Version classiqueVersion mobile
OpenEdition Books

Les espèces envahissantes dans l’archipel néo-calédonien

Marie-Laure Beauvais
Alain Coléno
Hervé Jourdan


Texte intégral

1Every year, an estimated 25,000 to 50,000 species go extinct on the Earth owing to changes caused by human activity. Many international organisations including the World Conservation Union (IUCN) consider biological invasions to be the second most important cause of biodiversity loss worldwide, coming just after habitat destruction. On small islands, where biodiversity is both exceptionally original and exceptionally vulnerable, it is the main cause of species extinction. The New Caledonian archipelago, which has a unique flora and fauna, is no exception. It is one of the ten “hotspots” of tropical biodiversity: the rate of endemism is 75-100% depending on the order or family of plants or animals and some species are found nowhere else on earth.

2In an economic context of increasing and increasingly free trade, New Caledonia is at risk of intentional or involuntary introduction of plant or animal species with the potential to become invasive. The risk has increased in recent years, as New Caledonia has become more dependent on imports, of food particularly. A proper assessment of this risk is important if the islands’ heritage and environment is to be protected. What makes the task especially complicated is that potentially invasive species do not have a particular biological profile allowing identification in advance. Such a large group of islands presents added difficulties: given the amount of trade between the islands, preventive control points cannot be limited to the international points of entry (Tontouta airport and the port of Nouméa).


3Worldwide, people have awoken late to the problems caused by invasive species? especially because, since the end of the last ice age, humans have never ceased to transport plant and animal species away from their natural range. Introducing new species was viewed as an effective way of improving the lot of human communities by bringing new sources of food to a fastgrowing population. Deliberate introduction of foreign species for utilitarian purposes is traditional? to such an extent that few European farmers, for example, know that they are growing Peruvian potatoes, Manchurian buckwheat, Mesoamerican maize and beans, Caucasian apples and Middle Eastern flax. Few farmers know that the ancestors of their turkeys came from Mesoamerica and those of their chickens from Indonesia.

4Introductions to strengthen a nation’s productive potential have always had their ardent defenders. From the 17th century on, the discovery of new continents including the Americas revealed the prodigious diversity of exotic flora especially tropical flora. Botanical gardens were created to acclimatise them to temperate latitudes. One of the first such gardens, the Jardins du Roy in France, was created in 1635 for the sole purpose of facilitating the introduction of exotic species; the success of these introductions, by Bernard de Jussieu (1699-1777) and other learned men, aroused much admiration. In 1793 the Jardins du Roy became the Museum national d’histoire naturelle, but the tradition continued. Around that time Geoffroy Saint-Hilaire (1778-1844), zoologist, created the menagerie in the Jardin des Plantes and the Société Impériale d’Acclimatation. The public’s taste for exotic plants and animals has never waned.

5Worry about the dangers of alien organisms emerged early on. The literature abounds in descriptions of examples of intentional or inadvertent introductions that led to epidemics in humans or animals; bubonic and pneumonic plague in the Middle Ages, epidemics of flu, cholera, smallpox and rabies, of mildew in plants, the spread of West Nile virus and SARS, etc. Governments have generally set up control systems to prevent such epidemics as far as possible, with biosurveillance, vaccination, eradication measures etc. These systems are mainly intended to deal with infectious agents and the reservoir or vector species that carry them; the corresponding risk is universally recognised by all and the measures, however restrictive they may be, are accepted unanimously.


6There is less unanimity when it comes to species regarded as “useful”: horticultural species, game animals, plants with agricultural potential, pets etc., which may be intentionally introduced (though sometimes for debatable reasons) and which then escape through negligence or thoughtlessness, their invasive potential unsuspected or deliberately ignored. Only twenty years ago, many scientists were fairly indifferent to the problem except in agronomy, even though the concept of an invasive species was first introduced in 1855, by Swiss botanist Alphonse de Candolles. But in those days, he was mainly addressing the question of a species extending its range and becoming cosmopolitan.

7Of course, not all species intentionally or inadvertently imported into a country establish themselves, even briefly, in the wild. Others may settle where they have been introduced and go no further. A species is only considered to be naturalised when it spreads naturally beyond the place where it has initially established. And the only naturalised species regarded as invasive are those that multiply in natural or manmade environments to the extent that they significantly alter the composition, structure or functioning of the ecosystem concerned. It is clear that the great majority of introductions do not survive. There is little discussion of this in the literature. Some species may remain unnoticed for years, then either disappear or develop into invasive species if changes in their environment give them a competitive advantage.

