THE MANGROVES OF BAIXADA SANTISTA: A PROPOSAL FOR CLASSIFICATION

Abstract

A study carried out from 1982 to 1986 in 33 different mangrove sites of Baixada Santista has shown that the forest height ranges from 4.5m to 13.2m, the average being 8m. The forest density varied ranging from 600 to 3,800 trees per hectare. As for the average diameter, a variation of 3.6 to 12.7cm was observed together with a total basal area of 3.6 to 31.1m² per hectare. The aims of this study were to classify the mangrove forests in groups according to their structural characteristics and degradation level and to develop criteria for this kind of classification. Cluster analysis of these sites according to their structural features showed groups of mangrove forests with different degrees of degradation. The analysis of the distribution of these groups indicated that the elements of the same group are not necessarily found close to each other although there is a concentration of them in some places in particular. From this observation, a transverse area (direction northeast - southwest) between the region of Sao Vicente and Santos estuary which shows a higher concentration of highly degraded mangrove areas, was delimited; whereas in the south of São Vicente estuary and to the east, near Bertioga there are less degraded areas. It is hard to tell to what extent the human activities affect this distribution, because this region is exposed to several types of impact.