Section 2: Nature Friendly Environments — Communities Making it Happen Ecological restoration in Hamilton City Bruce D. Clarkson Centre for Biodiversity and Ecology Research Department of Biological Sciences, The University of Waikato, Private Bag 3105, Hamilton, New Zealand [email protected] ABSTRACT Hamilton City has less than 20 ha of high quality indigenous species dominated ecosystem and only 1.6% of the original indigenous vegetation remains within the ecological district. A gradual recognition of the magnitude of landscape transformation has gathered momentum to the stage that there is now a concerted public and private effort to retrofit the City by restoring and reconstructing indigenous ecosystems. The initial focus was on rehabilitating existing key sites but has shifted to restoring parts of the distinctive gully landform that occupies some 750 ha or 8% of the City. A new initiative at Waiwhakareke (Horseshoe Lake) will involve reconstruction from scratch of a range of ecosystems characteristic of the ecological district over an area of 60 ha. This paper examines a vision for ecological restoration in Hamilton City within the context of policy, education and community dimensions that have triggered a shift from traditional parks and gardens management to ecosystem management. INTRODUCTION The Hamilton Ecological District (159 376 ha) plant species (de Lange 1996) and is regularly in northern North Island is one of the most visited by kererū (Hemiphaga novaeseelandiae modifi ed districts in New Zealand with only novaeseelandiae). Recently, native long- 1.6% of the indigenous vegetation remaining tailed bats (Chalinolobus tuberculatus) have (Leathwick et al. 1995). At least 20% of also been recorded in the area (E. Ganley its indigenous fl ora is threatened or extinct pers. comm. 2001). However, New Zealand’s and more than one-half of its indigenous widespread native nectar-feeding bird, bird species have gone. Hamilton City the tūī (Prosthemadera novaeseelandiae (9427 ha), in the centre of this transformed novaeseelandiae) is only a rare visitor here as it landscape, has only a few tiny remnants of is in the whole of Hamilton City. the former indigenous forest cover, perhaps less than 20 ha in total of high quality Although the indigenous biodiversity resource indigenous habitat. The largest remnant is is very limited, Hamilton City does possess an Jubilee Park (Claudelands Bush), a 5.2-ha extensive network of gullies. These extend reserve comprising kahikatea (Dacrycarpus from the Waikato River through many suburbs dacrydioides) forest (Whaley et al. 1997). of the City, occupying around 750 ha or 8% Another important remnant is Hammond of the City area (Downs et al. 2000) and are Bush (Fig. 1), which has semi-swamp forest considered a unique feature of the Hamilton dominated by pukatea (Laurelia novae- area (McCraw 2000). Four major gully systems zelandiae), with the regionally uncommon (Kirikiriroa, Mangakotukutuku, Mangaonua and waiwaka or swamp maire (Syzygium maire) Waitawhiriwhiri) and numerous minor systems present, and tawa (Beilschmiedia tawa) exist (Fig. 2). As McCraw (2000) has shown, forest on dryland (Stephens et al. 2000). the gullies are the result of the undermining of This is fl oristically the richest of the Hamilton a geological formation of sand, silt, peat and indigenous remnants. Despite its small size gravel known as the Hinuera formation. Around (1 ha), it supports an impressive 145 native 15 000 years ago, the Waikato River started Greening the City. ISBN 0-959-77566-8 93 © Royal New Zealand Institute of Horticulture (Inc.) 2005 Section 2: Nature Friendly Environments — Communities Making it Happen to cut down through this material creating its Investigation of ecological resources on public present channel and as it deepened, springs and private lands included a comprehensive were exposed along the riverbanks. As water survey, in order to identify key ecological sites drained from the surrounding land, these within the City (Downs et al. 2000). Some 67 springs undermined the banks, in a process key sites were identifi ed with a total area of known as spring sapping, causing slips and 76 ha and an average area of 1.1 ha. Extant creating a network of streams draining into the vegetation ranges from kānuka (Kunzea Waikato River. This process was repeated ericoides) forest of well-drained river and gully again and again giving rise to erosion and scarps to raupō (Typha orientalis) reedlands the formation of the steep-sided and intricate fringing peat lakes, with many intermediate types network of gullies that adjoin the river today. (Fig. 4). Gully fl oor vegetation is frequently Despite being poorly treated in the past, the dominated by the deciduous exotic tree grey gullies have