The situation in the gorge
The Kihansi spray toad (Nectophrynoides asperginis) is one of seven species in the genus Nectophrynoides in the family BUFONIDAE. The genus is endemic to Tanzania and all but one species are found only in the Eastern Arc Mountains (Box 1). The Kihansi spray toad, discovered in 1996, has one of the most restricted ranges of any vertebrate in the world. It was found only in a 0.02 km2 spray zone around the Kihansi and Mhalala waterfalls in the southern Udzungwa Mountains. The toad is dependent on the delicate habitat maintained by the spray from the waterfall. In recognition of the rarity of the genus Nectophrynoides, it is listed on Appendix 1 of the Convention on International Trade in Endangered species (CITES) thereby prohibiting any commercial trade. In addition to the Kihansi spray toad there are also three species of plant endemic to the gorge.

Since April 2000, 90% of the water that formerly maintained the toad's habitat has been diverted into a tunnel to power the Lower Kihansi Hydropower Project plant. This has caused 95% of the spray-dependent habitat to dry up thereby threatening the survival of the Kihansi spray toad and the unique gorge ecosystem. Repeated surveys have shown a decline in the population of spray toads in the gorge. The most recent reports (February 2001) indicate a severe reduction in toad numbers which seem to indicate a population crash.

The Lower Kihansi project has cost approximately $275 million and has been financed primarily by the World Bank, NORAD and the German bilateral credit institution Kreditanstalt fur Wiederaufbau (KfW). The construction of the dam has been undertaken by the engineering firm Norplan. The plant is run by TANESCO and can supply up to 180 MW of electricity to the national grid.

The Tanzanian government, the World Bank, NORPLAN and other stakeholders are currently reviewing and implementing a number of strategies to attempt to alleviate the impact on the gorge habitat and the Kihansi spray toad. Box 2 outlines some of the options available and looks at their relative advantages and disadvantages. Early Environmental Impact Assessments recommended a minimum flow sufficient to maintain the gorge ecosystem however TANESCO has only let through a bypass flow of 1.5 Ð 2m3/sec. This is not sufficient to maintain the ecosystem. In addition, even if a minimum flow rate is maintained in the short term, the threat of periodic sediment flushing from the dam could theoretically wipe out all habitat and toads in a matter of minutes. Periodically flow rates are planned to rise to as much as 60m3/sec (compared to the present flow rate of 1.5m3/sec and historic flow rate of 16m3/sec) in order to clear the dam of sediment.

Another solution that has been tried is to use artificial sprinklers. After much of the former spray wetland on which the toads depend had died, NORPLAN constructed some artificial sprinklers in an attempt to mimic the spray from the falls. However by the time the sprinklers were introduced the habitat had been altered and the toads could only be found concentrated on rocks receiving natural spray in the Kihansi River. Possibilities for the less desirable option, translocation, are being researched however this is not a proven conservation strategy particularly with a species with such specialised habitat requirements and it is unlikely that this approach could succeed.

The government, through the Wildlife Division, and the Wildlife Conservation Society (US) have also supported a captive-breeding programme in which 500 toads were sent to Bronx and Detroit zoos in the USA. Mortality rates amongst the captured individuals have been high (55% for adults and 45% for young) due to lung worm parasitism and secondary infections, placing their survival in captivity doubtful beyond the next six months.

At present the only option which seems to have a realistic chance of avoiding the extinction of the Kihansi spray toad and the loss of the gorge habitat is to close the dam. However given that the dam provides up to 33% of the nation's electricity this is neither economically nor politically acceptable. The outlook for the toad is therefore very bleak.

The bigger picture
The fact that this discussion is ongoing and that steps have already been taken to protect the toad are positive signs and seem to reflect a genuine commitment to biodiversity conservation on the part of the government and the donors. However what remains unclear is why the project continued largely unmodified once the new species was discovered in 1996 in apparent contradiction to the recommendations of an environmental assessment, the Convention on Biological Diversity and the donors' environmental policies.

When large development projects are carried out which have a potential impact on the environment it is normal to conduct environmental impact assessments known as EIAs (Box 2). In Tanzania, the National Environment Management Council is empowered to enable smooth management of environmental impact assessments. Whilst there is a relatively supportive policy environment for EIA (largely due to initiatives such as the National Environmental Policy, Environmental Protection Bill, National Environmental Action Plan, National Conservation Strategy for Sustainable Development, Land Policy), there is currently no national legal requirement for EIA in Tanzania, nor supporting institutional mechanisms. Nonetheless in line with NORAD and the World Bank's policies two such assessments were conducted for the Lower Kihansi project. Both were problematic, the first because it was inadequate and failed to research the sensitive spray zone habitat; the second because at the time that it was conducted TANESCO and the donors were unwilling to review significantly the plans for the project.

An environmental monitoring programme related to the second assessment included a study of the spray habitat resulting in the discovery of the Kihansi spray toad and the three endemic plants. Having realised how unique the site was, the assessment team recommended that the flow over the waterfall should be maintained at 7 m3 / s to avoid the area drying up. The developers then had three years to adapt the project in response to these recommendations. However, subsequently the flow has been to reduced to 1.5 m3 / s resulting in the loss of most of the spray habitat.

Overall the recommendations of the environmental impact assessments were not heeded. The situation in Kihansi demonstrates that for environmental impact assessments to be effective they must be integrated in the project design; they should be reviewed by an independent authority according to agreed standards; their recommendations need to carry legal weight and there should be more transparency surrounding their development including a wider process of stakeholder consultation.

Over the last twenty years nations, including Tanzania, have come together to try to agree on a strategy to prevent the loss of global biodiversity. One product of this has been the Rio Convention on Biological Diversity signed by 179 parties since 1992. Tanzania and Norway are both signatories of this convention and thus accept that they are responsible for conserving biological diversity and for using biological resources in a sustainable manner. NORAD and the World Bank also have their own environmental policies. The World Bank's policy includes the statement that Ôthe Bank does not support projects that involve the significant conversion or degradation of critical natural habitats'. In the case of the Lower Kihansi project there is a marked discrepancy between these policy statements and what has occurred.

For the Kihansi gorge further habitat loss could be avoided by maintaining a sufficient minimum flow over the falls as recommended by the 1996 assessment and by introducing measures to mitigate the potential threat of sediment flushing. More importantly however there needs to be a thorough review of the case of Kihansi with clear recommendations which can guide donors, NEMC and operators such as TANESCO so that future projects can avoid damage to such critical habitats. Donors and the government need also to uphold their commitment to environmental protection as set out in the Convention on Biological Diversity and their environmental policy statements.