“Ghost ponds” : Resurrecting lost ponds and species to assist aquatic biodiversity conservation

Abstract

Over the last century, around half of all ponds and small wetlands have been lost globally, predominantly from agricultural regions. These losses present a major conservation challenge for aquatic biodiversity and habitat connectivity. While the creation of new ponds is widely advocated as a means of restoring some of these lost habitats, this thesis presents an alternative approach – the resurrection of ‘ghost ponds’, historic ponds in-filled during agricultural intensification. Many aquatic organisms have evolved dormant propagules for surviving periods of habitat desiccation, and can remain viable for centuries buried in wetland sediments. While such long-term viability is well established in extant aquatic habitats, the fate of propagules buried within ghost ponds has remained unexplored. If their viability was proven, ghost ponds could present a crucial overlooked conservation resource. Here, I examine the potential conservation value of ghost pond resurrection within a typical agricultural UK landscape. First, historic declines in pond numbers and pond density are examined for this landscape, and the potential implications of these changes for aquatic biodiversity are explored using a space-for-time replacement approach. The conservation value of ghost ponds is then explored through a series of lab and field studies, that demonstrate the viability of propagules representing at least eight aquatic macrophyte species, after laying dormant for 50 – 150 years. Once resurrected, ghost ponds were quickly (<6 months) re-colonised by a diverse aquatic vegetation. With ghost ponds representing abundant, dormant time capsules for aquatic species in agricultural landscapes, these findings open up exciting new possibilities for aquatic habitat and biodiversity restoration on a global scale.