Lionel GARDES 1 & Bernard SALVAT 2 FRENCH OVERSEAS TERRITORIES

Transcription

1 CORAL REEFS IN FRENCH OVERSEAS TERRITORIES: A RETROSPECTIVE STUDY OF CHANGES IN HEALTH CONDITIONS OF THESE DIVERSIFIED AND VULNERABLE ECOSYSTEMS RECORDED BY MONITORING NETWORKS Lionel GARDES 1 & Bernard SALVAT 2 FRENCH OVERSEAS TERRITORIES ISLAND CONTEXT The ten French overseas territories forming the IFRECOR (French Coral Reef Initiative) network are islands scattered in the Atlantic, Indian and Pacific Oceans. Through their location, geomorphology, size, age and distribution, they are excellent representatives of the Earth s wide island diversity. They include islands that are either isolated (Îles Éparses, Réunion, Polynesia, Clipperton) or surrounded by islets (Martinique, Mayotte, Saint-Barthélemy, Saint-Martin, Wallis and Futuna), archipelagos (Guadeloupe, New Caledonia), groups of archipelagos and islands (Polynesia), and atolls (Polynesia, New Caledonia). The other French overseas territories (Saint-Pierre-et-Miquelon, French Guiana) have no coral reefs on their coastlines. They are oceanic islands, as opposed to continental islands. They are mainly of volcanic origin, but they sometimes also have significant sedimentary (in particular from previous coral formations) or metamorphic systems. The total area of emerged lands is about km 2, but these islands are very different in size, from about a hundred km 2 (Wallis and Futuna) to more than km 2 (New Caledonia). Coral reef areas around these territories also vary in size. Each territory has its own relief that influences the distribution of its population, economic activities, climate, and obviously of its coral reefs and their typologies. Réunion, Guadeloupe and Martinique have an aerial active volcanism, while volcanic activity is currently only underwater in French Polynesia and non-existent in the other territories. SOCIO-ECONOMIC FACTS The overseas territories under study are incorporated into France through a fairly large variety of statuses: Départements d outre-mer or DOM (Overseas Departments) (Guad- 1 Service Protection de la nature et Aménagement durable, Direction Régionale de l Environnement, 12 allée de la forêt, Parc de la Providence. F Saint-Denis de la Réunion. Lionel.GARDES@reunion.ecologie.gouv.fr 2 UMR 5244 CNRS-EPHE-UPVD, UMS 2978 CNRS-EPHE, Université de Perpignan. F Perpignan. bsalvat@univ-perp.fr Rev. Écol. (Terre Vie), vol. 63,

2 eloupe, Martinique, Réunion) where all mainland France rules and regulations apply; Pays d outre-mer or POM (Overseas Countries) (New Caledonia, Polynesia) and Collectivités d outre-mer or COM (Overseas Communities) (Mayotte, Saint-Barthélemy, Saint-Martin, Wallis and Futuna) where environmental affairs fall within the jurisdiction of local authorities. The Îles Éparses ( Scattered Islands ) now constitute the fifth district in the French Southern and Antarctic Territories (TAAF) and Clipperton is public property of the French State. The total population of those territories is in excess of Only 32 out of the 84 atolls of Polynesia are uninhabited, as are some Îles Éparses and Clipperton. The average population density varies greatly, from 12 inhabitants per km 2 in New Caledonia to 510 in Mayotte. However, these averages include extremely high variations, particularly in mountainous islands (i.e. most of them) where population density can reach 1000 inhabitants per km 2 or even more, especially in coastal areas often close to coral reefs. Each territory has at least one dense urban area. In New Caledonia (Southern Province) and in Polynesia (Tahiti and Moorea), more than 70 % of the population is concentrated in a very small part of the territory. The GDP per capita is high in most territories, particularly in comparison with the neighbouring island countries. It is generally over , except in Mayotte and Wallis and Futuna (< 4 000). In the most economically advanced islands, the service sector offers the greatest number of job opportunities (> 70 %). Unemployment rate can be high: 33 % in Réunion, 21 % in Martinique. Agriculture (sugar cane, banana, market gardening, cattle breeding) is important in these islands, especially in the West Indies and Réunion, and presents a certain number of local specificities, such as the banana in the West Indies, vanilla in Réunion and essential oils in Mayotte. Polynesia is the only territory with a major sea-related economic activity: pearl culture is the country s second economic earner after tourism. The only territory with a large industrial production is New Caledonia (nickel). Tourism often has a significant, if variable, role in the economy of these territories. Very few tourists go to New Caledonia. No tourist infrastructures have been developed in Wallis and Futuna. On the contrary, Guadeloupe, Martinique and Réunion are much-valued destinations, attracting to visitors a year. Polynesia has state-of-the-art structures and receives some tourists a year, contributing to a significant part of the economy. Ecotourism could be developed in the Îles Éparses to give value to the sites. One essential economic