Biodiversity restated: > 99.9% of global species in Soil Biota

Soil’s vast biodiversity is under severe threat from topsoil erosion and poisoning, potentially leading to widespread extinctions.

Getting your Trinity Audio player ready...

More than 99.9% of global species diversity is found within soils, according to a new review paper published in ZooKeys.

Comparing different studies on soil biota, author Robert J. Blakemore challenges previous estimates, which suggested a much lower proportion of life in soils. “Most life is found in Soil and most is microbial, affected by the current mass extinction event having profound effects influencing all evolution on Earth,” he says.


From the review paper: “Micro monde” progressions with microbial proportions greatly increased from Blakemore after Larsen et al.

“Soil filters and stores freshwater stocks (being subject to Earth tides!) and, as well as ~ 99% of human food, it provides most building materials plus many of our essential medicines/antibiotics. Thus, an important metric must be the scope and snapshot status of living or dormant Soil biota.”

One of the most recent estimates suggests that the soil realm is home to approximately 2.1 x 1024 taxa, which is thought to be more than 99.9% of global species biodiversity, mainly comprised of bacteria and other microbes.

Trending
ZooKeys publishes data through Darwin Core Archive format

The more you look, the more you find (lhs, pin-head after SCIENCE 2002; rhs, Bacteria on a pin tip courtesy Dr Kateryna Kon of Kharkiv National Medical University).

“Soil also supplies >99.7% of calorific food (just 0.3% from ocean plus 0.3% from aquaculture mostly fed with farmed stockfeed); with just about 6% total global protein from all fish; soil filters and stores most freshwater and is thus responsible for hydrological-recycle rainfall on land,” Blakemore says.

“My other paper last year on Biomass shows Soil houses >99% of organic carbon and it is the loss of this vital resources that is the greatest contributor to atmospheric carbon increase, despite the ‘greening’ effect on land.”

Blakemore, R. J. (2024). Biomass Refined: 99% of Organic Carbon in Soils. Biomass, 4(4), 1257-1300. https://doi.org/10.3390/biomass4040070.

However, this immense biodiversity is under threat. “Soil erosion is one of our greatest global issues of concern, and one of the most ignored. Droughts, floods, deserts, poisoning, capping and so on are affecting all soils and, due to this massive soil loss, plants are incapable of thriving. At the same time deforestation continues, mainly clearing for cattle pastures or soy fields to feed CAFO cows (or other stock),” the author says.

The loss of soil biodiversity has far-reaching consequences, leading to ecosystem degradation, reduced food production, and loss of potentially valuable resources, such as sources of medicines and antibiotics. Furthermore, soil loss inevitably results in silent species loss, mostly of microbes that are most dominant in soils, but also of more obvious soil macrobes, and specifically of earthworms, which are vital for soil health.

Around 7,000 ‘true’ earthworm species have been described, but estimates suggest the total number of earthworm species may be closer to 30,000-35,000 globally. “Due to their high endemicity and Soil’s heterogeneity, their unknowns are legion,” the author notes in his paper.

From the review paper: Global Soil Biodiversity Atlas (GBIF 2016) reporting ~ 667,000 soil biota or just about one third of known 2 million). Note that earthworms have 7,000 known and > 30,000 estimated species. Bacteria had 15,000 known species but estimated over one million (< 1.5% described). However, when microbes (excluding viruses) are properly considered and counted, as herein, soil unknowns are much higher (likely just < 0.0001% known at best). Vascular plants add ~ 400,000 species (cf. Anthony et al. 2023 with 466,000 angiosperm “Plantae”).

Earthworms enhance microbial activity, improve soil structure, and promote plant growth, which is why Blakemore suggests that “a simple solution to soil degradation is to attempt, in any way and at all times, to preserve and enhance earthworm populations.”

“Healthy soils are carbon-rich, hugely biodiverse and are a massive sponge for water – neither flooding nor drying during climatic extremes,” the author says, a reminder that healthy soils are not only vital for maintaining biodiversity, but also indispensable in supporting essential functions of planet and human survival.

“Due to the most pressing problem of topsoil erosion and irreversible extinction losses, a major shift should be realizing the overwhelming importance and fragility of our precious Soil,” Robert Blakemore writes in his paper.

Calling for a change in attitudes and funding to recognise the true scope of soil biodiversity, he encourages the formation of a dedicated Soil Ecology Institute that would catalogue, research and reverse the mass degradation of our planet’s most crucial, yet most neglected ecosystem – that of the Soil Realm.

References:

Blakemore RJ (2025) Biodiversity restated: > 99.9% of global species in Soil Biota. ZooKeys 1224: 283-316. https://doi.org/10.3897/zookeys.1224.131153

Blakemore, R. J. (2024). Biomass Refined: 99% of Organic Carbon in Soils. Biomass, 4(4), 1257-1300. https://doi.org/10.3390/biomass4040070.

Blog post on the topic by Robert J. Blakemore: https://vermecology.wordpress.com/2025/02/10/tandc

Tags: biodiversity, earthworms, soil