CAPTAIN CAMPBELL-WALKER'S LECTURE.

New Zealand Times, Volume XXXII, Issue 4988, 19 March 1877, Page 2

CAPTAIN CAMPBELL-WALKER'S LECTURE.

On Saturday evening Captain CampbellWalker, F.R.G.S., delivered a lecture in con- , nection with the New Zealand Institute at the Colonial Museum. There was a large attendance. His-Excellency the Governoivtook the chair, and briefly introduced-the lecturer. Captain Campbell-Wai-kee, said: Your Excellency, Ladies; and Gentlemen,—?tne subject of the papers I am about to read this* evening is entitled "The Climatic and cial Aspect of Forest Conservancy as apjihv cable to New Zealand. In the paper which I recently read at Dunedin on the subject of forestry, and more particularly State forestry,, in general I referred very briefly to the I; two points on which! have the honor"to address you to-night. They represent, however, the most important aspect in which the whole forest question may be viewed or, approached, and may be-said to embrace, directly or indirectly, . the whole subject. Were it not for climatic considerations, which we believe may be injuriously affected by the lack of a systematic and persistent system of foreßMon.. servancy, to the detriment of the health, .an* welfare of. the whole community, forestrymight well be left to private enterprise, and the spasmodic efforts of private individuals or local bodies, liable as they must always be to the influences and considerations of the moment, and the popular feeling not of the nation or general public, but of a comparatively small section, of. it, representing local feeling andinterests. Were it not for financial considerations which must ever be more or less paramount in the conduct of our affairs, _scheraes for the conservation, creation, and improvement of forests would meet with much less opposition and be much more generally adopted than.they are. ■ My object in addressing you to-night ia therefore twofold, and I shall endeavor to show—first, that the climatic influence of forests is a very important matter, which cannot be approached : too early or with too much care and deliberation in the life of a nation or colony; and second, that financial considerations may not only be made compatible with, but form a great inducement to, real forest conservancy, especially if it be commenced and. ally adhered to on a broad but ever careful system before the forests have been seriously injured or encumbered with a mass of individual or communal rights and privileges ; and further, that such financial considerations arc not antagonistic to the development of the timber trade and industry, or to the general wel-

fare and prosperity of the people. The subject of the influence of forests on rainfall, climate, and water supply of a country has of late years attracted much attention, and beeu freely discußsed not only in scientific but general circles. So far as the actual rainfall of a particular locality is concerned, the evidence and arguments adduced have beeu very conflicting, and I am bound to record my opinion, as stated in Dunedin, that so far nothing has been proved to establish the theory, that extensive denudation will, of itself, cause a marked decrease in the rainfall. Forest-clad mountains will doubtkss tend to induce rain-clouds to precipitate the moisture with which they are charged, but so will mountains without forests. No one would, I imagine, argue against the generally recognised fact that the rainfall in mountainous forest regions is as a rule greater than it is in an open plain exposed to similar atmospheric conditions ; but the question is, will the mere removal of the forest from the mountains of itself affeet the rainfall on them and in their immediate vicinity, and may not the presence of the trees be the effect of a considerable rainfall, and not its cause 1 I confess that I feel no sort of certainty one way or the other, and in this respect I do not think I am having with me, to my knowledge, Dr. Brundis, the Inspector-General of Forests in India, no mean authority, and doubtless many others whose minds are not made up on the subject. Recent observations in France, however, made with great care and complete seta of instruments, at different stations, do appear undoubtedly te establish the facts, (1) that throughout the year 6 per cent, more rain falls in the forests than in the open ; (2) that of the total rainfall 10 per cent is caught by the leaves in a forest, and does not reach the earth ; and (3) that the evaporation in the open country is five times as great as in a forest. So far as this colony is concerned, the evidence if .anything tends to prove that the rainfall has increased at stations in the neighborhood of which the forests have been extensively cleared. I have quite recently been going through the meteorological returns for the past ten years, and find that whereas the mean annual rainfall of Welling. -" IJtan