Browsing by Author "Vandvik, Vigdis"

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    Back to Africa: Monitoring Post-Hydropower Restoration to Facilitate Reintroduction Of An Extinct-In-The-Wild Amphibian
    (2014-08) Vandvik, Vigdis; Måren, Inger E.; Ndangalasi, Henry J.; Lovett, Jon C.
    Monitoring of the ecological efficiency of different restoration and mitigation measures is important to inform decision-making but can be challenging, especially in remote and low-resource settings. Species composition of the vegetation is sensitive to environmental variation, and can thus be used in restoration assessment, but this requires statistical approaches that can accommodate multivariate responses. We use principal response curves (PRC) to assess the efficiency of post-hydropower mitigation measures installed to secure the reintroduction of an extinct-in-the-wild amphibian back into its only native habitat. The endemic ovoviviparous Kihansi spray toad Nectophrynoides asperginis is only known from a wetland in the Lower Kihansi River Gorge in the Eastern Arc Mountains in Tanzania. River flow was diverted from the gorge for hydropower production in 1999, causing the spray wetland to desiccate, consequently threatening the toad and other plant and animal species dependent on the spray-zone habitat. To mitigate the toad population collapse, a sprinkler system was installed over a limited section of the original sprayzone wetlands to mimic the waterfall spray and toads were taken to the USA for ex situ breeding. The decline, extinction, ex situ breeding, and planned reintroduction of the species has driven substantial research on Kihansi spray toad biology. In contrast, the efficiency of the mitigation measures in restoring the spray-zone wetland habitat required for its successful reintroduction has not been formally evaluated. Here, we analyze re-sampled vegetation data from the spray-zone wetland over a period of eight years by means of principal response curves to investigate if the post-hydropower mitigation measures have successfully restored the pre-hydropower ecosystem. The results show that the spray-zone vegetation is recovering. The wetland flora and especially species important to the Kihansi spray toad have increased and the restored ecosystem has stabilized, favoring the reintroduction of the Kihansi spray toad to its native habitat. However, the wetland ecosystem is not restored entirely and continued mitigation measures are needed. Continued monitoring is essential to support evidence-based restoration, and we conclude that assessment based on vegetation monitoring coupled with principal response curve analyses provides a cost-effective and efficient monitoring tool for such proje
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    Back To Africa: Post Hydropower-Project Mitigation Effects on Wetland Vegetation in Relation To The Conservation of an Endemic Amphibian
    (Wiley, 2012-07) Maren, Inger E.; Vandvik, Vigdis; Ndangalasi, Henry J.; Taplin, James; Mbago, Frank; Lovett, Jon C.
    Developing countries are home to much of the world’s biodiversity due to their location in areas of high species richness and their native vegetation has not yet been totally transformed by human activity. Enabling economic and social development to proceed whilst retaining the high environmental values is central to the principle of sustainability, but activities under these three pillars of sustainability are often in conflict. Provision of energy from environmentally sound technologies is critical for economic development in Africa and hydropower offers a reliable way of doing this. The Lower Kihansi Hydropower Project in Tanzania is a model example of the application of technology to minimise environmental impact. However, although the footprint of the project is relatively small, it is located in a biodiversity hotspot where almost any development will have negative impacts on its many restricted range species. Globally, hydropower projects have been associated with negative biological impacts of flooding of the reservoir impounded by the dam. Less attention has been paid to the immediate downstream effects of dams, such as the loss of waterfall spray zones. We analysed the effects of the mitigation efforts by the installment of a sprinkler system to prevent extinction of the Kihansi Spray Toad Nectophrynoides asperginis, which is only known from this short section of the Kihansi River. We analysed re-sampled vegetation plots in the spray wetland habitat over a period of eight years to test if the post-hydropower project mitigation has aided the vegetation composition in approaching similarity to that of the pre-hydropower project conditions, testing two hypotheses dealing with habitat responses to the mitigation measures; (i) Does the instalment of the sprinkler system alter plant species composition in the former waterfall spray zone in relation to the controls? (ii) Do the mitigation measures succeed in restoring the wetland habitat and hence facilitate the re-introduction of the Kihansi Spray Toad? The results clearly show that the post-hydropower mitigations are successful as the vegetation cover and species composition with time approach that of the pre-hydropower project conditions. Overall, the proportion of weedy species decreased and wetland species increased with time since mitigation. However, results suggest that the wetland has not entirely reverted back to pre-project conditions and continued mitigation measures are needed. In conclusion, this positive trend in the wetland habitat development due to the mitigation measures may facilitate the reintroduction of the in situ extinct Kihansi Spray Toad in the near future.