Rivers: Dams, Canals and Channeling: Page 4 Endangered Species Handbook

Aquatic Ecosystems

Rivers: Dams, Canals and Channeling: Page 4

Africa's rivers have also been dammed, eliminating wildlife. Most recently, a dam on Tanzania's Lower Kihansi River, costing $272 million, has blocked the flow of a beautiful waterfall, the sole habitat of a newly discovered toad, the Kinhansi spray toad (Asperginus nectophrynoides) (Donnelly 2001). This tiny, translucent toad is confined to a 10-acre marsh sprayed by the waterfall. The major source of funds, World Bank, was informed of the imminent extinction of the toad and the loss of the waterfall in 1997, but took no action until Friends of the Earth president Brent Blackwelder wrote the bank's president on the topic of the seriousness of the situation and need for corrective action (Donnelly 2001). An artificial spray system was installed for the toads, and 500 of the estimated 11,000 remaining toads were shipped to the Bronx Zoo and the Detroit Zoo. The toads have proven extremely difficult to maintain in captivity, although breeding did take place at the Bronx Zoo. Tiny, wingless insects must be hand-gathered for these toads, which weigh only two-tenths of a gram, and the majority of the zoo department's staff is occupied in caring for the toads. World Bank employees are considering a $5 million loan to manage the habitat around the Kihansi Gorge to prevent the species from becoming extinct (Donnelly 2001). It is remarkable that the World Bank has been forced to consider the survival of a tiny toad, but unfortunate that the entire ecosystem is being destroyed for electricity production that could have been generated in a less destructive fashion.

The amount of fresh water collected by dams worldwide has increased in the past 40 years by 10,000 cubic kilometers, or 10 trillion tons, an amount equivalent to all the moisture in the Earth's atmosphere (Browne 1996). Much of the water retained in reservoirs is lost to evaporation, especially in arid regions. Geophysicists calculate that dam building will continue until all sources of recoverable water have been exploited, a time that is expected to come in the next century (Browne 1996).