Situated behind Butchers Dam, it encompasses the northern end of Flat Top Hill running north to south, bounded by Lake Roxburgh in the east and Butchers Creek and State Highway 8 in the west. Flat Top Hill is a miniature block mountain, at the foot of the Old Man Range (Kopuwai).

A dry land ecosystem, Flat Top Hill supports a diverse range of animal and plant life, including examples of regenerating native plant species that previously covered much of the lowland valleys of Central Otago. Dry land ecosystems are one of New Zealand’s most threatened ecosystems. Flat Top Hill is important for observation, recording and management of such ecosystems

The area also includes some interesting historical evidence of European and Chinese settlement.

Landscape and geology

The schist rocks of Central Otago were once sediments, washed from an ancient landmass more than 200 million years ago. The mud and sands settled, compacted and hardened into large areas of sedimentary rock (mudstone and sandstone) on the bottom of prehistoric seas.

Heat and pressure from movement in the earth’s crust, transformed these sedimentary rocks over a period of about 80 million years. The result was a layered metamorphic rock schist, with high quartz content and a tendency to split. The name ‘schist’ derives from the Greek word meaning ‘to split’.

Schist underlies most of Otago, and at Flat Top Hill the rock layers have remained horizontal and uplifted, forming flat topped ‘block’ mountains, or in this case, hills.

Just beyond the reservoir are some paleosols exposed by gold miners' sluicing, dating back 20-25 million years. They display a striking sequence of colours, the brilliant red, yellow and white material contrasting with the dull olive browns of the current soils.

The same types of soils are only found today in tropical climate regions – hot and steamy with lots of rainfall and lush forest. Together with other geological, animal and plant fossil clues, this indicates the type of climate that once existed here.

In contrast, this area is now the driest part of New Zealand, receiving less than 300 mm of rainfall annually due to its location in a rain shadow of the mountain ranges to the west and south. At its lowest point, the edge of the Roxburgh gorge to the east, the land is 140 metres above sea level. It rises to 550 metres on the schist rock plateau before falling again in a series of terraces to about 400 metres at the car park.

Vegetation

The semi-natural vegetation of Flat Top Hill is important, being a substantial example of native species growing in the driest environment in New Zealand.

Over 182 native plants have been recorded here, more than the average New Zealand forest. Incredibly, thirteen of them are ferns. Features of the vegetation are a set of native spring annuals of the genera Ceratocephalus, Myosotis and Myosurus. The native cottonwood (Ozothamnus leptophylla), native daphne (Pimelea aridula), mountain wineberry (Aristolelia fruiticosa) and porcupine shrub (Melicytus alpinus) are characteristic of the numerous shrubs native to this semi-arid inland area of Otago.

Like the ancient soils, the area has undergone significant changes, most recently as a result of human intervention. Over the past 150 years, fire, the introduction of exotic pasture grasses, grazing sheep and rabbit infestation, have dramatically modified the plant communities of Flat Top Hill. By the 1990’s, Flat Top Hill had become a bare landscape, holding little more in vegetation than native cushion plant (scab weeds), lichens, yellow succulent stonecrop and introduced thyme. Woody weeds such as briar, broom, gorse and wilding pines also became established.

Since being designated a Conservation Area in 1992, sheep and rabbits have been removed from Flat Top Hill. As a result, native grasses have recovered, overgrowing thyme and replacing large areas of cushion plants. Amidst refuges in the rock outcrops and tors, shrub land plants are re-establishing themselves. In time, Flat Top Hill should revegetate to a tussock shrub land system, with a mix of native and introduced flora and fauna.

Each schist rock and tor supports its own ecosystem of lichens, mosses, ferns and shrubs. In turn, these are host to distinctive insects and lizards, such as the Otago gecko (Hoplodactylus sp. Otago).

The semi-natural grassland and cushion fields within and on the crests of Flat Top Hill support many diurnal insects. Wasps, ants, beetles and moths, including the rare Alexandra chafer beetle, (Prondontria modesta) are found here. A special feature on Flat Top Hill are several small saline sites. Weathered from the schist parent material in an environment where the low rainfall allows minerals to accumulate rather than wash away, are small areas of salty soils. These soils host special salt tolerant plants such as Atriplex buchananii, usually found by the sea, and Puccinellia raroflorens, found only in the tidal banks of Stewart Island and some saline areas of Central Otago.

Gold mining history

In 1862, gold was discovered in Butchers Gully (now submerged under Butchers Dam). Water was essential for mining the gold and for survival. European settlers quickly learnt the value of water in the dry Central Otago climate. Butchers dam is itself a legacy to the need for water reserves in an environment that makes water the equivalent of “liquid gold”.

During the 1860s, Butchers Gully as it was known, teemed with goldmining activity. Although not as rich as nearby Conroy’s Gully, it was productive for many years.

Butchers shop

A store and butchers shop was set up mid 1865. During 1868, the road between Roxburgh and Alexandra was completed and Butchers Gully Hotel was built. It was later destroyed by fire on 29 January 1886, In May 1890, a replacement hotel was built and successfully managed by a succession of owners, until it was submerged under the Butchers reservoir in 1937. It is said that when the water level is low, the chimneystacks may be seen below the surface.

Butchers dam

Butchers Dam and its outlet tunnel (728 metres through solid schist rock) were built between 1935 and 1937 during the great depression in order to create a water reservoir for the nearby town of Alexandra. The dam and race are now only used for irrigation. The Last Chance Irrigation Company now owns the dam.

Chinese influence

The Chinese influence on Butchers Gully can be seen in the remains of a market garden, orchard, schist rock storeroom and surrounding stacked rock fence. These were the efforts of Lye Bow (Li Bo), a Chinese gentleman, one of the many Chinese miners who came to New Zealand in the early 1860’s. A popular character of this area, his unusual story is told in detail on the Interpretative Loop Track.

The property surrounded by the conservation area and Butchers Dam is in private hands, but is still known locally as Lye Bow.

DOC purchase in 1992

The Flat Top Hill Conservation Area consists of 813 ha purchased by DOC in 1992.