LETTER TO TŪPUNA MAUNGA AUTHORITY AND AUCKLAND COUNCIL: Extensive maunga slip damage lays bare the risks of mass-felling trees
This letter was sent to all Tūpuna Maunga Authority members, the Mayor and all Auckland Council Governing Body members, and also key TMA and also key Auckland Council officials.
Kia ora koutou
We request this letter be tabled for discussion at your next hui (TMA) and governing body meeting (Auckland Council).
We also seek Tūpuna Maunga Authority and Auckland Council’s responses to the question: What guarantees can you make that no future slips will occur if trees are felled on Tāmaki Makaurau’s maunga.
The extensive slip damage on a number of maunga has laid bare the risks inherent in your proposed tree felling programme. For example, as seen in the photos below, Ōwairaka, Maungakiekie and Ōhinerau all suffered significant slips during the 27 January deluge. Tellingly, all slips occurred on steep bare ground; many would have been even worse had it not been for nearby trees restricting their flow. Ironically, mostly non-native trees prevented further slip damage.
Planting more trees, and not cutting down the mature climate managing ones you have, is considered to be the best way to mitigate climate change issues. We are therefore asking that plans to rid the maunga of exotic trees are shelved permanently on the grounds that it would be irresponsible and unsafe to proceed in the light of the recent severe slip damage. The Climate Emergency is wreaking havoc and further severe storms are a certainty in the future. Mass felling healthy mature trees just because they are not native will create a ticking time bomb that will put local communities and neighbouring properties at great risk.
Mature trees are well known to absorb massive amounts of water and to stabilise soils, as graphically evidenced on the damaged maunga. This can be seen on Ōwairaka, where the slip occurred on bare ground directly below a row of tree stumps.
We note the Authority plans to plant mostly grasses, flaxes and shrubs on the maunga. Most of these small plantings will be on lower slopes, with the steep upper slopes to be left largely bare.
A massive slip on an un-treed section of Ōwairaka’s north-eastern slope threatened houses below in January 2023. The slip occurred just below the stumps of trees (seen to the right) that were felled some years ago. A group of trees further down the hill arrested the slip’s progress but were uprooted in the process and pushed on an island of land towards the homes. These trees and others around them were subsequently felled. Photo: Sharon Jones
The recent floods have dramatically demonstrated the dangerous consequences arising from Auckland’s inadequate stormwater infrastructure. There will be significantly more run-off around all of the maunga if 2500 mature climate managing trees are removed, not to mention the increased soil stabilisation issues that are likely to threaten surrounding homes and properties as is currently seen at Ōwairaka.
Non-notified resource consents have been issued for ridding Puketāpapa, Ōtāhuhu and Te Tātua a Riukiuta maunga of their exotic trees. All of those consents suggest that neither Tūpuna Maunga Authority nor Auckland Council have considered questions of stability, hydrology or stormwater runoff issues associated with mass-felling trees on those maunga. In addition to presenting very real risk to people’s wellbeing, it also presents unnecessary legal risk to both organisations and therefore ratepayers. All of those resource consents are clearly defective, so we request that they be put aside immediately.
Furthermore, we note the Authority has cited protecting archaeological features as one of the reasons it wants to fell the exotic trees. Many shell middens have been exposed by the Maungakiekie slips in particular and are now being washed away. It is clear that trees protect middens and other archaeological features under and around them from erosion-related harm.
We call upon the Authority to divert all of its multi-million tree felling budget into maintaining the existing trees and new native plantings, and also heavily planting all steep slopes at pace.
At Ōwairaka, despite the intention to remove nearly half the mature tree cover we observed no new plantings last year and only a handful the year before. Less than half of the intended 13,000 plantings have gone in there and those that haven’t died are nearly all low-growing species. The planting plans show the steep slopes are to be left unplanted. The same plans also show the plantings are to be well away from where the condemned exotics are. Furthermore, none of the planting plans appear to have involved consulting with local communities about them or taking their concerns or suggestions into account.
The number of intended plantings for Ōwairaka sounds impressive until compared with the native revegetation project on Tiritirimatangi Island. Taking size differences into account Ōwairaka would need more than 130,000 plantings of mostly trees to come close.
In addition to planting vastly more trees, we also encourage the Authority to engage expertise to assess water flows on all of the maunga. The Ōwairaka slip, for example, was caused by torrents of water cascading down the paved ring road and shooting off the side at a bend and onto steep open ground below, thus destabilising it.
A modest investment in adequate guttering and drainage – not to mention planting the bare slope – would likely have helped prevent a situation that has badly damaged the maunga, scarred it permanently, put homes below at risk and will likely cost millions to remediate.
Maunga slips January 2023
The Ōwairaka slip’s progress was stopped by a group of mostly exotic trees, all of which have since been felled. The slip started just below the stumps of trees that were removed some years ago.
Although some of the trees needed to be felled because they had been destabilised by the slip (seen here partially covered by black polyethene) and were at risk of toppling onto the houses below, the wisdom of removing all of the trees is questionable. Especially given there is now nothing to mitigate the effects of future deluges or slips.
This olive at Maungakiekie One Tree Hill helped stablilise the ground to the left of it thus preventing the slip from being wider.
Shell midden material being washed down hill after being exposed by a large slip at Maungakiekie One Tree Hill.
One of many slips at Maungakiekie that exposed shell middens. Note how the slip stops at the tree below.
Four slips occurred in one of Maungakiekie’s craters – all on un-treed parts of the slope.
An extensive slip at Ōhinerau Mt Hobson, which occurred on open ground between two olive trees.
More slippage on open ground at Ōhinerau Mt Hobson.