Soil Erosion

Dominion, Volume 37, Issue 283, 26 August 1944, Page 6

Soil Erosion

Sir. —With regard to the urgent matter of preserving every remaining acre of bush-cover on steep country in wet zones, for example, the Tararua Range and its foothills, there arises the Question of planting and reafforestation. Ihe newlyconstituted catchment boards should, and no doubt will, attend, in an early stage of their activities, to this aspect of their programme. Doubtless, also, they will promote engineering and protective works to check destructive processes already in operation, but this, though necessary, is merely “maintaining an ambulance at the bottom of the precipice.” The main ob- • iective will, or should be. to arrest the man-made cycle of accelerated erosion by rectifying as far as possible one of the primary causes. No comprehensive scheme can be put into operation by the catchment boards till a land-utilization survey has been carried out. The need for such a survey is vital aud should be put in hand without further delay. The' classification of lands for soil conservation purposes would probably be fourfold: (1) Steep country situated within a wet climatic zone., to be refforested in native growth by fencing it off and allowing natural regeneration of the vegetation to take place plus judicious planting of suitable native species belonging to the particular locality: (-). easier country withiu a similar zone or high rainfall or having a sunless aspect, to be planted with suitable timber trees with a view to a carefully controlled system of timber-cutting and replanting: (o> st->ep or rough areas of limited extent (deep gullies, etc.) situated within tracts of land classified as suitable for grazing or farming. These areas would require to be fenced off and planted or allowed to revert to scrub and ultimately bush, and lastly (4) the genuine grazing and farm lands—land that has by reason of its moderate slope and contour, sunfacing aspect, and/or its degree of ter* tility, a fair chance of economic production from grazing and tillage. In class (3) the use of permanent fencing material, i.e.. concrete, would in the long view be the cheaiiest.. Such wor.» would require to be subsidized, but the protection afforded to the adjacent flat lands would be such as to. fully justify a levy on the. general public funds, it may here be pointed out that the use of concrete posts and strainers on hill country is by no means impracticable. At Paekakariki. for example, concrete framing posts, measuring 12tn. by 1-in. o.v Bft. in length, have been taken up by tractor and sledge to hilltops rising lo H feet above sea level, aud the hills in thnt locality are exceedingly steep, (but they enjoy a reasonably dry climate hence their suitability for farming), lhe above size of strainers, is. however, unnecessarily large: a tin. by < in. post, if well reinforced, will take any ordinary strain; this size is Just one-third of the cubic contents of the other. . To return from this digression to the original point raised: the writer contends that till a land-utilization survey is carried out and acted upon, nnd a ban is placed on all further destruction of the natural bush-cover on steep, wet country, the work of the catchment boards can only be of a piecemeal ami makeshift nature. Prevention is better than attempted cure, and in a battle with the natural processes prevention may well be the more effective course to vursue. —I am, etc., G. L. ADKIN. Levin, Augus* 22.