BACK TO THE ROCKS.

Forest and Bird, Issue 22, 1 October 1930, Page 2

BACK TO THE ROCKS.

(By Captain E. V. Sanderson.)

In an instructive lecture delivered by Mr. B. C. Aston, President of the New Zealand Institute, at the annual meeting of the Wellington Horticultural Society, it was demonstrated how our forests developed upon the rock and pumice formation which at some remote period constituted the surface of this country. Initially moss-like growths, raoulia and such like obtained a footing depositing a modicum of humus as they lived and died. Thus were conditions prepared which were suitable for something of a sturdier growth such as tutu, wineberry, and other humus forming shrubs, while these in their turn prepared the soil for pohutukawas, manuka, tawhero, etc., and they in their turn deposited humus and eventually the forest was formed as we found it when our pioneers landed.

There is, however, a further aspect of the position when we come to consider how much of this humus-forming forest has been needlessly destroyed on the highlands which cannot continue to support pastoral industry beyond one or two generations, and add to this the ever-increasing destruction of the forests on our backbone ranges by plant-eating animals. Immediately these forests are sufficiently damaged or destroyed, surface erosion of the top soil sets in, and be it remembered that this top soil is rarely of any appreciable depth. Following upon this, the subsoil, loose stones and debris come down choking rivers and causing devastation and floods in our lowland agricultural lands.. So the process goes on, if unchecked, eventually assumingsuch proportions that checking is beyond human power. Then, indeed, erosion has assumed the mastery. Rocks begin to show up on the mountain and hill tops, then later on the lower spurs,, and eventually in the gullies, all the time spreading the debris over our once fertile lands lower down. Thus, in a country like New Zealand, where by far the larger proportion of our land is hill and mountain country, we are working back to the original rocks and at the same time forming other lands under the sea. All this is, however, nothing new. Plato warned us about 400 b.c., when writing of Attica which forms the eastern part of Greece, a country which has long since passed the heyday of its prosperity and where a once noble race ekes out a meagre existence. Apparently, however, the effect of forest depletion still goes unheeded in New Zealand. The following is the translation of Plato’s words by Arnold J. Toynbee:—Contemporary Attica may accurately be described as a mere relic of the original

country, as 1 shall proceed to explain. In configuration Attica consists entirely of a long peninsula protruding from the mass of the continent into the sea and the surrounding marine basin is known to shelve steeply round the whole coastline. In consequence of the successive violent deluges which have occurred within the past 9,000 years, there has been a constant movement of soil away from the high altitudes; and owing to the shelving relief of the coast this soil, instead of laying down alluvium, as it does elsewhere, to any appreciable extent, has been perpetually deposited in the deep sea round the periphery of the country or, in other words, lost; so that Attica has undergone the process observable in small islands and what remains of her substance is like the skeleton of a body emaciated by disease as compared with her original relief. All the rich, soft soil has moulted away, leaving a country of skin and bones. At the period, however, with which we are dealing, when Attica was still intact, what are now her mountains were lofty soil-clad hills; her socalled shingle plains of the present day were full of rich soil ; and her mountains were heavily afforested —a fact of which there are still visible traces.

There are mountains in Attica which can now keep nothing but bees, but which were clothed not so very long ago with fine trees producing timber suitable for roofing the largest buildings; and roofs hewn from this timber are still in existence. There were also many lofty cultivated trees, while the country produced boundless pasture for cattle. The annual supply of lain fall was not lost as it is at present through being allowed to flow over the denuded surface into the sea, but was received by the country, in all its abundance, into her bosom, where she stored it in her impervious potter’s earth and so was able to discharge the drainage of the heights into the hollows in the form of springs and rivers with an abundant volume and a wide territorial distribution. The springs that survive to the present day on the sites of extinct water supplies are evidence for the correctness of my present hypothesis.