Philippa Stevenson: Desirable ecospace lurking at the bottom of the garden

COMMENT

A Hamilton house that backed on to a gully was once a wondrous thing. It meant you had somewhere to chuck your lawn clippings.

Nowadays owners of gully sections are more likely to be working away at the bottom rather than the top, hacking back the weeds, hauling up the rubbish and worrying about the diversity and survival of their plantings.

Out of sight and - to all but a few enlightened souls - out of mind, gullies are Hamilton's key natural feature. The city is riddled with about 750ha of gully, or 8 per cent of its area. About 680ha are privately owned.

The renaissance from dumping-ground to desirable aspect has been driven partly by the property market - a swathe of central city greenery is a hot seller - and by greater environmental awareness.

Some dedicated property-owners have quietly worked away for 20 years or more to turn overgrown and weed-infested gullies into bushclad retreats just a stone's throw from suburbia's tarmac.

But things got really serious in April 2000 when Waikato University and the Hamilton City Council combined for a two-day seminar on the gullies. Everything went into the pot for dissemination and discussion: geology, vegetation (wanted and unwanted), bird and aquatic life, policy, restoration.

The seminar kicked off with the arresting thought that whatever plant and animal diversity survived in the untamed back reaches of the city did so because of neglect.

Rare surviving components of indigenous ecosystems such as small mahoe, kahikatea or cabbage trees had been joined by highly invasive exotic species such as willow and hawthorn.

The result was that amid the tangle of one gully within 300m of a large shopping mall there were more than 50 species of indigenous plants, and native birds including grey warbler, fantail, silvereye and morepork.

Waikato University ecologist Bruce Clarkson, a central figure in spreading knowledge about the gullies, describes them as the city's best-kept ecological secret. He says that with appropriate management, many can be restored to close to their original state.

In 1989, the city council moved to establish a gully protection zone and has since upgraded its policy to rate gullies as an important part of city planning.

As well as recreational green space and "visual relief" from the urban landscape, they are also vital to the city's drainage.

In March 2001, the council published a comprehensive guide to gully restoration, and a second edition was printed in August last year.

For the geologically inclined, the gullies' formation is linked to the wanderings of the Waikato River across the Hamilton basin over 5000 years. In that time, the river deposited alluvial flood plains along many courses.

About 14,000 years ago, the river began to carve out the deep channel it flows in now. As it did, it cut through the silt on the flood plains, exposing underground springs along the riverbanks.

The springs undermined the banks, causing slips and creating the intricate network of steep-sided gullies that now drain into the river.

Today, 500 people are on the council's gully restoration register, working to restore 42ha of gullies.

Council environment project officer Liz Hallsworth says the register has grown dramatically in just two years, and two or three people join every week. Most learn about it from others already involved, such as when they buy a gully-side property.

News of the initiative has spread outside Hamilton. Ms Hallsworth says she gets requests for information from all over the place - "even from the Mount, and they haven't got gullies".

Her sustainable environment team and the council's parks and gardens division will tell all at this month's Royal Horticultural Society's Greening the Cities conference in Christchurch. (October 21-25).

As well as showcasing the work on gullies, the two council departments will explain how one works with private landowners and the other with public gardens.

Other groups involved in gully restoration will also be at the conference and Mr Clarkson will give a talk on the biodiversity of Hamilton's gullies.

Also this month, the council is starting an advisory service for those on the gully register. It will provide experts to advise homeowners on how to tackle thorny or weedy or planting problems.

That's a long way from the "heave it and leave it" approach of just a few years ago.

* Email Philippa Stevenson