To assess the dynamics of seagrass beds, it is necessary to be able to compare their present day and former distribution patterns. In most cases, ancient data are available in the form of maps whose reliability must be estimated before comparison. In the study area (near Marseilles, France), a series of maps of the seagrass Posidonia oceanica beds spanning more than one century

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This paper summarizes present capabilities in studying mangrove vegetation from space. There is no standard image processing method that can be applied for the identification and delineation of coastal ecosystems. From a spectral point of view, it is practically impossible to characterize each of the sixty species of trees and shrubs that constitute the mangroves of the world. Nevertheless, some possibilities exist to map at global and at local scales mangrove areas from satellite products, combining several space data sets, interpretation of aerial photographs and ground surveys.The monitoring of mangroves can be considered as operational at a local level using remote sensing techniques, whereas monitoring of these ecosystems at global or at regional levels has not yet been achieved.

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