THE PROBLEMS OF NATURE CONSERVATION IN MADAGASCAR P. GRIVEAUD & R. ALBIGNAC* With an area of about 600,000 km2, Madagascar is one of the largest islands in the world. But this island is also a galaxy of very diverse environments, of micro-biotopes which are quite different from each other. Not only is the Great Island endowed in general with a unique flora and fauna derived from the fact of its long isolation, but this-flora and fauna vary greatly in the different parts of the island. /’ -- . -_ One need only pass through Madagascar quick ,ly to appreciate the ~ considerable difference between the rain forest of the East and the euphorbia bush country of the South-West, between the xerophyte forest and the palm savannahs, between the remarkable ‘Tsingas’ of the North- West and the mangrove swamps. In the East there are beaches of Poly- nesian aspect, the massif of the Isalo which resembles alruin, and areas with canyons like those in America. The traveller in Madagascar cannot fail to be struck by this variety. The fauna itself is very special. With its many species of lemurs, its carnivora, some of which, such as Cr_vptoproctafeyox, are the last survivors of ancient species which have quite disappeared from the rest of the world, its Centetidae, its couas and Vangidae, its curious Arclzaea spiders, and all its unusual insects, this fauna forms an inexhaustible scientific treasure. Unfortunately, numerous species are threatened with extinction. Some have disappeared already in our own day, such as the hippopotami, the great tortoises, the Aebyonzis and the Mullerornis, the giant running birds, and also some large species of Lemuridae. Those that remain are threatened a little more each day. THE ACTIVITY OF MAN Of all the phenomena capable of disturbing the balance of Nature, man is indisputably the principal force with which Nature has to contend. In Madagascar, as in other places, the impact of man in past ages has corresponded with the beginning of these disturbances of the natural balance. The first inhabitants of the island had nothing like all the means which mankind has today of upsetting what Nature has created, and * Entomologist and Zoologist at the O.R.S.T.O.M. 727 a Fig. 1. ‘Tavy’ in a forest. anyway they were few in number. The changes which they brought about in the original natural state of the Great Island were nevertheless quite substantial. It is indeed almost certain that we can attribute to these first inhabitants the huge fires which, at a remote period, must have swept through a large part of the forests, which scientists assume originally 1 covered the Great Island almost entirely. The chain reactions inevitably followed. The disappearance of large areas of forest led to climatic changes, particularly in the amount of rainfall, in the districts affected. ‘The botanical environment changed. The soil eroded, being inadequately held in check by the scanty vegetation. The fauna itself was badly affected. The animals found themselves cut off in a number of different environments, where the species continued to evolve more or less in isolation, giving rise to particular forms or sub-species. Finally, to this 728 historical period, going back between 500 and 5,000 years, may be dated the disappearance of all the mammals and large running birds which are completely extinct today. But as regards the latter, one may also presume that man hastened their extinction by indulging in excessive hunting. THE PHENOMENA OF EROSION It was at this time that various changes took place, which have sub- sequently only got worse. The notorious ‘lavaka’ erosions which we see today, veritable gnawing cankers which carry off the thin layer of arable soil and the earth itself towards the rivers and the sea, are of quite ancient origin. The ‘tavy’ agricultural methods, and the ruts made by the movements of herds of cattle are only aggravating this situation bit by bit. The ever-increasing growth in the population will only make the phenomena of erosion worse, unless appropriate measures are taken to stabilise the soil. The two most urgent measures are the suppression of ‘tavy’ methods and re-afforestation. THE FORESTS OF MADAGASCAR The primitive Madagascan forest formed and, where it still exists, still forms the only natural wooded environment where the animal species peculiar to the Great Island can live and evolve. For obvious reasons, as it was necessary to act quickly, we were unfortunately unable to re- plant the forests with native species, whose growth would have been far too slow. Trees of imported species were used, such as conifers, eucalyptus, mimosas, etc. These species, however, are most unsuitable for the native animals of-Madagascar. Anybody, no matter how ignorant he may be of these matters, who walks through the eucalyptus or pine forests, will notice