8In 1996 British biologist Mark Williamson established the so-called “tens rule”, based on numerous examples. According to him, of every 1,000 plant species introduced an average of 100 would establish successfully, ten would naturalise and one would become invasive. But however small the proportion of introduced species that actually become invasive, this does not belie the seriousness of the problem. Far from it, as Williamson’s example of the United Kingdom shows: of 12,000 species imported, 1600 established themselves successfully, 200 became naturalised and 39 proved invasive.

9The environmental and economic cost of these invasions can be very high (see pp. 189 and 199 sqq). Invasive species have spread and have affected virtually every type of ecosystem in the world. They have contributed to hundred of extinctions of other species, especially in island ecosystems. The risk of landscapes and ecosystems becoming uniform and homogeneous increases as human behaviour evolves. One example is the abolition of seasonal differences in the fruit and vegetables available on the market, with strawberries, cherries, melons and green beans available even in winter. This has meant introducing these domesticated species to countries at different latitudes and then transporting the produce across and between continents from their new site of production to the place of consumption. This process can facilitate the introduction of new crop pests. The risk is especially great with inter-continental trade in wild or ornamental plants in the form of seeds, propagules or whole plants.

10Economically, taking account of all business sectors affected by biological invasions? farming, fishery, shellfish farming, tourism, human health etc.? the costs engendered are enormous. For example, the invasion of beehives by the Varroa mite may cost New Zealand alone an estimated US$ 267 to 602 million. And according to recent work (published in 2000) by American researcher David Pimentel and his collaborators, who tried to aggregate the economic cost of all damage occasioned by foreign species in the United States, annual expenditure in that country amounts to US$ 137 billion.


11Because of their geographical isolation, small islands harbour many endemic plants and animals, often including species that are unique to that place. According to the World Environment Fund, an estimated 75% of bird and animal species that lived on such islands are now extinct, and between them the world’s small islands harbour one-sixth of endangered plant species. Thus their high rate of endemism gives island states their potential wealth, but also makes them vulnerable? to the effects of global warming (e.g. rising sea levels), natural disasters (bush fires, tropical cyclones, etc.), the impact of any mining and of course introduced species that may become invasive.

12The New Caledonian archipelago is one of the most temperate in the South Pacific. It has a sub-tropical climate affected by oceanic influences and the trade winds. With its temperate climate and many different water regimes, New Caledonia offers many suitable places for potentially invasive species to get established, be they from tropical regions, Mediterranean regions or places with an oceanic climate. The only living organisms that do not find favourable conditions here are those that need low temperatures at some point in their life cycle. However, the variations in rainfall between different parts of the archipelago may hinder the spread of some alien species, keeping them within one part of the archipelago.

13Another frequent factor in New Caledonia is tropical cyclones. In 25 years six cyclones have passed through southern part of the territory and eleven through the northern part. Given the distance from land areas large enough to be significant sources, and the westerly direction the cyclones move in, tropical cyclones cannot be a major means of transport for new organisms to reach the islands. They can however accelerate dissemination within the archipelago or to neighbouring islands, undermining the quarantine measures taken in some areas.

14Trade also favours the introduction of exotic species. In particular, food imports to the territory? fruit, vegetables, cereals, bovine livestock products? have increased significantly in recent years. Ornamental horticulture is also growing fast, with strong demand for imported exotic species. Many of these imported species are on the quarantine lists, as they are regarded as potential carriers of pests (see p. 167). Further, new points of entry to the territory are opening up with the development of mining and the accompanying increase in freight traffic, pollution, waste volume and flows of workers from abroad.

15Even a species that the public has come to regard as indigenous can cause considerable damage to ecosystems and biodiversity. One example is the rusa deer, which has become an integral part of New Caledonian culture although it was introduced less than 150 years ago. Twelve individuals were introduced in 1870. By 1990 there were 100,000 to 120,000 and their numbers are still increasing. The rusa deer has contributed significantly to the retreat of the primary forest formations on Grande-Terre, especially the dry forest, which now covers no more than 1% of the area it occupied before humans arrived (see the papers by J. Cl. Lefeuvre and M. Pascal et al.). Overbrowsing by the deer modifies the vegetation in places, suppressing the undergrowth in sclerophyll forest, for example. It also now threatens seven endemic dry forest species, all classed as endangered by the IUCN.

