Insular streams integrity in Ilhabela, Brazil

Abstract

Riparian zones are fragile, dynamic, and complex habitats, especially insular ones. We developed an approach relating 71 environmental variables from the rivers of Ilhabela (Brazil) through a rapid assessment protocol adapted to the rivers and their adjacent environments. The prominent disturbances were related to changes in the physical structure of the riparian ecotone. Height and type of riparian vegetation, stability of riverbanks, sediment deposition, and silting of the bed were the factors that most determined the state of the environment. We evaluated 20 rivers from the eight hydrographic basins of Ilhabela, of which 7 presented excellent conditions, 10 in good condition, and 3 in regular condition. The environments in the most populous portion of the island indicated more critical situations, given the anthropogenic impacts. Riverine management must consider the need for stricter observance of laws and occupation and zoning plans, aiming at environmental conservation and biodiversity.