Sustainable Agricultural Sciences
The humble earthworm physically engineers the ground beneath our feet, modifies how water, air and roots move through the soil, increases nutrient availability for plant uptake whilst cementing the soil together, influences above-ground plant susceptibility to insect attacks, is an important food source for wildlife – and yet earthworm populations in our farmland soils are a mystery.
More than 125 years ago, Charles Darwin highlighted the importance of earthworms - “Without the work of this humble creature, who knows nothing of the benefits he confers upon mankind, agriculture, as we know it, would be very difficult, if not wholly impossible”. They are colloquially known as farmers’ helpers and often ranked top for ‘usefulness’ in terms of soil health indicators by farmers. More than that, when I started this project, farmers would ask me ‘what is a good earthworm population?’ with an aspiration to use soil biology to benchmark soil management practices. It is an exciting time to be a soil scientist, but also a great responsibility to help realise the biological potential of farmland soils.
The basics of a good farmland earthworm population includes two key parameters – spatial abundance (widespread earthworm activity over the field) and earthworm diversity (all three ecological types of earthworms) - with surface-dwelling earthworms supporting efficient crop residue breakdown facilitating crop seedling emergence, topsoil earthworms mixing and mobilising nutrients for plant uptake, and deep burrowing ‘drainage’ worms forming permanent vertical burrows helping to reduce waterlogging of crop roots. This framework was the basis of developing an earthworm survey method that would be useful and used by farmers.
So began this citizen science project - a joint investment to create something to be used and be useful in the long-term. The first revelation was unexpected - the recruitment of volunteers to test the pilot earthworm survey method. Writing talks and earthworm demonstration workshops requires a high effort and time on my part, and I had presumed that people who attended these soil health events would be the people likeliest to participate. However, these were the groups with the lowest participation rates – good intentions, but the survey forgotten about until they next saw me. Instead, it was the online farming community, connected through social media and online forums that led to the best collaborations. A community of people publicly taking part, cajoling each other to take part, comparing and sharing results, directly requesting method support (that I could provide in real-time via YouTube method demos and photos of different earthworm types) and requesting a workshop to come together and discuss the strengths, weaknesses and improvements – to co-create the method for farmland earthworm surveys. The popularity of the pilot study prompted a new national Agriculture and Horticulture Development Board leaflet ‘How to count worms’ based on this method.
My presumption that I would have a few hotspots of surveys linked to workshops was outdated - through online communication, the idea had caught on and at least one farmer from each region (except London) in England took part, and the survey developed in real-time with two-way communications - an applied science revolution! The workshop (identified as the primary mechanism the participants wanted feedback) was held a week after the end of the survey period and together we identified participation barriers (duration and need to reduce the number of soil pit assessments), key training needs (earthworm identification support) and the need to develop from a paper based survey to an online platform for the Autumn survey. Overall, 3,000 hectares and almost 20,000 earthworms were studied by farmers in 2018, and we continued to discuss and digitise the survey ready for its application in 2019.
The initial results highlighted that earthworms are ubiquitous in farmland soils in England and we discovered some fields had exceptional earthworm populations (all three earthworm types in every soil pit and around 7 - 8 million worms per hectare). At both timepoints, approximately 50 % fields were found to have a good spatial abundance and diversity of earthworms. Whilst reduced and no-tillage are increasingly popular, conventional tillage dominates crop establishment practices in England and has done so for over 30-years, and tillage (habitat disturbance and loss of surface litter) and is well known to change the earthworm community structure (negatively impacting the litter-feeding surface and deep-burrowing earthworms). So, this result was not scientifically surprising, but it was useful to quantify, for example, that approximately 20 % fields had no deep burrowing ‘drainage’ earthworms (or signs of them).
I wrote the research up for publication in an open access online journal and for the first time used a pre-print server – enabling anyone to comment during the peer-review process. I received no comments, but it was popular – it is in the top 5 % of outputs ever monitored by Altmetric. After corrections via peer-review it was published – where it was picked up by the national press. Some journalists created their own results interpretations - including earthworm declines, bird declines, and/or attributing the results to pesticides - popular themes amplified by environmental lobby groups. Ironically, this jeopardised both the ‘citizen’ in our citizen science project and this type of reporting is detrimental to farmer collaborations, and the ‘science’ in our citizen science project which relies on both depleted and exceptional earthworm populations to be reported so that we can bridge the gap between scientific theory and what consistently works in practice. Some farmers complained to the National Farmers Union about the clickbait headlines and the potential detrimental impact on farmer/scientist collaborations. When I started this project, I never thought that the biggest communication issue would be how citizen science in agriculture can be reported.
This project has continued to develop – moving beyond a ‘do I have good earthworm populations?’ benchmarking, to a change in mindset about how to best tend to the ‘below-ground livestock’. This necessitates better connectivity to farming innovations and ideas around the world and the development of more sophisticated analysis – with image analysis identified as the priority development to support species identification and biomass estimates. This is why we’ve asked the global farming and scientist community to join us to create a snapshot of earthworms in farmland soils for #WorldWormWeek (23 – 31st March). It is somewhat fitting that the importance of earthworms was recognised by Charles Darwin over 100 years ago, and their value has evolved, helping to build new connections as we set about to discover the hidden world beneath our feet.
Stroud JL. Co-producers: open data can test trust. Nature. 2018;562(7727):344. doi: 10.1038/d41586-018-07059-9
Stroud JL. Soil health pilot study in England: outcomes from an on-farm earthworm survey. PLoS ONE. 2019. doi: 10.1371/journal.pone.0203909