Global warming threatens soil micro-organisms

A major international study conducted mainly at the University of Neuchâtel (Switzerland) has revealed that the Apodera vas shell amoeba is found almost exclusively in regions originating from Gondwana, the supercontinent that gave rise to some of today’s continents. The study also highlights the threat posed by global warming to the biodiversity of soil micro-organisms, of which this amoeba is one. These are just two of the conclusions reached by the twenty-eight contributors to this study, published in the scientific journal Diversity and Distributions.

This is the first time that the distribution of a micro-organism species has been modeled on a global scale in this way", enthuses study coordinator Edward Mitchell, professor at the head of the Soil Biodiversity Laboratory and thesis supervisor of Estelle Bruni, the first author of the scientific paper along with Olivia Rusconi, a former PhD student in the same laboratory. The geographical distribution of this terrestrial amoeba shows a much more marked presence in forests and peat bogs that are remnants of Gondwana, the supercontinent dating back some 200 million years and which, by fracturing, gave rise to the present-day continents of the southern hemisphere and India.

Against dogma

This result flies in the face of a prevailing dogma in the scientific community, which assumes that micro-organisms are present almost everywhere in the world. It is thanks to the abundance of existing data on this unicellular organism, easily identifiable under the microscope, that scientists have been able to compile more than 400 geographical points published over more than a century.

Conclusion? The species is present in regions of ancient Gondwana, but absent from the rest of the world, including territories such as the British Isles, which have been well studied for over a century and where the climate is thought to be highly favorable to the species. It is therefore unthinkable that the scientific community could have missed specimens of a species so easy to identify and common in bogs and forests", stresses Edward Mitchell, principal investigator of the study.

Shrinking habitats

Using a climate niche model, the scientists were able to show that the habitats suitable for this amoeba species shrank significantly during the last ice age (around 21,000 years ago). As a result of global warming, the shrinkage of suitable areas for the amoeba will worsen drastically by the end of the 21st century.

Our study thus raises for the first time the question of the threats to microbial biodiversity posed by global warming," concludes Edward Mitchell. Our results suggest that, like the iconic shell amoeba Apodera vas, many species of microorganisms are potentially endemic to small regions and therefore potentially threatened with extinction by ongoing climate change’.