The Hidden Treasures of Castle Hill

Forest and Bird, Issue 299, 1 February 2001, Page 22

The Hidden Treasures of Castle Hill

by

SARAH MANKELOW

n the skyline, grand castellated limestone outcrops create the battlements that led early European travellers to rename Kura Tawhiti as Castle Hill. Amongst these ‘fortifications’ lie hidden treasures, some of the rarest and most endangered plants in Canterbury, and indeed the world. Castle Hill Conservation Area lies in the high-country, inland from Christchurch on the road to Arthurs Pass, encompassing some of the limestone tors that dominate the basin between the Torlesse and Craigieburn ranges. The Castle Hill of today is quite different to the landscape that was an important mahinga kai, or food-gathering area, for nomadic Ngai Tahu. Once covered in Hall’s totara and tall shrubs, it was cleared mostly by fire and has been grazed for almost 150 years. Tussock and pasture now prevail, with only one stunted specimen of Hall’s totara remaining, a survivor that found sanctuary on a boulder of limestone. A number of rare plants hang on in small areas, however: in fact, several species were first discovered here.

Castle Hill attracted botanical interest as early as the 1860s when one of the first European settlers in the area, John Enys, found rare plants amongst the limestone outcrops. Enys’s name has been remembered in the Enys Scientific Reserve, established to protect bog pine from the ravages of grazing animals, opposite Castle Hill Village. In doing so, an even rarer plant was fortuitously protected. It was later discovered the reserve contained five adult plants of Hebe armstrongii, the first positive identification of the plant growing in the wild for more than 100 years. Today, seed from these plants is the heart of restoration initiatives and research to ensure it does not become extinct in the wild. Castle Hill is the site of the first reserve in New Zealand established specifically to protect a plant. Dr Lance McCaskill led a remarkable conservation effort in the early 1950s to save the Castle Hill buttercup, increasing numbers from 32 plants in 1948 to more than 300 today. These days, the reserve’s scientific value as the longest running plant-monitoring project in New Zealand is very important, even

though the buttercup has been discovered to be not as unique as originally thought. Once thought to be a separate species, the Castle Hill buttercup has proved to be just a different form of Ranunculus crithmifolius, which is widespread on the screes of the surrounding mountain ranges. The fenced Lance McCaskill Reserve has, however, protected several other small plants that are now rare and endangered, including a forget-me-not Myosotis colensot. Both plants can be looked at in a small garden just inside the reserve, as entry beyond the fence is by permit only. Myosotis colensoi, commonly known as the Castle Hill forget-me-not, is small but pretty. Its blue-green leaves grow into rosettes, forming attractive cushions. The white flowers are huge compared with the rest of the plant. The forget-me-not prefers open bare areas of limestone scree; because of its small size it is vulnerable to larger plants, in particular introduced grasses that can smother it. Other endangered plants at Castle Hill are not as favoured with looks as the buttercup and forget-me-not. Two in fact, a sedge and

a grass, may to most people lack charisma. But looks aren’t everything and in botanical circles, these ‘plain-Janes’ are special. Small and critically endangered is the sedge, Carex inopinata, only three centimetres high, fine-leaved, sprawling and very difficult to identify. It prefers to grow under a canopy of native shrub species around limestone tors. Limestone wheatgrass, Australopyrum calcis subspecies obtatum, was first described only six years ago when it was discovered on pastoral lease land, on Prebble Hill in Castle Hill Basin. Like the Carex, it is confined to limestone ecosystems where it grows under rock overhangs and under the shade of native shrub species. Limestone wheatgrass belongs to an ancient family of grasses; New Zealand’s only diploid grass. Compared to introduced grasses that grow more vigorously, it struggles to compete. Both the Carex and limestone wheatgrass grow in partial shade and would once have inhabited the floor of the forest and shrublands of Castle Hill. The best remnants of suitable shrub cover are amongst the limestone tors on private farmland, owned by

Castle Hill Station. With landowner cooperation, these areas have been fenced off to protect them from stock, rabbits and hares. A revegetation programme has been underway for the last five years attempting to recreate shrubland habitat on public conservation land. It is hoped that once a shrubland is re-established, these rare plants will be planted out underneath. Behind the fortifications of limestone, the botanical battle rages on. The battlefield is scarred by 150 years of fire and grazing and yet, pockets of original shrubland harbour refugees. The challenges that face those working to protect these survivors are many — habitat reduction, competition from weeds, impacts of grazing animals, rabbits, hares and other human impacts. Promoting

the protection of plants that are small, shy and hard to find is no less of a trial. Kura Tawhiti keeps its riches close to heart. SARAH MANKELOW, works for DoC, in Christchurch.

The Topuni of Kura Tawhiti @ astle Hill has recently had its Maori name, Kura Tawhiti, restored under the Ngai Tahu Settlement Act 1998. Kura Tawhiti literally means ‘the treasure from a distant land’. The area is designated a ‘topuni’ a public acknowledgement of the manawhenua authority held by Ngai Tahu over the land. The term comes from the traditional custom of chiefs extending power and authority over areas or people by placing a cloak over them. Under the topuni, the existing status of the land as a conservation area is unchanged, but the topuni status ensures that Ngai Tahu values are recognised, acknowledged and respected and Ngai Tahu may take an active role in management. The area is of special significance to Ngai Tahu. The Ngai Tahu ancestor Tane Tiki, son of the celebrated chief Tuahuriri, claimed Kura Tawhiti (Castle Hill). The nearby mountains were famed for kakapo and Tane Tiki wanted their glowing green feathers to make a cloak for his daughter Hine Mihi. These and other stories link Ngai Tahu to the landscape. The traditional knowledge of trails, rock shelters and places for gathering food in the area known as Kura Tawhiti form an integral part of past and present tribal identity.