Future ecological studies of Brazilian headwater streams under global-changes

this paper results from discussions triggered during the "stream ecology symposium" that took place at the xiii congress of the brazilian society of limnology in september of 2011 in natal, brazil. based on our experiences, we have raised several questions regarding ecological studies of headwater streams facing threats under global-changes and proposed numerous subjects to be addressed in future studies in brazil. these studies deal with the necessity of knowing species biology and the elaboration of models to assess changes (which implies the availability of time-series or large-scale data sets); the ecology of riparian zones and the interchange of materials and energy across the land-water boundaries; forest conversions and standardized sampling strategies and data treatment to assess global change.