and maritime feature of these overseas territories is that they contribute up to 97 % to the French Exclusive Economic Zone (EEZ) the world s second largest after that of the United States representing 11 million square kilometres of ocean. There again, EEZ surface area differences are considerable, from km 2 for Martinique to km 2 for Polynesia due to the significant number of islands and islets forming its five archipelagos (Polynesia s EEZ surface area is equivalent to the landmass of Western Europe). Activities of populations are more or less centred on the exploitation of the sea and their cultures are more or less coral environment-oriented. In the Pacific, there is total symbiosis between populations, reefs and lagoons. The socio-economic characteristics of the population of each overseas territory now mixed, now with natives, now only with (former) immigrants are essential when it comes to implementing protection and management measures. Fishing is an important activity, as well as aquaculture in some territories, again with contrasted situations. In Wallis and Futuna, people fish on a small scale and only for subsistence. In the other territories, commercial fisheries (especially deep-sea) coexist with subsistence fishing for local population supply and are sometimes major export earners. 24

3 CORAL REEF DIVERSITY IN FRENCH OVERSEAS TERRITORIES The reef and lagoon ecosystems of French overseas territories ( km 2 ) illustrate the extreme variety of contexts of the Indo-Pacific area, as well as the specificities of the Caribbean ecosystems which were cut off from the Indo-Pacific area by the emergence of the Panama isthmus some 3 million years ago and have undergone specific changes. Such wide diversity is visible both at geomorphologic level (150 different coral types in New Caledonia alone) and in terms of surface areas (from 12 km 2 in Réunion to km 2 in New Caledonia), coral and fish communities, or even biocenoses living there. The four most frequently found types of coral formations are fringing reefs, barrier reefs, non bioconstructed coral beds and atolls. There are also coral banks and curiosities such as double barriers in New Caledonia or Mayotte. Such diversity is partly due to the islands age and the physical features of the natural environments in which they are located. The youngest islands of volcanic origin are still characterized by intense volcanic activity, high slopes and sheer ocean depths on which very few reefs have grown (Réunion). The oldest islands either have developed an ocean plateau enabling the installation of a barrier reef and lagoon, or have subsided under sea level and are currently atolls. These coral reefs, or more exactly algo-coral reefs, are sometimes also associated with other ecosystems typical of tropical or subtropical coastlines, such as mangrove swamps and sea grass beds and algal beds. These ecosystem associations are a source of great biological productivity through the interactions they generate and are particularly developed in the French West Indies, Mayotte and New Caledonia. Like the great diversity of French territories, ocean biodiversity of lagoon-reef ecosystems is considerable and constitutes an exceptional natural heritage to be preserved. With 10 % of the world ecosystem area, French tropical marine biodiversity is representative of world oceans. This gives France an international responsibility in terms of conservation. There again, the number of known taxa, their endemicity rate or the specificities of the biocenoses they generate vary greatly from one territory to another. The closest to the maximum biodiversity centre of the Indo-Pacific area, New Caledonia has approximately marine species, of which over 300 coral species. Another specific feature is that the Caribbean has only 45 coral species, but as they are all endemic to this biogeographic area, the conservation policies conducted in the French West Indies happen to be absolutely necessary for the general preservation of these species. ENVIRONMENTAL IMPACT OF REEFS AND MEN Limited space in island territories combined with the significant economic and human development of overseas societies exert ever stronger pressure on coastal natural spaces. The fact that population is extremely dense along the shore increases pressure on marine coastal areas: domestic, agricultural or industrial waste, transport-generated pollution, increase in fresh water supply due to soil impermeabilization, which alters water transfer mode to the ocean; soil and coastline erosion; coast development (embankment work, protection from the sea, harbours, etc.); direct uses (see following section). In tropical island contexts, pollution stress is very quickly transferred to the sea. As a result coral ecosystems, which are adapted to environments very poor in nutrients and suspended materials, suffer impacts such as very fast algal development competing with coral development (eutrophication), coral growth reduction due to the decrease of light intensity available for photosynthesis made by zooxanthelas, direct coral death from hypersedimentation, deterioration of reproductive abilities, etc. To date, there is very little literature about the consequences of chemical or organic pollutants, particularly biocides and pesticides. As shown below by data acquired by monitoring networks, these impacts gradually modify coral ecosystem structuring. 25

