Study of Lichens of the Moroccan Atlantic Coast Safi - Essaouira: Bioindication of Climate Disturbances and Nitrogen Pollution

In order to explore an ecological correlation between lichens and global air pollution on the Moroccan Atlantic coast Safi - Essaouira, we used a qualitative approach based on the spatial distribution of lichenic flora, mainly saxicolous, which reflects special environmental pollution conditions. Used as good indicators of air quality, lichens can also reflect climate trends. The biological spectrum of studied lichens, characterized by the low presence of fruticose lichens (9%) and foliose lichens (17%) and the dominance of crustose lichens (74%), indicates the arid climate of the region. A comparison between ancient and current lichenic flora revealed the disappearance of Ramalina implexa, lichen with a tropical affinity, which probably had to disappear from this study area, reflecting the loss of a local tropical microclimate within an increasingly arid regional mesoclimate. This observation has been confirmed by the study of temperature and precipitation variations in the region since 1966 to 2020. The identification of 36 species of saxicolous lichens and their categorization by the eutrophication index revealed a gradient of nitrogen pollution that tends to shift the composition of the lichen community from a structure dominated by oligotrophic species to one dominated by eutrophic species. This trend revealed the southern phytogeographic limit of the species Coscinocladium gaditanum.