Effects of a hydropower plant on Coleopteran diversity and abundance in the Udzungwa Mountains, Tanzania

Abstract

Abstract. The effects of river flow diversion on biodiversity were assessed using Coleoptera as an indicator group in three habitats of the Kihansi Gorge (Udzungwa Mountains, Tanzania), before and after commissioning of a hydropower plant. Data collected using sweep netting and pitfall traps showed that the effect of diversion of the river flow was site-specific, affecting particularly the spray habitat. Rarefaction analysis of both sweep netting and pitfall samples indicated that the expected richness of Coleoptera declined significantly in all habitats after commissioning of the power plant. Sweep netting and pitfall samples showed that the highest Shannon-Wiener diversity index value before the diversion of the river flow was in the spray zone, but the index value decreased after diversion. Changes in the other two habitats were less prominent. Analysis of variance using diversity index values from five pitfall samples in each habitat type before and after commissioning indicated that there were no statistically significant differences in the diversity index between the two sampling periods or among the three habitat types. Renkonen's similarity index between habitats showed that pitfall samples had higher similarity (!87%) than did samples from sweep netting ( 69%). It is suggested that for mitigation purposes, artificial spray systems, which have been installed in other wetlands of the Kihansi Gorge, also be installed to cover the whole Lower Wetland in which this study was undertaken. In order to maintain overall biodiversity in the Kihansi Gorge, it is suggested that the ecosystem conservation approach be prioritised.

Initial Trends of Bird Assemblages Before and After River Diversion in an Endemic-rich African Forest

“…We do not yet have evidence of post-diversion changes in vegetation and invertebrates in the Upper Kihansi transect, but the wetland vegetation within the spray zone region has experienced major changes (Quinn et al in press), and the endemic Kihansi toad population (K.M. Howell, personal communication 2004) and insects of this microhabitat have declined since diversion (Zilihona et al 2004). Therefore, the decrease in numbers of A. virens after diversion may reflect changes occurring in the adjacent Upper Kihansi transect.…”

“…Given current findings that the spray zone vegetation has dramatically changed (Quinn et al in press), and that there have been correspondingly rapid declines in the Kihansi Spray Toad population (K.M. Howell personal communication 2004) and in insects (Zilihona et al 2004) since diversion, we emphasise the potential of using the Kihansi Gorge as a natural experiment to evaluate what factors associated with the river diversion alter species composition and drive certain species, including birds, toward local extinction.…”

“…Diversion of the river in 2000 following project commissioning has since severely altered the waterfall and diminished the spray effect (Zilihona et al 2004;Quinn et al in press). A pilot avifaunal study in 1995 identified some birds of conservation concern in Kihansi gorge (Rahner 1995), and pending commissioning, our main goals were to establish a sampling regime in the hot and cold seasons of 1999-2000 to compare the avifauna of the Kihansi Gorge to the adjacent Udagaje Gorge, the latter of which required confirmation as an adequate control site.…”

Tree Diversity in Western Kenya: Using Profiles to Characterise Richness and Evenness

“…If we would have used a single diversity index such as the Shannon, Simpson or Berger-Parker index, then we have obtained erroneous results. Studies that attempt to order communities in diversity (e.g., Dougall and Dodd 1997;Slik et al 2002;Mishra et al 2004;Zilihona et al 2004) should therefore not base the ordering on a single index, or even a combination of several indices, but use techniques developed for diversity ordering such as the Re´nyi diversity profile. Although the aim of our study was not to compare the performance of several diversity ordering techniques, we agree with To´thme´re´sz (1995) that the Re´nyi profile is one of the most useful methods for diversity ordering.…”

Environmental Impact Assessment of Power Development Project: Lessons from Thailand Experiences

“…Increasing demand of electric consumption is a major challenge for authorities trying to ensure satisfactory supply. And with this growing demand for energy capacity it is crucial to consider supply security and environmental sustainability, especially health risks, land use conflict, biodiversity depletion and global warming issues (Zilihona et al, 2004;Nakawiro et al, 2008;Conner and Roy, 2008).…”