Much of the human exploitation of land and soil has had a major negative impact on life below the surface. It is often agriculture that is mentioned, but Stella Ek has in her degree project at Linnaeus University, done in collaboration with Ecogain, instead looked at the impact of the building and construction industry on underground biodiversity.

- 'There are actors who make efforts in certain areas. But the majority calls for more knowledge and also regulation to support their work on these issues," says Stella Ek.

Biodiversity focusing on soil organisms, i.e. the life hidden below the soil surface, has received far less research and media attention than the species living above ground. This is despite the fact that around 25-30% of the world's biodiversity is represented in the soil, and largely faces the same threats.

The European Commission report 'Caring for soil is caring for life' (2020) states that 60-70% of soil and land in Europe is in poor condition. Policy makers are now trying to reverse this trend through better knowledge and regulation. The EU's Soil Directive is coming soon, and many predict that more and greater efforts will be needed in the future.

The construction industry has a big impact on life underground

Stella Ek's study highlights how human impacts threaten our soil organisms, with a particular focus on the link to the construction industry. By comparing literature and survey responses, she has identified the main activities that affect soil biodiversity, as well as the state of knowledge of the actors in the industry and how they deal with the challenges.

The results show seven high impact areas:

Removal of organic matter
During construction, the ground is leveled and topsoil is removed or mixed with other soil, construction waste and stones. This damages and degrades the quality of the soil and the conditions for life as it removes nutrients, changes the structure and makes it more difficult for roots to penetrate the soil or for water to infiltrate.
Soil sealing
When soils are covered by, for example, asphalt and concrete, the water and nutrient cycles are stopped, the heat balance is altered, the oxygen supply is reduced, and the carbon and nitrogen content decreases. All of this impoverishes the conditions for life in the soil and soil organisms risk dying.
Soil compaction
Occurs during transportation and in the use of heavy machinery or in the inefficient storage of soil. It forms a uniform, compacted layer of soil that prevents water and oxygen from penetrating, making it difficult for roots to grow, seeds to germinate, gases to exchange and digging creatures to move around. There is also a change in soil moisture content and an acceleration of surface runoff and soil erosion during soil compaction.
Soil contamination
Soil contamination in construction projects can result from spills, demolition and reuse of materials, or when older contaminants in urban soils are exposed. For example, oil spills create a film on the ground which blocks gas exchange and thus stops oxygen in the soil. This creates a shortage of air, resulting in suffocation of the soil biota.
Habitat change and fragmentation
Urbanization where the remaining natural vegetation is too small or isolated means that some species do not survive. Green spaces are often replaced with non-native ornamental species. However, exotic species can have very different characteristics that pose risks to ecosystem processes, affecting the soil water cycle or pH levels in a way that disrupts the natural system.
Management of invasive species
Earthworks and the transportation of soil, or the removal of soil when it is used elsewhere, can lead to the spread of invasive species. Flower lupine is an example of a well-known species that displaces other native species. This leads to changes in nutrient dynamics and affects the presence of microbial species in the soil.
Spread of plastics
There is a risk of leakage of plastics into the environment during packaging of materials and storage and waste, during transportation, and during cutting of plastic pipes, blasting and grinding at construction sites. A meta-study shows that microplastics reduce the growth and reproduction of earthworms, reduce soil bacterial diversity and can change the microbial community structure.

Stakeholders call for more knowledge and support

Some 20 of the largest public sector construction actors and a handful of private actors participated in the study. A majority say they need more knowledge about these issues and call for help in implementing compensation measures, but also for regulations, guidelines and training to better address the challenges they face in their work.

Soil contamination is the area where most stakeholders have procedures and take action to promote soil biodiversity. At the other end of the scale is habitat alteration and fragmentation, where most respondents say they never take action. Stella Ek believes the reason for this is the complexity of the issue, perhaps due to insufficient knowledge or lack of awareness. For instance, not everyone in the industry knows what invasive species look like.

- These are often complex issues and measures can differ depending on the conditions at a site or in a specific project. It is best to turn to skilled environmental consultants like Ecogain," says Stella Ek.

You can read the full study here.

The study aimed to investigate the state of knowledge of clients and contractors of building and civil engineering projects on issues related to the impact of anthropogenic activities on soil biodiversity in order to contribute to a better picture of the current situation. Consequently, no suggestions have been made regarding the most appropriate interventions to promote soil biodiversity. Further research could focus on which measures have a long-term effect and are economically and ecologically sustainable.

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