16As regards inadvertent introductions, the little fire ant is an emblematic example (see p. 189). This ant, Wasmannia auropunctata, is regarded as indigenous in a zone stretching from the Caribbean to Uganda, including almost all of tropical South America and Central America. In recent decades, as trade has spread it too has spread around the tropical belt. It was accidentally introduced into New Caledonia in the 1960s, spreading at first along with the Caribbean pine. It colonises farmland and urban areas as well as wilderness. Among other problems, its fierce bite makes it a major nuisance for mammals and humans, and it promotes pest damage to plants through a reciprocally beneficial relations with several homopterans and other planteating species. It also endangers biodiversity by reducing the number of arthropods in the areas it infests, changing the ecological balance.


17Worldwide, there are now a certain number of measures for protecting territories from invasive species, in particular quarantine measures, which have developed gradually as awareness of the problem of has increased. These systems appeared in the context of the plague epidemic that hit Europe in the late Middle Ages. The first examples, applied in the Adriatic ports in the late 14th century, obliged incoming ships to keep at a distance from the port for a period of forty days. This was considered sufficient time for any latent symptoms of the dread disease to be expressed. The duration was reduced as knowledge about infectious diseases increased. Although the objective link between the movement of humans and the development of epidemics had already been established in the 14th century and action taken on that basis, quarantine practices remained empirical until the late 19th century.

18In the late 19th century the Pasteurian view of epidemics took hold, including epidemics of plant and animal diseases. Increasingly frequent and rapid movements of people and goods made it clear that earlier observation about human diseases were equally valid for plants and animals. Repeated crop failures due to disease, particularly the collapse of European winegrowing when phylloxera became established, made it clear that new measures were needed. By the end of the 19th century, laws made quarantine mandatory for animals (Contagious Diseases (Animals) Act of 1869 in Great Britain, for example) followed in 1884 by a comparable Act in the USA. For plants, legal restrictions on trade were introduced in the late 19th century. The Berne Convention to counter grapevine phylloxera was drafted in 1881 and adopted in 1889, while in Great Britain and Ireland the Destructive Insects Act was passed in 1877 to prevent the introduction of the Colorado beetle, and in 1907 the Destructive Insects and Pests Act extended that cover to crop diseases.

19But not until the eve of the first World War did various European countries set up a complete import quarantine system. Thereafter nearly a century passed before a new dimension of the risk was taken into account? the notion of invasion by alien species and their impacts on the environment (see box). Nonetheless, there are still unanswered questions to which no existing law or other arrangement provides a solution. In particular, although invasive species that are potential pests for cultivated or wild plants are gradually being taken into account under the International Plant Protection Convention (IPPC), there are no arrangements for monitoring or regulating those that do not affect plants, or do so only very indirectly. Whence the difficulty of preventing or properly managing the risk (see p. 211). Similarly, there is currently no organised monitoring of invasive animal species not considered to be direct or indirect plant pests or vectors of diseases covered by the veterinary services.

Chronology of main protection measures
1911: France and other European countries introduce a complete import quarantine system.
1912: United States introduces similar provisions.
1929: The Rome Conference lays the groundwork for regulations that are later used for the International Plant Protection Convention (IPPC).
1951: IPPC adopted under the aegis of the FAO
1973 and again 1997: IPPC revised to bring it into compliance with GATT trade agreements. The second revision also lays down that the IPPC applies to the protection of cultivated and wild plants and includes protection against direct and indirect damage by pests, weeds included. The framework of the Convention thus extends to protecting the environment against threats to the life and health of plants and ecosystems from any pest. This new form of quarantine could be called ecological or environmental quarantine (compared to the earlier systems of sanitary and phytosanitary quarantine).
1992: adoption of the Convention on Biological Diversity (CBD), ratified by many countries but not by the United States. It addresses the question of invasive alien species and their impact on ecosystems, habitats and other species.
Since 1999: the FAO’s Interim Commission on Phytosanitary Measures (ICPM) has been working to clarify its role with regard to pests of plants.
2000: the Cartagena Protocol reintroduces the precautionary principle, but only as applied to the potential adverse effects of a living genetically modified organism.
2001: The Interim Commission on Phytosanitary Measures (ICPM 3) rules that invasive alien species that are pests of plants, are not yet present in a country, or are present but not widely distributed and officially controlled, may be considered quarantine pests and be subject to IPPC provisions.


