Earthworms might not be everyone’s favourite animal, but without them, our soil would not be the same and plant productivity would suffer immensely. They are a staple of our ecosystem, making sure that essential nutrients are recycled, and air and water move deep into the ground - a process that happens below our feet without us noticing.
A new study now sheds light on the abundance of these important creatures. Helen Phillips and her team at the German Centre for Integrative Biodiversity Research catalogues data from over 140 scientists over 6900 sites to map earthworm species across the globe.
“We found two surprising results”, says Helen. “Firstly, earthworm communities had lower numbers in the tropics, which is surprising as typically aboveground organisms show the reverse of this pattern.”
Secondly, the team found that it was climate that was the most important factor influencing the patterns of earthworm communities.
The study is the first of its kind and the results can provide an understanding of a big part of our ecosystem and how the climate influences this particular species. These patterns have been understood for aboveground organisms for decades, while it is only recently that the same attention has been given to species below ground.
“A lot of conversation actions are based on aboveground organisms. Protected areas are often placed where aboveground organism abundance is high. But given the importance of below-ground organisms, it is vital we know where their peaks in diversity are”, says Helen.
This study has revealed that areas of high diversity don’t necessarily match above and below ground.
“We also show that climate is the main driver of these patterns. As we know that climate has changed and will continue to change, this is an issue.”
Helen has worked on below-ground biodiversity before, collecting data from scientists on the impact of land use on biodiversity. She noticed that there was a lack of soil diversity in the data.
"I was aware of this problem when a position for this current earthworm study was advertised, and I thought: Yes! This is it! This project will use my skillset while addressing the issue of the bias towards aboveground organisms.”
With this in mind, Helen and her team want to continue to study the link between climate and earthworm communities. “We need to know how the communities may change with our changing climate and what that means for the services they provide us.”
During the curse of the study, Helen has fallen in love with earthworms. "For me, my favourite thing is that earthworms play such a massive role in our ecosystems. As a scientist, it’s really cool that we can actually measure the link between earthworms and these ecosystem services. And what I also find fascinating is the huge range of earthworm species."