vanished within a matter of decades<\/a>.<\/p>\nBy the mid-1960s, the inner gulf\u2019s sprawling green-lipped mussel (k\u016btai) reefs \u2013 more than 600 square kilometres of them \u2013 had been dredged to exhaustion for food and fertiliser.<\/p>\n
The commercial fishery collapsed soon after, and the shellfish beds never recovered on their own.<\/p>\n
In losing those k\u016btai reefs, the gulf lost one of its most powerful natural filters: each mussel can clear several litres of seawater an hour, cycling nutrients and binding the seafloor together.<\/p>\n
The living, three-dimensional seafloor that existed before is now largely sand and mud, its clarity clouded by sediment resuspension and its biodiversity thinned.<\/p>\n
Over the past decade, however, iwi, scientists and community groups have joined forces to try to reverse this devastating loss.<\/p>\n
The University of Auckland has partnered with Ng\u0101ti Wh\u0101tua \u014cr\u0101kei, Ng\u0101i Tai ki T\u0101maki, the Ng\u0101ti Manuhiri Settlement Trust, The Nature Conservancy Aotearoa, and the Revive Our Gulf Trust to re-establish shellfish beds that once filtered the gulf\u2019s waters and provided habitat for countless species.<\/p>\n
They share three lessons they\u2019ve learned along the way.<\/p>\n
Don\u2019t wait to begin restoring<\/p>\n
Marine restoration has become one of the fastest-growing frontiers in conservation science worldwide, from reviving coral reefs and seagrass meadows to rebuilding shellfish beds.<\/p>\n
Success, scientists say, much depends on first understanding what\u2019s breaking these systems in the first place and recognising that system breakdown is both relational and cumulative.<\/p>\n
In the Hauraki Gulf, researchers have observed how sediment, nutrients, over-harvesting and climate stress are increasingly colliding, often in ways that defy simple fixes.<\/p>\n
Revive Our Gulf science lead Dr Jenny Hillman says sediment is a case in point: while smothering some seafloor habitats, it can also boost the growth of others.<\/p>\n
![\"\"](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2025\/12\/Jenny-Hillman.jpg\")
University of Auckland marine scientist Dr Jenny Hillman says marine restoration is still in its early days, but the gains already seen show why it\u2019s vital to begin now. Photo: Chris Loufte<\/p>\n
\u201cIt\u2019s not as simple as just needing to remove sediment,\u201d says Hillman, senior lecturer at the University of Auckland\u2019s Institute of Marine Science.<\/p>\n
If there\u2019s a starting point to begin marine restoration, professor Simon Thrush says it\u2019s in recognising land and sea as a single system, as has been long-held within te ao M\u0101ori.<\/p>\n
\u201cWhen we\u2019re talking about restoration in harbours, there\u2019s now a recognition about also restoring contributing catchments and managing sediment loads that are flowing into the sea,\u201d he says.<\/p>\n
\u201cPeople are starting to think about the fact these systems are connected.\u201d<\/p>\n
Some may argue restoration can\u2019t begin until problems on land are solved, but Hillman disagrees.<\/p>\n
\u201cOur understanding of large-scale marine restoration is still evolving; even after more than a decade, we are still learning. Marine restoration as we know it is in its infancy, reflecting the complexity of the moana, and if we don\u2019t start now, then we\u2019re not going to be ready.\u201d<\/p>\n
She considers progress, not perfection, the realistic goal.<\/p>\n
That means working towards a place \u201cwhere systems are working better\u201d, even if harvesting kaimoana such as mussels can\u2019t begin again anytime soon.<\/p>\n
Mussels are ecosystem engineers<\/p>\n
Since 2021, more than 25 million k\u016btai have been reintroduced through the Revive Our Gulf programme, making it one of the world\u2019s largest shellfish restoration efforts.<\/p>\n
Each barge-load of mussels begins its life hundreds of kilometres away: spat collected from Te Oneroa-a-T\u014dhe (Ninety Mile Beach) are grown to size on farms in the Coromandel before being ferried north and released into sites such as Kawau Bay.<\/p>\n
The scale of work being led by the iwi partners is world-leading in restoring these types of shellfish, says Hillman.<\/p>\n
\u201cWe are learning as we go and it\u2019s a huge ongoing effort.\u201d<\/p>\n
Already, the k\u016btai have been demonstrating their ability as remarkable ecosystem engineers: creating habitat while filtering and recycling nutrients.<\/p>\n
But their influence runs deeper than filtration, with reef acting as a living engine of renewal, binding the seabed and supporting the wider web of marine life.<\/p>\n
![\"\"](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2025\/12\/Seahorses.jpg\")
Bigbelly seahorses sheltering among restored k\u016btai beds in the Hauraki Gulf\u2019s Okahu Bay: a vivid sign of the biodiversity returning to these rebuilt reefs. Photo: Shaun Lee<\/p>\n
Hillman\u2019s team has quantified their value in new ways.<\/p>\n
\u201cWe were the first in the world to look at how restored mussel beds can support the removal of excess nitrogen from the ecosystem and found that they can be really beneficial at some sites,\u201d Hillman says.<\/p>\n
The research has since expanded into carbon cycling, though the processes are complex: \u201cYou\u2019re essentially looking at all these multiple cycles happening at the same time and interacting.\u201d<\/p>\n
Although true success and scale will only come when natural regeneration processes are restored, these early experiments have generated significant learnings and shown immediate gains in marine biodiversity.<\/p>\n
