Human impact on dunes
It is not known how much Māori influenced the active dune lands, but their fires may have opened up more land to sand movement. From the mid-1800s, settler farmers cleared and burnt sand-binding native grasses, shrubs and small trees near the coast in order to run sheep and cattle. They removed the natural vegetation cover, allowing dunes to move inland.
Increase in dune lands
It is difficult to know the extent of dune lands, as they are continually moving. An 1880 estimate suggested that there were 40,000 hectares of drifting coastal sand. By 1909, the area was thought to have increased to 120,000 hectares. It is uncertain if the growth was entirely due to farming practices – research has shown that dune lands also had natural periods of expansion over the late Holocene (last 10,000 years), so some of the growth may have been natural.
In 1903, Parliament debated the Sand Drift Bill. One legislative councillor, John Rigg, outlined his view of advancing sands on the Kāpiti Coast:
‘It may be that its onward march may be checked by planting near the sea-shore, and that the evil may be mitigated; but from the sandhills the sand flies in clouds with every wind, and on a windy day it is carried for miles. In the neighbourhood of the sandhills it is with difficulty that you can breathe on such days. Your eyes and nose are full of sand, and the experience is altogether disagreeable.’ 1
The sand threat
Today dune lands are seen as unique ecosystems, but in colonial New Zealand there was a fear of drifting sands. Sand blew about in coastal areas, encroaching onto pastures and even burying a church at Waikanae on the Kāpiti Coast.
From the 1870s, the threat to productive land was recognised but little was done. In 1908, the government passed the Sand Drift Act – an ineffective tool which did nothing to arrest the drift of sand, but gave the matter official recognition. In places around the coast farmers had already taken things into their own hands and planted introduced marram grass (Ammophila arenaria) to stabilise the dunes. They had some success, but their efforts were piecemeal.
Looking for a solution
The Department of Lands was the first government agency to tackle what was seen as the sand problem. The botanist Leonard Cockayne was asked to write a report, published in 1909. His second report, in 1911, included a section on stabilisation methods. The French had stabilised dunes on the Gascony coast with extensive planting, and this was seen as a solution for New Zealand. Cockayne’s advice guided the government’s approach in the following decades.
The first step was to stabilise sand at the point of supply – the coast. Cockayne pointed out that only continuous vegetation cover would solve the problem, and that this should also be commercially valuable. Trials of sand-binding plants and forest trees were done at the mouths of the Rangitīkei and Waikato rivers, but they were not well funded.
Planting the dunes
During the economic depression of the 1930s, the Public Works Department took over the sand-stabilisation project. Gangs of men lived in camps, planting marram grass and other exotic species. By 1951, when the New Zealand Forest Service took on the job, 9,000–10,000 hectares of dunes had been planted in marram grass and yellow tree lupin (Lupinus arboreus), and 3,800 hectares of forest had been planted.
The Forest Service trialled different types of vegetation and ways of stabilising dunes. They mechanised the planting of marram grass and radiata pine (Pinus radiata), greatly increasing the areas they could cover. By the 1970s, they had a standard approach, starting at the beach and moving inland:
- Build fore dunes (dunes close to the sea), using barriers such as mānuka fences and radiata pine prunings.
- Plant marram.
- Sow yellow tree lupin.
- Plant radiata pine on the coastal edge.
- Plant commercial forests in the lee of the shelter achieved.
From the 1960s to the 1980s, the Forest Service established pine forests in large areas of Northland, Auckland, Waikato and Manawatū dune lands. These forests have been the largest factor in the reduction of New Zealand’s active dune lands.