as recorded for the first five years is 48709 and the number of days on wt>ich rain fell 153 ; that for the last five years of the decade is 57 - 862 inches, and the number of days 177! At Taranaki again, in the immemediate neighborhood of which I imagine the clearing has been extensive, the mean from 1863 to 1870 was 55-331 inches, and from 1870 to 1875 62-612 inches. Christchurch and Hokitika, with the lowest and highest rainfall in the colony, remain much the same during each of the periods of five years—the mean for the former being 113 days with 27-033 inches during the first, and 125 days with 25821 inches during the second five years ; whilst at the latter place the means are 197 days with 112'622 inches, and 178 day's with 115'418 inches respectively. We must, however, be careful how we accept these returns as conclusive evidence either way. The period over which they range is too.short to afford reliable data, besides which Br. Hector will, I imagine, agree that the returns are likely to be more reliable and accurate du< >g the last than the preceding five years. I would here point out that, so far as my observation goes, there is scarcely any point on which the popular or general opinion is more frequently erroneous and liable to mislead 1 than that of the rainfall of successive years or periods of years. lam pretty sure that most of the inhabitants of Wellington would give it as their opinion, in perfect good faith, that the rainfall had decreased of late years; whilst I was over and over again assured at Hokitika that, although rain might fall more frequently, the annual average there was not in' excess of that in other parts of the colony, th 6 real facts being as stated above. From all I 'have said you will gather that I think it better not to attempt to dogmatise on this point; and, with your permission, we will relegate it to a future occasion, when we may know more about it. The question of the influence of forests on climate and permanent water supply is, to my mind, in a widely different position, and nothing I think has been more clearly proved, both by scientific argument or theory and actual observations or practice, than that the wholesale and Indiacriminate clearing of forests exercises'an injurious effect on both, whilst the formation of plantations in dry and arid regions ameliorates tie climate and renders the water supply more cbpions and permanent. If we consider first tie question of climate we Bhall find a host of evidence tending to prove that the general destruction of forests has rendered it more trying, less, equable, and devoid of sufficient moisture ; in short, has caused it to deteriorate both with respect to its effects upon the health of man and other animals, and upon the fertility and productiveness of the soil, whilst the regeneration of forests, or the formation of plantations, improves it Let us first endeavor to understand clearly what is meant by the word "climate." A recent writer says : "The single word climate expresses one of the most important relations of man to the natural world aronttd him, a relation which concerns human existence in its every part. But taisi word climate, taken in its largest sense, comprehends within itself all those elements of matter and force the mutual influences and actions of which produce the phenomena so familiar to us under the single expression."

Dr. Dnnbeney, in hia lectures on the influence of;climate on vegetation, defines "the climate of a country to be its relations to temperature,

lifht, moisture, winds, atmospheric pressure, and .electricity." We all know the popular arid everyday meaning of the words good and bad climate, and what an important matter it ia' considered. Equally important, therefore, is all that influences it, amongßt which ranks the presence or absence of a certain proportion of forest area. Marsh, in his well-known work on " Man and Nature," published in London in 186*, says :—"One important conclusion at least upon the meteorological influence of foreßts is certain and undisputed, the proposition,'viz., that within their own limits and. near their own borders they maintain, .a.; more, uniform degree of humidity in, the atmosphere than is observed in cleared grounds." And, again, writing of the indiscriminate clearing in America : —"With, the disappearance of the forest all is changed. At one season the earth parts with its warmth by radiation to an open sky, and receives at another heat from the unobstructed rays of the sun ; hence the climate becomes excessive, 1 and the soil is alternately parched by the fervor of summer and seared by the rigors of winter. Bleak winds sweep unresisted over its surface, drift away the snow that sheltered it from the frost, and dry up its scanty moisture." Innumerable quotations could be given and irrefutable evidence adduced from the works of Hooper, Schleiden, Becquerel, Humboldt, and