Riparian forest potential to retain sediment and bromophenol concentrations in fish.

Biodiversity conservation has attracted growing concern and importance for global stability. The data presented by Luiz F. Pires and colleagues in this issue of the Anais da Academia Brasileira de Ciências (AABC) may soon earn some praise regarding a more effective stability of biodiversity. Their study aimed to check the efficiency of a riparian forest in trapping sediments coming from an upland sugarcane field, using the 137Cs technique aided by soil carbon isotopic ratio analysis. Riparian zones are ecotons located between aquatic and terrestrial systems, considered key areas for the stability of global biodiversity, serving as protection niches for wildlife, and acting as ecological corridors between forest fragments (Kajeyama et al. 2002, Rodrigues and Gandolfi 2001). Besides their ecological function, these “buffer zones” are considered important for waterway protection, being responsible for improving surface water quality. The main mechanisms involved in this function are the filtering and trapping of sediments which result from erosion on upland agricultural fields. These mechanisms are related to changes in surface roughness, water infiltration rates into litter layers, the presence of roots, and the improved structure of soil matrix caused by intense microbiologic activity in the soil (Ampontuah et al. 2006, Izidorio et al. 2005). The results obtained by the 137Cs technique and soil carbon isotopic ratio analysis indicated the efficiency of riparian vegetation in trapping sediments coming from agricultural lands and its importance as a conservation measure on the watershed scale. The results allow the statement that the minimum forest width of 30 m would not be enough to ensure the sediment trapping function of riparian vegetation for the local conditions of soil, climate, land use, topography, and kind of riparian vegetation, contradicting Brazilian Environmental Law (Law 4.771/65) if adopted for such conditions. Although the report of Pires et al. (2009) will undoubtedly be appreciated as a technical advance in the evaluation of the riparian zones related to the stability of global biodiversity, the results will likely generate even greater interest among Brazilian legislators as a significant indication regarding the necessity to reevaluate Brazilian Environmental Law according to the recent scientific evidence.