Conservation importance of semi-arid streams in north-eastern Brazil: implications of hydrological disturbance and species diversity.

摘要

Intermittent streams in the semiarid region of Brazil are distinctive landscape features existing as dry watercourses for most of the time. It has been recognized that the extremes of flooding and total absence of water flow are the principal hydrological characteristics of rivers and streams in this region. This is a consequence of complex climatic patterns that lead to an irregular distribution of the small amount of rainfall and low thermal amplitude. The latter is the main climatic difference between the Brazilian semiarid region and other semiarid lands. The expansion of water resource development has been a threat to the natural flow regime and the ecological integrity of rivers and streams in semiarid Brazil. Efforts to manage and conserve the natural flow regime of these systems are hampered by limited scientific information on the ecological processes driving their flora and fauna and the responses of biota to the high natural variability in flow regime. The most important issues in the conservation of streams in semiarid Brazil are the need for their recognition as important sites of biodiversity and that this diversity is closely associated with natural patterns of flow and the hydrological disturbances. Without the understanding of how the extremes of flooding and drought affect the aquatic fauna, the conservation strategies for Brazilian semiarid streams and their fauna will not be effective. Therefore, conservation efforts in semiarid Brazil must ensure that the processes sustaining biodiversity are maintained at multiple-scale and landscape levels and that the natural integrity of the riparian zone is maintained..