Boussingault, all tending in the same direction. The Rev. W. B. Clarke, F.R.S., &c, recently read a paper before the Koyal Society of New South Wales on the subject of the " Effects of Forest Vegetation on Climate," with the general tone and direction of. which I cordially concur, though unable to agree with him in all his deductions and conclusions. He quotes largely* from Schleiden and Marsh, and gives an extract from an essay by the late Sir Henry Holland, in the " Edinburgh Review," viz.,— "It is the forest which actively ministers to the climatic condition of the earth, which, extirpated by.the axe or restored by planting, changes both the face of nature and the distribution and destinies of human life." The case of some parts of Africa and Asia Minor, the Mauritius, St. Helena, Ascension, Madeira, ft'c.i have all been given by various writers, and quite lately Dr. Croumbie Brown, formerly Government Botanist at the Cape, has done excellent service by publishing a series of works on the subject entitled " The Hydrology of South Africa," " Kebrissement in France," " Forests and Moisture, or Effects of Forests on Humidity of Climate," the last of which I have not seen. Professor Laurent, of the Forest School at Nancy, has also written on the subject, and "instances Fontenoy and Provence as places where the felling of forests has uiftoted the climate." So much for the influence of forests on climate generally. We next corne to that of their effect on the water supply and its regulation. Most of the authorities already quoted have written also on this point, but I prefer quoting from other sources

of more recent dates. The paper by Monsieur Clane, from which I quoted in my Dunedin lecture, is a clear and exhaustive treatise on the subject. He refers to actual observation made by MM. Becquerel and Boussingault, and to those of M. Mathieu, of the Forest School at Nancy, and M. Fantral, of a more recent date. He states that the results M. Mathieu has obtained are singularly uniform, and they have been reproduced bo often that even so careful and conscient'onß an observer as M. Mathieu considers that they may be held to be dependant on a general law of nature. His observations lead to the conclusion that while on the' one hand forests tend to lower the general temperature of a country, andso to promote the fall of rain at_ regular interval, and in moderate quantities ; on the other hand they ward off sudden meteorological changes, which are dangerous inasmuch as they cause sudden and heavy falls of rain, which result in floods and other like disasters. M. Fantral's results corroborate those of M. Mathieu and M. Cantegiel, Inspector of Forests, near Toulouse, in the extreme South of France, has also carried out a similar series of observations, extending over a number of stations, with precisely similar results. Boussingault's example of the Lake of Valentia, in Venezuela, has been often questioned. This lake has noknown outlet, and when Humboldt visited it the water was decreasing' in a marked degree, the forests in the neighborhood being at the same time, largely cleared. Twenty-five years later Boussingault found its dimensions increasing, which he ascribes to the war of independence having occasioned a cessation of clearing, so that less timber was being cut down and a new growth springing up. He infers that this is the true explanation from the fact that other lakes in the neighborhood, around which the forests had been left in their natural state, had shown no such fluctuations. The lakes of Neufchatel and Geneva have also been mentioned by Humboldt and Jaussure as instances of the same result. The case of the island of Ascension seems very conclusive, as it appears matter beyond doubt that the only spring in the island was dried up when the trees were removed, and commenced to run again when the forests were restored. St. Helena is also quoted as an instance in point, as are Mauritius and St. Vincent, the district of So'ith America lying between the Orinoco and the Andes, and many other localities I have myself observed the drying up of springs and decrease of the average amount of water in some of our mountain forests in India in which extensive clearing has taken place, and think there can be no reasonable doubt that such clearing does affect injuriously the supply of water for springs and permanent supply in the streams and "rivers. Hof Rath Wex, in a paper contributed to the Vienna Geographical Society in 1875, actual states that the decrease of water in the Elbe and Oder has been 17 inches ; Rhine, 24 ; Vistula, 26 ; and | Danube, at Orsova, 55 inches in 50 years. Not less conclusive in my opinion is the evidence at our disposal regarding what M. Clane calls the mechanical action of forests through the roots in retaining in its place the earth, especially on the sides of mountains and hills. It is impossible to treat this part of our