In a corner of Epsom, an affluent neighbourhood in urban Auckland known for its grammar schools and heritage architecture, there is an ancient rupestral woodland where indigenous broadleaf trees spring improbably from apertures in a sloping scree of volcanic boulders. This is a fragment of an old rock forest that once covered more than 5000 hectares of the isthmus. Today, remnant tracts snake sinuously around genteel homes in a slow tussle for real estate.
Withiel Thomas Reserve, the only readily accessible part of the forest, has been open to the public since 1948, when it was gifted to the city by the Thomas family after 50 years of care. It’s not well known, it’s not well sign-posted, but it oozes intrigue for the curious plant hunter. If you can find the entrance, which is little more than a hole in a hedge, be intrepid, go in, go in.
A pohutukawa, arms outstretched, greets the visitor, torqued branches corkscrewing up into the sunshine. In the canopy, puka, mangeao, tītoki and māhoe compete for light. Saplings are scrawny and aspiring, mature trees are spindly and veering, having linear conversations with each other. Pigeonwoods seem most anxious, jetting upwards from rangy roots. “Multiple water shoots are a sign of stress, of canopy dieback,” explains Ewen Cameron, curator of botany at Auckland War Memorial Museum. “But it’s natural—the rock forest has virtually no soil, just a build-up of leafy humus between the rocks.” Nīkau abound, mostly juveniles. According to Cameron, they are not native to Withiel: “They’ve most likely sprouted from seed from nearby garden specimens, and there may be insufficient soil to see many reach maturity.”
Elegant small trees—kawakawa, mapou, coastal karamu and houpara—are ensconced and fecund, creating a fluttery understorey. Rock-bound plants seem to throw themselves into the moments of light that hit the ground—Peperomia positively reaches for it. Seedlings proceed with optimism, wherever they can find a foothold. Ferns with names worthy of a Harry Potter novel—shining spleenwort, hanging spleenwort, hound’s tongue and leather fern—sprout like whiskers from wrinkles and pocks in basalt faces. Lichens and mosses cohabit like old married couples. Tui holler from the treetops. Fantails flit about for flies.
There is a constant hum of traffic in Withiel for it is a thoroughly urban reserve, close to Gillies Ave, an arterial thoroughfare. But this place is far from common.
The unexpected terrain, the botanical mix, the airiness of the understorey, the morphology of certain species—these things give the rock forest an otherness compared with most of Auckland’s native bush. It is, in fact, an exceptionally rare and endangered ecosystem.
It has always been rare. Ecologists use the term historically rare when referring to ecosystems that amounted to less than 0.5 per cent of New Zealand’s pre-human landscape. Volcanic boulderfields, the specific basalt terrain on which rock forests grow, amounted to just 0.02 per cent. Though it might have seemed a large and inexhaustible resource at first, since man arrived, an original 5133 hectares has been whittled down to just 29, or 0.0001 per cent of the country’s land area.
Māori arrived on the Tāmaki isthmus in the 13th century or earlier. Its volcanic cones provided highly defensible settlement sites whose fertile landscapes could support large communities. For periods of time over six centuries, Māori settled in pā on 29 cones and gardened 4000 hectares of volcanic soil. But we don’t really know how they interacted with the rock forests, because those who followed obliterated any evidence.
European settlers arrived in a region that had been abandoned for about a century. In their eyes, scoria cones and basalt boulderfields were ripe for the picking—sources of rock conveniently located for new urban works. As the scoria cones were decapitated (just 15 remain), boulderfield ecosystems were annihilated—deforested, quarried and cleared for houses, gardens, paddocks and roads.
Rock forests on Mt Wellington/Maungarei, in the gullies of Penrose and at Western Springs have been completely consumed by urbanisation.
Epsom rock forest, on the lower north-eastern slopes of Mt Eden/Maungawhau, is the best remaining example of the ecosystem. It once spanned 50 hectares but is now reduced to just three, split over many properties, private and public. Not only is it divided on paper, it is discontinuous on the ground, too, a double fragmentation that imperils its future.
About half of Epsom rock forest is in public ownership: 0.4 hectares in the grounds of Government House, 0.6 hectares on Almorah Rd and 0.7 hectares in Withiel Thomas Reserve. Cameron considers Government House forest and Almorah forest to be barely modified relics, portals to the ancient forests of the isthmus. But he suspects that Withiel forest is regenerating from trauma, such as a short period of quarrying in the earliest years of colonial settlement.
