Over 60 years have passed since Rachel Carson’s influential book, Silent Spring, highlighted the dangers of pesticides. The negative impact on wildlife has escalated, potentially more than ever before.

“Across nearly every nation, there is a trend of increased pesticide toxicity,” explains Ralph Schulz from RPTU University Kaiserslautern-Landau, Germany.

The risks associated with pesticides depend on both the volume used and their toxicity levels, which can vary significantly among species. To quantify the overall pesticide burden, Schulz and his team formulated a metric called “applied toxicity.”

The team investigated the use of 625 pesticides across 201 countries from 2013 to 2019, incorporating both organic and conventional pesticide data.

They averaged toxicity data from regulatory bodies in various nations, assessing the toxicity levels to eight major organism groups: aquatic plants, aquatic invertebrates, fish, terrestrial arthropods, pollinators, soil organisms, terrestrial vertebrates, and terrestrial plants. This enabled them to calculate the total toxicity per country or organism group.

Globally, applied toxicity rose from 2013 to 2019 in six out of eight organism groups. Notably, pollinators saw a 13% increase, fish a 27% rise, and terrestrial arthropods—including insects, crustaceans, and spiders—experienced a 43% increase.

“This increase does not automatically translate to direct toxic effects on these organisms,” Schulz clarifies. “However, it serves as an important indicator of the toxicity levels of the pesticides currently in use.”

Numerous studies indicate that pesticide concentrations in various ecosystems, such as rivers, often exceed regulators’ assessments during approval processes.

“While this particular index does not account for it, significant evidence exists,” Schulz remarks, emphasizing that risk evaluations tend to underestimate real-world exposures.

The rise in the combined applied toxicity stems from two key factors: the increased use of pesticides and the replacement of older varieties with more toxic alternatives, spurred primarily by the emergence of pest resistance. Schulz notes, “In my view, resistance will only exacerbate with more chemical pesticide use.”

Pesticides like pyrethroids pose notable risks to fish and aquatic invertebrates, even when applied in minimal amounts. Neonicotinoids also significantly threaten pollinators.

Calls to eliminate glyphosate, known as Roundup, are growing. Although glyphosate’s overall toxicity is relatively low, its widespread use contributes to cumulative toxicity, according to Schulz. A ban could backfire if more toxic herbicides are adopted following the ban.

Reducing pesticide usage could lead to unintended consequences; declining farm productivity may necessitate more land clearance, resulting in biodiversity loss.

During the 2022 UN Biodiversity Summit, nations pledged to reduce biodiversity loss. Schulz states, “Overall risk from pesticides” has yet to be precisely defined, but he believes that the aggregate of applied toxicities could serve as a metric.

While this method has its limitations, he insists that no perfect measure of overall pesticide use exists. Roel Vermeulen of Utrecht University in the Netherlands adds, “Despite the uncertainties, the alarming trends it reveals are undeniable.” He warns, “The world is drifting away from UN objectives, which spells bad news for ecosystems and ultimately for human health.”

“Crucially, this study illustrates that a small number of highly toxic pesticides are responsible for the majority of overall risk, highlighting clear and actionable targets for significant benefits,” Vermeulen asserts.

Transforming agricultural practices will require broader societal shifts. “Consumers must adopt dietary modifications, minimize food waste, and pay fair prices that truly reflect the environmental costs of production,” he concludes.