Abstract

The importance of the biological richness of the Mediterranean basin is recognised by all participants and it is considered as one of the 25 hotspots in biodiversity in the Earth. This status is due to the high number of species (plants and animals) and the elevated number of endemisms. These endemisms are in many taxa around the 18% of the total Mediterranean species. The necessity of a interdisciplinary approach, from descriptive to molecular taxonomy and from small scale to landscape processes, was emphasised. Considering that this area is the most seriously affected by anthropic activities, the Mediterranean should be considered as one of the conservation priorities in Europe. The contributions to this electronic conference come from different countries and different specialities. I will try to summarise them following the key points addressed by the chair:

1. Is this a local or a basin-wide problem?

The evidences of diversity degradation are not fragmentary and there are too many data showing a general degradation of the Mediterranean ecosystems (e.g. fishing statistics, habitat losses, changes in the coastal landscapes). However, following some points emphasised by Ferdinando Boero, it is recognised that there is a lot of loss that may remain hidden because poor knowledge, and that some of the fluctuations detected may not be considered a threat. Nevertheless, some losses in traditional fisheries and slow-growing organisms (e.g. corals or Posidonia) may require centuries to recover. Other colleagues, as Joan Cartes, commented possible evidences of diversity losses in deep-water communities. Although, the absence of ancient data (before the 80's) make these evidences speculative. However, he provided some examples of changes and local extinctions in the fisheries of the red shrimps (caught deeper to 800 m). This losses/variations could be induced mainly by fishery activities (and perhaps by supplementary anthropic actions, e.g. eutrophication, natural variations in environmental conditions). The importance of eutrophic-pollution and overfishing actions as the main causes in the biodiversity decrease was also stressed by Sotiris Orfanidis and Zbynek Vecera and some interesting data on the pollution of the Eastern Mediterranean basin were included in the discussion.

2. Is it evident in all margins of the basin?

The necessity of a historical perspective of the biodiversity losses was stressed. Historical data exist, although they are not easy to summarize (and they will be indirect evidences in many cases). There are some archaeological studies demonstrating historical changes. This perspective should be addressed from joint works historians-ecologists.

It was suggested that, at least for some invertebrate groups, we have explored a small portion of the basin and their occurrence and abundance data are unfortunately scarce. This aspect avoids a general perspective of their fluctuations and extinction rates. Additionally, we have a limited knowledge of the interactions between some abundant species (e.g. some commercial fishes) and poor unknown species (e.g. gelatinous predators). These points were discussed by Ferdinando Boero and Domingo Lloris.

3. Has it affected larger organisms only?

Ferdinando Boero explained some interesting examples of small species losses. Some intertidal hydrozoans have disappeared during last decades, however, he emphasises the necessity to document extinction and changes. Unfortunately, very few people know enough to realise that an invertebrate is disappearing (except if it is very conspicuous one). He pointed out the necessity to detect threats in conspicuous and inconspicuous species, considering the importance of most species in this complex ecosystem. This point stressed the exigency for more specialists in the different taxa. Although, in several groups the knowledge is still partial, in general we have an acceptable level of taxonomic knowledge for most groups. This knowledge can provide us the trends about the increase or decrease in species richness after several decades of ecosystem degradation.

Ferruccio Maltagliati described his experiences with biodiversity loss at genetic level in brackish water species and he argued that the loss of biodiversity is "cryptic", but with important implications for the evolution of the population (in some instances of the whole species). He stressed the necessity of a genetic monitoring of species, mainly in those species with low dispersal capabilities and restricted geographical ranges. Raquel Goñi also raised an important issue, recommending to predict the sensitivity of particular taxa to disturbance. This prediction would need a complex approach (e.g. genetic, species or community) and mainly needed in long-lived organisms.

