Buried alive: Aquatic plants survive in ‘ghost ponds’ under agricultural fields

Carl Derek Sayer,Rachael Davies,Jan Christoph Axmacher,Stephen John Lambert,Emily Alderton

doi:10.1016/j.biocon.2017.06.004

Abstract

The widespread loss of wetlands due to agricultural intensification has been highlighted as a major threat to aquatic biodiversity. However, all is not lost as we reveal that the propagules of some aquatic species could survive burial under agricultural fields in the sediments of ‘ghost ponds’ - ponds in-filled during agricultural land consolidation. Our experiments showed at least eight aquatic macrophyte species to germinate from seeds and oospores, following 50–150years of dormancy in the sediments of ghost ponds. This represents a significant proportion of the expected macrophyte diversity for local farmland ponds, which typically support between 6 and 14 macrophyte species. The rapid (<6months) re-colonisation of resurrected ghost ponds by a diverse aquatic vegetation similarly suggests a strong seed-bank influence. Ghost ponds represent abundant, dormant time capsules for aquatic species in agricultural landscapes around the globe, affording opportunities for enhancing landscape-scale aquatic biodiversity and connectivity. While reports of biodiversity loss through agricultural intensification dominate conservation narratives, our study offers a rare positive message, demonstrating that aquatic organisms survive prolonged burial under intensively managed agricultural fields. We urge conservationists and policy makers to consider utilizing and restoring these valuable resources in biodiversity conservation schemes and in agri-environmental approaches and policies.

Highlights

Intensive agriculture has contributed significantly towards global habitat loss and biodiversity declines (Henle et al, 2008; Tscharntke et al, 2012)
We show remarkable longevity of aquatic plant propagules beneath cropped agricultural fields, and highlight the great potential of ghost pond restoration for aquatic biodiversity conservation in global agricultural landscapes
The propagule bank of GP50 was dominated by viable P. natans seeds and non-viable Lemna trisulca seeds, with only one viable charophyte oospore identified during Tetrazolium chloride (TZ) staining

Summary

Introduction

Intensive agriculture has contributed significantly towards global habitat loss and biodiversity declines (Henle et al, 2008; Tscharntke et al, 2012). With around 75% of all ponds lost across large parts of the UK since the start of the 20th century (Rackham, 1986; Williams et al, 2010; Wood et al, 2003), and with similar levels of pond loss recorded in many agricultural regions across the globe (Agger and Brandt, 1988; Curado et al, 2011; Serran and Creed, 2015), ghost ponds could represent a major and overlooked resource for the resurrection of aquatic species ostensibly lost from the agricultural landscape Both the ‘resurrection’ of ghost ponds, and the translocation of their sediments to newly created sites, could provide highly valuable approaches in aquatic conservation. Ghost pond restoration could help to reinstate the historic landscape connectivity between aquatic habitats

Methods

Results

Conclusion