What happened at Mauao should be central at the election

2026-01-28 - 16:04

Comment: After our tūpuna arrived in the area at least seven centuries ago, Mauao became a densely settled, engineered and prized stronghold whose vegetation was shaped by human occupation long before Europeans arrived. Māori settlement in Tauranga Moana began soon after the great waka migrations, with people from Mataatua, Takitimu, Te Arawa and Tainui establishing themselves around the harbour. The maunga quickly became one of the most important places in the rohe, and remains so. ScreenshoThis artwork by Fred Graham at Mt Maunganui public library depicts the story of Mauao. Disappointed in love, Mauao hoped to sink beneath the waves of Te Moana nui a Kiwa. However, as the mountain reached the ocean it was stopped by the first rays of the morning sun. When Ngāti Ranginui returned from the East Coast in the 17th century they established a massive pā on Mauao. This was a landscape-scale settlement, not just a small fortified area. The Ranginui pā covered about 40 hectares and was terraced from the summit down all sides, with fortifications encircling the mountain and returning toward the southern base. European observers such as John Carne Bidwill wrote in 1839 that the landward sides of Mauao were “terraced from top to bottom” and that the soil forming those terraces was largely made of cockle shells, showing that people had lived there for a very long time and brought shellfish up onto the slopes to create living and working platforms. William Colenso, climbing the maunga in 1838, was struck by the scale of human modification, saying the hill had been “strongly fortified”, that it had been inhabited “to the very top”, and that house sites, fireplaces and ancient excavations were still clearly visible. Reverend John Kinder sketched this view from Tauranga Harbour on July 9 1858. Paekoroki Tauranga Library Collection This kind of occupation is impossible without widespread clearing and ongoing vegetation control. Terraces, whare platforms, storage pits, defensive lines, maara kai and access routes all require open ground and constant maintenance. The Ranginui pā extended down toward Waikorire (Stoney Point / Pilot Bay) and across the summit, meaning large parts of the slopes and ridges must have been cleared or kept in low vegetation for generations. After Ngāti Ranginui, Ngāi Te Rangi occupied and used it until the early 19th century, meaning the same open, engineered landscape continued to be maintained. Fire also played a role. Records exist of a major fire on Mauao in November 1842, and Māori and European accounts alike describe shells and timber being gathered from the mountain for burning into lime and for fires during the 1830s and 1840s. That sits within the wider pattern of our ancestors using fire to clear and maintain open ground for pā, travel, cultivation and kai collection. On a steep, strategic cone such as Mauao, maintaining visibility, access and defensibility would have made burning and repeated clearing especially important. ‘The Mount, Tauranga’. Postcard published by A McGlashan, postmarked 1915. Collection of Justine Neal By the time Europeans began to describe Mauao in detail, the maunga was already an archaeological landscape rather than a forested one. Bidwill described it as a “high round hill standing near the sea upon a flat sand beach”, its slopes cut into terraces and its soil composed largely of shells rather than forest loam. In 1841 Dr Ernest Dieffenbach wrote that there were “many traces of a former and very extensive native village on its sides”, although it had by then been deserted because of warfare. This desertion did not mean the land reverted to forest; the terraces, earthworks and midden-rich soils continued to define the vegetation patterns. When Māori occupation ended after the Ngāpuhi raids around 1818 and later conflicts, Mauao became largely empty of permanent residents, but it did not return to bush. Instead, it was described as scrub and dunes. By 1835 it was “almost deserted” and covered in scrub and sand, not forest. Fires continued to occur, both accidentally and deliberately, further preventing reforestation. When the Crown took control in the late 19th century, European administrators immediately began planting trees, especially exotic species, to “green” the mountain, implying that much of it was still open land. Pilot Bay (Waikorire), Mount Maunganui, probably photographed by John Welsh, c.1920-1925. Postcard published by A.J. Mirrielees (No 45) Collection of Justine Neal All of this means that though Mauao certainly once carried natural coastal forest and shrubland, by the time Europeans arrived it was already a heavily human-shaped place. For at least several centuries it had functioned as a fortified, inhabited mountain whose slopes were