4. Is the erosion of marine biodiversity generalized as to require a concerted effort and action from all countries?

Biodiversity is not simply the number of species in an area. It is a complex aggregate including genetic variability, species interactions and landscape/ecosystem processes. Hence, biodiversity losses will be at different levels. Whereas total extinctions are few, dramatic declines in population sizes represent a real threat that needs interdisciplinary efforts and concerted actions from many countries.

Abstract

In more than 30 posted comments, the participants have almost unanimously declared the existence of identifiable changes in the Mediterranean biota that may represent a serious threat. Overfishing, industrial and urban growth and pollution, and incorporation of alien biota, either man-enhanced or as a natural process, appear as the main causes responsible for the observed changes. However, the lack of historical perspective (extreme scarcity of long-term studies except for exploited species) preclude to isolate natural (i.e., controlled by climatic oscillations) from human-induced changes. For the same reasons, it is very difficult to quantify the rates of alteration.

1.Are evidences of significant biodiversity losses in the mediterranean?

In the first day of discussions, it was concluded that the reported losses of habitat, changes in coastal physiognomy, etc. in the Mediterranean suggested a general ecosystem degradation. Unfortunately, it is difficult to separate some of these observations from the effect of natural oscillations. Ecosystems are by definition something dynamic, and probably the only stable system is made of petrified wood (and only partially). For this reason we cannot expect a strict constancy in all the ecosystem descriptors (and taxonomic composition is one of them). Nevertheless, the significant changes observed in the biotic composition in some areas, and the growing evidences for a tendency of the Mediterranean to evolve into severely "simplified" ecosystems, seem to confirm the rigour of the symptoms, and their extension from local to basin-wide scales. The symptoms appear to be more evident in bottom communities, both in shallow coastal and deep water ecosystems, but the observed plankton changes are important too, or at least suspiciously coincident along the last three decades.

2.What are the rates of biodiversity losses?

The lack of adequate studies (long series of descriptors at appropriate time and space scales, including amongst other climatic, hydrographic and taxonomy data) preclude a clear distinction between natural, climatic-controlled cyclic changes, from irreversible, human-derived alterations. Fishery statistics are probably the only existing long-term data that can give some insights about the rate of ecosystem transformation in the Mediterranean. However, the data are fragmentary, focused in some exploited species, refer mainly to biomass, and don't inform about the accompanying fauna.

3.Predators, species invasion, and suggestions

The change of trophic structure of deep ecosystems, either by increased loads of OM, or by overexploitation of top predators, has been suggested to account for part of the diversity loss. The incorporation of alien species (Atlantic, via the Gibraltar strait, or from he Red Sea are also considered a threat. A possible compensation for the losses of Mediterranean species by exotic incorporations cannot be considered as a gain. The scientific importance of taxonomic studies has been emphasized, as a necessary step to detect any structural and functional change in Mediterranean ecosystems. At the same time, the nonexistence of adequate historical perspective must be corrected, and the collection of selected data for uninterrupted long time-series encouraged.

In general, alien or immigrant species have not caused significant impacts on the Mediterranean marine ecosystems. However, it is cause for concern the increasing record of non-indigenous species in the Mediterranean whose ecological role and effect on biodiversity conservation is unknown. Participants argued about the main historic and anthropogenic causes favouring that the Mediterranean have received a high number of allochtonous species, not fully recorded yet. Present knowledge and reliable data on species identity, introduction date, geographic origin, dispersal vectors and distribution ranges are very limited. The ecological impact of invasive species is poorly known because it is rarely investigated. Both planktonic and benthic communities appear to be equally affected by invasive events. More joint research is necessary for obtaining a better knowledge of the present and future impacts caused by immigrant species.

Invasion affects biodiversity by adding species that may outcompete and displace autochthonous ones. Most allochthonous species that establish reproducing populations within the Mediterranean constitute neither a nuisance nor have commercial value. Most allochthonous species do not undergo outbreaks that would turn even an innocuous species into a "pest". However, the number of allochthonous species that develop populations is increasing. The special vulnerability of the Mediterranean Sea to invasion by allochthonous species stems from its position between the Atlantic, Pontic and Erythrean regions, its history, and heavy anthropogenic impact.

