THE INFLUENCE OF FORESTS ON CLIMATE.

Daily Telegraph (Napier), Issue 3610, 6 February 1883, Page 4

THE INFLUENCE OF FORESTS ON CLIMATE.

Dr. Sehomburgk, the director of the Botanical Gardens at Adelaide, has added to his recently issued report an appendix on the .subject of the influence of forests usually lias the effect of reducing the rainfall, while, on the contrary, the planting of trees broadcast over the country is one of the best methods -which can be adopted for ameliorating its climate and increasing the annual fall of rain. It cannot, indeed, be proved that the climate of South Australia is altering for the worse in this respect. In fact, a comparison of the meteorological records will show that the annual average rainfall for the colony during the past ten years had been 21 "lin., as compared with Snin. for the previous ten years. The fact is thot in the agricultural districts of the colony, and especially in those which were not originally timbered, the bringing of the land into cultivation lias had the effect of .slightly favoring the fall of rain. Ploughed land attracts moisture to a much greater degree than the unbroken soil. In considering the effects which the removal of forests per w has in altering the climate in South Australia the only direct test that could betaken from the records issued by Iho Government astronomer is the experience of the neighborhood of Adelaide. If the time is divided -which has elapsed since 18U9, the year in which observations were commenced, into two periods, there is found for the first an average rainfall of 22-Sin., and for the second one of 21.7 in. It will thus be seen thai, on the whole, the rainfall at Adelaide is diminishing, though vvvy slightly, and perhaps the diminution in the amount of timber may have something to do with the change. Dr. Sehomburgk, in searching for illustrations of the effect of trees on climate, goes further afield, and brings forward some .striking instances, in which it is evident that loss of "forests means loss of rainfall, and rice cvrsn. He recalls how the Russians, by burning down some of thcTranscaucasian forests at the time of their struggle with the Circassians, converted the country from n fertile land into a desert, simply through the cutting off of a supply of rain. Similar instances of rain having deserted a country denuded of forests have occurred in the Mauritius, in Jamaica, the Azores, and, it may be added, to a still more remarkable extent in several of the smaller West India Islands. No sooner had the forests of those places been destroyed than the springs and rivulets ceased to iiow, the rainfall became irregular, and even the deposition of dew wafTalmost entirely checked. On the other hand, it is generally accepted as a fact that Mehemet Ali increased the fertility of Egypt enormously by planting trees. lie alone planted some '20,000,000 on the Delta, his successor followed up the work, and it is a noteworthly circumstance that the rainfall rose from din. to 40in. Planting lias, also, it would seem, produced remarkable effects in Trance and Algiers. Extensive regions have been planted with gums and other trees, winch, for the most part, grew to about :j(lft. or 40ft. in height, and it is noticed that the quantities of rain and dew that now fall on the adjacent land are