that they are almost lifeless and contain hardly any animals. If we want to preserve what is left of the remarkable fauna of Mada- gascar, we must above all conserve its natural habitat as much as possible by stopping the disturbance of the biological balance. THE UNINHABITED REGIONS There is one point, however, on which it is difficult to interfere. This is the progressive and inexorable reduction of the uninhabited regions in the face of the population growth. This phenomenon has already reached alarming proportions in other parts of the world, and is now ,beginning to make itself felt in Madagascar. Only a few dozen years ago, there was no need to go more than a few kilometers from a town in order to find 729 large numbers of birds. Continually driven away from their native marshes which have been converted one by one into rice fields or fish-ponds, and disturbed by farmers, hunters and, alas, more and more poachers, they are being reduced every year. It is possible to foresee that within a few decades they will completely disappear within a radius of 100 to 200 km around large towns. In this instance also, the answer is not to try and replace these creatures with introduced species, when we do not know what results these intro- ductions will have, but to save what remains by setting aside here and there enough uninhabited areas for these species to be preserved. INTRODUCTIONS In practice it is almost always impossible to predict what upsets introduced species will cause to the evolution of the balance of nature. Nature, in her wisdom, has established this balance everywhere, and man tends to disturb it more and more. Plants and above all the majority of animal species need well defined areas for their reproduction, which are called ‘territories’. If man introduces foreign species into these territories, very often they gradually eliminate the original flora and fauna and take their place. We shall just quote a few simple specific examples: The introduction of mimosas, although it permitted a certain amount of re-afforestation of denuded ‘tanety’ areas, gradually became an in- vasion, and no room was left for any other forest species in places where they were introduced. The water hyacinth (Eichhornia crass$es), which originaIIy came from tropical America, has invaded a large number of lakes and rivers in Madagascar, thanks to its fantastic ability to reproduce itself by runners. Certain lakes, canals and rivers have gradually been totally blocked. In the animal kingdom, some introductions have had very doubtful, if not disastrous results. Among the fishes, for example, the Tilapia has the merit oftcombatting to some extent the invasion of certain aquatic plants, and at the same time of providing tasty food, but bit by bit it is upsetting every aquatic environ- ment. Being herbivorous it eats the plants, but if it gets into the rice fields ’ it can cause serious damage, and gradually it changes lakes and ponds into bare sheets of water. As a chain reaction, many animals and insects disappear, as they can no longer find the shelter and the food they need. The lakes are abandoned by the ducks who no longer find on the banks the shelter necessary for nesting and protection of the species. The introduction of one bird, the Martin, Acridoteres tristis, on the East coast has been followed by the gradual disappearance of many other species, whose territory the Martin is invading more and more extensively 730 and to its own benefit. At Tamamave, for example, these foreign birds are practically the only ones to be seen. But other introduced animals have brought about much more dramatic results. Let us mention the case of a cochineal insect, which was unfortunately introduced into the South of Madagascar with the object of reducing the spread of cactus. In a very short time we have seen not the reduction, but the almost total disappearance of the cactus. Now in this desert region of the South, the fleshy parts of the cactus formed the essential basic food for cattle and numerous other animals, so now large sums must be spent in fighting against the cochineal and in replacing the old cacti with new selected, resistant and spineless varieties, which are not establishing them- selves easily. The certainly accidental introduction of the rat (Rattus rattus) must now be paid for dearly, since this species has gradually invaded the whole island, displacing the native species of rodents, which were much less prolific and had their natural enemies. Let us be content with these few examples, as the subject is unfortunately. too vast. THE ABUSE OF CHEMICAL MATERIALS We must now start on the last chapter of disturbances to the balance of nature. This deals with the consequences of the dissemination of the countless products of which our modern civilisation is ever more prolific.