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Reforestation in arid zones with especial reference to Eucalypts

by A. METRO, Director, Forest Research Station, Rabat, Morocco

These remarks are directed to serious students who realize that, in order to raise the standard of living of a great many people, it is an urgent necessity to undertake the collective reforestation of the subtropical zones of the globe.

There are other important tasks, naturally, but there are few in the general program and particularly within the sphere of FAO activities, that are so acutely urgent or cover such a vast field.

This is apparent to anyone who has flown over the vast expanses of countryside, from Spain to India, which have been ruined by deforestation and centuries of human mismanagement, from the days of Solomon to the world wars of our century. Everyone who has known this territory is in agreement, from Leon, the 16th century Spanish geographer to Chateaubriand in the 19th century and Wendell Wilkie in our own time. Slowly and inexorably man carries out the tragic threat uttered by Jeremiah to Mount Lebanon: "I will make thee a wilderness... and I will prepare destroyers against thee, every one with his weapons: and they shall cut down thy choice cedars, and cast them into the fire" (Jeremiah 22: 6,7).

Yet the ravages are even greater and more extensive than they appear to the statesman flying above these lands, or the historian objectively considering man's destiny.

The phytosociologist knows the depth and extent of the evil, having studied the composition of plan associations, their natural evolution and their development under various influences. He can prove how, species by species, every kind of wood growth down to the humblest shrubs has been systematically eradicated in the vicinity of certain rural centres. Thus degradation goes on, creating vast landscapes where the richly-coloured and luxuriant spring vegetation makes us forget for a short time the summers without shade, the torrential rains of autumn and the fireless winters.

The evil is apparent, too, to anyone who, at the beginning of winter, has seen bands of women and children pulling up roots, gathering thistles, or collecting cow-dung to dry and burn. There is the same very grave shortage of fuel, and of wood for other purposes, in the ramshackle shanty settlements on the outskirts of big modern African towns.

The sterility of the countryside is, indeed, the work of man, since small sacred groves may be found almost everywhere, "marabouts" in North Africa and small coppices surrounding Chinese temples and monasteries.

Elsewhere great forest stands probably owe their survival to the fact that life was insecure and unstable for many centuries and there were very few inhabitants living within narrow boundaries.

These fine forest stands, such as those of cedar and of certain varieties of oak in North Africa, meet all the requirements; they have reached a state of equilibrium with the surrounding area which they protect, and natural regeneration follows regularly on methodically conducted felling. In other words, intensive modern silviculture may be applied there.

Falling between these two extreme types, which unfortunately occupy areas very different in size,1 there are large expanses of intermediate forests which may give the scientific observer a false impression. Such stands, in fact, are usually no more than a collection of isolated trees without any proper forest floor, or associated vegetation, as is often the case in stands of thuya, cypress, juniper, etc. Such stands cannot prevent wind or water erosion nor can they regenerate themselves naturally in their present surroundings.

1 During the recent war there was a heavy drain on stands which formerly were very strictly preserved.

These ancient groves have been the witnesses - and the victims - of many vicissitudes, sharing the trials of the people who just manage to live at their expense. Although they may live for many more years, these trees are nevertheless in a state of retrogression, they are no longer a part of their living environment, they belong, in fact, to the past.

Various species of Eucalyptus, the author of this article considers, may provide many of the answers to afforestation of arid zones. How, well they caw do is seen in this fine grove of E. camaldulensis in a North African plantation.

There is still time to conserve and to regenerate some of these last remnants of the forests by giving them the necessary care and rest, but, unfortunately, existing conditions threaten them with a very different fate. Their condition is bound to deteriorate because, as the local population progress in various ways they need more timber and their requirements are multiplied as they increase in numbers. Therefore, the trials facing the forest increase by geometric progression.

The necessity for finding food and employment induces more and more native workmen to clear and cultivate any so-called waste land; and such activity meets no opposition. Now, cultivated fields cannot be used for grazing, and soon, over vast tracts of land in many regions, pasturage will be possible only in wooded areas. Flocks will accumulate in these, and only such moral barriers as regulations and advice can be used against this policy of necessity.

