Contenu du sommaire : Menaces sur la flore et la faune dans les pays tropicaux.

A Sad Tale for Happy People. The author has chosen Mauritius as an example for his story. The island embraces all the possible forms of actions by man upon an ecosystem. It is also a perfect example of how its landscapes have been altered by him, often defaced in a cruel manner.

Diversity and Uniformity ; Remarks on the Development of Farmed Tropical Flora. The farmed floras of tropical regions have developed and continue to develop in a direction that often leads to a degradation of their quantity. The manner and reasons for this development are considered here, as well as some of the effects resulting from such an evolution. Also discussed are some possible measures that can be taken to arrest the erosion of biological diversity of tropical cultigens.

Threats to Flora. The intertropical world of vegetation has endured and continues to endure destruction and/or significant transformation both as regards its ecosystems as well as its components. The sharp demographic growth everywhere in the world has accelerated these new transformations of space by favoring the appearance of various menaces : fire, farming after land has been cleared and burned, savannah fires, animal introductions, introductions of various plant species, and anthropic actions.

Struggle Against Desertification ; the Benefits of Defensive Measures. The desert, like a chancre, gnaws the surface of the earth. If drought in the Sahel has occurred during two crucial periods, there is no doubt but that over-grazing is the main cause of the reduction in the vegetation cover. To fight against the extension of deserts, no miracle remedy exists. The simplest forms of defensive measures show that vegetation recovers quickly. The different stages of this regeneration are analyzed by the author who has studied an area of 600 hectares in the National Wildlife Research Center of Saoudi Arabia. There, in the space of three years, the number of flowering species that were counted has doubled. Bare stretches regress, woody plants lose their ball-shapped forms and thrust their leafy boughs in all directions. Perennial graminaceae multiply their grain clusters. Local annual plants proliferate abundantly and eliminate the non-consumed growths. Once protected, the possibilities of the regeneration of desert plants elicit astonishment.

Extinction and Preservation of Insect Species. Among terrestrial arthropoda, preservation problems are posed in a special manner for several interdependant reasons : high diversity, a biological and taxonomic lack of knowledge, the growth and demographic dynamics. This results in «incalculable» losses that affect preferentially species that have restricted ecological living areas and that are heavily dependant upon the mesological context.

The Amphibians of Tropical Regions : Factors of Decline and Extinction. Amphibians are excellent indicators of the «state of health» of the ecosystems in which they live. They are currently in sharp regression throughout the world, mainly because of the disappearance or alteration (notably by draining or because of pollution) of wet zones and on account of landclearing, followed by a replacement of the forest with farm crops. This last development is particularly important in all the tropical regions of the world.

Risks and Perils for Birds from Europe Wintering in Tropical Africa. The decline in the number of many species of migratory birds that nest in Europe is explained by the play of unfavorable factors that are of human origin and that affect their wintering areas in Tropical Africa. The factors that seem most to harm the various species are the alteration and disappearance of habitats because of desertification and hydraulic facilities in the Sahel-Soudanese zone, as well as the use of pesticides affecting, in particular, the consumers of large insects.

Threats to Birds in the Afro-Tropical Zone. The main risks to the disappearance or to the decrease of birds in the Afro-Tropical zone (mainland and islands) are presented with the aid of several examples showing the effects of the destruction of habitats, of pollution, of capture, of changes in their environment and of man introducing various species foreign to the areas.

Causes of Disappearance of Tropical Terrestrial Mammals. Beginning with a typology of the main threats to which wild mammals are exposed, the author outlines the dimensions of the gravest crisis this group has known in the past sixty-five million years. In general, the mammals are menaced because of one among them, a proliferating and very active semi-predatory animal, man. Tropical mammals are subject to three sorts of pressure : direct attacks, contractions of their natural environments, and destructive side-effects due to ecological imbalance.

