“Ghost ponds” – How to resurrect in-filled farmland ponds to assist aquatic biodiversity conservation in agricultural landscapes

Abstract

Growing recognition of the importance of ponds for landscape-scale biodiversity has led to considerable interest in their conservation, focusing on new pond creation, or existing pond restoration. However, there is a third approach; the re-excavation of 'ghost ponds' -former ponds deliberately filled-in due to agricultural intensification. Previous work has shown ghost ponds to retain viable sediment propagules of many aquatic plants for over a century, allowing for the rapid re-colonisation of resurrected pond sites. Here we detail the practicalities of the ghost pond resurrection approach, describing how to locate, identify, and excavate ghost ponds in agricultural land. We also report on colonisation by aquatic macrophytes and water beetles (Coleoptera) for three ghost pond resurrections in Norfolk, eastern England and make comparisons with neighbouring extant ponds restored to open-canopy conditions via major scrub and sediment removal at the same time. Ecologically important macrophyte taxa, including charophyte and Potamogeton species, successfully established in the ghost ponds and within one year they supported a comparable species diversity to the adjacent restored ponds. Our findings show that, where appropriate to land management goals, ghost pond resurrection could be a very valuable conservation approach within farmed landscapes.

An evidence-based study mapping the decline in freshwater ponds in the Severn Vale catchment in the UK between 1900 and 2019

“…For the Severn Vale average distances between ponds increased from 154.6 to 179.2 m between 1900 and 2019. Similar increases of distance between ponds have been previously reported (Alderton, 2017;Thornhill et al, 2017). A number of studies demonstrate the detrimental effect increased distance can have on plant species (Bosiacka and Pieńkowski, 2012), amphibians (Jeliazkov et al, 2013), invertebrates (Delettre and Morvan, 2000) and water birds (Sebastián-González et al, 2009).…”

“…It is also common, especially when the original purpose of anthropogenically created ponds no longer exists, for ponds to succeed and become terrestrialised areas of scrub (Sayer et al, 2012;Goodrich et al, 2015). Restoration of "ghost" ponds can facilitate the rapid re-colonisation of aquatic macrophytes (Alderton, 2017) in addition to providing a range of other biodiversity benefits (Williams et al, 2004;Oertli et al, 2005;Davies et al, 2008;Lewis-Phillips et al, 2020).…”

“…Temporal mapping of ponds using historic maps can precisely locate and quantify lost ponds, which is particularly useful to practical pond conservation efforts in several ways. Firstly, by establishing the historic location of individual ponds, we can prioritise locations at which the existing seed bank can be used to facilitate pond establishment (Alderton, 2017). Secondly, by establishing the extent and distribution of pond loss at a landscape scale, we can prioritise areas within the pond network (Céréghino et al, 2007;Hill et al, 2021).…”

Practitioner perspectives on the application of palaeoecology in nature conservation

“…A classic example of this would be dredging, where with proper communication, cores could be collected prior to it taking place or from "saved" areas that have not been dredged. This would provide opportunities to study, for example, the effectiveness of restoration techniques or appropriateness of restoration targets (Alderton et al, 2014;Bennion et al, 2018). There is perhaps also a point here regarding palaeoecologists taking adequate time to better understand typical land management practices in their areas of study so that they may account for the potential impacts these can have on their samples.…”

De la faculté de juger les zones humides

“…9. On pourrait parler de « zones humides fantôme » pour faire écho au travail de Alderton et al (2019).…”