SLU's knowledge bank

Earthworm’s burrowing and capacity to deliver ecosystem services threatened by soil compaction

Last changed: 17 May 2023
earthworm in soil.

Earthworms are important “ecosystem engineers” that contribute to a range of vital soil ecosystem services, including food production. But earthworms are sensitive to disturbances in their environment. A new thesis has increased the quantifiable scientific evidence of the extent to which soil compaction impacts earthworm burrowing activity, also called bioturbation, and the amount of energy they need to burrow. It has implications for soil life, soil structure and soil functions that are essential to food production.

There are billions of organisms in a single teaspoon of soil. They are involved in different processes regulating the capacity of soils to deliver ecosystem services such as climate and water regulation, or making nutrients available to crops.

Earthworms are one of the larger soil organisms contributing to the function of our soils. Their burrowing activity and cast production make space for water and oxygen to move through the soil, as well as provide space for plant roots and other soil organisms to flourish.

Along with the development of modern agriculture, the number and activity of earthworms have reduced in soils that have become compacted by heavy agricultural vehicles. A decline in earthworm activity has consequences for our food production and other important soil functions.

Elsa Arrazola Vasquez, PhD student at the Department of Soil and Environment, has measured the impact of soil compaction on earthworms burrowing and energy costs in three different earthworm species.

-We wanted to see how the burrowing of earthworms change in compacted versus non-compacted soils, and to provide quantitative data that could be used to refine models to estimate earthworm burrowing under severe soil compaction and impacts of climate change, says Elsa Arrazola Vasquez.

Soil compaction affects different species differently

Elsa Arrazola Vasquez examined three earthworm species that are common in temperate zones, including Swedish agricultural soils. These were Aporrectodea caliginosa, Aporrectodea tuberculata and Aporrectodea longa, which are part of two different ecological groups (endogeic and epi-anecic).

The earthworms were selected to assess if species of different ecological groups respond differently under various compaction scenarios. The burrowing of all species turned out to be negatively affected by soil compaction, but the magnitude of the impact differed between the species, this could be associated with differences in foraging behaviour and morphological traits (muscle development and use).

-This was a very important finding. A. caliginosa was much more affected by compaction. Different processes in the soil are driven by different earthworm species, so the fact that A. caliginosa is more affected will have negative implications for the soil processes and associated ecosystem services related to A. caliginosa, including nutrient cycling, water storage and soil aggregation, says Elsa Arrazola Vasquez.

Moving through compacted soil requires more energy

Elsa Arrazola Vasquez could also see that earthworms change their way of burrowing when they are exposed to higher levels of soil compaction.

-Instead of moving through the soil by pushing particles aside, A. caliginosa started to ingest the soil to be able to move forward. This implies that this earthworm species adapts its burrowing mode when compaction levels are too high.

Moving through compacted soil requires more energy from the earthworms. The energy costs to create a volume of burrow or cast increased by around 50% for two of the species. 

-This suggests that earthworms are spending more energy on burrowing and need more energy to produce cast in compacted soils, which could be harmful in terms of their long-term energy requirements. It means that there is less energy for reproduction, for instance. It could also have implications on the entire soil ecosystem, as other soil organisms that are influenced by or depend on earthworm activity will be negatively affected and thus certain soil processes could be hampered, for instance nutrient availability and soil pore creation, Elsa Arrazola Vasquez explains.

Relevant to future soil management practices

In their results, Elsa Arrazola Vasquez and her team could distinguish that earthworm burrowing mode might depend on the level of soil compaction in combination with the level of soil moisture. Soil compaction was more severe in soils that also have higher levels of moisture, which means that there are more profound implications for the earthworms’ burrowing in such soils.

-This is worrying from a climate change perspective, as heavy rainfalls and droughts will be more frequent. Climate change might thus worsen the effect of soil compaction on earthworms’ burrowing, says Elsa Arrazola Vasquez.

What can be done to improve soil conditions so earthworms can thrive?

  • Agricultural vehicles need to be designed in a way that minimizes the risk of soil compaction. For instance by reducing the wheel loads and creating an even weight distribution.
  • Soil management practices should be designed to reduce negative impacts on the biological activity. For example, incorporation of organic residues (e.g. straw) or reducing the intensity and depth of tillage.
  • Avoid compaction in the first place, and especially avoid compaction in wet soils since the combination of very moist soils and compacted soils seem to have a larger negative affect on earthworm burrowing.



Earthworms support other soil organisms and soil functions, which makes them important to the soil ecosystem and the ability of the soil to deliver ecosystem services such as producing food. Amongst other things, earthworms mediate nutrient cycling, carbon and climate regulation, as well as water regulation and purification. Earthworms typcially divided into three different ecological groups, Epigeic, Endogeic and Anecic. Recent research has suggested that earthworms have traits from different group, so a species could be epi-anecic, for example.

The epigeic group consists of species that live in the organic soil layer, feed mainly on fresh litter, have small body sizes (1-4 cm), and have a weak muscular system as they do not burrow within the soil.

The endogeic earthworms are inhabitants of the upper mineral soil layers, usually have medium body size (5-15 cm), have a moderately developed muscular system, and create an extensive horizontal burrowing network.

Earthworms in the anecic group move throughout the soil profile, feed mainly on litter in the organic soil layer and bring their food to deep soil horizons, have larger body sizes (10-30 cm) and a well-developed muscular system, and build vertical unbranching burrows.

Soil compaction

Soil compaction is a reduction of soil porosity, which will disturb the water and gas movement in soils, potentially causing oxygen deficiency, and reducing water infiltration. In agriculture, the degree of soil compaction varies due to management practices such as ploughing, seedbed preparation, and machinery traffic.

Soil compaction has a key role in shaping earthworm burrowing activity. Understanding the impacts of soil conditions such as soil moisture and soil compaction on earthworm burrowing is important to foresee the effects on soil functions driven by earthworm activity.

How was the research conducted?

The overall aim of this thesis was to provide a better understanding of the impacts of soil compaction on burrowing by different earthworm species. Three experimental designs were conducted to investigate this, along with infra-red time-lapse imaging (video), isothermal calorimetry, respirometry and X-ray image analysis. The experiments were carried out either in controlled conditions (lab) for short periods (days), or semi-field conditions for extended periods (months). Local agricultural soils and earthworms species commonly found in Sweden were used for all the experiments.

Related pages:


Elsa Arrazola Vasquez


Elsa Arrazola Vasquez
PhD Student in Soil Mechanics and Soil Management
Department of Soil and Environment