biodiversity

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.

The Southeastern Fishes Council Technical Advisory Committee reviewed the diversity, distribution, and status of all native freshwater and diadromous fishes across 51 major drainage units of the southern United States. The southern United States supports more native fishes than any area of comparable size on the North American continent north of Mexico, but also has a high proportion of its fishes in need of conservation action. The review included 662 native freshwater and diadromous fishes and 24 marine fishes that are significant components of freshwater ecosystems. Of this total, 560 described, freshwater fish species are documented, and 49 undescribed species are included provisionally pending formal description. Described subspecies (86) are recognized within 43 species, 6 fishes have undescribed subspecies, and 9 others are recognized as complexes of undescribed taxa. Extinct, endangered, threatened, or vulnerable status is recognized for 28% (187 taxa) of southern freshwater and diadromous fishes. To date, 3 southern fishes are known to be extinct throughout their ranges, 2 are extirpated from the study region, and 2 others may be extinct. Of the extant southern fishes, 41 (6%) are regarded as endangered, 46 (7%) are regarded as threatened, and 101 (15%) are regarded as vulnerable. Five marine fishes that frequent fresh water are regarded as vulnerable. Our assessment represents a 75% increase in jeopardized southern fishes since 1989 and a 125% increase in 20 years. The trend for fishes in the southern United States is clear; jeopardized fishes are successively being moved from the vulnerable category to that of imminent threat of extinction.

In this article, I describe the importance of large river-floodplain ecosystems and some of the consequences of altering their natural processes, functions, and connectivity. Then I contrast the species-focused management typically employed by natural rescue agencies with the ecosystem approach. I define ecosystem management as working with the natural driving forces and variability in these ecosystems with the goal of maintaining or recovering biological integrity. I focus on flood pulses both because they drive these systems and because the great floods of 1993-1994 in Asia, Europe, and North America heightened public awareness, thereby creating an opportunity to change river management policies.
I draw my examples largely from the upper Mississippi River and Illinois River because I am most familiar with them. They also exemplify both the conflicts between development and conservation of large floodplain rivers that have occurred world wide and the more recent restoration and rehabilitation efforts that are beginning in Europe and the United States.
The Mississippi River and Illinois River comprise the Upper Mississippi River System, which the US congress designated as both a "nationally significant ecosystem" as well as a "nationally significant waterway" in the Water Resources Development Act of 1986.Plans for even greater expansion of navigation capacity are currently being developed by the US Army Corps of Engineers. But federal and state natural resource agencies and several environmental groups fear that the integrity of the upper Mississippi is being compromised. They have issued their own strategies and plans for conserving and restoring the river.

The most often heard claims in support of large scale hydroelectric development are: (1) hydropower generation is 'clean', (2) water flowing freely to the ocean is 'wasted', and (3) local residents (usually aboriginals) will benefit from the development. These three claims are critically examined using case histories from Canada and elsewhere in the world. The critique is based mainly on journal articles and books, material that is readily available to the public, and reveals that the three claims cannot be supported by fact. Nevertheless, large scale hydroelectric development continues on a worldwide basis. The public needs to be well informed about the environmental and social consequences of large scale hydroelectic development in order to narrow the gap between its wishes for environmental protection and what is really occurring.