It is believed that impoverished biotas are more prone to invasions. The Levantine Sea has less than half the number of benthic species found in the Mediterranean Sea. This faunal impoverishment has been attributed to its comparatively late recolonisation following the Messinian crisis, to Pleistocenic climatic fluctuations and to the basin's extreme oligotrophy. The prevailing high temperature and salinity may prevent the arrival of Atlantic species. When tropical organisms arrive, few ecological obstacles prevent their successful implantation. Increased pollution (from agricultural run-offs to industrial wastes), unsustainable fishing practices and engineering projects (dams, landfills etc) have caused wide spread disruption of the littoral ecosystem and decimation of the Mediterranean biota.

It is difficult to provide conclusive data on the possible scenarios deriving from the introduction of species in the Mediterranean. Not enough data are available to forecast the effect of invading species on marine communities. However, some previsions may be attempted based on the general ecological characters of invaders. Taking into account the main source of human-mediated invasions (ballast waters, aquaculture, etc), invaders are apparently represented by resistant, fast growing, adaptable species to variate conditions and stressed environments.

There are marked differences about the impact of invasive species between eastern and western Mediterranean. The eastern basin is mainly invaded by Lessepsian immigrants. In the western basin the most important invader, the algae Caulerpa taxifolia, was apparently released from a public aquarium. Considering that ship ballast water affects equally both basins, western countries are more proned to introductions through aquaculture. The cold seawater temperature of the western basin in winter is not a barrier for the arrival and settlement of some Lessepsian immigrants. Since the fifties Caulerpa racemosa has reached the Italian coast and Mallorca. The seagrass Halophila stipulacea has passed the Siculo-Tunisian sill as other organisms like the fishes Leiognathus klunzingeri and Pomadasys stridens, the gastropod Cerithium scabridum, and the pearl oyster Pinctada radiata.

No taxonomic surveys are made in areas highly sensitive to alien species introductions, as harbours and aquaculture sites. None study on the transport of organisms in ballast-water has been attempted in the Mediterranean. The co-ordination among scientists undertaking research in this field is poor.

Very few scientific projects are investigating the occurrence of alien species and invasive events in the Mediterranean. The International Commission for the Scientific Exploration of the Mediterranean Sea (CIESM) is preparing an atlas of species that entered recently into the Mediterranean from both the Red Sea and Atlantic Ocean. The list is very long. For most species there are just a few records and their impact is negligible. However, some species have an enormous impact along the Levantine coast (Egypt, Israel, Lebanon, Turkey) where 95% of total shrimp fisheries are Red Sea penaeid prawns, 50% of the volume of fish trawled is composed by Red Sea species and where large shoals of the scyphomedusa Rhopilema nomadica extends more than 100 km in length. The ecological and functional role of most of these species is ignored. To know the biological and socio-economic consequences caused by alien and immigrant species requires scientific research (taxonomy, ecology, environmental forecast). The scientific cooperation would promote international regulations to prevent the arrival of allochtonous species and the control of their environmental impact.

In 10 posted comments it has been discussed the lack of effective conservation measures in the development plans and their insufficient incorporation into developing initiatives on Sustainable Management. It has been agreement regarding the need to face urgently the impact of human practises on marine ecosystems and biodiversity, mainly in the coastal zone, implementing effective management measures. It has been commented the need to perform a real Ecosystem-Based Management (EBM) based on indicators and limits of sustainability.

A new understanding of complex systems could be showing that ecosystem state shifts can cause large losses of ecological and economic resources and restoring a desired state may require drastic and expensive intervention. In this case the challenge will be to sustain a large stability domain rather than to control fluctuations.