The first clue to Withiel’s disturbance is in the incidence of its puka, which is rare in adjacent parts of the forest. Puka is a sun-seeker, growing most often as an epiphyte that sends down aerial roots from a high perch, and staying subordinate to its host tree. In Withiel, however, it grows on the ground, issuing tentacular surface roots that weave to find purchase in the loose terrain.
“This suggests that there was an abundance of light on the ground and few host trees when puka began to establish in Withiel,” says Cameron. Another clue to disturbance, pointed out by the late snail enthusiast Jim Goulstone, is Withiel’s dearth of tiny native land snails, which occur in diversity and abundance in adjacent forest tracts.
There are numerous small, privately owned patches of rock forest, the most notable being a 0.4-hectare tract at Rannoch, an arts and crafts mansion on Almorah Rd that houses part of a huge collection of New Zealand modern art overseen by the Wallace Arts Trust. Rannoch’s rock forest comes right up to the eaves of the house and towers over the driveway. It is in these close quarters that large-scale sculptures commissioned for the site nestle among the trees. The sculpture collection borrows atmosphere from its ancient woodland setting, enjoying a backdrop that is a sort of mysterious hinterland, while a winding path through the understorey lends serendipity to several of the sculptures.
Cameron suspects that Rannoch forest is, like Auckland Council’s Almorah reserve next door, a direct descendant of old isthmus vegetation. Certainly, it has benefited from having had only three owners in 100 years, and today, Sir James Wallace considers himself not just its owner, but also its custodian. Fallen trees and branch debris are cleared from around sculptures, but other than possum trapping and removal of weeds, the remainder of the forest is left to itself.
Nobody knows how old the Epsom rock forest is, nor when it formed, how it formed, or how it has changed over time—but it can’t be older than the lava boulders on which it grows. Carbon-dating suggests that Mt Eden erupted 28,000 years ago—a fountain of lava producing gassy, frothy scoria that heaped up around the vents as cones, then burst through weak points in the sides.
Overlapping lava flows emanated north-east, breaking up as the surface cooled to form embankments of piled rock that is the volcanic boulderfield that underpins the Epsom rock forest. Later, plant life crept onto the naked scoria cone, its lava flows and boulderfields, and eventually a forest grew. (A similar process happened more recently on Rangitoto, but there the forest is dominated by pohutukawa.)
Since Mt Eden erupted, the whole planet has reached a glacial maximum swiftly followed by the warm interglacial period we currently inhabit. Pollen studies on the Auckland isthmus suggest climate-driven drifts from beech-podocarp forest 30,000 years ago to podocarp-broadleaf forest 20,000 years ago, when rimu, kahikatea and matai would have dominated. Around 12,000 years ago, a warmer climate encouraged pohutukawa, and it became wetter, enabling tree ferns to populate the understorey. From 6000 years ago, the climate became drier, with greater seasonal extremes, allowing kauri to become prevalent. But, as Cameron informs me, “There isn’t enough soil in the rock forest for a pollen study that might explain its history.”
Isthmus forest was almost completely destroyed by Māori fires between the 13th and 18th centuries, and it is likely that volcanic zones, from crater rims to ash fields, were burned earliest, freeing up rich soil for cultivation, while other forest on clay soil would have remained for longer. Some isthmus rock forests seem to have avoided those fiery events, perhaps because the underlying boulderfields lack soil for cultivation.
Shells found in middens on Mt Eden date a settlement to the mid-16th century. By then, or a little later, the cone was a fortified pā for as many as 2000 people whose community was part of a relatively populous, prosperous and peaceful confederation of Māori known as Te Waiohua.
The mountain’s 50-hectare rock forest would have been a valuable and convenient pantry and medicine cabinet, providing herbs, berries, bark and leaves, and maybe a few kererū. Rock forest boulders may have been taken for walls, buildings or terracing. As for trees, there may have been some harvesting of timber.