cut into terraces, whose soils were built up with shell and refuse, and whose vegetation was kept open by repeated clearing and fire. What many people now think of as Mauao’s ‘natural’ form is in fact the result of layered Māori engineering, defence, abandonment, fire and later European tree-planting, grazing and track making, rather than a pristine pre-human landscape. Recent history Over the last 100 years Mauao has shifted from being a lightly visited holiday place with remnant Māori earthworks and open scrub to one of the most intensively used cultural landscapes in Aotearoa, and that transformation has had profound consequences for vegetation and slope stability. In the early 20th century when most of the mountain was still open, with scrub, fern and sand dominating rather than forest, local European authorities began planting trees in an attempt to “green” and stabilise the slopes. By the 1920s and 1930s, tracks were cut, pines and other exotic species were established, and the Domain Board actively managed vegetation to make the mountain more attractive and accessible. Over time this produced the patchwork of grass, exotic trees and regenerating native bush that many people now mistake for a natural landscape, but it was in reality the product of ongoing human intervention layered on top of centuries of human modification. Waikorire, 1950 From a geological perspective Mauao is not a stable lump of hard rock but a steep-sided rhyolitic lava dome that erupted about 2.35 million years ago, made up of extremely strong volcanic rock that weathers into very weak, fine-grained soils. The mountain has three distinct zones: sheer rhyolitic bluffs at the top, a middle terrace that for decades was used as sheep pasture, and lower slopes made of thick, sensitive volcanic soils sitting over older lava and agglomerate. This combination is inherently vulnerable because while the underlying rock is strong, the weathered soils are dynamic, weak and easily destabilised when saturated with water. Two main soil layers dominate the slopes: a sandy silt overlying a silty clay, the latter having high plasticity and a tendency to lose strength when wet. Historical aerial photographs show that landslides have been occurring on Mauao at least since 1943, long before the dramatic failures of recent decades. When these landslides are mapped through time, they cluster strongly on the lower slopes and in places where vegetation is sparse and the ground has been cut into by tracks and drainage lines. Many of these failures are shallow rotational slides, debris flows and debris avalanches, all of which are triggered when heavy rainfall drives water into the weak soils, raising pore water pressure and causing the ground to lose its strength. Rockfalls from the steep rhyolitic bluffs are also a constant hazard, with boulders up to a cubic metre in size able to bounce and roll down into the lower slopes and track network, a process that has been modelled and observed in detail. Waikorire, 1967 The last 20 years in particular have been a period of increasing stress on this already fragile system. During this time Mauao was used as pasture for sheep on the middle slopes, while a dense network of walking tracks, drains and retaining structures was constructed to support nearly a million visitors a year. Grazing suppresses deep-rooted vegetation and compacts the soil, while track construction and ‘development’ at the base commonly cuts into the toes of slopes, removing the natural buttresses that help keep the ground in place. The geotechnical analysis of Mauao published in this short paper in 2014 (where much of the geotechnical information in this post comes from), shows that many landslides initiate where these toes have been undercut and where vegetation cover is thin or absent, creating zones that are primed to fail when heavy rain arrives. Repeated fires, including a significant burn on the northern slopes in 2003, have further weakened root systems and exposed soils, adding to the instability. Inventory mass movement map of Mount Maunganui; 1943 – 2011 figure in Spatio-temporal distribution of mass movements on Mount Maunganui, New Zealand, Martin, Z. & Brideau, MA (2014) The last major slip in the small gully above the camp ground happened in 1977. NIWA historical rainfall data suggests 1977 was not a particularly wet year with 80mm being the highest daily rainfall recorded. 1974 and 1979 had 150mm-200mm on a few days. By comparison, rain gauges in Tauranga and nearby catchments on 22 January recorded 100mm-164mm of rain in 24 hours. 