Soil Microbes Matter

In this episode of Unconfined, Leo Horrigan tells us about a new CLF book he wrote and all the ways we could use microbes to regenerate healthy soil, sink carbon, and grow more nutritious crops.    

Making the Most of the Microherd

By Christine Grillo                                                                                                                                                                    Subscribe to Host Notes

One of my favorite fun facts from talking with Leo Horrigan is that less than 1% of all species of microbes—by which I mean, viruses, bacteria, fungi, protozoa, and helminths—in the world are pathogenic. The other 99% of microbial species are either harmless or beneficial to humans, living in water, soil, air, and our bodies. As Horrigan puts it, we should spend more time and energy nurturing microbiota than trying to kill them.  

Horrigan, a food system correspondent who has worked at the Johns Hopkins Center for a Livable Future for more than 20 years, has written a new book, What If Soil Microbes Mattered?: Our Health Depends on Them. Recently, he came on our podcast to stump on behalf of these essential tiny creatures. His reasoning, which is echoed by food systems experts around the world, is that we humans need to do a much better job of growing food, conserving the natural ecosystems that still exist, and regenerating soil. Microbes and biological farming are the keys to realizing this vision. 

Last year, on Episode 7, Horrigan and I talked extensively about things like exudates, microaggregates, and mycorrhizal fungi. This time, we chatted at a higher level, discussing the symbiosis between plants and microbes and the natural intelligence of soil, which is the concept that soil involves dynamic properties and complex biological relationships that allow it to self-regulate, support life, and regenerate.  The upshot is that we should all be paying much more attention to the soil food web, a living system that empowers soil to do it all: create habitat, defend plants from pests, provide food for the plants (and therefore people and other animals),  trap carbon, and act as a buffer against extreme weather events such as floods and droughts of magnitudes that deviate from normal conditions and cause significant disruption. Certain fungi, for example, can break down toxins, and the fungi are still learning. (In the book, Horrigan writes that some microbes can decompose toxins such as pesticides and other recalcitrant environmental pollutants. Who knows what they’ll learn to break down next?)   

Horrigan uses a term I love—microherd—to describe the millions of microscopic organisms that make up an essential and foundational role in the soil food web and enable it to perform its myriad services. And, he says, just as you would not poison or damage a “macroherd”—say, for instance, cattle—we should not poison or damage our microherds by using herbicides or tilling. Once again, he says, humans have been just a bit too clever for their own good, applying chemicals and inventing production methods that are unnecessary in a system with healthy soil. “Let’s just stop disrupting these brilliant systems that have evolved over millions of years,” he says.