Grass won’t hold the hills
Increasing grassland production and productivity created unanticipated environmental costs. There was a belief that a stable grass and clover cover would hold soil in place. But in the 1930s concern mounted about loss of soil as grassland pushed ever further into the hills.
The devil’s work
Soil conservator Doug Campbell described the erosion problem on Molesworth Station in 1945 with particularly vivid language:
‘[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 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 mountain side in a final gesture of triumph to choke rivers.’1
There was a growing international awareness of the costs of soil erosion. Much of it stemmed from the United States and its ‘dustbowl’ experience of the 1930s economic depression. There, wind blew away the topsoil. In New Zealand, following the removal of forest cover, the main problem was water run-off causing gullies and slips in hill country. Soil erosion was a New Zealand-wide problem, but was especially severe in the eastern hill country of Hawke’s Bay and Gisborne, with its underlying mudstones.
Initially, the problem was viewed as a flooding issue as eroded soil was deposited on river plains, raising river beds. The government proposed a Rivers Control Bill, which would authorise engineering works to attempt to control river channels. When the legislation was passed in 1941 it had become the Soil Conservation and Rivers Control Act.
Increased knowledge of soil erosion, and the new legislation, saw a comprehensive system of river catchment management put in place in the 1950s and 1960s. This focused on planting new forests, preventing and reducing soil erosion, and preventing flood damage.
The first hydroelectric dams were built before 1900. Catchment-wide planning began after the Second World War in response to rising demand for electricity, as industries, towns and cities grew. From the 1950s more dams were built. Most of these were in the lower and upper Waitaki River basin in the South Island, and on the Waikato River in the North Island. In the late 1960s and early 1970s more sophisticated engineering schemes such as the Tongariro and Manapōuri developments moved water between catchments.
In 1990 nearly 80% of the country’s electricity was supplied by hydroelectric generation. The last major dam to be built was at Clyde in Central Otago, commissioned in 1992. By this time, dam building had become unpopular with many people due to a growing realisation of their environmental effects such as sediment build up behind dams, blocking fish passage and unnatural downstream river level fluctuations.
Increases in electricity demand over the 1990s and 2000s were met by thermal sources (gas, coal and geothermal). Wind power was widely promoted from the mid-2000s, due to the reliability of New Zealand’s winds. However, wind turbines were increasingly subject to public protest, mainly on aesthetic grounds.
Gold and coal
Gold was New Zealand’s major export in the 1860s and 1870s. Coal mining on the West Coast of the South Island, where there are rich reserves of high-grade anthracite coal, reached a peak in the first half of the 20th century. The lower-grade coals of the Waikato are used for power generation, which creates carbon dioxide – a greenhouse gas. Mining also had localised environmental effects such as polluting streams with sediment. The Resource Management Act 1991 has largely reduced these effects.
Both coal and gold mining underwent a renaissance in the late 1990s and 2000s. Solid Energy, the state coal company, was joined by private enterprises, such as Pike River Coal. In the early 2000s the West Coast was producing more coal, mainly for export to East and South Asia, than it had previously.