Plant communities along the banks of rivers dammed for hydroelectric power contain significantly fewer species than those along neighboring free-flowing rivers. Riverbanks provide a variety of environments for plant life. The inflow of nutrients and sediments; changing water levels over the seasons; and waterborne dispersal of seeds all contribute to the biodiversity. There is considerable debate among ecologists about how well plant populations recover and reestablish themselves alongside new, regulated water courses. The team compared both the simple number of species and an index of "species richness," which compensates for differences of riverside areas. The team found about 1/3 fewer species around storage reservoirs of hydropower systems than at comparable undisturbed sites; the index of species richness was only about 1/2 for these sites. By studying the vegetation alongside regulation schemes between 1-70 years old, the team found that the number of species increases along the water's edge initially, but then the community development appears to halt and the communities look permanently different. These results are likely to fuel debate on the relicensing of hydropower systems to regulate water. Different options are briefly discussed.
American Rivers produced abstract