The wetlands are dynamic ecosystems, having greater biodiversity and special botanic- ecological structure. These ecosystems are always changing under the influence of natural and human factors by passing through healthy threshold and destruction. One of the approved regulations of Ramsar convention and AGENDA 21 about wise use of wetlands and immigrant birds, for member countries is the measurement of ecological characteristics and sustaining the biodiversity in order to evaluate the environmental consequences in wetlands. To understand the effects of socio-economical activities of human societies around wetlands on vegetation structure of these ecosystems, the present research has been carried out in 7 indicator wetlands in northern Iran, located in southern coast of Caspian sea during 1995-2005. The evaluation of the changes in relative density of observed plants on water surface has been done by Distance Method and the statistical analysis has been carried out by using the ANOVA with SPSS9 software. Based in the results of the research, the following plant species: Azolla filiculoides, Nympha alba, Phragmites australis, Nelumbiym nuciferum, Juncus articulatus, Scirpus maritimus and Utricularia neglecta are the increasing species and the following plant species: Lemna minor, Butomus umbelatus, Sparganium erectum, Salvinia natans and Iris pseudacorus are the decreasing species in northern Iran’s wetlands
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