According to a British study, in soil subject to human impact the restoration is slower organisms living underground than in surface. New perspectives in research are needed to protect biodiversity
by Matteo Cavallito
Poor land use produces obvious damage to the entire fauna living there. But subterranean living species – such as invertebrates and bacteria, for example – seem to pay a higher price than their surface peers. The restoration of underground fauna takes more time to return to baseline conditions, That’s the hypothesis suggested by a research published in the journal BMC Ecology and Evolution.
The investigation, by a team of scientists led by Victoria J. Burton, a researcher at Imperial College London, at the same time highlights how the analytical models most commonly used to explain the impact of land-use change on naturally occurring organisms are not always well suited to describe the effects of this phenomenon in the subsurface.
“Land-use is a major driver of changes in biodiversity worldwide, but studies have overwhelmingly focused on above-ground taxa,” the research states. “The effects on soil biodiversity are less well known, despite the importance of soil organisms in ecosystem functioning.”
Analyzing 19,651 assemblages of surface soil and 7,155 samples collected from depth in different areas characterized by different land uses, the researchers analyzed the populations of vertebrates, invertebrates, plants and fungi. The survey looked at areas such as agricultural fields, forests and pastures while also assessing soil characteristics. Finally, the researchers examined territories untouched by humans, where primary or secondary vegetation (the result of natural regeneration following a long period of rest) was present.
The research then assessed trends in the presence of surface and subsurface organisms for each habitat observed.
“We found that land use affects overall abundance differently in soil and above-ground assemblages,” the scientists explain. “The abundance of soil organisms was markedly lower in cropland and plantation habitats than in primary vegetation and pasture. Soil properties influenced the abundance of soil biota in ways that differed among land uses, suggesting they shape both abundance and its response to land use.”
A slower recovery
Although the results are not really surprising, the gap found between different organisms was greater than expected, Victoria Burton said in a note published by the Natural History Museum in London. “It may be that these differences are driven by some groups doing much better in certain habitats than others,” she explained. “So I hope to dig deeper into this in the future to see how different organisms respond.”
One of the most relevant aspects is the different recovery rates. The gap between the presence of surface organisms and that of their subsurface counterparts was particularly evident even in secondary vegetation, that is, in those areas long abandoned by humans.
This suggests that the recovery of biodiversity after the end of human impact is faster at the surface than underground. Finally, acidity levels are also crucial. In soils characterized by higher acidification, a more pronounced difference between the presence of soil organisms and others was observed.
New research models needed
In short, the study showed that biodiversity variation follows different rhythms above and below the land surface. This aspect thus highlights the need for further investigation. But also the importance of updating methods and indicators that seem to be overly skewed. “Organisms that live in the soil and leaf litter (henceforth, soil biodiversity) are particularly poorly represented in indicators and assessments of the global state of nature,” the researchers say.
“This is despite the fact that they comprise 23% of described living species, support ecosystem services, such as nutrient cycling, soil formation and water quality, valued at $2.1 trillion per year worldwide and form the second largest carbon pool on Earth.”
In order to find solutions to biodiversity decline, therefore, it is worth experimenting with a change of perspective in research as well. “If we only measure how animals like birds and butterflies respond to changes, we might be putting restoration policies in place that don’t help – or even harm – soil species, which could hold back wider recovery,” Burton says. “To restore ecosystems, we need to take a broader view above and below ground.”