In the last decades of this century, the mangroves have been studied under several points of view, being aim of ecological, biological, geomorphological and social-economical researches.

In spite of the account given to the mangroves, these ecosystems suffer a lot of kind of impacts, mainly those induced by men. On the other hand, nowadays, the concernig of scientific researches is directed on the losing of mangrove areas due to erosion and sedimentation processes as a consequence of the rise of the sea mean level. There are no doubt the ecological conditions of the mangrove to response to erosion and depositional events of the coastline, provocated or not by wideworld climatic changes.

This paper analyses the geomorphological and phitogeographical changes on the São Mateus River mouth, in Conceição da Barra, Espírito Santo (Brazil), between the years of 1970 and 1998. The mangroves are seen under the biogeographical point of view - helped by the most adopeted methods in geomorphological reaserch - which understanding of the distribution in time and space, is enphasized by the interrelation of the elements that composes the landscape, such as climate, hidrography, landform, soil and the man.

Based on methods elaborated by Ab'Sáber (1969) and Ross (1992) and conceptuals by Thom (1984), we tried to understand the causes of recent configuration of the São Mateus River mouth, and mainly, the distribution of the mangroves, through distitive scales and timing analysis.

In this way, the hidrographic complex of the São Mateus River is the largest spacial unit analysed, which geomorphological, climatical and land use characteristics are interpreted in a more abroaded form. A more detailed analysis is made at the Sao Mateus River mouth where the mangroves are studied as biological indicators of the erosive and depositional events, through their biotic and abiotic characteristics.