Soil Microbiomes

Here’s a sustainability-relevant subject about which we’ve not reported, yet it’s the foundation for our lives.  It enables trees and the myriad of plant life we need to grow our food, to oxygenate the air we breathe, to support our buildings and our personal movement.  Evidently, climate change is actually affecting the soil that underlies our lives.  Comments afterwards.


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How Climate Change Is

Affecting Soil Microbiomes


By Amanda Abrams

Modern Farmer

JULY 11, 2022


Often overlooked, diverse microbes are the key to healthy soil. How will a warming planet affect them, and what can farmers do to mitigate some of those changes?

Most creatures used to illustrate the tragedy of climate change are the familiar variety: Polar bears. Monarch butterflies. Sea turtles. Our soil, however, is often overlooked—it’s teeming with billions of microscopic organisms that comprise the most biodiverse environment on Earth. Like all living things, they’re affected by climate change, too.

There’s a fact that frequently gets mentioned when people talk about soil:


There are more microorganisms

in a teaspoon of healthy soil

than there are people on Earth.


The matrix of living creatures that recycle plant and animal life is incredibly complex, with bacteria, protozoa, fungi, actinomycetes, nematodes and others interacting in countless, largely-unmapped ways. And so, how might drought, excess rainfall, heat and increased CO2 affect those relationships?

Soil microorganisms are the foundation of all life on earth, so it’s a vital question for everyone. If the microbes are out of whack, everything else will be too. But for farmers, it’s particularly crucial. Conventional agriculture, with its chemical inputs and soil degradation, already throws microorganisms and their ecosystems out of balance, with disastrous long-term effects on harvests. Climate change could massively exacerbate the problem.

Exactly what that will look like is unclear. As weather and growing conditions change, could the bacteria and fungi that help plants take up nutrients, for example, shift in their balance with less-beneficial microbes? Could existing pathogens become more powerful? Could there even be a mass die-off?

Jennifer Martiny, a professor of ecology at UC Irvine who focuses on microbial diversity, says:


“Whatever happens, it probably won’t be

extreme. Microbes won’t go extinct. They’re

very adaptable; they’ll probably survive.”


But beyond that, says Martiny, while it’s certain that microorganisms will be impacted, no one knows exactly how.  She says:


“The composition of microbes will change

with climate change. It will affect function-

ing.  But predicting it is pretty hard.”


There are a number of reasons for that uncertainty. The biggest one is the incredible complexity of the soil microbiome and the web of relationships there. Fungi interact with other types of fungi, with bacteria, with the single-celled organisms called protists, with plant roots—and all of it is invisible to the naked eye. Researchers’ efforts to outline that range of connections are still at a very basic stage.

And then there’s the fact that soil microorganisms break down plant organic matter and either store the resulting carbon in the soil or release it into the atmosphere as carbon dioxide. If climate change speeds up their respiration of CO2, it could create a vicious cycle that exacerbates climate effects. The opposite could occur, too, meaning that microbes could dampen the effects of climate change by storing more carbon underground.

Determining what’s likely to happen in the case of increased atmospheric CO2—or other factors like greater heat, and more or less water than usual—has another layer of difficulty: those conditions are hard to mimic in a long-term research context. And the experiments that have been done have largely taken place in naturally-occurring settings like forests and grasslands, not agricultural environments.

Scientists have made some observations about how soil microbes respond under new conditions related to climate change. A colloquium of experts from across the country gathered virtually in November to discuss the topic. A subsequent report determined that climate warming can reduce the diversity of microbes, increase the complexity of their relationships, and speed up their decomposition of soil organic matter. New pathogens are likely to emerge.

The researchers had a caveat, though: these findings might not apply to all soil. After all, the composition of microbes on one farm might be totally different from that of another. “It depends on the soil, always,” says Janet Jansson, chief scientist for biology at the Pacific Northwest National Laboratory and a participant in the colloquium.

But Jansson emphasizes that, across the board, microbes tend to be adaptable. She says:


“There’s a funny thing with micro-

organisms: if you give them a

change in environment, resource

or condition, they kind of find

their way.  You can have low num-

bers of some, and given the right

conditions, they’ll start to flourish.”


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While the research report focused on what farmers might do, we need to also ask what each of us could do.  Some comments from D …


“There was a study done that compared Amish farms to those traditionally farmed, using pesticides and herbicides.  The results of the study were: 

“The Amish farm could withstand drought and heat and still put out an abundance of food. 

“Under the same conditions, the traditional farm lost most of its crops. 

“Amish farms have deep levels of rich organic soil.  Most traditional farms lose soil every year.  The moral of this study is that the deeper and richer soils built up over time with organic materials can withstand harsher climates. 

“So, for a homeowner, what does that mean? 

“Around a home or where you live, ensure good organic material is put in your gardens, and allow it to build up over time.  If you still have grass, periodically put organic material on top of the grass, again, to enrich the soil. 

“The more you can support organic farmers, such as by patronizing them at farmers’ markets or by joining an organic CSA, the healthier your local soils will become. 

“Finally, let the natural cycles flow.  For instance, if leaves fall and remain under a tree, let them remain there, instead of removing them.  It’s food for the tree and the soil.”


These are not actions that are likely to be addressed by any government agencies.  If we want healthy soil, and all the benefits it provides, it’s up to each of us.

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