4 ACTIVITIES ON CORAL REEFS Leisure activities and tourism The development - often considerable - of tourist activities is generally evidenced by the high number of sea-oriented activities. Scuba diving comes first, with to dives a year in Guadeloupe, Martinique and Réunion. Skin diving is also very much appreciated and can generate damage to coral banks in some highly frequented bathing areas. Other activities include boat excursions, yachting, motor or wind-propelled craft, canoes, etc. The geomorphologic and biological originalities are turned to good account for world-famous diving events, like in the Tuamotu passes in Polynesia. Those activities sometimes take place in limited sectors, thus increasing potential use conflicts, as in Réunion where they are all located on 40 km of coast or in Guadeloupe where most dives take place in Pigeon Islet. Reefs are sometimes used so intensively that managers are forced to take regulatory measures such as implementing permanent anchoring systems and underwater paths, or limiting access to certain sites, etc. Overuse of reefs may be curbed through the implementation of Protected Marine Areas or management plans for reef and lagoon areas and their resources. Fishing Ocean resources are generally overexploited both for commercial and subsistence fishing. Some very destructive fishing practices are still used: dynamite, crowbar and poisonous substances in Polynesia, traps in the West Indies. A dramatic drop in some species stocks has been observed, especially in Crustacea in Polynesia and Réunion; fish communities are dismantled due to the reduced number of largesize fish. In addition, it is very difficult to control small-scale fisheries because they are often informal. In many territories, 90 % of fishing activities are concentrated on coral reefs. To compensate for coastal ecosystem overexploitation, developments of solutions like Fish Aggregating Devices (FAD), deep-sea fishing or aquaculture are often implemented. Reef protection To address very strong pressures on many coral reefs and protect these extremely vulnerable ecosystems, projects for Protected Marine Areas (MPAs) are studied almost everywhere, particularly in heavily anthropized areas (Nouméa lagoon in New Caledonia, Réunion, Moorea, etc.) with the view of creating more favourable conditions for sustainable development. Although enforceable regulations vary greatly from one territory to another, MPAs are being implemented in all French ultramarine territories. Protection objectives and statuses differ considerably (Natural Reserves, Fishing Reserves, Maritime Areas Management Plan, Biosphere Reserves and soon Marine Natural Parks). They are generally aimed at controlling the gathering and removal of marine organisms, and deal with other coral reef uses to extremely different extents. The most wide-ranging developments to date are found in New Caledonia, where 18 MPAs are distributed over ha of lagoons and a request for the inscription of reefs on the UNESCO World Heritage List is to be submitted, as well as in Réunion, where a National Marine Natural Reserve is currently being implemented to protect 80 % of its reefs. So far the UNESCO World Heritage Committee has included no French coral site in its list. New Caledonia submitted an application for its reefs and lagoons to UNESCO in January The property nominated is distributed over six sites. The request is currently under examination. The second international body (RAMSAR Convention, for the protection of wetlands of international interest) only includes one French site: the Grand Cul-de-sac Marin in Guadeloupe (1993). Lastly, the UNESCO Man and the Biosphere program (MAB) lists two French Biosphere Reserves: the Guadeloupe Archipelago (1992) and the more recent Tuamotu Reserves (2007, Fakarava district, Polynesia). 26

5 The efficiency of MPA status by definition covering maritime territories is relative and depends on the objectives sought. Over the years MPAs have clearly proved to be efficient tools in preserving marine (especially fish) resources or for community management of use conflicts in some coastal areas; however they are often unsuitable for coral habitat conservation insofar as their direct action capacity in terms of land pollution control is generally very limited. MPAs should rather be considered as catalysts for decision-makers to better take into account ocean ecosystem vulnerability when it comes to developing adjoining territories. Coral reef protection can be ensured on a long-term basis only through efficient coordination of marine environment and catchment basin grass-roots policies. Lastly, it is important to note that though awareness of catchment basin pressure on coral reefs is still far from perfect, it is more and more taken into