The overall toxicity of pesticides applied worldwide has risen significantly from 2013 to 2019, affecting various groups of organisms despite a United Nations goal to reduce risks by 2030. Researchers developed a measure called applied toxicity to assess this burden across 201 countries. The trend highlights growing challenges from pesticide resistance and shifting chemical use.
More than 60 years after Rachel Carson's influential book Silent Spring raised alarms about pesticide dangers, their impact on wildlife appears to be intensifying. A study published in Science analyzed data on 625 pesticides used in 201 countries between 2013 and 2019, including both conventional and organic options. By combining usage quantities with toxicity levels for eight organism groups—such as aquatic plants, fish, pollinators, and terrestrial arthropods—the researchers calculated total applied toxicity per country and group.
Globally, this toxicity increased for six of the eight groups over the period. Pollinators faced a 13 percent rise, fish a 27 percent increase, and terrestrial arthropods, including insects and spiders, saw a 43 percent jump. "In more or less all countries, the trend is towards increasing applied toxicity," noted Ralf Schulz from RPTU University Kaiserslautern-Landau in Germany, the study's lead author.
These rises stem from higher pesticide volumes and the adoption of more potent chemicals, largely driven by evolving pest resistance. "Resistance is, in my view, something that can only increase if you use chemical pesticides," Schulz added. Certain classes stand out: pyrethroids pose risks to fish and aquatic invertebrates despite low application rates, while neonicotinoids threaten pollinators. Even glyphosate, the widely used herbicide in products like Roundup, contributes due to its sheer volume, though its individual toxicity is moderate; replacing it could elevate overall toxicity if alternatives are more harmful.
Environmental monitoring often reveals pesticide levels in rivers and soils exceeding regulatory predictions, underscoring underestimation in risk assessments. At the 2022 UN biodiversity summit, nations pledged to halve pesticide risks by 2030, though the term "risk" remains undefined—applied toxicity could serve as a metric.
Experts caution that the index has limitations but reveals concerning patterns. "The world is currently moving away from the UN target rather than toward it. That is bad news for ecosystems and ultimately for human health," said Roel Vermeulen from Utrecht University. He emphasized that a few highly toxic pesticides drive much of the burden, offering targeted intervention points. Broader changes, including dietary shifts, reduced food waste, and pricing that accounts for environmental costs, will be essential for sustainable farming.