It would also be a great mistake to attempt to define the extent of this problem using only the classical concept of "rate of forestation." Rate of forestation figures worked out for very extensive regions give a false average and make it impossible to ascertain which portions are very densely forested and which insufficiently or not at all. Also, by including those forests which either have been over-exploited or are heavily mortgaged in apparently accurate calculations, the gravity of the situation is obscured. The problem must be tackled from several angles, with particular reference to the dynamic evolution of the stands. There is a vast tract of land, broad enough to be called a zone, whose extent has not been even estimated, which forms an artificially dry and sterile belt around the world, passing through Spain, North Africa, the big Mediterranean islands, Libya, the Middle East, Iran, Pakistan, and China; the trees growing there supply neither the immediate nor the future vital needs of the local inhabitants (firewood, tannin, etc.) and there are too few of them to resist erosion caused by sun, wind, water, etc.

This report cannot enter upon either a more detailed discussion of general matters or their illustration by particular cases. Whether the problem is examined from the biological aspect, or whether it is considered comprehensively, as the economist or sociologist sees it, deforestation is proceeding at the same pace as material progress. Should it be allowed to become an accepted fact and should we resign ourselves to considering deforestation as a symbol of the blind progress of the civilized world or as an historic aspect of the frittering away of our resources?

Must we be content with applying short-term remedies? Is it sufficient to check the process by conserving existing forests? With our concepts of human solidarity and our desire for effective action, should we not, instead, tackle the problem of reforestation positively and seriously?


It is important to specify clearly that the problem in question is not merely that of providing sufficient quantities of wood, bark, or wood products, to that half of the world which has been deprived of such necessities by the carelessness of their forebears. Some experts2 have shown that there still are enough forests on the surface of the globe to provide an almost inexhaustible supply, both for trading and for world fuel supply, of such commodities as boxwood, lumber, paper, and foodstuffs, etc.

2 Notably Egon GLESINGER in "The Coming Age of Wood".

It would still be necessary to stop the unchecked rate of waste now taking place and to arrange for rational management both from the industrial and the forestry standpoint, with particular emphasis on natural regeneration and on the prevention of soil lateritization in tropical countries. It could be claimed that on a global scale the area under timber would still be sufficient from an economic standpoint.

But the economic standpoint alone is insufficient. The problem of rational land use and land capability classification exists in all the deforested zones. of countries forming part of the "sterile belt". Many writers have pointed out that in the formulation of their program for certain Mediterranean countries, agronomists and economists should bear in mind the concept of ail equilibrium between forest, bush, and pasture areas.3

3 KUHNHOLTZ LORDAT: "La Silva, le saltus, et l'ager de Garrigue".

A discussion of this very important, subject would be useful, but even where are concerned only with land suited to forestry purposes, such a phrase is understood differently according as to whether it is used by botanists or by foresters. A clear definition of its use here must, therefore, be made.

When the soil over a greater or lesser period of time is untouched by man, then, in most parts of the world and especially in those of interest to us, brushwood growth springs up and is followed later by a number of forest types, finally working up to what is known as the forest climax.

Perhaps the word "forest" itself derives from this phenomenon since the Latin foris (outside) originally designated those lands beyond the living area and the cultivated fields.

But this forest climax is not always reached. Certain soils, either because of the altitude or latitude or because of their chemical composition, never lead to this forest climax, but give rise to prairies, steppes, or deserts. Such soils are not suited to forestry purposes while others are.

The forester working not only on behalf of trees but also by means of trees for the good of mankind uses an even stricter definition: of those areas which are biologically suitable for forest and were cleared for cultivation a very long time ago, some as in temperate Europe, can be used for agriculture or pasture indefinitely. These lands are definitely suited to pasture or agricultural use.

There are, however, other soils which, in a stable world economy, are more suitable for forestry on a medium or long-term basis than for other forms of use such as arable land, pasture, etc., which would eventually ruin the soil by erosion.

Such areas are definitely forest land and should be designated for development as woods or forests.

