The dirt is alive with a million bacteria, but it appears they have unequal levels of representation. Researchers at the University of Colorado Boulder have created the world’s first atlas of soil microbes, and have found that a small number of species represent more than half of their populations worldwide. ‘A teaspoon of soil can have a million bacteria individuals, or cells,’ says Manuel Delgado-Baquerizo, soil ecologist. ‘Each of these can belong to one of thousands of different species.’

Delgado-Baquerizo’s research was designed to discover the proportion of different types of bacteria species across the globe. However, he found that the same species kept reappearing. ‘Of more than 25,000 bacteria species, we found that just 500 – two per cent of the total – accounted for half of the species in soils everywhere.’

When he says everywhere, he means everywhere. ‘We collected soil samples from 237 different locations across six continents and 18 countries,’ he lists. ‘They spanned an entire range of climates, from deserts to grasslands to wetlands.’ Variations of the 500 turned up in all of them.

Although microbes make up a large portion of the ecosystem’s biodiversity, little is known about what particular species can do. ‘We know that soil microbes are key for processes such as plant production, nutrient cycling, breaking down toxins, even climate regulation,’ says Delgado-Baquerizo. ‘What we don’t know is which species are doing it, even among the most common.’

The new atlas could help researchers focus on the most abundant 500 species – a ‘most-wanted list’ – to determine what they are doing in world soils and why they are so dominant. Understanding their role in the ecosystem could hold the key to maintaining and enhancing soils in the future.

This was published in the March 2018 edition of Geographical magazine

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