account, as evidenced by the construction or upgrading of many urban water effluent treatment plants. MONITORING CORAL REEF HEALTH PRIOR TO THE CREATION OF PERMANENT MONITORING NETWORKS Prior to the establishment of networks monitoring reef health in accordance with the IFRECOR (French Coral Reefs Initiative) national strategy, levels of knowledge and the age of available data were extremely variable from one territory to the next; they were highly dependent on the availability of scientific expertise in the area and on the cultural, social and economic importance of reefs and lagoons in each locality. Reference data for the health of coral ecosystems is thus sporadic data, resulting from studies which were mainly carried out in the early 1980s. There is one exception, that of French Polynesia, where permanent stations were set up in 1971 on the reefs of Moorea. These are now a worldwide reference sector for knowledge of reefs, their evolution and resilience. While the data was often sparse and incomplete in comparison to today s standards and protocols, it allows for a partial assessment of past evolution and the identification of a certain number of factors and processes of reef deterioration, whether anthropogenic or natural. CURRENTLY OPERATING NETWORKS Most networks monitoring coral reef health were progressively set up during the 1990s: the first phase saw the implementation of a long-term (every 7 years) monitoring project in Mayotte, set up in 1989, and of two networks in French Polynesia, one annual and one biennial, which were created in 1991 and 1993 respectively. A second phase involved all territories, and allowed for the generalization of annual networks, in Réunion, Mayotte and New Caledonia (all in 1998), French Polynesia (in 2000), Martinique (2001), Guadeloupe, Saint-Barthélemy and the Îles Éparses in the Indian Ocean (2002). A network was also created in Wallis and Futuna in 1999, but monitoring is only carried out there on a three-yearly basis, due to the geographical isolation of the territory. There is no regular monitoring of reefs on Saint-Martin, but current knowledge suggests that the reef communities on the island are undergoing the same changes as those of neighbouring Saint-Barthélemy. There are thus nearly 150 currently operational stations systematically and permanently monitoring the health of reef communities. Finally, it should be noted that monitoring networks are currently developing in connection with the assessment of Marine Protected Areas. These networks aim to meet general targets (studying the health of habitats) as well as specific targets such as the assessment of the effect of reserves on fish resources. This development should be reinforced following the recent creation of the National Agency for Marine Protected Areas, set up in SUBJECTS OF MONITORING Throughout the various territories, monitoring is carried out into benthic (coral reef fauna) and fish sectors. Less systematic monitoring is also carried out into coral reef recruitment, tissue 27

6 necrosis on coral colonies, sedimentary fauna, mobile benthic invertebrates, algae and plant population and illnesses affecting cultivated species. In response to significant bleaching phenomena over the past few years and to the presumed increase in bleaching frequency arising from global warming, networks for the continuous monitoring of seawater temperature have been set up on a growing number of reefs in most locations. Finally, as well as those monitoring temperature parameters, networks for monitoring the physical environment are also being created, particularly in relation to the implementation of the European Water Framework Directive (WFD): these monitor the quality of water (physical chemistry, nutrients, bacteriology and chemical contamination) and sediments (chemical contamination); new networks are also being set up in consideration of natural risks, such as tsunamis, earthquakes, volcanic activity or hurricanes, as well as the consequences of climate change. The series of physical chemistry or chemical data produced by these networks still often cover too short a period of time, and are not fully representative: as a result, they cannot be studied in relation to biological data in multi-factorial analyses, but they do nonetheless pave the way for interesting research opportunities for the coming years. LOCAL NETWORKS LINKED TO INTERNATIONAL NETWORKS During the second phase of network development, all French territories devised methodologies adapted to local or regional specificities, which nevertheless followed international guidelines laid out during the construction of the Global Coral Reef Monitoring Network (GCRMN). Since 2000, they have also all, at intervals, contributed to the provision of data for regional GCRMN hubs and to the drafting of regional and international summaries coordinated by the Network, which are published every two years. Another network is also under development: the Reef Check network, whose particularity is the setting up of a simplified monitoring method, adapted for use by non-specialists and