Legend has it that in the late 17th century, Mt Eden/Maungawhau, as a result of an act of treachery, was declared tapu. The pā was abandoned and the community relocated to neighbouring cone One Tree Hill/Maungakiekie, from where they continued to garden the Epsom valley. In the mid-18th century, Te Waiohua’s Arcadian existence came to an abrupt end with a series of brutal battles. Those not killed or enslaved fled into exile. The victors, Ngāti Whātua, were so few as to barely inhabit their newly acquired land, and the entire isthmus returned to a state of self-determination for a century.
The British arrived in 1840. Auckland quickly grew from a beachfront of raupō huts to a busy port city, so that by the 1860s, some of its more affluent families had decided to move to the countryside, untamed as it still was. Mt Eden was perfect for its proximity to downtown and for its views out to the Hauraki Gulf and across the semi-agrarian landscape that fanned out below. The nicest outlook, arguably, was to the north-east towards Rangitoto, but this was the side of the mountain with the toughest terrain—the lava buttresses and scree slopes of the rock forest. Nevertheless, three gentlemen’s residences built along Mountain Rd in the late 1860s marked the beginning of a new neighbourhood.
Clifton (or Firth’s Castle) and the Macfarlane residence (now the site of Mercy-Ascot Hospital) were built on the lava pedestal above the scree slopes. Photographs from the period show that their grounds were cleared of the dense scrub that had grown over the mountain, and were planted with pines.
A third residence, Rockwood House, was different—its name is a bit of a giveaway. Built for the land agent William Aitken around 1865, the house was set at the edge of the rock forest. Watercolourist Alfred Sharpe painted Rockwood in 1876 with its 40-acre forested estate sweeping off to the east behind the house, running from Mountain Rd to Gillies Ave between Gilgit Rd and Seccombes Rd. (The Southern Motorway, built in the 1960s, today cuts through it.)
Beyond Rockwood estate, the rock forest carried on eastward across Gillies Ave and down the slope to Newmarket, and southward along Gillies Ave towards Albury Ave. There was also a tract where Government House stands, running down to Withiel Thomas Reserve. Subdivision of Rockwood and other rock-forest estates got under way early in the 20th century. While land sales advertisements written by owner/agent Aitken described native bush as desirable surroundings, other commentators have described it as barren land that needed to be cleared. Great portions of rock forest were usurped by mansion footprints that also included stables, garages, driveways and gardens. Subdivision was halted in the 1980s when it was realised that the area might lose, not its forest, but its built-heritage character. Consequently, many properties remain large and a few decent tracts of rock forest have survived, left to nature by successive owners—wild nooks among the mansions.
Rannoch is one such property. Another is its neighbour Glade Hall, built in 1915 for Hubert E. Vaile, who was instrumental in the design and construction of Auckland War Memorial Museum. Set within 1.4 hectares of rock forest between Almorah Rd and Gillies Ave, its grounds were once described as “beautiful glades… traversed by delightful sylvan walks”. Its lamp-lit carriageway of “incomparable loveliness, bordered for the whole length by native trees”, ascends 70 metres from Gillies Ave, hewn into rock up to four metres deep, looking now like an ancient holloway. The property was purchased by dairy industrialist Sir William Goodfellow in 1936, and sold in 1952 to a government department. In 1999, rather rundown, it was put up for sale.
Local residents knew that at least half of its grounds were still covered by native forest, so when a prospective developer made an offer to buy the property, conditional upon consent to build up to 14 townhouses, neighbours alerted Cameron, who pointed out the rarity of the site and its cargo of flora and its fauna. When forest trees were highlighted with red spray paint marking the boundaries of proposed housing units, the mayor called upon the prime minister to stop the sale. It was a small but high-profile public outcry. In late 2001, a deal was finally struck and 0.63 hectares of Epsom rock forest was purchased by the Department of Conservation and vested in Auckland City Council. (A developer has since demolished the mansion and divided its land into several titles, which, at the time of writing, are for sale again.)
Cameron had, in 1999, surveyed the site, noting major weeds such as tree privet and 50 per cent ground cover of Tradescantia. There were exotic strays from the old mansion garden, which may have sprouted from thrown cuttings, and a monstrous fruit salad plant that had spread into the forest realm from the carriageway. There were magnificent king ferns, māmaku tree ferns and nīkau palms, all native but probably planted. Mangeao, described back in 1943 as “conspicuous and truly magnificent”, had been damaged by possums nearly to the point of obliteration. There was plenty of work to be done. However, the rock forest had had its 15 minutes of fame, impetus was lost and the next decade brought little change.
