When settlers cleared the land for farming in the 19th century, they soon saw the problems caused by heavy rainfall. School inspector and naturalist Henry Hill recorded the effects of torrential rain near Gisborne, in December 1893: ‘When going through the district shortly after the floods took place, I was surprised to find how much the appearance of the country had changed. Thousands of breakaways or slips were to be seen, some of them of large extent.’ 1 Hill surveyed the affected areas, and estimated that a 4-inch (10-centimetre) layer of soil had been washed away.
Widespread erosion occurred after the First World War when returned servicemen, settling on blocks of forest-covered hill country, cleared the land of trees.
In February 1938, Kopuawhara works camp near Gisborne was washed away with the loss of 21 lives. This was followed a few weeks later by floods in the Esk Valley of Hawke’s Bay, which damaged hill country and buried downstream farmland under metres of silt. There were calls for action on flood control. After a committee of enquiry, the Soil Conservation and Rivers Control Act was passed in 1941.
Soil conservation under way
Under the 1941 act, a Soil Conservation and Rivers Control Council was set up to oversee catchment boards and river control programmes. The council and catchment boards had the power to regulate burning and land use, and levy rates.
Initially, farmers were concerned that the law would affect their livelihood and farming methods. In practice, however, a strong voluntary ethic evolved, reinforced by community pressure and subsidies for approved remedial work on farms. There was university training for soil conservators, and farm demonstrations of wise husbandry.
A new philosophy
1950s publicity about soil conservation was aimed at farmers, but the wider relevance was clear. Geographer Kenneth Cumberland, an influential advocate, wrote: ‘Every citizen is concerned with this; no New Zealander can escape its implications … all have a personal stake in the urgency and thoroughness which we accord to the formulation of plans for conserving and developing land.’ 2
Satanic spell on soil
This dramatic account of high-country erosion at Molesworth Station was made by Doug Campbell, a strong advocate for soil conservation:
‘[O]ver vast areas the mantle of soil has been torn or stripped off. Remnants of it are found towards the base of the slopes as though some satanic spell had been cast on the mountains and hills, and the soil had been atrophied and sloughed off. Exposed skeleton rock seems to grin with malice or frown with disdain on man’s handiwork as it creeps and flows down the mountainside in a final gesture of triumph to choke rivers.’ 3
Soil conservation today
Today, soil conservation and erosion control are an accepted aspect of land use. Many erosion-prone areas have been withdrawn from agriculture, either by using them for exotic forestry or by allowing them to revert to native forest.
By the 1980s it was realised that erosion in the steep alpine region of the South Island was caused by actively rising mountains. Conservation efforts have moved to dissected hill country, especially areas underlain by soft rocks, which wear away easily. Such country was badly affected by Cyclone Bola in 1988, and the Manawatū floods in 2004. Debate continues about whether this land should still be farmed, or should be planted in trees to stabilise the slopes.