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CUNNINGHAM: A CENTURY OF CHANGE IN RUAHINE RANGE FORESTS 11 A CENTURY OF CHANGE IN THE FORESTS OF THE RUAHINE RANGE, N0RTH ISLAND, NEW ZEALAND : 1870-1970 A. CUNNINGHAM New Zealand Forest Service, Napier SUMMARY: Botanists describing the Ruahine Range prior to 1920 made no mention of the forest debility described by later writers. In the 1870s and 1880s the lowland forests were cleared from round the southern half of the range and grazing commenced on the northern and western plateaux. Opossums (Tricho.surus vulpecula) were liberated in the 1880s and red deer (Cervus elaphus) first entered the range about 1900. By the mid-1920s deer had modified forests; in the northern part of the range. By 1940 deer damage was extensive and opossum damage had been noted. During the 1950s some forest canopies were severely damaged by opossums, and considerable forest collapse occurred during the 1960s. There has been subsequent recovery in some places and continuing forest deterioration in others. INTRODUCTION damaged by bark stripping by the Maori, in earlier The Ruahine Range (Fig. 1) runs from near the times. Ngaruroro-Taruarau River junction in the north to Between 1845 and 1852 the botanist William Wharite Peak in the south, a distance of some 90 km. Colenso crossed the Ruahine Range several times, Since 1870 considerable changes have occurred in his usual route being across the northern portion the forests of the Ruahine Range. Throughout the of the Mokai Patea Range, over Puketaramea to range forests have been modified, largely by intro- Te Atua Mahuru, and down the Makaroro River duced animals, particularly opossums (Trichosurus to Hawkes Bay. In his published account of vulpecula), deer (Cervus elaphus and Cervus nippon), these journeys (Colenso, 1884) he included detailed and goats (Capra hircus). In many parts of the range descriptions of the vegetation. Although he men- forest deteriorafon has occurred, particularly since tioned encountering dead, decaying, and windthrown 1920. Deterioration may consist of a greatly reduced trees, and fallen logs in riverbeds, there is nothing shrub tier; the loss of ferns, moss, and humus from in his text to suggest any form of unnatural or the forest floor; or defoliation, death and collapse spectacular forest debility. On the contrary, he of the forest canopy. In a simplified form, the wrote eloquentiy at times on the richness and health observations of changes are summarised in Table 1. of the vegetation. No objective measurement of these changes was Wild pigs (Sus scrofa) were liberated in the North made before 1970, and this paper attempts to Island in the 18th century and by 1840 were describe the patterns of change by examining in probably established in the Ruahine Range area. chronological order the field descriptions recorded Colenso (1884) mentioned that pig hunting had been by various people who have travelled or worked in conducted on the flanks of the Mokai Patea prior the range. Throughout this paper botanical names to his visit in 1848. He also recorded the presence, have been brought up ,to date and measurements prior to 1850, of landslides on both sides of the converted to metric. range. Recent work by Grant (1965) and Stephens (1977) provides further evidence of periodic storm THE FORESTS PRIOR TO 1870 damage and slope instability in the Ruahine Range Maori habitation of the Ruahine Range appears during the past few centuries. to have been light and sporadic. Pre-European fires The forests of the Ruahine Range prior to 1870 occurred in several places in the north-west Ruahine may be regarded as having been largely uninfluenced Range from the Mokai Patea through to the by European man or his introduced animals. Pohokura basin. Some of the burned areas were near known Maori routes across the range (Elder, THE PERIOD 1870 TO 1920 1965). Batley (1956) found that totara (Podocarpus Between 1870 and 1920 the forests in the region totara) in the north-west Ruahine Range had been of the Ruahine Range started to undergo consider- New Zealand Journal of Ecology 2: 11-21 12 NEW ZEALAND JoU RNAL OF ECOLOGY, Vo.L. 2. 1979 0 ~EA(~U NAWIU• l I AY .,.,, AUAHINE RANGE .I,. ,.......,.,, FIGURE l. Map of the Ruahine Range. CUNNINGHAM: A CENTURY OF CHANGE IN RUAHINE RANGE FORESTS 13 TABLE 1. The main changes in forests of the Ruahine Range from 1870 to 1970. Period Main changes Causes Pre-1870 Forest generally healthy and complete, Maori fires and barkstripping. with only slight modification. Erosion scars present. Rainstorms. 1870 to 1920 Clearing of foothill forests, and European fires; also of some parts of the range. sheep and cattle grazing. Opossums and red deer enter the range; sheep and cattle present. 1920 to 1940 Severe modification of beech forests. Deer. Goats noted in south; opossums noted in north. 