Two decades of monitoring earthworms in translocated grasslands at Manchester Airport

Abstract

Construction of a second runway at Manchester Airport included a mitigation package of habitat restoration with relocation of earthworms as prey items for protected vertebrates. Translocation of turf in blocks was the standard method used for four of five monitored sites with loose soil moved at the other. To assess earthworm communities at these translocated grassland sites, monitoring was undertaken each October (1998–2019) by digging and hand sorting of soil, followed by vermifuge application. Fourteen earthworm species were recorded, representing all ecological groups, but the majority were endogeic species, dominated by Aporrectodea caliginosa. Total earthworm numbers fluctuated during the monitoring period, with lowest density at 4 m−2 and highest more than a hundred times larger. The overall mean from all sites across the monitoring period was 151 ind. m−2. The differences between sites such as total earthworm numbers and species richness were clearly influenced by the translocation method and specific site topography. Created Hummocks to 3 m for hibernating amphibians proved successful with grassland soil establishing well. Lumbricus terrestris failed to establish due to translocation technique. Using non-metric multidimensional scaling, integration of environmental data with earthworm records showed effects of soil moisture content, pH and rainfall on abundance of ecological groupings and particular species. In general, earthworm community composition was dynamic over the monitoring period suggesting that this and population size needs to be appraised over realistic timescales, which may be best monitored in decades.