TOP-SOIL DEPLETION.

Forest and Bird, Issue 29, 1 April 1933, Page 2

TOP-SOIL DEPLETION.

(By Capt. E. V. Sanderson.)

Some pages in human history reflect no credit upon mankind. First in importance is that page which describes man’s treatment of the soil. Man was placed in a garden. He has transformed vast areas of it into desert. He has destroyed the cover on thousands of acres; he has laid waste wide stretches of pleasant country; he has made human life all but impossible in many places. The world is full of examples. Mediterranean nations now eke out a bare existence where once they maintained a flourishing civilisation. China periodically suffers from famine brought about by man’s own destructive hand, says Mr. Arthur M. Hyde, Secretary of Agriculture, in “American Forests.” In New Zealand, where we have an extremely mountainous and hilly formation, the evils following deforestation are very pronounced even in the comparatively few years which have elapsed since the forest was destroyed. European authorities assert that it takes 400 years on an average for a forest to build one inch of top-soil, while agricultural and pastoral pursuits destroy an inch in from 10 to 50 years, according to the steepness of the country and the intensity of the destruction of tree and shrub growth. In New Zealand the loss of top-soil through over-grazing of steep country is probably much more than 1 inch in 10 years. When it is remembered that it is the top-soil which supplies us with our food and clothing per medium of the growing of wool, butter, meat, etc., such facts should make us pause and think. If the forest is removed from steep country, it is not only that area which is affected, but the water rushing, down the forest-denuded slopes carries all manner of debris into the streams and rivers, filling their beds, causing them to spread over adjoining fertile lower lands, while the richest and finest material is that which reaches the sea, as is plainly shown by the discolouration during floods. Well might we learn from the experiences of older civilised lands such as in America, where it is estimated that 21,000,000 acres—an area exceeding the total area of arable land in Japan has gone entirely out of use owing to destructive erosion. China, however, can always provide the best instances of the results of erosion owing to deforestation, due it is said to the old-time belief that to plant trees would disturb the spirits of the soil. \ In China some of the large rivers have in the course of hundreds of years brought down such gigantic amounts of

debris from the deforested inland country -that the industrious Chinaman has had to continue raising his protecting stop-banks until now some rivers run at a higher level than the surrounding arable lands. Every now and again, however, the river confinement fails to hold the sudden rush of the mighty waters; the river breaks down its banks, flooding hundreds of square miles and carrying Chinamen, huts, bamboo fences and everything movable down towards the sea. There are, however, plenty of Chinamen, and directly the floods subside the drowned ones are replaced by others, who for the time till the rich silt robbed by the waters f 1 om the inland hills and deposited l by the flood, calmly awaiting their turn to follow their predecessors down to the sea when next the flood breaks loose. Japan, on the other hand, has learned her lesson and for thousands of years has so well managed her agricultural and forest lands that erosion has almost been mastered, despite a dense population of 80,000,000. Are we doing likewise in New Zealand? Readers are invited to look round and see the denuding of the soil on hill and mountain slopes, and remember that Nature decrees that the fittest shall survive. Our forest service, of course, know all about these matters, but so far have failed to give sufficient attention to this the higher side of forestry; rather has their work been confined to the timber side of forestry alone, and well might the mere exploiting of our indigenous forest be considered the only thing possible when the position is so absurd that they have not even got control of the forests assigned to them so far as the inhabitants beneficial or otherwise are concerned, and we hear of purely sporting bodies talking about State forests as “our deer forests.” Could forest absurdity reach greater heights? Let us again remember Nature decrees in all things that the fittest shall survive be it nation, bird, fish, insect or plant. Such places as the Sahara Desert were once considered to be raised sea bottoms, but modern thought now believes the Sahara to be the original home of Homo sapiens (intelligent Man), a perhaps over-flattering term—otherwise the Garden of Eden—but Homo sapiens learned to use or rather mis-use fire and sharp-edged tools, with the result that he destroyed the forest and left behind what we now see. Shall we here in New Zealand follow in the usual footsteps of the Anglo-Saxon Homo sapiens, or be wise in time and learn to sacredly conserve the remnant of our irreplaceable indigenous forests, and thereby avoid the superhuman task of substituting them with vastly inferior exotic forests, so far as water conservation is concerned, and at a cost which New Zealand could not in the remotest degree afford or even contemplate.