ack at Kaikoura township, our route south takes us along State Highway 1. The hills now are much reduced after the soaring peaks behind Kaikoura, and it is not until you reach Spye, some 111 kilometres further south, that the Canterbury Plains open out before you. This wide expanse is the country's most distinctive and easily defined geographical area by far the largest, contiguous area of lowland we have.

This long, coastal plain is flanked on the west by the soaring peaks of the Southern Alps and from these to the coast run the great rivers of the plains - the Waimakariri Rakaia and the Rangitata - all running eastward to the sea.

Geologists estimate that less than a million years ago the waters of the Pacific Ocean lapped right up to the base of these mountains, but slowly, by glaciation, and by the action of the rivers, the mountains were eroded and the debris in the form of gravel carried down to the sea. These coarse gravels were deposited at the river mouths in great fan-like deposits pushing simultaneously seawards and sidewards to eventually join up and form the plains. At the intersections of these deposits, smaller rivers such as the Ashley, the Selwyn and the Ashburton now flow.

These deposited gravels reach depths of up to a kilometre, while the soil cover is comparatively thin (on average 20 to 25 centimetres) and often fragile, mostly made up of loess but also with some alluvial patches near the rivers.

Early Pakeha settlers thought the Canterbury Plains had always been grass-covered but research now indicates that almost this entire area was covered with totara-dominated forest up to about 2000 years ago. Then huge fires devastated many areas, but particularly those along the drier, eastern coast of both islands. The most affected areas were in the MacKenzie Basin and Central Otago but also, to a lesser degree, South Canterbury.

After the arrival of the Maori much of the remaining forest of the Canterbury Plains was burnt. Why this was done can only remain a matter for speculation. The clearing of land for agriculture or building, to allow bracken, the source of fern root, to establish itself, to facilitate cross-country travel - none of these alone could account for the sheer magnitude of the burning that was done. The only reasonable explanation is that once fires were lit in these drier eastern regions, they soon got out of control and very large areas were burnt.

South of Spye, an exquisitely exact pattern of paddocks stretches south as far as the eye can see and west to the foothills of the Southern Alps, which dominate the landscape of much of the South Island. You can best appreciate this scenery from the air in spring or summer when the variety of crops create a vast checkerboard of varying colours, but good views can also be had from hill lookouts such as those on Banks Peninsula

One of the most persistent features of the Canterbury Plains is its braided rivers. These are formed by the deposit of wide expanses of shingle which originate as rock debris eroded from the mountains. Large rivers cut through this accumulated shingle and their constantly changing courses have created riverbeds over a kilometre wide in some places. When crossing rivers such as the Rakaia by train one wonders when the bridge will end.

No native trees grow here, but there are a number of shrubs such as the thorny wild Irishman and several Hebe and Epilobium species. More typical are the scabweeds which form dense and often colourful mats. The common scabweed forms greenish-grey patches over a metre wide and mossy scabweed is found in golden moss-like colonies.

The birds of these areas are unique too. Wrybills, black-fronted terns South Island pied oystercatchers, black-billed gulls, banded dotterels and the - very rare black stilt are all braided riverbed breeders and the wrybill breeds nowhere else. The birds return each spring and after their chicks fledge generally move to the coast or migrate northwards with some of the banded dotterels even wintering in Australia.