Introductions of Animal Species ; When Preservation Serves as. a Screen for Business Enterprises Engaged in «Moving Fauna». After some reflections of a general nature on the problems posed by the hasty introductions of exotic animal species, the author proceeds with the examination of a project proposed by a French business firm concerning the implantation, in the heart of Guinean (pre-forest) savannahs, of three thousand five hundred ungulates originating from Southern Africa. The history of this project and of its abandonment, due to the opposition it raised among the technicians of the involved country, is retraced with the object of avoiding the repetition of such mercantile attempts, especially in tropical countries where budget resources, all too often limited, have to be used parsimoniously in order to protect natural environments.

Preservation Areas in French Western Africa : To-day and to morrow protected or divided areas ? Only a better understanding and a better consideration of the role played by fauna and protected areas will enable governments and managers of National Parks in Africa to protect correctly nature, their natural ressources and their environment.

Reproduction in captivity and reintroduction ; a passage phase necessary for threatened species. The author explains how certain zoological parks have become protectors of threatened species. When a species attains a sufficient population level in captivity, its reintroduction can be considered. The case of the Oryx of Arabia, reintroduced into its natural environment, where it originated, is a good example of such recuperation.

Extinction and Conservation of Species in the Tropics : What Future for Molluscs ? Of some 100 000 species of Molluscs, three-quarters live in the sea, and the remaining quarter on land. Marine species are often distributed over vast areas extending for millions of square kilometers. Collection of specimen shells concerns over 10 000 club-member collectors worldwide and the marine curio trade is fed by several thousand metric tons of live-taken shells per year. However, despite obvious local depletions, no marine mollusc has yet become extinct. By contrast, non-marine species have much smaller distribution areas, often in the order of a few hundred or a few thousand square kilometers, and are thus far more vulnerable to extinction. Their present conservation status is far worse than that of marine species, and dozens of non-marine species have already become extinct this century. The highest toll is being exacted on island faunas. Considering that there are thousands of threatened species and that we remain ignorant of their biology, only the preservation of habitats and ecosystems is likely to save this part of our biological heritage. Small protected areas, covering a few tens or hundreds of hectares, although too small to maintain viable vertebrate populations, would probably suffice to preserve most threatened invertebrate species.

Threat and Conservation of Coral Reef Species. The coral reef ecosystem is a major feature of intertropical coastal areas spreading over more than 100 countries. It is one of this most diverse and productive marine ecosystem. Human threats to coral reefs are studied. No species can be considered as being endangered, i.e. in the process of disappearance. However, degradation of some habitats and overfishing of some species constitute a threat for some stocks. Recommendations are suggested.

Current Problems Regarding the Conservation of Cetacean Species, Particularly in Intertropical Zones. It is possible to be relatively optimistic regarding the future of large cetaceans, which now benefit from complete protection. On the other hand, schools of pelagic dolphins are currently menaced because of present commercial fishing methods (purse-senne, driftnets) that result, in certain regions, in a large number of accidental captures. In addition, the changes brought about in river and coastal environments, as well as increased pollution, threaten of extinction several species of small cetaceans. The conservation of all species in the future the preservation of the overall environment.

The Commercial Over-Exploitation of Wild Fauna and its Regulation by the Washington convention (or CITES). The International Convention for the Trade of Endangered Species of Flora and Fauna (CITES), the workings of which is explained, has been ratified to date by 105 nations. Its efficiency varies according to the species concerned, the channels followed and especially the consumer countries. The concrete examples of rhinoceros horn, spotted feline hides and ivory illustrate one failure and two successful results of this Convention.

S.O.S. Genoms ! Know, Manage and Preserve Genetic Heritage. The authors discuss the objectives, methods, limits and interest of projects concerned with the protection of wild species and domesticated races, or with their genetic patrimony. The conclusions derived show that the state of present techniques and the cost of their implementation require, first, that the problems be considered on a case by case basis, and, secondly, that the objectives of preservation and their feasibility in relation to very clearly defined human interests be scrupulously delineated. Contrary to opinions only too widespread, the preservation or the restoration by natural methods of animal populations in the process of disappearance by working, at the beginning, with small numbers, does not ineluctably lead to systematic failure, the different species being able to react in a very heterogeneous manner to the long-term reduction of an initial variable polymorphism.