20New Caledonia’s biosecurity situation and system should be considered within the international context (see p. 219). An incorporating Act passed on 19 March 1999 set up New Caledonia’s governing structures and allotted them specific competencies. For natural resources and the environment, outside of New Caledonia’s territorial waters the French state has the competencies resulting from international agreements, while New Caledonia is competent to regulate and exercise the right to exploit, manage and conserve biological and non-biological natural resources within its exclusive economic zone. It is also competent with regard to zoosanitary and phytosanitary regulations, and for slaughterhouses. The provincial authorities are responsible for all fields not attributed to the responsibility of the French state, the New Caledonia government or the communes. The provinces are responsible for protecting their environments. They regulate and exercise the rights of exploration, exploitation, management and conservation of biological and non-biological resources of inland waters including harbours and lagoons, the soil and subsoil, and territorial waters.

21The Consultative Committee on the environment, set up by an act of parliament in 1999, includes representatives of the French state, the New Caledonia government, the provinces and the communes. Its composition, attributions and mode of operation were laid down by a decision of Congress. Ports and airports are under the responsibility of the New Caledonia government. Public health, zoosanitary and phytosanitary regulations exist, but they do not explicitly cover the plant or animal species liable to interfere with strictly environmental aspects. There remains a lack of harmonisation among different initiatives and there is no coherent set of protection measures against invasive species. Also, success in combating such species depends on the involvement of the New Caledonian population (see p. 229). In the light of these facts, and of the damage already done by invasive species in New Caledonia, those responsible for the environment in the provinces (Northern, Southern and Loyalty Islands) decided to commission an expert group review from the Institut de recherche pour le développement (IRD).


22New Caledonia’s provincial and territorial authorities have taken a number of initiatives on invasive species in recent years, with a view to setting up a structure to define a collective strategy for protecting and conserving biodiversity. They also felt the need for an accessible record of current knowledge on the issue, and asked the IRD to conduct an expert group review.

23In July 2004, the IRD’s Consulting and Industrial Liaison department was asked to examine the issue and formulate the IRD’s response. A mission went out to Nouméa to talk to policy makers and actors in the field as widely as possible and learn of their experiences and questions. This laid the groundwork for a preliminary framework of the review.

24The review proper began in December 2004, when the initial workshop was held. The aim of this workshop was to bring together scientific experts on invasive species and the New Caledonian environmental policy makers who had asked for the review, to formalise the questions the review was to answer and suggest a precise framework, a set of specifications. This stage of the process, which is absolutely essential, must bring to light all the expectations and motivations of the review’s sponsors.

25This is why it is so important to meet all the actors directly or indirectly involved in the field the review is to cover. The specifications as subsequently written up must reflect precisely the sponsors’ requirements. Clearly, however, the experts’ contributions, based entirely on data drawn from the published literature and such “grey literature” as is available and reliable, may not be able to meet all the sponsor’s expectations. That is why the experts leave themselves a margin for simply quoting expert opinion on points not sufficiently documented. They also recognise the need to provide conclusions as relevant as possible to the operational decision bodies’ possible future needs, taking into account the particular situation of each of the archipelago’s administrative entities.

26The first two months of 2005 were spent bringing together a panel of internationally reputed experts capable, between them, of covering all fields within the scope of the review. The Consulting and Industrial Liaison department commissioned David Simberloff of Tennessee University and Bernard Chevassus, Chairman of the Museum national d’histoire naturelle, to peer review all the experts’ papers and the synthesis report.

27The panel of experts held their first meeting in April 2005 in New Caledonia. One purpose of that meeting was for each expert to take personal and group responsibility for the fields covered by the specifications and the sponsors’ questions. The scope and framework for each of the papers had to be discussed and decided. And a collective work schedule had to be fixed. The panel had to define the necessary time and space limits to produce a coherent, pertinent document fulfilling the requirements of an expert group review on invasive species in New Caledonia by December 2005.

28The experts held their second and final working meeting in mid-October 2005. They reported on progress on their contributions and settled problems of consistency. An outline of the synthesis report was presented to the steering committee.

© IRD Éditions, 2006

Conditions d’utilisation :