now been recognised (Clarkson & willow (Salix cinerea), though beneath this is Downs 2000) as the central focus of a city-wide often an understorey dominated by indigenous restoration of indigenous ecosystems because plants including ferns, māhoe (Melicytus they are the main wildlands in an otherwise ramifl orus) and cabbage tree (Cordyline entirely built landscape (Fig. 3). australis). Even where weeds are dominant, gullies still provide some important ecosystem RESTORATION AND POLICY BACKGROUND services, such as supporting desirable wildlife. The signifi cance of the gullies as a potential Native birds persist even in these highly modifi ed focus for landscape enhancement was systems, with seven species, including morepork highlighted as early as 1972 (McLeary 1972) (Ninox novaeseelandiae novaeseelandiae), New but only in recent years has the move to make Zealand kingfi sher (Halcyon sancta vagans), use of them gathered momentum. A Gully silvereye (Zosterops lateralis lateralis), fantail Protection Zone had been in force since 1989, (Rhipidura fuliginosa placabilis) and grey warbler but this related more to building requirements (Gerygone igata), widespread (Innes 2000). than protection of gullies per se and was ineffective at protecting ecological features or The original gully vegetation can be deduced preventing infi lling of gullies associated with from historical records, from the composition of subdivision development. In recent years, extant remnants and from macrofossil deposits to meet the requirements of the Resource (Clarkson & Clarkson 2000). This information Management Act (1991) and obligations of provides a context for developing restoration international agreements such as Agenda 21, goals and gives an indication of the diverse the Hamilton City Council has undertaken a range of native plants appropriate for restoration substantial information gathering exercise to plantings. Recent publications such as the improve knowledge of natural values within Gully Restoration Guide (Wall & Clarkson 2001) the City. This has included an evaluation of and Botany of the Waikato (Clarkson et al. a range of ecological, landscape and hazard 2002) provide information on which plants to areas, and the preparation of a map based use, where to plant them (Fig. 5) and how to on the boundaries of these areas, termed an look after them. Environmental Protection Overlay (EPO). This map forms part of the District Plan, which The benefi ts of gully restoration are numerous also sets out policies and rules relating to and wide-ranging. These include improved components or layers of the EPO, developed in environmental, aesthetic, scenic and cultural consultation with the community (Vare 2000). values. Native plants perform important As well, a gully management plan (Hamilton ecosystem functions. The nectar-producing City Council 2001) has been developed kōwhai fl owers (Sophora microphylla) feed providing a comprehensive plan for restoration native birds, the fl eshy fruits of the native of the publicly owned gullies but recognising conifers like rimu (Dacrydium cupressinum) feed the need also to involve the owners of adjoining the birds and in turn are spread by them, and privately owned gullies. the lacebark (Hoheria sexstylosa) grows into 94 Section 2: Nature Friendly Environments — Communities Making it Happen a good-sized nurse tree within fi ve years and performance of locally sourced ecotypes or fl owers profusely every autumn. Reintroducing races, as well as the need to conduct authentic a range of plant species once found in Hamilton restoration in important reserves such as gullies could also address the local shortage Hammond Bush. Native species propagated of native plant resources for rongoā (traditional from ecosourced plant material have been used Māori medicine) (McGowan 2000). As well as successfully in numerous restoration projects enhancing terrestrial habitats, gully restoration throughout the City, and this is a technique now benefi ts aquatic life in streams. Riparian employed by staff at the Hamilton City Council planting leads to cooler, more shaded streams Nursery and several private and community with stable undercut banks — the preferred plant nurseries. An Ecosourcing Coordinator habitat of some native fi sh species including the has been appointed using joint funding from the banded kōkopu (Galaxias fasciatus) and redfi n Hamilton City Council and the Department of bullies (Gobiomorphus huttoni) (Hicks 2000). Conservation, Waikato Conservancy. From the pioneering work of people like Alwyn Matching species preferences to site conditions Seeley, Peter Morris and the Edgar family, we through careful site selection is rewarded by know that it is possible to have a good canopy greater survival and growth