VANISHING SOIL

New Zealand Herald, Volume LXXV, Issue 23111, 9 August 1938, Page 7

VANISHING SOIL

MENACE OF EKOSION LESSONS FROM ARCHAEOLOGY THE FATE OF EARLY CITIES PROBLEM FACING DOMINION [by telegraph —own correspondent] GISBORNE, Monday "It must not be supposed that largo cities which have been uncovered by archaeologists in North Africa and the Bible lands were built upon a desert. At their prime they woro centres of fertilo areas. Several of the earliest civilisations were simply swallowed tip beneath the sands which they themselves invited," said Mr. 0. G. Thornton, district engineer of tho Publio Works Department, addressing Gisborne Rotarians to-day on the subject of "Our Vanishing Soil." Mr. Thornton pointed to the lessons of archaeology and of more recent historical periods concerning the fate of nations which allowed the fertility of the soil to waste and vanish. On tho basis of these examples and also of evidence which every river in the district has been providing for some months, he sounded a warning of what must eventually befall civilisation of today unless conservation of the soil is practised on a scale far beyond anything yet attempted in this generation. Recent Happenings After reviewing the results of topsoil denudation, Mr. Thornton stated that he would try to give his audience an idea of what had been happening in their own district within recent months. "The greater part of the more productive lands consists of soil formations which are peculiarly liable to erode, especially after droughts," he said. "There has been much compara- -1 . tively recent alteration in the levels of the land, which makes it very ready to move. Some compensation is to-be found, however, in the fact that on fairly wide areas underlying rocks quickly break down and form fresh soil to replace the loss. "Measurements taken at various bridges over the Waipaoa River show that between Kaitaratahi and the sea the river channel contains a great deal more silt and shingle than it did 40 years ago, and during that time the capacity of the channel has decreased by one-third. In various river branches above Whatatutu, bridges and 'roads have had to bo raised or abandoned. River flats in Waiapu, on which a large j Maori population in that area so greatly I depends, have been destroyed to a very ' appreciable extent. Enormous ravines j have developed from what were only j tiny watercourses 20 or 30 years ago. " Effects of the Rain I "Nearer Gisborne in the past month or so three enormous landslides have dammed rivers to a considerable depth and caused much uneasiness until it could be ascertained that the dam wag cutting down gradually," continued the speaker. "Actual computations from an j aerial map of the catchment areas of the Kopuawhara and Maraetaha Streams show that 1250 acres o:f soil slipped away in five or six hours of heavy rain. After almost every light rain every one of the numerous streams iin the district tells the same* sorry tale of dirty water, which means vanishing wealth, or the finer particles . and fertile organic constituents of tho soil being washed out to sea % ■ "Erosion from farm lands is wreaking havoc on highways and subsidiary - roads over the greater part of the district, and it is nofc in the least difficult to visualise many of the valley roads disappearing in, the river beds and even main highways in many places becoming submerged in a few years under the increasing tide of rubble and silt. The Fight That Lies Ahead "Nothing is more certain than that every farmer on hill land in the Poverty Bay and east coast districts needs to do all in his power to check even the most moderate signs of erosion whenever they occur," said Mr. Thornton. "Erosion always takes away capital assets and taken a very scanty population of 10 people to the square mile, including towns, only some 50 years or even less to break down so much of the balance which Nature has developed over thousands of years. ' "The men on the land are insufficient in number to repair tho damage which i the axe, fire and grazing of stock for J i export have caused, but they still have . ' ■ the same indomitable spirit which sub- \ . dued the wilderness in . bygone years, ; and we may trust that it will carry : ; them through the fight to hold their ' soil, the fight which surely lies ahead."