1940 to 1950 Canopy defoliation in rata-kamahi forests. Opossums. Damage to kaikawaka. Deer. 1950 to 1960 Heavy mortality in rata-kamahi forests. Opossums. Reduction or elimination of understorey species throughout range. Deer, goats. Defoliation of red beech. Insects. Widespread ill-thrift of kaikawaka. Unknown. Increase in frequency of "slips". Forest instability. 1960 to 1970 Widespread collapse of former rata-kamahi forest. Death, decay, wind. Introduction of conifers and willows for erosion control. Concern for stability. Continuing ill-thrift of kaikawaka. Unknown. Continuing high incidence of slips. Forest instability. Some indications of forest recovery. Decline in deer numbers. able change. In the south, extensive tracts of forest evidence that erosion and instability were features were cleared on both sides of the range, and by of the Ruahine Range before the deer build-up of 1900 the present pattern of farming in the Manawatu about 1920. Alexander McKay (1888) observed that and southern Hawkes Bay had emerged. Apart from the Mangaatua Stream used to spread widely when localised fires and incursions of cattle, the forest on in flood, and deposited large quantities of shingle the flanks of the southern Ruahines remained largely and boulders over the higher part of the alluvial intact. However, removal of forest from adjacent flat. In a later paper (McKay, 1900, he described piedmont fans prior to 1920 contributed to river large landslips in the headwaters of the Makaretu instability in this region in later decades (Mosley, River. Kennedy (1914) mentioned slips in the moun- 1978). In the north and west the easier and more tains as being a source of shingle in the Ngaruroro, open country was grazed from the 1880s and and Aston (1914) referred to the extensive shingle burning of the grass and scrubland, and some slips of the Ruahine tops. forest, was associated with this. A serious fire also Apart from the changes caused by fires and destroyed much forest in the upper Tukituki localised storms there is no evidence that the (Moorcock) area in the 1880s (Elder, 1965). Ruahine forests were seriously damaged or Opossums were liberated in the Pohangina Valley unhealthy before 1920. Two well-known botanists, in 1883 (Pracy, 1962). During the same year red B. C. Aston and F. Hutchinson, spent three days deer were liberated at Matapiro, about 25 km east in the Makaretu headwaters in 1913 and crossed of the north-eastern Ruahines (Logan and Harris, the northern Ruahines near Colenso's route in 1967) and probably entered the Ruahine Range January 1914. Aston made a solo trip to Wharite about 1900. By 1918 deer were common in the Peak two months later (Aston. 1914). Although they northern Ruahines (Elder, 1957). Further red deer had observed kamahi (Weinmannia racemosa), rata liberations were made on the western flanks of the (Metrosideros robusta), tree fuchsia (Fuchsia range between 1902 and 1922. Although some of excorticata) and kaikawaka (Libocedrus bidwillii, all the Ruahine erosion has been attributed to the of which showed widespread mortality or ill-thrift development of high deer populations, there is also 50 years later, they made no mention of any 14 NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 2. 1979 damage. In fact, Aston (1914) noted that at 823 m occurred on flats down the Waikamaka; on one on the Mokai Patea ridge such plants as tree fuchsia, such flat under red beech the following description broadleaf (Griselina littoralis) and lacebark (Hoheria was made: ". practically all undershrubs except sexstylosa) ".. flourish in a marvellous manner." ee fuchsia, Coprosma rhamnoides and Pseudo- Given the observational powers of Colenso, panax anomalus have been killed; mahoe (Melicytus Hutchinson, and Aston, and the fashion in those ramiflorus) and broad leaf torn to the ground; days towards written detail, it is difficult to bel:eve fivefinger (Pseudo panax arboreus) barked completely that such forest debility as was later described to 1.5 or 1.8 m in height and of course dead; a could have escaped notice or gone unrecorded. It scene of desolation. A few minute herbs and the must be concluded that before 1920 the Ruahine grass Microlaena avenacea remain on the forest Range forests were generally in a healthy condition. floor." Kean and Newcombe (1937) described in con- THE PERIOD 1920 TO 1940 siderable detail the destruction by deer of kiokio By the mid-1920s there was a high deer population (Blechnum capense) and the importance of its on the northern Ruahine plateau. At that time rhizomes in stabilising loose slopes, and stated: (Elder, 1965) the forest floor was bared, roots were "On one place where recent slipping had occurred exposed, and by 1932 the mountain beech (Notho- on previously fixed steep scree slopes the area fagus solandri var. cliffortioides) forest was already immediately adjacent was found to still have traces a shell on the slopes of the north-eastern plateau, of the fern on it. It may be safely assumed in this which was the area of the densest deer population.

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