Passive stewardship is far from harmless. Epsom rock forest is continually under threat from weeds that crowd out true forest species, possums that devour extraordinary quantities of vegetation, and rats that consume native seeds, affecting the forest’s ability to regenerate.
Local conservation volunteer Sel Arbuckle has for decades been a guardian of Epsom’s rock forest remnants, from taking out rucksacks full of Tradescantia weed, to discouraging young people from paintballing and smoking dope there. Arbuckle is something of a rock-forest legend, but is the first to admit there is only so much one man can do in his free time. Removal of mature tree privet, for instance, was going to require manpower and funding.
Eventually, the Albert-Eden Local Board was alerted to champion the site’s restoration, and in 2014 agreed to fund a five-year pest and weed eradication programme. It found early success in the discovery of a small population of the fern species Pellaea falcata, which has not previously been recorded there. Once easy to find in Auckland’s lava fields, the fern is now declining nationally, and critically at risk in Auckland.
As a young child, field ecologist Melissa Marler played in the “mythical” rock forest when visiting her grandmother, whose house backed onto Withiel Thomas Reserve. “There were pathways through the bush,” she says. “Many remain today but have been closed off in places, presumably to make it more difficult to get near private houses.”
The area’s remnant rock forest is also designated a Special Ecological Area (SEA) under Auckland Council’s new Unitary Plan. Light tree-trimming, pest control and planting of locally indigenous species are permitted, but a long list of other activities require a permit, including excavation, alteration of soil levels, destruction of any indigenous plant, and introduction of exotic plants. In 2013, a landowner was prosecuted by Auckland Council for removing native trees and volcanic rock in the SEA, and fined some $15,000.
But damage can take the shape of well-meaning activity, too—over-severe tree trimming causing the forest edge to recede, garden waste dumped in the forest introducing inappropriate seeds and cuttings that sprout, and the expansion of shade-tolerant exotics, such as Clivia. Even indiscriminate weeding can set the forest back generations.
A stone’s throw from Almorah and Withiel is Government House. Its well-maintained park-like grounds are known for exotic plantings dating from the 19th century, including enormous, buttressed fig trees. The grounds also include a sumptuous slice of rock forest.
Governor’s Lawn was once a grazing paddock used by horses that pulled carts to and from the adjacent quarry (now Eden Garden). Levelling off the ground for the massive paddock required tonnes of rock to be removed. It’s ironic to see a large lawn appropriated from rock forest within metres of a precious fragment of the same. The forest clings onto a modest slope of boulders in a thin strip at the periphery of the estate. There are many karaka trees, several of them quite large, some māhoe and a fat knobbly-barked mangeao. Coastal karamu is dotted all about. Kawakawa dominates at eye-level, as it does in other seams of rock forest, but here, uniquely, it is accompanied by whau, the shrub after which the mountain is named. King ferns and nīkau have nuzzled into deeper humus near the base of the slope.
A decent path, by rock-forest standards, keeps estate visitors out of trouble, passing by outcrops with angular juttings and jigsaw cracks, pausing at a park bench where the tranquillity of this forest can be absorbed. Boulders are wrapped in moss on this steep, south-facing slope, but it has been so dry of late that the moss feels like baize, and hound’s tongue ferns droop crisply over boulders like seaweed above the mid-tide mark. The forest is interwoven at the edges with ornamental mass plantings of hen and chicken fern and Monstera deliciosa, and there is a big clique of silver ferns. The urban conservationist’s bugbear, Tradescantia, is evident, along with the silvery shimmer of Lamium.
Government House rock forest is as ancient as the tracts around Almorah, but feels nowhere near as wild. Perhaps its role as an element within a refined parkland makes it seem urbane, its proximity to a vast lawn makes it seem becalmed, its blended edges make it seem self-aware.
Almorah, by contrast, seems complex and forgotten; Withiel, striving and urban.
Each to its own, a community of micro forests, forest keepers and forest dwellers.
By writing about the rock-forest ecosystem and its place in urban Auckland, I hope I am contributing in some way towards its survival. But I am conflicted, too. It is too precious to be popular.
Cameron advances a wise thought: “Public recognition of the rock forest, knowing it and loving it, is its salvation.”
So go to Withiel, go in, go in. But go lightly.