When forest returns are calculated, not only must cash profits be taken into account, but also those indirect and intangible benefits such as soil protection, both of forest land and of adjoining areas, climatic factors (windbreaks), etc. This land use value is thus a matter of topography, of soil type, of climate, and in many cases of economic and historical factors.

A part of one of the big areas of replanting in Morocco, using acacias (dark zones) and eucalypts (lighter areas).

The lower photograph shows another Moroccan site, the degraded forest of Mamora, with patches of oak, insufficient to form a forest, now inter-planted with Eucalyptus camaldulensis. In the foreground the effects erosion are already visible.

The two photographs in this page give some idea of what can be done in North Africa with modern methods of afforestation.

Thus, certain soils which have become so degraded on account of misuse that they are now suitable only for forests or mining. Forestation, in this case, may be the last remaining alternative.

For this reason the reforestation of each country must not be considered as an isolated technical problem, but as part of an overall forest policy integrated in general planning and taking into consideration many factors which we will not discuss here.

There are, however, some difficulties common to all reforestation problems.

Difficulties arising from the physical environment

First of all, within the geographic limits established earlier, the forester must carry out his task under extremely arduous physical conditions.

Most of the countries under consideration have a Mediterranean climate with long, sunny summers, dry and hot, with temperatures often rising to 45°C, in the shade and with no rainfall from the beginning of June until October. Nevertheless, the winters are also often rather severe.

'This type of climate is not only difficult in itself, but is also extremely changeable; the mean temperatures and rainfall vary from year to year. There is often a considerable annual rainfall, but it occurs in the form of heavy downpours occurring on a few days only in which most of the water is lost by runoff. The amount of useful rainfall is very uncertain.

All these extremes are aggravated by the deterioration of those regions to be reforested; the "mesoclimate" is not softened by any vegetative cover or there are hot, dry winds. The deterioration limit has been reached and, beyond it, tree growing, even of native species, becomes almost impossible.

Difficulties arising from the Human Element

It is obvious that most of the destruction has been wrought by people pressed by their material needs. They have often reduced their inheritance to such a level that immediate considerations take precedence over any future plans.' Many of the countries in the Middle East, moreover, are inhabited by people of nomadic origin to whom the whole concept of forestry as a means of using the land is completely foreign.

' In certain parts of Morocco the State is undertaking the reforestation of collectively-owned land; this will contribute considerably to the fortune of the tribes owning the land. Nevertheless, these tribes expect to receive an annual indemnity until such time as the increased is completely theirs.

Difficulties inherent in all very large land-use problems

In order to cope effectively with problems of rural economy and land use in these areas, the work must be undertaken on a vast scale. Not only are the present needs in wood of the inhabitants very great, but they will increase rapidly and the areas suitable for forestry are almost always extremely big it will be quite useless to expect any direct benefits from reforestation of such areas, if this is not carried out extensively. Reforestation is only effective against wind and water erosion when it covers considerable areas. Again, planting of commercial forests cannot be justified unless the yield is sufficient to meet the indispensable requirements of average factories, such as those for the processing of cellulose.5 This has been well understood and demonstrated by certain big Spanish and Portuguese companies.

5 In this connection it should be pointed out that establishing a wood-processing plant for producing pulp or viscose is not possible unless a production of at least 20,000 metric tons annually is contemplated. Such a production corresponds approximately to a wooded area of from 6,000 to 10,000 hectares. It may be calculated that the industrial reforestation unit is about 10,000 hectares and that this area corresponds to an investment of roughly $2.85 million.

Under the conditions we have outlined, reforestation is expensive; climatic deficiency must be overcome by a careful use of the land, either by digging trenches along contour lines on the slopes or, on flat territory, bay deep plowing.

The implementation of a complete reforestation scheme, therefore, involves problems of financing, which in most cases can only be solved by the State. Under present conditions capital is indispensable; the paper industry has made little investment in recent years in forest production or reforestation in Western Europe, and the present impoverishment is due to this fact. We mention in passing that modern administration of national forest funds aims at uniting private capital and public money in a fluid partnership.

