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Non-indigenous marine species in the Mediterranean Sea—Myth and reality

Bonanno, Giuseppe, Orlando-Bonaca, Martina
Environmental science & policy 2019 v.96 pp. 123-131
biodiversity, decision making, ecological invasion, ecosystems, environmental impact, invasive species, issues and policy, long term effects, stakeholders, uncertainty, Mediterranean Sea
The spread of non-indigenous species is a global phenomenon that affects most ecosystems. Although invasion biology is a well-investigated discipline, there are still gaps in knowledge that may prevent obtaining a complete and realistic picture of the impact and scale of biological invasions. It is important, indeed, to distinguish between knowledge (reality) and what is taken for granted (myth). This study focused on the state of knowledge regarding the non-indigenous marine species currently present in the Mediterranean Sea. On the one hand, the information is overall exhaustive as regards the total number of non-indigenous species, their traits, invasiveness potential and vectors of spread. In particular, the Mediterranean is one of the best-monitored seas thanks to the international networks of marine scientists. On the other hand, however, scientific evidence does not suffice to draw general conclusions on the real magnitude of the ecological impact of non-indigenous species. Most studies, indeed, have investigated very few invasive species, generally at local scale, while the long-term effects of non-indigenous species are poorly known. The myth does not consist in stating that there is an ecological impact on Mediterranean marine biodiversity but in taking for granted that we are currently able to assess the magnitude of this impact. These uncertainties have inevitable consequences at decision-making and management level that could be mitigated through open interaction between stakeholders involved in policy and science on the one hand, and society on the other hand.