Nature is under threat from rapidly rising pesticide use

An international target to slash pesticide use is unlikely to be met – with just one country on track to meet the goal.

In 2022, nations at the biodiversity conference COP15 agreed to halve the risk of pesticides by the end of the decade. But, halfway towards the deadline, the use of these compounds is actually rising overall. Only Chile is currently on track to meet the target, with many other countries way off course.

New research reveals that these rises are being driven by a core group of pesticides, including neonicotinoids and pyrethroids. Around 20 pesticides are responsible for over 90% of the toxic impacts on insects, worms and a variety of other wildlife.

As these species play critical roles in nutrient cycling, pollination and food webs, the declines could be catastrophic for the health of ecosystems that are vital for global food security and biodiversity. Professor Ralf Schulz, a co-author of the study, says that the results confirm what many scientists had already expected.

“We’ve known that the use of pesticides has been steadily increasing for decades, but the scope of previous research has been limited,” Ralf says. “Our research shows that in the 2010s, the applied toxicity of pesticides around the world grew substantially.”

“This rise is driven in part by the higher use of pesticides as farmland expands and farming practices intensify, but also because we’re using more toxic pesticides than we used to 20 or 30 years ago. This has consequences for all wildlife, but particularly plants, insects and many different invertebrates.”

The findings of the study were published in the journal Science.

The growing impact of pesticide pollution

While pesticides are intended to protect crops by targeting specific pests, their toxic nature means that their impacts are hard to control. Pesticides have spread into a wide variety of animals from chimpanzees to orcas, with consequences for their development, immune system and reproduction.

Smaller species are most affected. Pesticides are among the biggest threats to the life in soil, harming and killing worms, mites and insects that help to maintain soil fertility. Meanwhile, pollinator populations are plummeting around the world, with pesticides thought to be one of the many reasons for their decline.

Until now, however, the impact of pesticides has never been looked at on a global basis. This changed following the COP15 agreement as researchers wanted to track the progress being made towards the goal. By combining data on the use of pesticides in the 2010s and how toxic they are to different species, the team found that the overall levels of toxicity resulting from these chemicals rose sharply.

Insects and other terrestrial arthropods were the most affected, with levels of toxicity jumping by 42.9% between 2013 and 2019. This follows studies that show insect populations are in freefall, declining by around 2.5% each year as many species head towards extinction.

Soil-dwelling organisms and fish were next, with levels of toxicity rising by around 30% for each group. Aquatic invertebrates, pollinators and land plants followed, with rises of between ten and 20%.

In contrast, levels of toxicity for aquatic plants and vertebrates during the study period fell. However, the researchers warn that the declines vary significantly across the world and that levels of toxicity for vertebrates started to rise again by 2019.

The team also analysed which areas of the world the use of pesticides was focused on. They found that more than half of the toxicity of pesticides was found in just four major crop-growing countries – China, Brazil, the United States and India.

The potential for recovery

Though the study’s results are alarming, there is cause for hope.

As only a relatively small number of pesticides are responsible for most of their toxicity, restricting and phasing out the use of these compounds would give many ecosystems a chance to recover. Ralf says that the speed at which an ecosystem recovers varies, but can be very quick if the conditions are right.

“If a whole landscape has been intensively sprayed with pesticides for decades, it will take a long time for species that have been driven out to return to the area,” he adds. “However, if there are patches of wild areas nearby where wildlife persists, then an ecosystem’s recovery will be much faster.”

An example of how quickly nature can recover from pesticide use is the global effort to phase out DDT. This pesticide caused bird of prey populations to plummet by making their eggshells perilously thin. Restrictions on its use in various countries, followed by a global ban on its use in farming, have helped species such as the peregrine falcon to bounce back from the edge of extinction.

Similar efforts to eradicate pesticides such as neonicotinoids, which has proven devastating for bees, are building around the world. The EU has banned a variety of neonicotinoids since 2018, with research in France suggesting that insect-eating bird populations are starting to recover as a result.

As one of the world’s largest users of pesticides, China has also introduced policies that are significantly reducing its dependence on these compounds. Levels of chemical pesticides in the country peaked in the mid-2010s, and have since been in decline.

The researchers hope that countries that have increased their use of pesticides, such as the UK, will adopt similar strategies to help their ecosystems recover. As global temperatures rise and habitats are destroyed, cutting the impact of pesticides will give more species a fighting chance at survival.