SOIL EROSION NO MERE CATCHWORD

Rotorua Morning Post, Issue 5282, 19 December 1946, Page 3

SOIL EROSION NO MERE CATCHWORD

DANGER TO DOMINION EPFORT MUST BE MADE TO CONSERVE LANDS. \ The extent of the authority conferred up'on the Soil Conservation and Rivers Control Council, an'd deleigated by it to district catehment boards, has been the subjeet of some critical discussion among land-owners who, believe in the general principle of conservation but who take a dim view° of the duties whieh the operation of conservation mig'ht place upon them individually. This point of view on the vast programme of soil-erosion control thronghout the Dominion was dealt with by Mr. J. R. Hair, chairnian of the Poverty Bay Catehment Board, addressing the Gisborne Rotary Club. Having briefly reviewed the powers vested in catehment boards, which include many which may affect future farming practice in the district and are designed to enforce co-operation for the public good where it is not forthcoming on a voluntary basis, Mr. Hair commented that many people were still asking v/hy such powers should be necessary. "The answer is to be found in what has occurred in the past and what is occurring* at present in foreign countries and in New Zealand itself," he continued. "Recent research has disclosed that the eourse of history ha& been influenced to a surprising degree by erosion of the soil, and the failure or improvement of the agricultural : and pastoral resources of nations. ! "It is being- argued that these fundamental t'hings were the causes of the fall of nations, and that battles lost and cities destroyed were merely the results. It is certain, anyway, that ruined cities of North Africa and the Middle East, now iburied 'by windblown sand and surrounded by arid desert, were once# the prospevous centres of green and fertile farm lands, irrigated by canals which can still be faintly traced on aerial photographs. U.S. Fight to Save Soil. "At present the most prosperous civilisation of all time, that of the United States of America, is, paradoxically enough, threatened with disaster by soil erosion of truly alarming proportions. From the Pacific Coast to the Atlantic seabdrd soil is being lost, and in some areas in t'he central Ptates, -the countryside is already desert. "However, with characteristic realism and energy, Americans are tackling the immense problem on an immense scale. The Soil Conservation Sarvice, a Federal Goverament agency, covering- the whole country, has been created and local authorities such as the Tennessee Valley Authority, which is.akin to our own catehment boards, deal with the local problems with vigour and inspiring- results. "The comforting thougJnt, 'it can't happen here,' does not apply. Most emphatically it can and does happen here — right in Poverty Bay and on the East Coast. The results of quantitative surveys carried out by the Department of Scientific and Industrial Research are not yet available, but a brief consideration of the 'geology of this district will suffi.ee to show how prone our land is to erosion and to the destructive forces of running rvater in particular. "As you all know, our hill country consists of papa rock or mud-stone covered with more or less clay derived from these underlying foundations by the normal weathering processes. In very few places can the country withstand the cutting action of fast-fiowing water from our relatively abundant rainfall. The recent geological history is characterised 'by a series of uplift periods, as can Teadily 'be deduced from the remnants of raised beaches along the coast and river terraces inland. Nature's Delicate Balance Disturbed. "Prior to the arrival of Europeans, the rivers and streams were still busily engaged, except near the sea, in overtaking these uplifts by cutting- down, into the recently raised land, steepening the slopes of hillsides and generally performing the nonnal jobs rivers are meant to do. Geologically speaking this erosion was rapid, but as long as the natural bush and , serub cover was there the erosion was, by man's calendar, a leisurely business, much more igentle and gradual than one would suppose when looking at the steep slopes and razorback ridges. so characteristic of our hill country to-day. "Now the bush and scrub ;have almost all gone and the delicate balance of Nature is upset just enough to render the country infinitely more vulnerable to erosion than it had ever been." After reviewing- various forms of erosion, Mr. Hair said it would be appreciated that all erosion occurring* locally was caused by two agents, namely, water, the active one, and gravity, the passive one. Nothimg* could be done to control water from the moment the raindrop bit the ground to tlie moment it crossed the river bar to reach the open sea. "Assuming at the outset that we do not intend to clothe the whole countryside wtih forest, but intend rather to maintain the present acreage in pasture, it will be apparent that something can be done to control t'he water ■ by providing- a denser pasture cover for the rain to fall on," he continued. Slowing Rate of Erosion. "More rain will soak in and less will run off — the abundant grass will hold this moisture for its own purposes, usinig it frugally and not permitting it to he evaporated on the first windy or sunny day. The cover of sward will reduce evaporation and the capillary transfer of deep-seated (moisture, so that cracking of the country in time of drought will be minimised. The trickle of rainwater that is not absorbed will flow hesitating-ly among" the blades of grass, and never get the same chance to pick up speed and sconr the surface soil. * "In Poverty Bay and the East •Coast district the country is naturally

so vulnerable to the forces of erosion that good pasture alone will not restore the balance upset by falling tbe bush and slow down the rate of erosion to the leisurely tempo of bygone times. Trees must be planted as well — about as many trees as are, in any case, necessary for enhancing' the beauty of the countryside, providing timber, shelter and shade could, in association wtih good pastures, and in a generation or so, keep erosion within reasonable bounds. "All tres. break the impact of raindrops and channel them to their roots, the roots seek "'out ground moisture within a reasonable radius and the tree uses it for its own growth processes. It is surprising the extent to which trees will" dry out country that would otherwise be wet and subjeet to niovement. Moreover, the- xoots of many varieties are so widespread and tenacious that strengh is so.imparted' to the country about, while waterloving trees such as willows, send their roots into water channels lfning sides and bottom' wtih an erosion resistant mat. "The problems of river and stream control will increasingly be solved by tree-planting eitber as single trees, as components of water control str:**u> tures, or in spQcially contrived patterns to check and quieten t'he flow and to line sides and bottom with protective l-oots." '