thus easier to implement, with the aim of involving civil society or sea users in the monitoring of their coral reefs. In the French Caribbean, the highly specific nature of the ecosystems has led to the elaboration of specific monitoring methodologies and regional networks such as the Caribbean Coastal Marine Productivity Program (CARICOMP). Finally, there are many other monitoring protocols, which illustrate the variety of aims pursued: rapid assessment protocols, photo-interpretation, the manta tow technique and quadrats and transects of different geometries. KNOWLEDGE OF FRENCH CORAL REEF HEALTH Reference data and major trends for the period Structuring of reefs and coral communities is usually influenced to a considerable degree by cyclonic events (destructive tides and hypersedimentation), which are particularly frequent in the archipelago of Guadeloupe, as well as in Saint-Martin, Saint-Barthélemy, Réunion and Îles Éparses, and which occur more occasionally in French Polynesia in connection with the most powerful El Niño phenomena. Epizooties covering a considerable geographical span, as illustrated by the massive mortality rate amongst diadem urchins and coral of the Acropora palmata species, may also play a significant role in recent changes to the coral ecosystems of the Caribbean. Conversely, in the Indo-Pacific, sporadic explosions of the Acanthaster planci sea star population (between and ) were the cause of a decrease of around 20 % in the coral coverage on certain Polynesian sites, and have decimated 90 % of the coral at one monitoring station in New Caledonia over the last two decades. Alongside these natural events, and the high level of economic development of the islands over the last thirty years, the reefs in the French Caribbean and Réunion have shown signs of deterioration since the early 1980s, with coral communities being gradually replaced by algal communities. 28

7 In Mayotte and New Caledonia, the considerable pressure brought to bear on mangroves and water catchment basins by the expansion of human activities has led to a significant alteration of the health of fringing reefs, which are particularly vulnerable because they develop close to anthropogenic pressure zones. Very little information is available concerning the evolution of the state of the coral reefs in many sectors of New Caledonia, Wallis and Futuna, Îles Éparses, Mayotte (with the exception of fringing reefs) and Saint-Martin for the period prior to the setting up of the permanent networks at the end of the 1990s. Knowledge acquired within the framework of permanent monitoring networks Information relating to the state of health of coral communities: Two major categories can be identified within French islands after analysis of information gathered within the framework of permanent monitoring networks. The first includes the Pacific territories (Polynesia, Wallis and Futuna, New Caledonia) and Mayotte, where, despite inter-annual variations and extremely disruptive exceptional events, the general state of health of coral reefs appears to have been maintained in the sites which have had long-term monitoring, owing to the reef communities good resilience and moderate pressure from human activity. The second includes territories of the French West Indies (Guadeloupe, Martinique, Saint- Barthélemy and Saint-Martin) and Réunion Island, where monitoring reports demonstrate a progressive loss in coral cover to the benefit of algae communities, despite periods of several years of stability and even recovery. This phenomenon is particularly significant on the outer reef slopes. Moreover a critical stage in the history of coral cover in the reefs of the West Indies has begun since the major bleaching event of This deterioration is also visible in the appearance of patches of necrosis and a progressive increase in their surface area on the corals, in parallel with the decline in other indicators of health condition. This phenomenon is under study in Guadeloupe: in addition, the available data suggests a link between the intensity of anthropic pressures on coral reefs (greater in Guadeloupe than in Saint-Barthélemy) and the development of necrosis (more abundant in Guadeloupe). According to available data, coral recruiting also appears more severely affected on the reefs exposed to various forms of pollution (such as Guadeloupe), than on those less impacted by human activity (Saint-Barthélemy). The monitoring reports bear out that the quantitative variations, be they positive or negative, are often linked to fluctuations in the genus Acropora in several Indo-Pacific territories. Still with relation to species or the communities they form, a detailed analysis of the data gathered by the monitoring networks operating at this level of precision also testifies to an overall reduction in biodiversity, revealed by the disappearance or replacement of the most sensitive species by ubiquitous or more resistant species (in Réunion Island, for instance). Lastly, the longest-established networks are beginning to provide data relative to the reefs resilience, notably