One thing is sure, however: neither the State nor private capital will undertake reforestation seriously unless they are assured quick and substantial profits.

Choice of species

For this type of reforestation, the forester must use species fulfilling the following essential requirements:

(1) adaptation to physical environment (species resistant to summer drought)

(2) adaptation to the human element (species throwing out new shoots freely and resistant to fires)

(3) financial returns

Botanists and foresters alike agree that the best results for soil protection and for bringing the land back into use as forest will be obtained in most cases by making use of species which are already part of the aboriginal vegetation.

Unfortunately, in so far as Mediterranean vegetation is concerned, most species grow fairly slowly and in all cases yield is small and returns slow, the only exceptions being certain varieties of pine and cedar which cannot be used unless there is an adequate rainfall. The choice, therefore, inevitably falls on exotic species.

From a general standpoint, European foresters have a great tradition in the science of acclimatization, starting as early as the 16th century and continuing with ups and downs until the present time. They know that exotic species must be tried out methodicaly in arboreta and that the choice of species should not be limited to over-strict geographic or ecological concepts. Nature cannot be dealt with by Cartesian philosophy; an overscientific concept of the problem should occasionally be corrected by the use of imagination and courage, always bearing in mind the great adaptability of many species.

Further exploration essential

In order to supply arboreta in deforested subtropical countries, and particularly in order to increase their very small number, teams of ecologists, foresters and plant experts should go prospecting under the guidance of local botanists. Those richly wooded tropical and sub-tropical areas of Australia, southern California, Mexico, the foothills of the Himalaya, etc. would provide them with a wide choice. The exchange of seeds of forests species should be increased, and a cordial relationship be established more and more on the international level between research stations, collectors, and the seed trade. Personal contacts, both in the -field and in laboratories, should improve the relationship between these groups. Work is already being done in this direction. The way has been shown. It only needs to be followed more quickly.

It is with this thought in mid that FAO has organized a study tour to take place in September, 1952, when a group of foresters from many nations will be taken across the Australian continent. The object is that they be shown:

(1) the variety of habitats existing on this continent and the many uses, to which local species may be adapted, mainly the very numerous varieties of Eucalyptus;

(2) how the Australians, applying the findings of research conducted by their great scientific and industrial organization, the C.S.I.R.O., have been able to make full and varied use of their only apparent resource;

(3) how a great modern country is practically living in a eucalyptus age, using this wood for their houses, their bridges, mines, telegraph poles, paper both for newsprint and writing, cardboard, plywood, etc.

Already the program in this field is well under way; it started under the auspices of Ferdinand von Müller, around 1860. Many varieties of eucalyptus were introduced in a great number of countries (Brazil, Belgian Congo, Cameroons, Ceylon, Chile, Ecuador, France and North Africa, India, Israel, Italy, Jamaica, Kenya, Nigeria, Paraguay, Peru, Puerto Rico, Portugal, South Africa, Spain, Turkey, Uganda and the United States).

Some observations concerning the progress made in this world experiment may be useful, although the Mediterranean section is the only one really familiar to the author:

First of all it appears that several species of eucalyptus are suitable for reforestation in those sub-tropical countries already mentioned on account of their exceptional qualities and their ability to thrive under difficult conditions.

Several of these (for instance: E. camaldulensis, globulus, cladocalyx, gomphocephala, sideroxylon) are extremely adaptable and appear able to acclimatize themselves in surroundings very different from their own natural habitat, which is rather restricted.6

6 With the possible exception of E. camaldulensis.

The above species are fairly hardy, they are easy to grow, and in most sub-tropical countries they quickly reach a size sufficient to eliminate the danger of damage from grazing animals; this ensures a very heavy yield. Vegetative cover does not grow well in their shade, and this is a factor preventing brush fires. They throw out new shoots easily and can stand the effects of fires, which are the most permanent source of trouble for reforestation projects. The above qualities prove how well these species are adaptable to what may be called the human element.

