Seventeen volunteers came from the local area & from as far away as Cambridge & Kent to spend a day breaking up samples of soil to search for earthworms in Grove Farm under the guidance of Kieron Brown, National Earthworm recorder.

This is our second time sampling earthworms on Grove Farm, with many more being found this time compared to our dry conditions last September. A big thank you to Kieron for organising & running the event and to all our volunteers.

The role of earthworms in the ecosystem

Earthworms are nature's recyclers and an indicator of a healthy ecosystem as they respond to a variety of environmental and ecological factors such as changes in soil chemistry, moisture, pollution and effects of land management practices.   Earthworms consume their own body weight in organic matter every day, breaking it down and turning it into nutrient-rich soil through their excretions (known as worm castings).  The consumption and therefore reduction of organic matter helps to control pests and diseases that can harbour harmful organisms to plants as well as helping to repair damaged soil.  Their casts can contain 5 times more nitrogen, 7 times more phosphorus, and 1000 times more beneficial bacteria than the original soil, thus helping plants to thrive. 

Additionally, through burrowing into the ground they loosen, mix and oxygenate the soil as well as create channels that allow water to penetrate it. This activity helps to maintain the soil structure, which is essential for plant growth and also improves drainage helps prevent waterlogging. Research from the European commission has shown that soils without earthworms can be 90% less effective at soaking up water.

Finally earthworms are a crucial part of the food chain providing a protein food source to birds, hedgehogs, frogs and much larger creatures such as badgers.

Overall, earthworms contribute to the overall biodiversity and sustainability of any ecosystem and their presence (or lack of) indicates an area's soil health.

Methodology of the Survey

During the survey day we carried out two different sampling methods as different species of earthworm inhabit different micro habitats.  A description of the three types of earthworms can be found on the Earthworm Society of Britain's web site here, as can a more detailed description of sampling.

Soil Pit Sampling 

Searching for Anecic earthworms (who live in permanent vertical burrows in the soil) and Endogeic earthworms (who live in horizontal burrows in the soil).

A spade is used to dig a soil pit of a standard pit size for the National Earthworm Recording Scheme (approximately 25cm by 25cm, to a depth of 10cm).  In total there should be 5 soil pits dug per site and they only need to be a couple of meters apart.

The soil from the pit is placed into a sorting tray and sorted through by a group of volunteers by hand searching for earthworms, with earthworms removed into a container for classification.

Microhabitat Search

Looking for Epigeic earthworms who live on the surface of the soil in leaf litter.

Searching under deadwood and other items such as stones and rocks as well as leaf litter, with earthworms removed into a container for classification.

After recovery the earthworms are then classified into adults and juniors. with adult earthworms being retained.  A count of the junior earthworms is carried out, recorded and then returned to the sites where they were found.

Adult earthworms are usually those with saddles, which are a ring around the earthworm found in the skin of the earthworm and occasionally with a light-coloured pigment.  This is where Keiron during our survey earned his sandwich for the day as depending on the worm, these can be very difficult to identify.

Once selected the adult earthworms are then preserved in ethanol.  The earthworms are then taken by Kieron for identification.  It's only when the earthworms are preserved that they can be identified as they return to a stable size and their key characteristics can be observed under a microscope.

It is hoped through the use of different survey types and areas in Grove Farm that we will be able to assess the diversity and abundance of earthworms, with the aim to gather reliable data that can be used to monitor changes in the earthworm population over time and inform future conservation efforts.

Next Steps 

Now that the earthworm survey has been conducted, we'll wait to see what the results of the survey tell us and guide us in our plans for Grove Farm's future.  We do have the results from our previous survey below, where 9 different species were found and hope for new discoveries on site. 

Endogeic earthworms

• Aporrectodea caliginosa

  
  

• Allolobophora chlorotica

• Aporrectodea icterica

• Aporrectodea rosea

• Lumbricus castaneus

• Lumbricus festivus

• Lumbricus rubellus

Anecic earthworms

• Aporrectodea longa

• Aporrectodea nocturna

Species in bold indicate species noted as rare or extremely rare in Natural England (2014). Some species may have been under-represented in the data used within the Natural England (2014) report that estimated the rarity of British earthworm species and may in fact be more common and widespread than reported. Aporrectodea nocturna was not assessed in Natural England (2014), but is considered rare.