It has been also indicated that changes over time cannot be meaningfully interpreted in relation to sustainable development considering only the ecosystem constraints/limits and that references corresponding to the socio-economic aspects of the human activity are also needed. It has been suggested that the huge economic pressures should be tempered down and in this context some initiatives to build a framework for protecting biodiversity and improve sustainability were mentioned. The Earth Summit in Rio de Janeiro in 1992 (UNCED Rio) and its Agenda 21. The Code of Conduct For Responsible Fisheries adopted by FAO October 1995. At European level, the Habitats Directive 92/43/EEC. This directive aims to conserve fauna, flora and natural habitats of EU importance. The Protocol concerning Specially Protected Areas and Biological Diversity in the Mediterranean Sea entered into force in December 1999 within the framework of the Barcelona Convention. This new Protocol contains novelties regulating the protection and management of endangered and threatened species, and conservation and sustainable use of biodiversity.

The general opinion is that the moral concerns on the loss of marine biodiversity is not enough to convince the managers about the necessity for a policy on resource management. Actually, economy tends to prevail over morals. A more promising would be if scientific research is able to demonstrate unequivocally to the Mediterranean society what are the resources and services provided by marine ecosystems, how the society is dependent on them, and how are they, in turn, dependent on biodiversity/ecosystem function. Moral concern is not enough and to convince the managers is our task.

In any case some event like, the occurrence of red tide algae has been quite detrimental for the tourist industry in the Adriatic. The invasion of Caulerpa is harming both fisheries and tourism. Over-fishing is the cause that only through subsidies the fishing fleets can maintain their activity and that more than 80% of fish consumption in the Mediterranean corresponds to products imported from other regions. It should be possible to use such arguments to promote research into factors affecting the resilience of the Mediterranean ecosystem to invasive species, the likeliness of blooms of nuisance species or into how living marine resources can be exploited in a most responsible way.

Nevertheless, it has been also pointed out that at the same time that an unchallengeable scientific advice is provided, is urgent to take management actions based on the Precautionary Approach; i.e. When evidence of a threat for sustainability exists the most conservative measure, based on the best scientific information available at that moment, should be implemented.

There hasn’t been an overwhelming participation on this topic, but all the participants have made their points forcefully and a general agreement is evident. A summary of these contributions is as follows:

All opportunities are to be taken and used to monitor biodiversity changes, either through the use of individual species easy to survey (big macrofauna or macroflora species, charismatic or invasive, and so on), indicator species, or communities. We should know well:

• the exact taxonomic (and eventually genetic) signature of the used organisms;
• their ecological role;
• reliable previous data on which to base the comparison.

This implies promoting existing efforts to elaborate national or regional floras and faunas, and encourage them if these efforts do not exist already. This in turn implies fostering taxonomy, be it old style (based mainly on morphology) or new fashion (genetic screening). Also, the compilation of long term series of data are encouraged, from plankton inventories to photographic censuses of benthic communities, from commercial fish catches to weather and hydrographic data. The nature of these monitoring efforts imply that there is to be a previous knowledge, be it in the form of specialists on the different taxonomic groups, or on the ecological functioning of the littoral or marine communities to be surveyed, or on long term series of data on plankton, benthos, fish catches and so on. Thus the active participation of marine research institutes and experts on these areas is mandatory in these monitoring efforts.

