The fields of England may be hiding a muddy secret. Pockmarking the landscape are the echoes of "ghost ponds" – ponds filled in with soil that are not properly drained. From these, researchers have now resurrected dormant seeds from their dank graves, after being preserved within the soil for over 100 years.
At the start of the 20th century, it is thought that there were up to 800,000 agricultural ponds across the countryside of England and Wales. Since then, however, many have been filled in so that less than a quarter of these persist today. But new research published in Biological Conservation shows that the seeds have survived in the sediments of these ghosts ponds and that they can be resurrected, even after 150 years buried underground.
“It was surprising because these buried ponds have been subject to all the pressures of intensive agriculture, such as compaction, fertilizer, and herbicide use,” explains University College London’s Emily Alderton to IFLScience. “Most published research on aquatic or wetland seeds from wetlands that have been converted to agriculture through drainage suggests the seed bank doesn't survive.”
“We think the difference might be that small ponds are just filled-in, buried wet, compared to large wetlands that are drained, where the desiccation damages the seeds,” Alderton continued.
They found that they could uncover the ghost ponds and then germinate the seeds found buried within, reviving eight different species.
The team didn’t only take the seeds and grow them in isolation. They also fully dug out three ghost ponds, following the contours of the original wetland, and then monitored them to see if they’d re-establish. They found that all three ponds started to show signs of life and, what’s more, many of the species that started growing were found to be from the seeds still preserved in the sediment and were not simply blown in from the environment.
The researchers also found the eggs of at least two crustacean species, suggesting that even some animals might have survived all this time too, although they did not test the viability of these eggs. Using the seeds from the sediment is advantageous, as they may contain locally or even nationally extinct species.
Wetlands provide a whole host of functions for us, from filtering and cleaning water to protecting against flooding and storms. And yet during the past century, over half of the planet's wetlands have been destroyed, mainly as people convert the fertile lands to farming and agriculture. This latest study gives some hope that there is the potential to turn back the clock for some of these habitats.