Value of artificial ponds for aquatic insects in drought-prone southern Africa: a review
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REVIEW PAPER
Value of artificial ponds for aquatic insects in drought-prone southern Africa: a review Michael J. Samways1 • Charl Deacon1 • Gabriella J. Kietzka1 James S. Pryke1 • Carlien Vorster1 • John P. Simaika2
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Received: 12 May 2020 / Revised: 27 June 2020 / Accepted: 19 July 2020 Ó Springer Nature B.V. 2020
Abstract Artificial ponds assure continuous societal water supply, especially during droughts. Obligate aquatic and amphibiotic insects readily inhabit novel water bodies, as many possess mobility traits for opportunistic colonization. We review here the value of artificial ponds (\ 2 ha) (and reservoirs;[ 2 ha) for local aquatic insect diversity in mostly dry and drought-prone southern Africa. We compare these ponds to natural pools, wetlands, and stream deposition pools. The region has a highly varied topography and physiographical zones. Flat, arid areas largely support widespread insect generalists, while the mountainous orographic zones support an additional rich fauna of localized endemics. However, the many ponds ([ 0.5 million) have greatly changed the local distribution patterns of surface freshwater across the region, increasing the area of occupancy for many aquatic insect species, especially dragonflies. We focus on the extent to which aquatic insect assemblages have benefitted from new ponds and reservoirs. We conclude that these novel ecosystems benefit almost all lentic aquatic insect species, while also enabling population resilience during droughts. However, while these benefits are substantial, these ponds are not a substitute for natural still waters, which are still required to maintain all indigenous lentic aquatic insect diversity. Keywords Artificial water bodies Drought Insect diversity Pondscape Reservoirs Water use
Communicated by Nigel E. Stork. This article belongs to the Topical Collection: Biodiversity appreciation and engagement. & Michael J. Samways [email protected] 1
Department of Conservation Ecology and Entomology, Stellenbosch University, 7602 Matieland, South Africa
2
Aquatic Ecosystems Chair Group, Department of Water Science & Engineering, IHE Delft Institute for Water Education, PO Box 3015, 2601 DA Delft, The Netherlands
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Biodiversity and Conservation
Historical background and climate of southern Africa Any biodiversity assessment must consider the early history of the focal ecosystems as a baseline for current drivers of change. Here we focus on southern Africa, south of the Kunene and Zambezi Rivers, encompassing Botswana, Eswatini, Lesotho, southern Mozambique, Namibia, South Africa, and Zimbabwe. The African landmass separated from the rest of Gondwanaland about 145 mya. Apart from some glacial and peri-glacial conditions at the highest elevations (Fitchett et al. 2017), the region has had no extensive glaciers for over 200 million years. However, there has been substantial tectonic uplift, tilting and erosion, and this activity has prevailed since the late Neogene, leading to establishment
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