Earthworm Watch - The Results


Victoria Burton
Victoria teaching children about earthworms (c) Earthworm Institute John Hunt
Victoria teaching children about earthworms (c) John Hunt (all rights reserved)

Victoria Burton has always been interested in the natural world, spending her school summer holidays recording the biodiversity of a local woodland and conducting live mammal trapping and tadpole rearing projects.

She completed a BSc in Natural Sciences with the Open University in 2011, before going on to study for a MSc in Taxonomy and Biodiversity at Imperial College London. Her PhD research included running a citizen science survey: Earthworm Watch.

Earthworm Society of Britain's  Anthony Roach interviews Victoria about the results of this survey...

Earthworm picture
Surface feeding Lumbricus festivus () Victoria Burton (all rights reserved)
How did you become interested in earthworms and what is it about the soil that compelled you to study it for your PhD? Why?

My mum remembers me playing with earthworms as a child and one of my earliest memories is walking on dewy grass watching earthworms stretching out across the ground! However my scientific interest started when I did my MSc in Taxonomy and Biodiversity at the Natural History Museum, London. One of the modules was run by Dr Paul Eggleton on soil and leaf-litter invertebrates and I was awed by the huge diversity of life right underneath me here in the UK. I went on to do my MSc project on soil life and volunteered in the Soil Biodiversity Group at the Museum before starting my PhD.

Earthworms are referred to as 'Nature's Ploughs' due to their activities but what do they do physically to soils and why are they so valuable?

The burrowing activity of earthworms forms channels in the soil which allows water and air to enter - both are needed by most plants for healthy growth. Earthworms also eat and digest dead plant material and their casts (earthworm manure!) has more nutrients available for plant growth than undigested plants. Deep-living earthworms are particularly valuable as they pull down dead plant material from the surface and mix it into the soil.

Earthworm picture
Soil feeding Allolobophora chlorotica on leaf (c) Gilles San Martin (all rights reserved)
As a fan of Charles Darwin, I understand he spent quite a lot of time studying earthworms? What did he discover?

Yes Charles Darwin spent many years studying earthworms which he brought together in his final book - The Formation of Vegetable Mould through the Action of Worms, with Observations on their Habits. His major contribution was calculating how much soil earthworms move to the surface by measuring the rate that stones and ancient buildings are buried. He also experimented with earthworm senses and found they can feel vibrations through soil but cannot hear, and which foods they prefer. You can read more about Darwin’s earthworm experiments on the Earthworm Watch blog.

Earthworm picture
Eisenia fetida the brandling worm (c) Rob Hille (CC BY SA 3.0)
Earthworm Watch employed the use of citizen science. Can you tell me more about citizen science and the benefits of using it?

My wider PhD topic is on how the diversity of soil life differs between land uses, such as woodland, cropland, grassland and urban areas. I had difficulty finding enough data on soil animals in urban areas though - it’s not easy for scientists to collect information from people’s gardens and other green spaces. Citizen science recruits members of the public to help scientists with their research so was ideal method to help me obtain data from urban areas, and over a much larger area of the country that I could on my own.

As the lead scientist for Earthworm Watch what were the aims of the project and what did you hope to find out from your research?

The main aims of Earthworm Watch where to find out which habitats have more earthworms, and the relationships between earthworm numbers and soil properties such as moisture, texture and carbon content. I also wanted to find out if the different types of earthworms prefer different habitats.

Earthworm picture
Aporrectodea rosea soil feeding earthworm (c) Chih-Han Chang (all rights reserved)
What have been your key findings from the final published results and what does this tell us about earthworm and their habitats?

I found that earthworms strongly prefer moist, clay and loam soils - there were double the number of earthworms than in sandy or dry soils. We also found 20% more earthworms in sites which used organic fertiliser (such as manure or leaf mould) compared with sites with no fertiliser. The numbers of earthworms did not differ as much between habitats as I expected - the only habitat earthworms did not do well in were flower beds. I did find differences in the type of earthworms in each habitat though - the highest numbers of deep-living and soil-feeding earthworms were in lawns, meadows and vegetable beds but surface-feeding earthworms preferred shrubs and hedges. You can read the full results on our website.

From these results, what actions can all of us take in gardens and community spaces to help maintain and improve earthworm populations?

A really clear finding from Earthworm Watch is that earthworm numbers are boosted by using organic fertiliser such as manure, compost or leaf mould, so making and using your own compost should help to increase earthworms in your green space. Since different earthworm types prefer different habitats, creating a variety of habitats should increase the types of earthworms in your site. You could also join the Earthworm Society of Britain to find out more about earthworms and support their study and conservation.

Earthworm picture
Aporrectodea caliginosa (c) Victoria Burton (all rights reserved)
Have you found any link between types of earthworms and their role in storing soil carbon such as decaying leaf litter in the soil?

Unfortunately I did not get a clear answer for this question, the data suggests there are more earthworms in soils with higher carbon content but the relationship does not quite meet the standard scientists use to decide if a result is statistically significant. This is common in scientific research - more data are needed!

With climate change leading to more unpredictable weather such as intense rainfall and flooding, can earthworms play a role in mitigating some of these impacts?

I think earthworms do have a role in mitigating climate change. In particular, the deep, vertical burrows of deep-living earthworms are good at draining away excess water and can help with flood prevention. By using growing methods that benefit earthworms, such as no-dig methods, cover crops, and using organic rather than artificial fertilisers, we can benefit from increased earthworm numbers.

Earthworm picture
Surface feeding Dendrobaena veneta (c) NHM Harry Taylor
Finally, what has been some of the highlights for you of working on the project for the past 3 years?

Earthworm Watch has been an amazing experience! Some highlights that first come to mind are appearing on London Live local television, on one of my favourite radio programmes - Gardeners’ Question Time, and winning a British Ecological Society Public Engagement Award. Earthworm Watch has also expanded my writing audiences - as well as the scientific writing of my thesis and papers I’ve had the opportunity to write a blog post for the Guardian Gardening Blog, articles in the Natural History Museum magazines, and even had an article translated into Welsh! However, what I’ve enjoyed most is travelling around the UK doing surveys and talking about earthworms to young people, whose enthusiasm gave me a boost on the rockier parts of my PhD.

Going further

Earthworm Watch was developed by Earthwatch Europe, The Natural History Museum and the Earthworm Society of Britain to better understand the ecosystem benefits of earthworms. If you would like to learn more about earthworms and soil health, visit the Earthworm Society of Britain website, or you could join one of the Learn to Love Earthworms courses. Don’t forget to see what other research projects you can take part in with the Natural History Museum and Earthwatch Europe.

Creative Commons License
Except where otherwise indicated, this work was created by Victoria Burton on behalf of the Earthworm Society of Britain and is licensed under a Creative Commons Attribution 4.0 International License.