The world is facing a soil crisis that could badly hit food production, according to alarming new research, which warns that climate change is likely to damage soil fertility much more than expected.
A 17-year study, published in the journal PLoS One, into the effect of global warming on microbes -the tiny bacteria, fungi and other micro-organisms that determine soil health – reveals them to be far less adaptable to changing conditions than scientists had thought.
This raises concerns that they won’t be able to carry out essential functions, such as eating leaves and other organic matter in a process which converts them into nitrogen and other minerals that plants need to grow.
“If the microbial community is not as resilient as we had assumed, then it calls into question the resilience of the overall environment to climate change,” said report author Vanessa Bailey, of the Pacific Northwest National Laboratory in the US.
It is often said that “microbes run the world” because they are so numerous and lie behind countless ecosystem services in the soil. These include producing humus – the dark organic material in soils – and providing a critical water filter system for trees, in return for feeding on their sugars.
More than a billion of them are estimated to be contained in a teaspoon of soil, which will host thousands of species of which only around a tenth are known.
The study involved swapping soil samples between two sites on a mountainside in 1994 – the higher location had a warmer, drier climate than the one 500 metres below.
Seventeen years later they went back to check on the microbes’ activities, focussing on their rate of respiration – how quickly they convert carbon in the soil to carbon dioxide as they break down the organic matter -to get a broader sense of their ability to adapt to the changing conditions. But they found very little change.
The microbes’ that had been native to the higher site naturally respired at a faster rate because they were used to greater levels of rainfall and vegetation, or carbon. They continued to respire at a faster rate at their lower elevation – even 17 years later. And the microbes taken from lower down the mountain demonstrated very little change when they were moved uphill, the research found.
The research findings mean that we can’t simply assume that microbes – and the soil -will nimbly respond to climate change in a way that many scientific models had assumed, said co-author Ben Bond-Lamberty, a soil microbiologist with the Joint Global Change Research Institute.