Nations Educational, Science, and Cultural Organization in 1986.

Th e park provides the best example of the “laurisilva, ” a humid, subtropical, evergreen forest that, during the Tertiary, covered southern Europe and North Africa but then disappeared from these areas during the last ice age. Today laurisilva is a relic forest present mostly in the Macaronesian archipelagos. On La Gomera Island, evergreen forests grow on particular highly evolved soils of volcanic origin, unique in the Canary Islands (Jiménez Mendoza et al., 1990). Th e presence of this evergreen forest on the central plateau of La Gomera contrasts sharply with the arid ecosystems at lower elevations on the island. Traditionally, such ecosystem diff erences have been attributed to the humid Mediterranean climatic conditions prevailing in the area and to the mitigation of drought periods by the incidence of wind-driven fogs (Santana Pérez, 1990). Recent work has raised questions, however, about the relative importance of fog as a source of water to the fores