SOIL EROSION

Gisborne Herald, Volume LXVI, Issue 19985, 10 July 1939, Page 13

SOIL EROSION

MAINTENANCE OF COVER FINDINGS OF COMMITTEE STATUTORY MEASURES FURTHER RESEARCH URGED Further researcli and statutory measures to handle the serious question. of soil erosion and .conservation problems is recommended by the special committee set up to inquire into measures for the prevention, of land erosion, in New Zealand. The problem facing the committee v:as that, of investigating the steps necessary to maintain a vegetable cover in New Zealand adequate to control soil, erosion. Soil erosion, as distinguished from normal erosion, was defined as that, accelerated erosion that has taken place owing to man's interference with, the primitive vegetative cover. Reviewing the whole body of evidence before it, the committee considered that the position was serious, for soil erosion, if uncontrolled, is a process that accelerates .rapidly. Permanent production must ultimately be based on a more stable vegetable cover, .combining in due proportion forest, shrub land' and grassland. Only so can the forces of erosion be adequately controlled and water supplies necessary for the closer development of the country be fully protected Alarmist Attitude Deprecated The committee, however, deprecated an alarmist attitude. As was inevitable in the development of a young country, mistakes have been made, but in few places is the damage wholly beyond repair.

The primitive and the present vegetative .cover were considered for New Zealand as a whole, and the country divided into units, acording to the major topographical features. These units were then discussed in detail.

The committee’s report makes the following general recommendation: —

“That statutory and administrative measures should be taken .at the earliest opportunity to inaugurate a programme to handle the serious soil erosion, soil conservation and land utilisation problems that now faces us. Tn such a programme the most effective factor will be the preservation and .establishment of a stable vegetative cover in which forest land, shrubland, and grassland have most important parts. Further, such a programme should include the active collaboration and co-operation of foresters, agrostologists, botanists, agriculturists, engineers, and soil technologists.’’ The following summary represents the main findings of the committee: — General Accelerated erosion is largely due to the instability of the vegetative cover of the land under man’s regime. The restoration and maintenance of a stable vegetation cover is mainly a problem of wise land use, especially as concerns forest and .grassland management. Forest The minimum forest and shrubland area required for erosion control in New Zealand is a properly distributed 20,000,000 acres. A large part of this can be timber producing. The natural distribution of forest is limited by climate. Native forests do not grow, nor should forestry be attempted, in areas with a rainfall less than 30in. per annum. .Attempts at commercial forestry on such areas have always failed in the past and occasioned great losses, as well as inducing widely spread tree diseases.

New Zealand already’ has the required minimum, acreage of forest and shrubland for erosion control, but the distribution is faulty and, as a whole, it is inadequately protected.

IT soil erosion is lo be controlled a proper distribution of protective forest must be secured and the forest

von—whether Slate or privately owned —maintained .as forest by statute. Proper and adequate finance is needed to effect this. Tussock Grassland The natural tussock grasslands have deteriorated over large areas and no longer function adequately in controlling erosion. The chief agents of deterioration are burning, overgrazing and rabbit infestation, and, at higher levels, red deer. * Remedial measures consist in controlling the agents of deterioration and re-establishing an effective grass cover and a balanced grazing in equilibrium with it. Sown Grassland On flat and easy country, which can be cultivated and sown down, erosion control presents few difficulties, but on much surface-sown hill land conditions have become far from stable. Over large areas, the carrying capacity has fallen; other areas hpve been invaded by second growth and abandoned. The immediate causes of deterioration of these hill grasslands have been the closely related factors of falling fertility, invasion of second growth and soil erosion; the basic reasons . are the difficulty of maintaining a non-arable pasture coupled with the low economic return therefrom.

The present situation has arisen because (a) farming lias been attempted on land unsuited to permanent pasture ib) the establishment and maintenance of many pastures has, in the light of present knowledge, been faulty. The. maintenance of hillside pastures has proved more costly than was originally anticipated.

If the situation is to be remedied (a) farming should be restricted to areas that can be permanently grass controlled (b) the management of land that can be converted to permanent grassland should be improved. This calls for the consideration of such questions as the greater use of cattle, closer subdivision, spelling of pastures, top-dressing and resowing. Grassland Economies Conditions of land tenure and the economics of the aspects of farm management affecting erosion control are subjects of prime importance and should be specially •investigated. Knowledge of these matters is imperfect. The problem of erosion control is largely connected with the development of marginal lands and it is doubtful whether these can be developed efficiently by private enterprise alone. Cultivated Land There is some evidence of erosion on sloping cultivated land and appro-

priate known methods of control should be further practised. Sub-Alpine Vegetation In the sub-alpine belt the only practicable way of improving the plant cover is to protect it as far as possible from grazing and browsing animals, and from fires. Sand Dune Vegetation Methods of controlling sand drifts are well known and are being successfully practised in. many areas. Insufficient attention is being paid to apparently minor breaks in established pasture. Flood Control Reafforestation and grassland management both play important parts in flood control. Personnel of Committee The committee was set up by the Hon. D. G. Sullivan, Minister in charge of the Department of Scientific and Industrial Research, to inquire into and report on measures necessary .for the preservation of vegetation in New Zealand, with special reference to the incidence, control and prevention of land erosion. In addition to representatives of the Departments of Agriculture, Forestry and Scientific and Industrial Research, the committee included Prof. C. A. Cotton, of Victoria University College, an expert physiographer, and Prof. E. R. Hudson, principal of Canterbury Agricultural College.