Creating new populations to conserve the endangered Silene cambessedesii in the Iberian Peninsula

Summary

Silene cambessedesii, a Vulnerable annual coastal-dune plant endemic to the eastern Iberian Peninsula and the Balearic Islands, had declined from four Spanish populations to just one, Platja d'Almenara in Castellón, after marine storms and human activity destroyed the others. Spain's Valencian Wildlife Service set out to create protective neopopulations near this last native site, since the species produces abundant seed in ex-situ cultivation despite modest germination rates around 40-79%, making nursery propagation via traditional seedbeds straightforward. Since 2012, the service has carried out seven plantations and one sowing trial along 30 km of coastline between Moncofa and Sagunto, using 52 to 816 nursery-grown individuals per site depending on production availability, with plants needing only initial watering thanks to reliable dune microclimate humidity. Annual monitoring found the four plantations established in 2012-2013 became apparently stable, typically showing weak recruitment in the first one or two years followed by rapid growth once a soil seedbank accumulated; the oldest plantation, begun with just 52 plants, held 2,863 reproductive individuals by 2015, and the four earliest plantations together reached 3,461 individuals against 7,487 at the native site. A concern is that plant vigor declines after three to four generations of ex-situ propagation, requiring periodic renewal from fresh wild seed, and both natural and planted populations face habitat degradation from beach-maintenance practices tied to tourism quality standards. The project rates itself successful, crediting the dunes' naturally moist conditions and the species' biology, while flagging the need for stronger cooperation among local, regional and national authorities and continued monitoring of genetic renewal in the seed stock.