1970s Rainfall The increasing pressures identified above all came together in January 2011 when Cyclone Wilma delivered intense rainfall over a short period, triggering about 80 landslides across Mauao, including eight large failures that closed tracks and reshaped parts of the mountain. Detailed modelling of one of these debris avalanches showed that the slopes were generally stable in dry conditions but became unstable when groundwater pressure rose during storms, which is exactly what happened in these fine volcanic soils as we saw last week. In other words, Mauao is not steadily collapsing, but it sits in a precarious balance that is tipped whenever intense rain, vegetation loss or human modification pushes it past a threshold. Before a large slip at the same site in 1977, a ring of large old pine trees stood above the gully slopes. This series of photos shows how they were gone by 1978 and more vegetation on the slope lost by 1994. Since those 2011 slips, vegetation management has increasingly been recognised as a core part of risk management as well as ecological restoration. Scientific work shows that root systems and surface cover materially increase soil strength and help drain water, while bare or grazed slopes are far more likely to fail. This is why the modern approach, reflected in post-2011 management and the 2018 Joint Management Plan, has moved away from grazing and toward active revegetation with native species, along with careful control of track alignments, drainage and slope cutting. The Joint Management Plan, developed by the Mauao Trust and Tauranga City Council, committed to the removal of exotic and wilding tree species. The aim is not simply to make Mauao greener but to rebuild a vegetated skin that can absorb rainfall, bind soil and reduce the frequency and size of landslides on a mountain whose geology will always make it sensitive. Satellite image series from 2005-2025 showing the clearance of a few of the remaining exotic trees around 2018-19 in the small gully slope above the camp ground. Hopefully an independent investigation into the tragic loss of lives this week will look into the land management decisions as much as the risk assessment and warning systems – not to apportion blame, but to ensure decisions can be as robust as possible, not just on Mauao, but everywhere as we face more frequent and severe extreme weather events over this century. Mauao sits at the intersection of culture, recreation, geology and climate. Its dramatic slopes are built of ancient volcanic rock and fragile soils that respond sharply to heavy rain, and its surface has been reshaped by human occupation and use, including housing, fortifications, food cultivation, tree-planting, grazing, fire and track construction. The last century, and especially the last two decades, have shown that when vegetation is stripped back and slopes are cut into, the mountain responds with slips and rockfalls. The shift toward native revegetation and more cautious land management is not just about restoring a natural look, but about respecting the physical reality of the maunga and reducing the ongoing risks for humans who still want to connect with our tūpuna maunga. So what? Inaeanei, he aha? What happened on Mauao on January 22 2026 was not an unpredictable accident. It was the collision of ancient geology, centuries of landscape modification and more recent land-use decisions, and a climate that is now delivering more intense rain than the systems we built were designed to handle. When cyclones such as Wilma, Hale and Gabrielle triggered massive landslides, cause billions of dollars damage to public and private assets and claim human lives, scientists keep telling us to address the risk and the causes. Those warnings are rarely translated into national climate-risk policy, long-term funding, or a coherent adaptation strategy for communities that sit at the frontline of climate-driven hazards. When policy is put in place – such as the $4.5 billion Climate Emergency Fund established in 2022 – populist Governments like the current administration bin the policies to help fund tax cuts for the wealthy. PM Luxon speaks to media at Mauao on 23 January 2026. Bryce Edwards provided a good summary of media coverage and what was missing from politicians and journalists in the wake of the tragedy. In an election year, New Zealanders should demand more than expressions of sympathy. We should be demanding a government-wide commitment to climate-risk reduction, including binding emissions cuts, fully funded adaptation plans, and a national programme to stabilise vulnerable landscapes like Mauao, Pāpāmoa and Te Tairāwhiti using science-informed, Indigenous-led land stewardship. The Prime Minister’s failure to even acknowledge climate change in his State of the Nation speech just days before this tragedy is not a neutral omission – it’s a warning sign of a political system captured by particular industries and voters still refusing to face the scale of the danger. This article was originally published at Manu Caddie’s Substack and is reproduced with permission