In late winter 2014 Britain experienced a series of Atlantic storms which brought with them the highest rainfall since 1910 (January had 176mm of rain, and the winter’s total up to 1 March 2014 was 516 mm). Soils couldn’t hold any more water in many places and there was serious, and well-reported, flooding in several areas. How much a soil can cope with flooding is partly a function of worm activity.
Studies at UCLan have shown that the macropores created by deep-burrowing earthworms can be a major factor in water movement away from the surface. Dr Kevin Butt (Reader In Ecology, within the Geography and the Environment section at UCLan) featured on the BBC Farming Today programme on 25th February explaining more about this vital ecosystem service provided by the lowly worm.
The perception is that earthworms will drown when submerged for lengthy periods of time or at best only escape by vacating their burrows and potentially being swept away. The reality is very different.
Kevin explained that earthworms obtain oxygen from the air through their skin (they do not have lungs or gills) and can also do the same from water (H2O) where oxygen is present. They will not therefore die, but may have problems associated with feeding and reproduction underwater. Prolonged inundation might have a negative effect on population size – some animals would die – but the next generation – present in the soil as cocoons – would hatch and repopulate the given area.
Experiments have shown that these too can survive under water and even contain a natural anti-freeze which prevents death under sub-zero soil conditions. Floods may have reduced earthworm activity, but as soon as standing water has gone, tell-tale earthworm casting at the soil surface will reveal that these animals are once more providing ecosystem services.