When thinking about the consequences of climate change, its influence on soils may not be the first thing that comes to mind. Yet the condition of all kinds of ecosystems is linked to the condition of their soil. For example, agricultural lands with fewer nutrients in the soil yield less food. And in nature reserves with unhealthy soils, plant and animal populations will decline. Moreover, under the right conditions, soils are able to capture carbon, reducing the amount of CO2 in the air and thus mitigating climate change.

Role of micro-organisms

The health of soils is largely determined by micro-organisms: the millions of bacteria and fungi that live in every handful of soil. These microbes release nutrients from organic matter in the soil and strongly influence how much CO2 soils can retain – or emit. A team of biologists from various European countries therefore decided to investigate how climate change affects micro-organisms in different kinds of soils. The team was led by Franciska de Vries from the University of Amsterdam, who at the time of the experiments was still working for the British University of Manchester.

Heat, drought, floods, frost

The scientists took soil samples from thirty different areas spread across Europe. In their laboratories, they then looked at what happened to the microbes when they exposed the soil samples to simulated heat waves, droughts, floods and frost. Not just to higher temperatures: after all, climate change is more than that. An important consequence is also an increase in more extreme weather events, including more frequent droughts and floods. The results of this large-scale study have now been published in Nature.

Franciska de Vries: ‘What is special about our study is that it is the first time that this has been investigated experimentally, and on such a large scale. Previous studies that looked at the effect of climate change on soil microbes were often either local, observational studies or they worked with models. But we really looked at what happens to different communities of soil bacteria and fungi when they are temporarily exposed to extreme conditions.’

Predictable

The main conclusion of this study is that the effect of the different aspects of climate change on the micro-organisms is very predictable – if you know which microbes are present. Under the influence of the tested weather extremes, some microbes become less active and go into a ‘dormant’ state more often. Others go into ‘overdrive’ and can, for example, cause an accelerated breakdown of organic material. The first type of reaction will lead to a decreased release of nutrients, which will affect the plants that grow in such a soil. The second type of response causes more CO2 emissions from the soil, which has a reinforcing effect on climate change.

Local conditions

‘In order to predict how soils in a certain location will be affected by climate change, it remains necessary to know the characteristics of the microbial community in that location,’ says de Vries. ‘For example, we saw that soils from places with an already warmer climate contain microorganisms that are less sensitive to heat. Of all the soil types we examined, microorganisms in soils from colder, wetter areas turned out to be the most sensitive to the various tested aspects of climate change. This means that the consequences for the health of soils in, for example, The Netherlands may well be greater than elsewhere.’

She adds: ‘Our research provides important new insights that can be used as a guideline for further research and for soil management strategies. Hopefully, in this way, we can safeguard the health of our ecosystems in the face of increasing climate challenges.’

Details of the publication:

Christopher G. Knight, (…) Franciska de Vries, Soil microbiomes show consistent and predictable responses to extreme events, in: Nature,2024, DOI: 10.1038/s41586-024-08185-3.