\u201cWe\u2019ve found increased numbers of small snapper, for example, so it\u2019s clear that the beds are having a benefit,\u201d she says.<\/p>\n
As well as drawing in snapper and blue cod, Hillman says k\u016btai also appear to help sustain an entire web of life beneath them, \u201cright down to the microbes and tiny worms living in the sediment\u201d.<\/p>\n
It\u2019s no wonder scientists regard mussels as powerful natural filters. Yet they\u2019re also careful to point out that there\u2019s only so much these shellfish can do to repair damaged ecosystems.<\/p>\n
\u201cIt\u2019s never as simple as \u2018if you do this, this will happen\u2019, because ecology \u2013 or the real world \u2013 is more complicated than that,\u201d Hillman says.<\/p>\n
Scaling up takes more than science<\/p>\n
New ideas are already reshaping what scaling up marine restoration could look like.<\/p>\n
Hillman was recently awarded a $1 million Smart Ideas research grant for a three-year project exploring how to rebuild coastal habitats using artificial horse mussel beds made from repurposed Greenshell mussel shells.<\/p>\n
The work aims to stabilise seafloors, enhance biodiversity and test whether engineered shell structures can jump-start recovery in degraded systems, while turning thousands of tonnes of aquaculture waste into a useful resource.<\/p>\n
By combining marine restoration with circular-economy thinking, the project could help communities restore more coastline, more quickly, and at lower cost.<\/p>\n
Turning pilot beds into reef networks, however, remains a daunting task \u2013 and not just for the practical challenges involved.<\/p>\n
Hillman says the process is costly and complicated. Because marine restoration is still in its infancy, New Zealand has no uniform restoration guidelines, meaning councils have different requirements, and different sites require different considerations.<\/p>\n
Biosecurity concerns and data gaps add further hurdles, and what works in Mahurangi may not in Marlborough\u2019s Pelorus Sound, where she\u2019s also been involved in mussel restoration.<\/p>\n
Restoring reef ecosystems at scale is the long-term goal, but Thrush notes that success doesn\u2019t always have to be measured in hectares.<\/p>\n
\u201cIt\u2019s easy to think about an objective like restoring 50 square kilometres over a period of decades, but it\u2019s perhaps more important to think about what success means in terms of a year.\u201d<\/p>\n
![\"\"](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2025\/12\/Barge.jpg\")
Deploying k\u016btai into the Hauraki Gulf: millions of mussels are released from barges like this to rebuild lost reef habitat. Photo: Shaun Lee<\/p>\n
For both researchers, that success depends as much on people as on science. Hillman says she has seen iwi partners with differing perspectives come together around restoration work \u2013 \u201cthat kind of social success should not be underestimated\u201d.<\/p>\n
Hillman views her own role as simply providing the science that supports mana whenua and communities as they work to restore and protect the moana.<\/p>\n
\u201cIf we\u2019re putting this level of effort and time into it, then we want to work in a way that supports a shared responsibility for the moana.\u201d<\/p>\n
That collaborative philosophy underpins Revive Our Gulf, where iwi partnerships have guided where and how k\u016btai are laid, creating a sense of shared guardianship.<\/p>\n
Thrush says future decision-making should better reflect a te ao M\u0101ori worldview \u2013 one that recognises the interconnection between living and spiritual realms.<\/p>\n
Iwi leadership, he adds, seen in r\u0101hui on depleted beds and proposals for Ahu Moana co-management, shows how restoration can evolve beyond \u201cbureaucratic limbo\u201d, often moving faster and more effectively.<\/p>\n
Marine restoration is often seen as an effort to bring back what was lost \u2013 but Hillman and Thrush emphasise that it\u2019s just as much about building resilience for what lies ahead.<\/p>\n
\u201cIt\u2019s about restoring into the future rather than restoring into the past,\u201d says Thrush.<\/p>\n
\u201cPeople made the mess, and people will have to help fix it \u2013 and we can use nature to help us if we learn how to work with it.\u201d<\/p>\n
The world is facing unprecedented environmental challenges. Planetary Solutions, an initiative of the Sustainability Hub at Waipapa Taumata Rau, University of Auckland, and Newsroom, explores these issues \u2013 and the practical ways we can all be part of the solution.<\/p>\n","protected":false},"excerpt":{"rendered":"Picture vast expanses of sub-tidal mussel reefs, enough to cover 80,000 rugby fields, amid clear, unpolluted coastal water.…\n","protected":false},"author":2,"featured_media":182406,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22],"tags":[273,111,7439,139,69,84870,147,22190],"class_list":["post-182405","post","type-post","status-publish","format-standard","has-post-thumbnail","category-environment","tag-environment","tag-new-zealand","tag-newsroom-pro","tag-newzealand","tag-nz","tag-planetary-solutions","tag-science","tag-university-of-auckland"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/182405","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=182405"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/182405\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/182406"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=182405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=182405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=182405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}