Posidonia density in the Mediterranean Sea could decline by 90 percent by the mid-21st century

  • An study done by CSIC reveals that water warming could produce a functional extinction of this marine species meadows

  • the water surface temperature during the summer could increase 3.4 degrees by the end of the century

Mallorca, 21st May 2012.  The study done by researchers at the Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB) reveals that the plant density of the marine species Posidonia oceanica could decline by 90 percent by mid-21st century because of surface water warming of the Mediterranean Sea . The results, which were published in the latest issue of the journal Nature Climate Change, suggest a «functional extinction» of species with a stage of emission of greenhouse gases «moderately optimistic».

The work that has been done in the framework of the Spanish projects VANIMEDAT-2, MEDEICG and ESCENARIOS, and the SESAME European project, examines the temporal evolution of maximum surface temperature expected during the 21st century in the western Mediterranean. To do this, scientists have used global climate model projections and two regional models.

 ”All models project a quickly warming of the Balearic Sea surface water in summer along the 21st century, what would result in increase in the frequency and intensity of heat waves. On average, the water surface temperature during the summer could increase 3.4 degrees by the end of the century. Since 2050, every summer temperatures would exceed 28 degrees and precipitate the acceleration of the Posidonia mortality ”, explains Gabriel Jordà, researcher at the IMEDEA, a joint research center between the Spanish National Research Council and the University of the Balearic Islands.

Posidonia, that grows extremely slowly, is characterized by its millenary longevity and because forms vast meadows up to 40 meters deep. Among the benefits that the species ecosystem brings, we may highlight the burial of carbon dioxide, the recycling of nutrients, the protection of the coast from erosion and the increase of biodiversity.

Plants of this species that inhabit the seabed of the Balearic Islands are now in recession, not only due to water heating but also by local disturbances such as pollution and vessels anchoring. According to Carlos Duarte, researcher of the IMEDEA (CSIC-UIB), the species has no options but adaptation, what ”is unlikely considering its low rates of sexual reproduction and mutation,” or “decrease drastically until near extinction.”

Scientists have examined the species density progress according to three effects mitigation scenarios. The researcher at the IMEDEA (CSIC-UIB) Núria Marbà explains, “Mitigation of local disturbances in 2010 would delay ten years the functional extinction of grasslands, but if mitigation occurs in 2030, extinction would delay only two years. Actions to mitigate other local disturbances, despite being beneficial, only modestly increase the resistance of the species to marine warming.”

“The only solution to ensure this millenary ecosystem continue providing services beyond the 21st century is the quick international action to reduce greenhouse gases emissions at levels well below considered in this study,” added the scientists.

Citation: G. Jordà, N. Marbà, C.M. Duarte. Mediterranean seagrass vulnerable to regional climate warming. Nature Climate Change. DOI: 10.1038/Nclimate1533.

Source: Communication Department CSIC

Fuente: Dpto. Comunicación CSIC