in Polynesia, Mayotte and Réunion, where a recovery in the outer slopes of reefs that had been completely destroyed has been observed over a period of 10 to 20 years according to the contexts. Information relating to the state of health of fish communities: The health monitoring networks also supply information on the evolution of the structure and diversity of fish communities dependent on or linked to the coral ecosystem. However, data resulting from this monitoring generally only concerns the list of species selected for sampling. The available results demonstrate that the evolution in the health of reef coral communities influences the evolution of the structuring of fish communities. Yet one family, the Pomacentridae, would appear to dominate populations, whatever the general state of health of the coral populations and whatever the biogeographical zone. Nonetheless, the species encoun- 29

8 tered evolve with the relative importance of corals and algae: planktivorous or omnivorous Pomacentridae (e.g. Chromis sp., Dascyllus sp.) when the colonies of branched Acropora are in good health; herbivorous Pomacentridae (Stegastes sp., etc.) on disturbed reefs. This difference between oligotrophic or disturbed reefs is also to be observed in the relative abundance of species which are typically corallivorous (notably certain Chaetodontidae) and herbivorous (essentially Acanthuridae and certain Scaridae). However, it would appear that new balances are emerging within these modified communities, illustrated by a relative stability of specific diversity over a short period (10 years of monitoring on average). At quantitative level, the monitoring carried out in the entirety of the French territories indicates overall stability of numbers and biomass of fish encountered on the transects during the decade of available monitoring data. However, while fish populations might thus appear to be relatively balanced, this balance is composed of situations which contrast according to the territories: (1) good health of the populations and a state probably close to the conditions of reference in New Caledonia; (2) populations adapted to the sometimes profound modifications of the reef communities and which, in spite of these modifications, have achieved a new balance (French West Indies, Réunion). The variability of fish density observed is, moreover, extremely high within the territories and from one region to another. Lastly, the fish populations of many reefs illustrate the strong direct pressures linked to the development of fishing activities: in Moorea, Polynesia, the density of fish of commercial interest decreased between 1987 and 2002; in Réunion Island, predators having a high trophy value and notably the piscivorous species are extremely scarce even absent from a certain number of sectors; in Martinique, the classes of sizes below 10 cm in length correspond to almost 90 % of the sampled numbers. In contrast, significant changes in biomass, but also in species wealth, have been reported in the MPAs in Guadeloupe, Saint-Barthélemy and New Caledonia, attesting to the interest of establishing tools of this type with a view to the long-term conservation of fish communities. Information relating to coral bleaching: No bleaching event was recorded during the 1970s in Moorea (Polynesia), at a time when permanent monitoring was already in place. The first observations of major bleaching go back to , then 1987 (French West Indies and Polynesia) was a historic year in that bleaching phenomena were recorded, to various degrees, in all the French territories but also worldwide. Moreover, a major event occurred in 2005 in the Caribbean islands, giving rise to massive mortality and a 30 to 50 % drop in the rates of coral cover in Guadeloupe, Martinique and Saint-Barthélemy. Yet taking into consideration the whole of the national lagoon-reef territory, bleaching phenomena - less global and with variable degrees of impact or impact localized to certain reefs - have been recorded at almost annual frequency since: 1991, 1993, 1994 (Polynesia), 1996 (New Caledonia 80 to 90 % of the coral formations affected around Nouméa), 1998 (everywhere), 1999 (Guadeloupe), 2001 (Réunion, Polynesia), 2002 (Polynesia), 2003 (Réunion, Martinique), 2004 (Réunion), 2005 (West Indies). Although no bleaching events were reported before the monitoring networks were set up, the data presented above would seem to point to an increase in their frequency during the past 20 years, a dynamic whose link with the undergoing process of global climate warming is widely accepted by the scientific community. The data available on the effects of the most powerful events demonstrates that on average the events affected at least 50 % of the coral colonies in the Caribbean islands, and caused very severe losses in coral coverage, linking with a mortality rate in the region of 20 % in Polynesia and 15 to 30 % in the West Indies. In addition, the impact of bleaching varies according to the species; it affected 100 % of Agaricia agaricites and 50 to 80 % of the colonies of Montastraea spp. on a site in Martinique in It is likewise important to note that the general state of health of coral organisms (illustrated notably by the extent of observable necrosis), linked with the intensity of pressures 30

