Biological diversity and current threats of lotic ecosystems

Although 100,000 out of approximately 1.75 million species described by scientists live in fresh water, knowledge of the total diversity of fresh waters is woefully incomplete, particularly among invertebrates and microbes, and especially in tropical latitudes that support most of the world’s species. If trends in human demands for water remain unaltered, and species losses continue at current rates, the probability to conserve much of the remaining biodiversity in fresh water will be very low. Lotic ecosystems are increasingly impacted by multiple stressors that lead to a loss of sensitive species and an overall reduction in diversity. Global environmental change (such as climate) occurring at the global scale, together with nitrogen deposition and runoff, are superimposed upon all of the threats. In this chapter, I conduct an extensive review of published studies that have qualitatively and quantitatively examined the species richness and the current major threats of a special component of freshwater systems: The lotic ecosystems.