Impactos do desenvolvimento do potencial hidroelétrico sobre os ecossistemas aquáticos do Rio Tocantins.

Abstract

The priority given to the construction of hydropower plants in Brazil is mostly due to the large hydroelectric potential available in the country and the economic advantages that this energy source presents. In order to meet the increasing demand, during the years many plants have been constructed allover the country. Regardless the obvious success concerning the main objective of such facilities to supply energy for economic development these plants have caused environmental and social impacts with different levels of severity to the aquatic ecosystems and the human communities living in the region. The objective of this work was to identify environmental problems and impacts to the aquatic ecosystems in Tocantins River related to the development of its hydropower potential in order to contribute to the target of making compatible energy generation and biodiversity protection.. The scenario considered included those powerplant in operation and those to be constructed, with feasibility studies and environmental licenses already approved. The Causal Chain Analysis methodology was used, in order to starting with the main environmental problems, to be able to identify the environmental impacts and their immediate, sectoral and root causes. The impacts were ranked according to the characterization matrix, having the fish communities as the main indicators. The impacts considered the most relevant were: (i) degradation of water resources, (ii) loss and changes in habitats, (iii) changes in the ecosystems stability, (iv) reduction of fish stocks, (v) interference with benthic communitites and microorganisms populations, (vi) changes in the food-chain and (vii) interference with the dispersion of fishes and mammals. The knowledge about the existing biodiversity and the identification of the main existing and potential impacts on the aquatic ecosystems of Tocantins River represents an important step for development of effective policy options to minimize the environmental degradation associated to the electric sector.