Widespread Agricultural Pesticide Use is Killing Soil Biodiversity

ON 05/05/2021 AT 07:57 PM

A new exhaustive study of agricultural pesticide use just proved what biologists had long feared. The chemicals are wiping out invertebrates which form the foundation for all life within and which grows out of the soil.

The review article that revealed all this, “Pesticides and Soil Invertebrates: A Hazard Assessment,” was published on May 4, 2021, in the journal Frontiers in Environmental Science.

With principal research for the article carried out by scientists at the University of Maryland’s Department of Entomology; the Center for Biological Diversity based in Portland, Oregon; and Friends of the Earth US based in Berkeley, California, the work represents what the backing organizations for the paper call “the largest, most comprehensive review of the impacts of agricultural pesticides on soil organisms ever conducted.”

The authors’ approach in investigating those impacts included analyses of “275 unique species, taxa or combined taxa of soil organisms and 284 different pesticide active ingredients or unique mixtures of active ingredients.” By digging into almost 400 separate studies of the subject matter, scientists investigated biodiversity in the soil microbiome on a broad scale, investigating the impact of pesticides on species’ biomass, reproduction rates, growth and abundance, behavioral changes in the chemicals’ presence, overall diversity, biochemical biomarkers, and death rates.

The researchers were especially focused on looking at the effects of pesticides on species that were not supposed to be the target of the pesticides. In war terms, which is what this is in some ways all about, one can think of what the researchers were trying to understand was how much “collateral damage” there has been the many species which make the soil rich and thriving.

After coming up with a list of over 2,800 “tested parameters” about what defines health and biodiversity in the soil, the researchers found that 70.5% of those metrics showed “negative effects” on the soil microbiome. The damage to biological diversity in the ground was broad-based, appearing “across all studied pesticide classes, and in a wide variety of soil organisms and endpoints.”

The scientists blamed the destructive biological shock wave these pesticides have left in their wake on the agrochemical industry’s increasingly more lethal poisons, as well as how the pesticides are applied. Those applications are in bulk, overused, in recent years applied directly on the soil itself in mass volumes, and often now embedded in seed coatings to enable embedding the pesticides well below the surface. There they can migrate more effectively to destroy the microorganisms and larger invertebrates which, in a colossal paradox, are the whole reason the soil is a good place to grow crops in the first place.

As the article explains further:

“Soil invertebrates perform a variety of different ecosystem services essential for agricultural sustainability. Soil biodiversity enables self-perpetuating ecosystem functions that fuel specialized processes such as soil structure maintenance, nutrient cycling, carbon transformations [and carbon capture potential to absorb atmospheric emissions], and the regulation of pests and diseases). Burrowing activity by soil organisms modifies soil porosity by increasing aeration, water infiltration and retention, and reducing compaction. Earthworms alone can construct up to 8,900 km of channels per hectare, decreasing soil erosion by 50% via increased soil porosity and water infiltration. Nutrients travel through multiple soil layers by means of foragers, tunnelers, and ground-nesting insects including beetles, ground-nesting bees, ants, and termites, and detritivores like nematodes, springtails, earthworms, millipedes, and woodlice, transform decaying material and minerals into usable forms, cycle nutrients, and increase soil fertility.”

This is about far more than just the presence of insects which might represent a minor inconvenience to the big agricultural industry.

As Center for Biological Diversity scientist Nathan Donley, a co-author of the study, said, in a statement released as the article was published, “Below the surface of fields covered with monoculture crops of corn and soybeans, pesticides are destroying the very foundation of the web of life."

Donley noted that government regulators have long overlooked the impact of these pesticides on so-called “non-target” species in the soil “for decades.”

“Study after study indicates the unchecked use of pesticides across hundreds of millions of acres each year is poisoning the organisms critical to maintaining healthy soils,” he added in the statement.

“The level of harm we’re seeing is much greater than I thought it would be,” Donley explained further in a separate interview with reporters about what is happening. “Soils are incredibly important. But how pesticides can harm soil invertebrates gets a lot less coverage than pollinators, mammals, and birds – it’s incredibly important that changes.”

"Beetles and springtails have enormous impacts on the porosity of soil and are really getting hammered, and earthworms are definitely getting hit as well," he continued.

He also pointed out that, "A lot of people don't know that most bees nest in the soil, so that's a major pathway of exposure for them."

As to his recommendations, Donley said his team’s findings show “it’s not just one or two pesticides that are causing harm, [and] the results are really very consistent across the whole class of chemical poisons.”

What is needed, the researchers suggest, is a complete rethinking of the importance of soil biodiversity to the health of all species. As the researchers point out, our mass-production, monoculture, yields-at-any-cost approach to crop production must be reconsidered, literally at the ground level. Microorganisms and the billions of small invertebrates which populate the soil should not be thought of as miniature terrorists which threaten the financial success of big agriculture. They must instead be considered as important partners in enabling soils – and the crops which grow from seeds embedded within them – to be fully alive and thrive.

Then the government regulators, the ones who set rules and policy for the agricultural industry, must radically reshape review processes for the allowance of pesticide use, so as to preserve not just life in the soil – but life everywhere.