subject without reference to the preceding one, the argument being that forests by their presence act as storehouses of moisture, both from their leafy canopy which covers the earth and the bed of dead leaves on its surface, the loss ot moisture by evaporation being by these means reduced to one-fifth, as stated above: and that further, the bed of dead leaves acts like a sponge, soaking up and retaining the rain and regulating its distribution, whilst the i oota not only " act as vertical drains, promoting the descent of the water into the lower strata of the earth, there to nourish the springs," but bind the soil on the mountain sides together, and prevent its being carried away into the valley below. In short, it may be said that the forests exercise both a preventative and curative effect—first, preventing the rapid running off of heavy rain, and storing it up for gradual distribution; and second, impeding the flow of water in its course if already accumulated and coming down from bare or snowcovered heights above.' The disastrous effects caused by over-clearingof forests, in the shape of torrents and inundations, have been felt in many ! countries ; but I think it will suffice if we instance France, where the subject has attracted more attention and at last been more thoroughly grappled with than anywhere else. The case of France may also be considered as peculiarly applicable, and affords a valuable lesson to this country, for it was in the fancied best interests of the owners of sheep and cattle that the forests on the Alps and Pyrenees were gradually destroyed, to make way for more grass and more sheep ; indeed, it is only quite recently that the representatives of these interests in the communes affected have really awoke to the fact that their interests and lives were at stake, and appear anxious to cooperate with the forest officers in re-clothing the hills. Dr. Croumbie Brown, in his book on " Rebrissement in France,". already men-, tioned, gives a detailed account of the causes which led to the clearance of the forests in the Higher and Lower Alps, the Loire, and the Pyrenees, the results in the shape of torrents, landslips, inundations, &c, and the remedial measures now in progress, which are calculated to extend over 140 years and cost at least half a million sterling, besides the pay of the forest officers employed. Our time to-night does not admit of my following him even very cursorily; but I would strongly recommend a perusal of this and other works by the same author by all who take an interest in th« subject. (They nre published by King and Co., London.) The description which he gives, and which is unfortunately corroborated by far too many authorities to be doubted, of tbe devastations committed by the torrents, gradually augmenting year by year as each patch of forest and scrub was removed, ia truly appalling. The disappearance of the forests from the mountains gave up the soil to the action of the waters, ■ which swept it away' into the valleys, and then the torrents becoming more and more devastating buried extensive tracts under their deposits, tracts which will probably be for ever withdrawn from agriculture. The prediction of an inspector of forests, quoted by Surell in his "Etude sur. lea Torrents des Hautes Alpes," has already been literally fulfilled:—" The crunta denuded of their vegetable soil no longer permiting the' infiltration of the waters, these will flow away rapidly on the surface of the ground. Then the springs will dry up, and the drought in summer being no longer moderated by their irrigation all vegetation will be destroyed." These results and far more aerious ones in the shape of enormous ,loaa both of human life, that of cattle, sheep, and property, have all come to pass. The loss of property by the inundations in the south of France in 1875 was estimated by Government at £3,000,000 sterling, and it is. stated that 3000 persons loat their lives. The indirect results in the shape of temporary or permanent damage to agricultural ilintricts" by the deposit of atones and shingles brought from the mountains by the flood waters cannot be estimated, still less the damage to pastoral lands on the mountains themselves. It may be Btated generally that the results of excessive clearing i of forests and abuse of pasturage on the French Alpa and Pyrenees have reduced their capacity as a sheep and goat carrying area to suph an extent that they cannot carry the half of what they did fifty years ago; whilst the damage resulting to the agricultural districts below from the drying up of springs and streams, the torrents caused by heavy rain, and the melting of the snows and their effect on the river banks and channels, followed by long droughts in summer, is simply incalculable, and such as cannot be repaired, even at a large expenditure, within two generations. The French Government, after much delay and difficulty, the reHtilt of local prejudice and cupidity, have undertaken the task of "reboisernent" in reclothing of the mountains with forests, commencing with the most important points, viz,, the sources, head waters, and courses of streams and the gullies, extending up to the higher|ridges, where water, whether from the clouds G*r melting snow?, is first precipated and accumulates. The results appear, so far, to have been satisfactory; but it ia admitted that it will probably take a longer time and much more money than originally estimated to mitigate or prevent the recurrence of the disasters, which have been steadily increasing in magnitude during the past century, whilst the improvement of the