A great popular movement is taking place in Morocco near those large reforestation tracts which were started during the last 20 years, either by private owners or by the State, on government or collectively-owned land belonging to the tribes; this movement is known as callito by the Moroccan agricultural laborers. Young seedlings are distributed, and sometimes even stolen from the nurseries, and are set out individually around a group of houses or a village. This movement has only just started, but it does not appear over-optimistic to hope that a collective forest conscience will eventually develop, stimulated by the interest now centered on each tree individually.

Creating an Interest in Trees

Let each forester examine his conscience properly Is there one who, as he acquires a deeper knowledge of his profession, is not more and more conscious every day of the complexity of forest biology problems? Can these problems be understood intellectually by those groups whose outlook is limited to problems of work and daily bread? Can they even be understood by those groups having a higher degree of culture? The personal opinion of this author is that it will be possible to persuade entire races to respect and love their natural forest heritage fairly quickly and easily, and that this can be brought about by having them take part in the planting of trees yielding both reasonably swift returns and obvious material advantages. From the teaching standpoint one must begin with the idea of the single tree and proceed to that of forest.

Psychologically this sequence seems even more important.

Limitations of Eucalypts

The tremendous advantages that may be derived from the use of a small number of eucalyptus species and the fine results in forestry that are attributable to them must not blind us, however, to the fact that they cannot meet every requirement. On the one hand, although eucalypts may be used over a large area, nevertheless their use has ecological limits; these species cannot stand either extreme cold in winter or great droughts in summer; on the other, the eucalypts do not meet certain technological requirements.7

7 Another drawback to the use of eucalyptus species, for instance, is the small amount of humus they provide. This is a debatable point, but in any case the matter may be remedied by planting acacia understoreys in eucalyptus stands.

It is well known that wood produced by the same species in different localities hardly ever has the same qualities and differs according as to whether it is grown in Australia, its natural habitat, or in South Africa. When growth is very rapid, the effort which takes place within the cells appears to have an adverse effect on the wood produced.

Have other species of eucalyptus, included among those introduced into various countries during the past 75 years, better qualities, perhaps, or greater suitability from the technological and ecological standpoints?

May there not also be varieties or natural hybrids among these species cultivated in plantations and which may be able to give good results financially when they have been studied technologically and ecologically? It is from this double standpoint that international collaboration becomes a necessity. All the extremely interesting studies carried out in Australia on eucalypts, mainly by the forest services and by the C.S.I.R.O., should be brought to the knowledge of all reforestation specialists, but it is equally urgent that the degree to which they can acclimatize themselves to various regions of the world be carefully worked out.

The time appears ripe to supplement the observations made in Australia by a summing up of world-wide experiments which have been conducted for nearly a century and which so far have been insufficiently considered.

Very weighty studies have been published in South Africa, South America, New Zealand and the United States, and in various Mediterranean countries. Probably there are others, and it is because the author deprecates such involuntary omissions that it is his personal desire to have a comprehensive and exhaustive study of the problem made.

In this article M. Metro has remarked how in parts of Morocco, the "fellahs" are beginning on their own to plant trees, notably eucalypts, round their dwelling and thus showing the success in creating an interest in forestry where none previously existed.

Such a plantation is that seen above, the owner standing proudly in front of the trees which now surround his homestead.


To sum up, it is certain that many regions in the greater part of the sub-tropical zone are suited to forest. They should be set aside for reforestation both for economic and social reasons.

The work to be undertaken is both urgent and of vast scope. It is difficult from the human and from the technical standpoint. Foresters have a certain number of eucalyptus species with which to solve the problem. These are fairly simple to put in production and they meet the essential requirements; they may be made use of immediately. No theoretical, sentimental or aesthetic considerations should be allowed to stand in the way of all those who feel responsible towards other members of human society.

Not merely the simplest solution should be considered, however. All parts of the world must be surveyed methodically and useful species chosen. But, in any ease, better use should be made of the genus Eucalyptus, whose worth has been proved by experience over the past hundred years.

In this way, a collective solution, both in time and in space, will have been found to satisfy the main principle of productivity, that when the laborer's work is done, he should be certain of having accomplished a useful task.

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