9 sustained from other sources, is a major factor in sensitivity of colonies to bleaching and influences their subsequent capacity for zooxanthellae recovery. This significant influence on the survival capabilities of corals was clearly established in studies carried out in Guadeloupe. In Polynesia (Moorea), significant inter-annual variability of the rate of coral recruitment (between 2002 and 2003) has been linked with the bleaching event of No direct link between coral bleaching and the structure of reef fish populations has yet been established. On the other hand, the increasing number of bleaching events could end up by making this link in the long term, owing to its probable consequences on the general degradation of the quality of habitats and therefore the shelters available for reef fauna. CONCLUSIONS All the French territories now have networks monitoring the state of health of coral reefs. These networks, whose development has been favoured by the IFRECOR (French Coral Reef Initiative) via a national approach, implement internationally recognized monitoring methods. They are thus able to make a significant contribution to assessing the evolution of the state of conservation of coral ecosystems worldwide, within the framework of the GCRMN (Global Coral Reef Monitoring Network) of the ICRI (International Coral Reef Initiative), an initiative which is supported by France in the general context of the development of human activity and of climate change. The information generated will also be useful in the framework of France s participation in international conventions on biological diversity, sustainable development and climate change. These conventions include France s firm commitments in favour of coral reef protection. Over the past decade, the health condition of French coral reefs has remained stable overall, but their ecosystems are often characterized by communities whose composition or functioning are different from their conditions of reference of the 1970s. Within the framework of the km 2 of coral worldwide, the km 2 of French lagoons and reefs are, with the exception of the zones close to urban areas, in a relatively satisfactory state and only mildly threatened, apart from the general consequences of climate changes. This general national observation hinges on the insularity of French overseas territories, their oceanic isolation and the very limited demographic pressures when it comes to the overseas territories of the Pacific (French Polynesia, New Caledonia) which make up 95 % of French lagoon-reef areas and only 21 % of the French population living overseas. This context is in no way comparable to that of Asian countries, which are more continental and more subjected to pollution, and whose reefs run a high risk of deterioration in the decades to come. This general finding of the reefs being mildly threatened nonetheless masks a more contrasted situation in the Overseas Departments (West Indies and Réunion Island), where coral ecosystems are much less extensive (less than 1 % of the national heritage), while they are subject to the pressures exerted by 70 % of the French overseas population. In addition, in a context of weakening of health condition consecutive to the increase in anthropic pressures, the spiralling number of natural phenomena impacting the reefs directly (damage caused by cyclonic swells) or indirectly (temperature elevation causing bleaching and coral mortality, hypersedimentation, demographic explosions of predators, epidemics, acidification of seawater reducing the calcification of organisms with a calcareous test, etc.) raises profound issues on the capacity of ecosystems to tolerate or adapt to these aggressions. In the French West Indies, as in all of the Caribbean countries, reefs can therefore be considered as being under medium threat, which is preoccupying with regard to biodiversity conservation owing to the extremely high endemicity within this biogeographical zone. Public policies are increasingly taking into account the exceptional natural heritage of coral reefs, encouraging better protection and measures for sustainable management of habitats and resources. This improvement is, in all likelihood, not capable of counterbalancing the general development of overseas societies, which continues apace. 31

10 Oceanic insular systems, which so clearly illustrate a world where space and resources are limited, must today turn resolutely towards models of sustainable development. Indeed, it is of the utmost urgency to reduce the pressures which weaken coral communities and make them more vulnerable to repeated episodes of abnormal rises in seawater temperature, with the dual aim of conservation of natural heritage and protection of the coastlines, together with the human or economic activities which develop there, in the face of the predictable effects of climate change. 32