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Prof. Tom Crowther: ‘Microbial soil life is crucial for climate regulation’

Ecologist Prof. Tom Crowther of the Swiss Federal Institute of Technology in Zürich and co-chair of the advisory board of the UN Decade on Ecosystem Restoration, speaks about climate change mapping and the role of soil biodiversity.

As a global ecosystem scientist, you founded the Restor platform, an online hub known as the ‘google maps for nature’. What’s in there for microbiology science?

Tom Crowther pictureTom Crowther: Our Restor platform has lots of data about soils, climate and macro species like terrestrial plants and animals. However, unfortunately until now, we have very little globally available data on soil microbiome diversity. For that reason, it is our top priority as scientists to study these ecosystems globally so that we can generate the information that would be urgently needed on Restor.

On the other hand, with more than 100 000 participants on the Restor platform working in nature conservation and restoration, we now have access to an extraordinary new set of data from the experts working on the ground.

They report that, when you restore an ecosystem, it is essential to restore the soil microbiome that supports it. By adding native, diverse mixtures of soil from nearby ecosystems to degraded soils, natural regeneration rates can increase by 30-40% as plants move towards their natural state.

Could a better understanding of microbiome biogeography and biochemistry help predict the best ecosystem sites for natural carbon sinks? What can satellite observation tell us?

Tom Crowther: We start to understand the complex feedback mechanisms in and between terrestrial systems regarding climate change linked to the global distribution of microbial systems. Northern forests, for example, are dominated by fungi, whereas bacterial webs dominate in the southern tropical forests. The tropical forests have faster carbon cycles causing higher emission rates.

With global warming, the cold-adapted regions like the Arctic are heating up fastest, and the microbiome is likely to respond . Consequently, we estimate that warming is stimulating microbial activity in the Arctic and sub-Arctic regions, enhancing the loss of carbon from soils. We estimate that these increased soil carbon losses could increase carbon emissions by 12-15%. The warmer the climate, the more soil carbon emissions we are likely to see.

What is the role of soil microbiomes, including fungi, in carbon sequestration and storage?

Tom Crowther: Firstly, the soil microbiome is a crucial parameter for soil fertility and plant growth which means that they directly facilitate food security and carbon capture into ecosystems. Secondly, microbes are essential for stabilizing the carbon that enters the soil, which is the process that makes sure that carbon stays in the soil. Ultimately, soil microbes are the most diverse organisms on earth and they regulate the largest pool of carbon on land.

Besides animal breeding, rice cultivation globally generates 20% of food-borne methane gases into the atmosphere. Do we understand enough about plant-based carbon cycles?

Tom Crowther: We learn that healthy diversity is key in fighting climate change. If biodiversity is missing, there is no healthy carbon storage possible because we are losing species’ mixtures and the functioning of those ecosystems. More species above and below the surface means that more carbon is sequestered in the long term. Our ecosystems-thinking needs to include microbial communities.

Might planting trees for climate change mitigation pose an additional risk?

Tom Crowther: Just planting trees is not necessarily recovering nature. When done right, it can be fantastic, but when done wrong, it might generate more destructive monocultures. In most cases, the best way to restore an ecosystem is to allow them to reover naturally. And in others, it is about working with people to actively manage biodiversity for the economic sustainability of local communities who depend on it.

We can already show global maps of soil carbon loss, showing significant losses in areas of intensive agriculture, and also in high latitude Arctic regions. But we are also starting to see the signs of soil carbon gains, where holistic management of mixed crops can promote biodiversity and soil health. Or where natural peatland or forest regeneration have been successfully implemented across the globe.

Ultimately, across all ecosystems, it is becoming increasingly clear that promoting life aboveground requires that we protect and restore the diversity of life belowground.

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