pasturage on the bills or undoing the damage already caused below is mere matter of conjecture. The measures proposed to be adopted at first included, in the interests of the shepherds, a large proportion of regazanement or returfing, as distinct from reboisernent or reforesting; but the late floods, especially those in the valley of the Garonne, appear to point conclusively to the comparative uselessness of the former as a remedial measure, and I believe instructions have been issued to substitute reboisernent, or at least lebuissonement (the planting of shrubs) wherever practicable. Such is a brief outline of the facts relating to forest denudation, its results, and the extensive measures of reboisernent which have been forced upon the State in the interests of the community in France. To quote the words of Surell, writing some years ago :—" The country is becoming depopulated day by day. Ruined in their cultivation of the ground, the inhabitants emigrate to a great distance from their desolated land, and contrary to the usual practice of mountaineers, many never return. There may be seen on all hands cabins deserted or in ruins, and already in some localities there are more fields than laborers. The precarious state of. those fields discourages the population left. They abandon the plough, and invest all their resources in flocks. But these flocks expedite the ruin of the country, which would' be destroyed by them alone. Every year their number diminishes in consequence of want of pasture grounds. One commune, St. Etienne, which supported .25,000 sheep fifteen years ago, supports no more than 11,000 now. Thus the inhabitants, .who sacrificeall their soil for the flocks, will not even leave this last inheritance to their descendants." The work of reboisment must not be mistaken or mixed ud with that of the planting of Pinus maritima on the low and sandy coasts at the mouth of the river Gironde, with the main object of fixing the shifting sands. In the Australasian of February 10 there is a letter from Mr. Hunter, M.8.F.C.5., on the subject of the influence of forests on the climate and.water supply of Victoria, and in the same paper is an editorial headed " Forest and Lake." Both Mr. Hunter and the editor warmly advocate increased conservancy and improvement of the forests, which it is admitted on all hands have been allowed to deteriorate and be destroyed in a most Bhameful manner, with the worst effects on the climate and water Bupply. Without going so far as Mr. Hunter, and estimating the annual increase in yield of wheat at eight bushels, which at sa. per bushel would represent two million a year more of wealth without any extra expenditure,—minute calculations which unsupported by facts I consider are likely to damage rather than improve an otherwise good case, —I cordially agree with the editor, who sums up the argument by stating that " it is however possible for each colony to conserve local advantages which it owes to nature, and in this category we place not only forests, but water of every size and form." " Let the Government not attempt to shirk its duty by handing over to local bodies the manauagement of forests, but let it grapple with the whole question in a statesmanlike manner, and earn, even though it may not immediately win it, the gratitude and respect of the people whose interests have been entrusted to its care." Our time to-night will have been Bpent to little advantage if you do not feel that this colony is eminently one possessing great " local advantages which it owes to nature," in the shape of forests and supply of water. These advantages it is our duty, aswell as our interest, to preserve ; and I think New Zealand ia lucky in possessing statesmen like her late Premier, Sir Julius Vcgel, who have looked ahead and seen the necessity of grappling with the difficulty in time, that is before the damage haa actually been done, and when the necessary. measures can be applied, as I hope to show you to-night, by a very small temporary outlay, securing not only immunity from the damage and destruction which have taken place elsewhere, but a considerable and steadily increasing forest revenue to the State. (To be continued.)