Pond Management Network (POMAN)
Between 2002 and 2013, a network comprising 455 small freshwater bodies has been gradually constructed in nine Estonian counties. The focal species are amphibians: three threatened species listed in the annexes of the EU Habitats Directive (92/43/EEC) – the northern crested newt (Triturus cristatus) and the common spadefoot toad (Pelobates fuscus) in Eastern Estonia, and the natterjack toad (Bufo calamita) in Western Estonia – and the common frog (Rana temporaria) on Hiiumaa Island for providing food supply for the critically endangered European mink (Mustela lutreola). The pond construction (restoration or creation) is aimed: (i) to halt the decline of small and isolated populations of the focal species; (ii) to secure the increase of their populations by providing high quality breeding sites. However, the ponds serve as refuge or novel habitats for many other species, including threatened invertebrates.
The pond network has been constructing according to five principles:
- Clustered design – to increase colonization probabilities and support the existing populations of threatened amphibians, ponds have been constructed in clusters (3–26 ponds in each), with distances between ponds < 500 m and at least one constructed pond within 200 m of an existing breeding pond of the focal species.
- Non-intensive land use context – land cover within 50 m from any constructed pond consists mainly of a mosaic of forest and (semi)natural grassland (for the crested newt); (semi)natural grasslands and small extensively used potato fields or vegetable gardens (for the common spadefoot toad); or semi-natural grasslands or open sandy habitats (for the natterjack toad).
- Variation in vital characteristics – to assure different hydroperiods and improve the cluster quality, ponds have various depths (0.4–2.5 m), sizes (12–8000 m2) and widths of shallow littoral zone (0.2–15 m). Existing ponds have been (a) cleaned from bushes and high dense vegetation (e.g. Typha latifolia), (b) extracted of mud down to the mineral soil (mostly clay), to assure the quality and transparency of water as well as to eliminate the fish (for that purpose, the ponds were also pumped dry), (c) enlarged (if very small) and levelled on banks to create shallow littoral zones with warm water.
- No connection to running water (ditch, stream, river) – to avoid fish introduction or sedimentation; by necessity, existing ditches have been blocked for that purpose.
- On-site guidance – each pond construction is unique (depending on the relief, soil, hydrology, presence of drainage system, surrounding habitats etc.) and guided in the field by experienced amphibian experts.
- amphibians as focal species in pond construction: long-term and large-scale impacts, and the representation of threatened macroinvertebrates (dragonflies, water beetles)
- nestedness of species assemblages in pond ecosystems
- effects of land use changes on habitat parameters of a threatened dragonfly, Leucorrhinia pectoralis
PhD projects involved
- Lars L. Iversen (University of Copenhagen) “Conservation of aquatic insects in ponds and temporary waters”;
- Elin Soomets “Focal species in wetland management: comparing the restoration of naturalness and creation of novel habitats“;
- Liina Remm “Impact of artifical forest drainage on biodiversity”;
- Riinu Rannap (completed) “Impact of habitat loss and restoration on amphibian populations”.
 Rannap R., Lõhmus, A., Briggs, L. 2009. Restoring ponds for amphibians: A success story. Hydrobiologia 634: 87–95.
 Rannap, R., Lõhmus, A., Tammaru, T., Briggs, L., de Vries, W., Bibelriether, F. 2012. Northern natterjack toads (Bufo calamita) select breeding habitats that promote rapid development. Behaviour 149: 737–754.
 Rannap, R., Lõhmus, A., Linnamägi, M. 2012. Geographic variation in habitat requirements of two coexisting newt species in Europe. Acta Zoologica Academiae Scientiarum Hungaricae 58: 73–90.
Publicity [in Estonian]
Rannap, R. 2011. Elu kaladeta tiigis. Loodusesõber 4: 30–35.
Rannap, V., Rannap, R., Lepik, I. 2012. Tiikide korrashoid toetab looduslikku mitmekesisust. Eesti Loodus. 10: 26–29.
The construction of ponds has been financed by EU LIFE-Nature projects LIFE00NAT/EE/7083; LIFE04NAT/EE/000070 (http://www.envir.ee/114585) and LIFE08NAT/EE/000257 (http://www.keskkonnaamet.ee/dragonlife); Stiftung Artenschutz, Species Conservation Foundation “Lutreola” (http://www.lutreola.eu) and the Estonian Centre of Environmental Investments.
Photos 1–2. An overgrown depression before (August 2010) and at the time of the restoration for the crested newt (October 2011). Photos: R. Rannap.
Photo 3. Ponds created for the natterjack toad. Photo: R. Rannap.