Soil Animal Biomass Declining Sharply — Dare to Know

Soil animal biomass is declining as tiny organisms get smaller and scarcer. Find out why this poses a threat to our global food system.

Like most people born on a farm, I have undying respect for the soil. I’ll even go so far as to correct people who refer to it as dirt or to families who till the Earth as dirt farmers.

Soil is a living entity that needs as much nurture and support as the crops that arise from it. It isn’t something we can take for granted, nor is it some manufactured commodity that comes in plastic bags from the garden centre.

Soil also isn’t a single organism. It’s an ecosystem of its own, supporting a diverse community of tiny animals. Their role is to decompose organic matter like dead plant tissue and recycle it as nutrients for the Earth’s fruits.

The quality of the soil depends on the skills of the farmer who cultivates it. It depends even more on the health of the climate and our planet as a whole. Agriculture has limits, and it always operates in the context of Nature.

The trade journal eLife published a study this week from the Helmholtz Centre for Biological Research (UFZ) about soil animal biomass. The study found that the microscopic animals who make up our soil are getting smaller.

They’re also getting scarcer. For instance, the study found 47% fewer mites and springtails in soils from developed land than in undisturbed meadows.

Animals who live in warm climates are smaller than those who live where it’s cold. Polar bears weigh far more than sun bears, for example.

Heat favours small bodies with fast metabolisms while cold favours larger bodies and slower metabolisms. Small animals dissipate their heat while large animals conserve it.

A similar thing is happening to soil animals. As the climate crisis pushes up average temperatures and we experience more severe weather like droughts, smaller species fare better than their larger cousins.

Similarly, within each species, smaller individuals edge out other specimens. So, the total quantity of living material hosted by the soil is falling fast.

That’s only part of the story. The reason that there are fewer soil animals overall is land use.

Our enormous population growth has been met by high intensity, high-yield food production. In recent decades, our driving concern has been to pull more and more calories out of each hectare of land worldwide.

We’ve steadily increased the concentration of ploughing, grazing and mowing on the land. The push for ever-greater yields has also forced farmers to apply higher volumes of chemical pesticides and fertilizers.

All of this high-yield monoculture crop production takes a toll on soil animals. It robs them of niches in their subterranean microcosm, and it deprives them of their food sources.

They either die out as a result or make their way into more natural green spaces if they can find them. Either way, farms end up with fewer organisms to fertilize the soil.

The average size of the soil animals combined with their total numbers is called their biomass. That’s the grand total by weight of all the living stuff in a field’s soil.

Both climate change and overproduction are threats to soil biomass. Now that they’re happening at once, our soil fertility is facing a crisis.

We’re living in a time of mass extinction. The United Nations panel on biodiversity tells us that two of the main factors in the loss of species are land use and climate change.

The state of our soil reflects that. The number of individual soil animals is declining, and so is the quantity of soil animal species. Larger specimens are also dying out in the process.

The reason this matters is that soil fertility is a function of soil biomass. When individuals’ size declines along with the absolute number of individuals, the health of the soil suffers.

Unfortunately, the story gets more depressing. Many people in the back to the land movement argue that the way out of this puzzle is to move to more eco-friendly farming methods.

On the contrary, the researchers found that organic agriculture doesn’t help much. Regardless of eco-friendly claims, organic farming practices do nothing to mitigate the effects of climate change.

Soil animals continue to be stunted on “green” farms despite their gentler cultivation techniques. So going green on the farm isn’t the answer to declining soil biomass.

Team leader Dr. Martin Schädler from the UFZ put it this way, “Not everything that threatens to break down as a result of warming can be saved by environmentally friendly land use.”

The study confirms the hard truth that ecologists have been telling us for decades. The only way to mitigate climate change is to eliminate greenhouse gas emissions at their source.

Dr. Schädler concurred grimly, “We can’t assume that we’ll come up with anything else.” When it comes to global warming, there’s no free lunch.

It’s fascinating that in a handful of soil, we can see the two most significant threats to Nature of all time. Our soil’s fertility is suffering from both mass extinction and climate change.

Our intensified, factory farming is driving soil animals out of our fields and leading to their extinction. At the same time, climate change stunts their growth, further shrinking the soil biomass.

The research team from UFZ has sent us back to the drawing board. Our global society has to find ways to reduce our carbon emissions from burning fossil fuels.

Our governments can impose direct regulations, a carbon tax or a market-based approach like a cap and trade system. Economists can advise policymakers on the best plan for a given country or region.

What matters is that the debate needs to be at that level now. Whether climate change is real or caused by humans or a crisis are settled questions.

We’re now left with a brief time to come up with the best strategy to mitigate the crisis and then discover how to make it happen before it’s too late.

We always have more to learn if we dare to know.
Learn more:
Shrinking dwarves
Climate change and intensive land use reduce soil animal biomass via dissimilar pathways
Climate Crisis Becomes Undeniable
Finding New Ways to Share the Land
Soil Biodiversity Now Tracked Globally

Originally published at on July 29, 2020.

Enjoying my Freedom 55 while blogging about science and delivering selective business to business writing services.

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