On the precise tools to assess possible changes in Mediterranean biodiversity, there is a general agreement that some of these can be particular species whose ecological and biogeographical role is known; these can be indicator species (of whatever clue, from pollution to tropicalisation), or simply easily identified ones although perhaps less clearly related with some biodiversity trend. Their abundance, decrease, spread, etc. can be followed on the entire Mediterranean perimeter. Among the suggested species are the "fragile" sessiles: corals, sea fans, sponges; the "engineering species": calcareous lithophyllid algae, vermetid gastropods, some burrowers; and some "exotics" - fast- spreading thermophiles in particular - as they clearly demonstrate human impacts. The benthic communities more akin to receive natural or man- made erosive impacts are also candidates, from seagrass beds to coralligenous bottoms, from marine caves to slope canyons. The study of some of these “hot spots” of biodiversity in the Mediterranean should be encouraged. In some cases, there can be whole community descriptors (such as species diversity, species richness, and so on) which, applied to well established taxocoenoses, can give a hint of what is going on. Many of these descriptors and biomarkers have appeared in the scientific literature of the last half century, in the form of indexes of environmental quality, pollution, vulnerability, fragility, ecotoxicological and so on. We can use these, only their standardization is needed. Some of these descriptors, such as the genetic markers, can be hard to apply or to follow, for various reasons (such as extreme expertise on rare taxonomic groups or sophisticated laboratory methods), but others need only routine surveys and long data series, some of which already exist.

Some national or international efforts already in force should be encouraged, such as those aimed at monitoring hard bottom benthos as a tool to detect biodiversity changes; or the long-term monitoring of protected areas in different countries, as a very useful by-product of these rather pristine areas. This encouragement should be done both at the national and European level, and with special care not to forgot the Southern and Eastern, non-European countries, were most of the Mediterranean biodiversity resides. At the administrative and international level, some of the means to be promoted are: the convening of biodiversity workshops aiming at the proposal of some routine surveys on well-agreed species, communities and/or biomarkers; the developing of PEET (Partnership for Enhancing Expertise in Taxonomy)- like projects; promoting the funding of normally submitted research projects with a clear biodiversity side; the implementation of Biodiversity Observatories all along the Mediterranean Sea, which should follow the monitoring protocols issued from the workshops. These activities should be taken into the main goals of already existing research associations or programmes (CIESM, MAP, SPA-RAC, ICRAM, UICN, WWF, and so on) or under a new (and effective) scientific umbrella.

Conservation strategies in the Mediterranean may be aimed at the preservation of individual species perceived to be under particular threat (e.g. monk seal), whereas other efforts may be aimed at the conservation of ecosystems (e.g. habitat directive). The question is whether species vs. ecosystem-oriented protection and management strategies are most effective and to what extent past may inform future decisions.

Concern was expressed that in general retrospective analyses are precluded by the lack of benchmarks against which to measure the outcome of particular conservation strategies. In the absence of benchmarks (pristine ecosystems or protected for a long time), long-term data sets would be needed but these are rare. Hence, it appears that at present we are not well equipped to assess changes resulting from conservation measures unless the magnitude of the changes is very large. This strongly argues for foresight in establishing studies and sampling schemes with adequate spatial and temporal coverage in association with any conservation measure implemented.

In spite of these shortcomings, experience and common sense have taught us the following:

1. Arguments in favour of single individual species conservation approaches

2. Arguments against individual species conservation approaches

3. Arguments in favour of ecosystem-oriented conservation

4. Arguments against ecosystem-oriented conservation strategies

Is the simple view that one strategy is optimal for all beaches adequate or should the management of this situation be delivered a la carte? How to reconcile the desire to have stable beaches with the need to preserve marine biodiversity down slope?

Most beach management actions are done without considering the beach as a live, fragile ecosystem which extends well beyond the human users to include other organisms inhabiting the beach ecosystem or using it during a certain stage of their life cycle such us sea turtles. Beach management and conservation strategies must include protection measures for sea turtle nesting beaches and coastal foraging habitats throughout the Mediterranean; not only in their main nesting beaches but in all the beaches of this sea, because important gaps still exist on the biology and distribution of these animals in the Mediterranean. Every beach can be a potential nesting beach for sea turtles, as it was demonstrated with the nesting event occurred last year in a beach of Almería (south-east Spain).

