decisions that have shaped their ancestral land and seascapes" in Te Awanui and their access to kaimoana had "dramatically decreased" as pollution increased.
Ngāi Te Rangi "considers that further urban development and growth is unacceptable", he wrote.
Ngāi Te Rangi Settlement Trust chairman Charlie Tawhiao endorsed the commissioner's report and said mātauranga Māori knowledge "could play a significant role" in better management of harbour waters like Te Awanui.
He said the harbour was "inextricably linked" to iwi members' identity "through place names, tribal histories and traditions, our marae within our respective hapū estates and papakainga".
"We have witnessed the degradation of the wellbeing our taonga over many generations," he said.
"Without healthy estuaries, we are heading for wider marine eco-system collapse ... We owe it to our mokopuna to turn the tide on this trajectory and to keep the pressure on those charged with managing our taonga to do better."
Upton's report also called for New Zealand's estuaries and the waterways that feed into them to be treated as a "single entity" from mountains to the sea and to be included in the National Policy Statement for Freshwater Management 2020.
Scientists from across the country backed the new findings and recommendations when they were released last week.
Niwa scientist Dr Andrew Swales said: "Sedimentation rates that are tenfold higher than prior to catchment disturbance have transformed many estuaries from sand- to mud-dominated, highly turbid systems."
Dr Candida Savage from the University of Otago's Department of Marine Science said the report highlighted "how estuaries have typically 'fallen through the cracks' in terms of legislation".
Niwa's freshwater and estuaries chief scientist Dr Scott Larned said the "real challenge" would be setting contaminant limits.
"Environmental monitoring is costly, but the need for monitoring data is inarguable," he added.
When asked about the report, Tauranga City Council environmental programme leader Radleigh Cairns told the Bay of Plenty Times Weekend the council "fully supports" Upton's recommendations.
She said the council was working with industries, property developers and tāngata whenua as well as the wider community on education programmes to protect the harbour, and was part of the Tauranga Moana Advisory Group.
"We monitor sediment discharges from subdivision and residential development and are currently in the process of strengthening rules around this through Plan Change 30."
Bay of Plenty Regional Council catchments general manager Chris Ingle said the council was "fully committed" to meeting environmental targets set by both central government and the region's communities.
"Our environmental programmes provide funding and advice to thousands of landowners across the region, enabling positive improvements in the region's estuaries ... Project Parore, supported by council, is a positive example within the Tauranga Harbour catchment that delivers a 'mountains to the sea' community-led approach towards the restoration of our land, waterways and harbour habitats."
Once on the brink of local extinction, the Hunua Ranges kōkako have slowly bounced back.