Most managed beaches are going through recurrent interventions to maintain a certain size which implies a high frequency of perturbation and, consequently, a high degree of artificiality of the beach ecosystem. These "hard approaches" to beach management seem driven by the explosive combination of economical and political interests, which represent the most serious threat for the preservation of biodiversity. Concerns were raised about the significance of this highly artificial ecosystems to maintain the overall biodiversity of the coastal zone. Frequent beach interventions can have detrimental effects on adjacent ecosystems or provide open space for the invasion of alien species such as the whelk Rapana venosa in the Adriatic Sea. Preservation of marine biodiversity can not be reconciled with the introduction of alien elements/factors of disturbance in the ecosystem. Beach abandonment was seen as the most sound, effective target for beach management in the long-term, although politically and socially unacceptable in the short-term. A forecasted scenario of sea level rise and widespread coastal erosion supports beach abandonment as a management option, which can be achieved through the sound use of dedicated taxes on tourism along a time scale of a generation (30 years).

What to do in the mean time? Shall we let beaches which natural regulatory mechanisms have been discontinued by urbanisation be eroded altogether? Will this erosion not affect equally the submarine rooted communities which we are trying to preserve? How to reconcile short-term with long-term goals?

Posidonia beds can be also at risk in an erosional coast, and intervention to maintain the beach and the Posidonia beds can be positive at the local scale. This may result, however, in managed Posidonia beds, or "Posidonia gardens" with, perhaps, little value for the preservation of biodiversity and the natural ecological processes. They can be a tourist attractor and an educational tool to convey the message of biodiversity preservation to the society, if done in a compatible way and with the adequate scientific control.

Shall we abandon all intervention to restore natural systems on the grounds that they may become gardens or shall we exert responsible management where human action has compromised the natural processes that sustain ecosystems? Is any extent of damage tolerable?, If not, should a zero tolerance policy extended to all activities on the sea and the littoral zone? what should be an acceptable time-scale for recovery when management has been caused?

Posidonia oceanica growth is slow and recovery of disturbed meadows may take centuries provided the habitat is still favourable to Posidonia recolonization. Understanding of how the spatial structure of Posidonia beds is affected by the balance between physical perturbations (natural hydrodynamics, beach management) and the potential for recolonization via both sexual reproduction and vegetative propagation is still limited and prevents the elaboration of models to predict the effects of different beach management options and set acceptable time scales to evaluate their succes. Beach management policies that include a zero tolerance for damages to Posidonia beds seem appropriate to maintain the important resources and services provided by this ecosystem. Zero tolerance for damage, however, should be based strong scientific knowledge to facilitate communication to society and confront the tourist industry.

Posidonia beach cast material serves important roles in initiating dunes, transferring nutrients to the dune vegetation, and preventing, by increasing the roughness of the beach surface, erosion and wind transport of the sand. Removal of Posidonia oceanica is therefore acting directly to increase beach erosion. Recent experiences in the island of Menorca, where a successful beach management plan that does not remove Posidonia oceanica except in limited areas, where it uses special tools to do so, has provided evidence of the benefits for the beach stability and, therefore, beach users. This program is supported by tourist local entrepreneurs, which suggests that current attitudes can be changed through demonstration and education programs. Once the benefits from alternative management options are demonstrated, the tourism industry can become a strong force to push for sustainable beach management. To implement with success coastal management actions that incorporate goals such as biodiversity maintenance, or long-term sustainable use of natural ecosystems is necessary to demonstrate the society the benefits it gets from healthy coastal ecosystems. Concerns were raised about placing a strong focus on the services provided to human society by Posidonia meadows for it could be interpreted as an excuse to disregard those species with not known services and, therefore, a threat for biodiversity preservation.

Because it is a slow growing species, Posidonia oceanica forms a ecosystem with low resistance and resilience. Posidonia reforestation is not a tool to be considered in current beach management programmes for it can not achieve a scale adequate to compensate for the many losses occurring, but it may be an educational tool, in the same way as planting a tree will not help achieve healthy forests but conveys a strong educational message to the citizens that do. Collection of Posidonia fruits and seedlings and the establishment of these programmes could help to preserve part of Posidonia genetic diversity.