The government is seeking to increase the use of pesticides which scientists claim are causing overwhelming negative effects on hundreds of species of microbes, fungi, plants, insects, fish, birds and mammals that they are not intended to harm. Globally their use is a major contributor to the biodiversity crisis says a new international study which assessed the impacts of pesticides across all types of species in land and water habitats.
Wide-ranging negative effects of pesticides were seen for over 800 species found on land and in water, including impacts on how fast they grow, their reproductive success, and even behaviour such as their ability to catch prey, find plants to forage upon, move or attract mates.
Pesticides can also affect organisms’ metabolism and damage cells says the study which was led by East China University of Science and Technology and included scientists from the UK Centre for Ecology and Hydrology (UKCEH) and the University of Sussex.
They analysed more than 1700 existing lab and field studies of the impacts of 471 different pesticide types – either insecticides, fungicides or herbicides – in agricultural, commercial or domestic use.
The researchers say that, unlike previous studies which have tended to look at specific groups of species such as bees, fish or plants, or specific habitats, they have considered representatives of the whole spectrum of species found in the natural world.
“Our study provides an unparalleled insight into the consequences of pesticide use on the natural environment globally,” said co-author Dr Ben Woodcock, an ecologist at UKCEH. “Pesticides are a necessary evil, without which global food production and farmers’ livelihoods would likely collapse.” But overuse of pesticides not only threatens beneficial species they are not intended to target but can also enable pests to develop resistance to the chemicals, rendering them ineffective he says
The University of Auckland’s Associate Professor Melanie Kah at the School of Environment thinks the study work is “fantastic because it puts all the lines of evidence together, suggesting that pesticides are toxic.”
Ms Kah was the principal investigator of a scientific project funded by the Royal Society on “Building the foundation to improve the risk assessment of pesticides in Aotearoa/New Zealand” in 2024.
“What’s important is the scale of the analysis,” she says. “This review draws from 1700 studies, so it gives us a better feeling of what happens at the global scale, and the results clearly point towards negative effects of pesticides on non-target organisms.
“We need to improve the way we assess the risk associated with pesticides. In New Zealand, our regulatory framework is completely outdated. Some substances that have been phased out in Europe decades ago are still in use here, for instance. And I think we haven’t been given the resources by government to phase out those old substances and to consider newer chemistry.
“It’s a very short-term vision – pesticides increase productivity, no doubt. But in the longer term, this study shows that the price to pay as a society will probably be much higher. We are not only compromising the health of our ecosystems and people but also the reputation of New Zealand as a producer of high-quality, clean and green products. If there are excessive pesticide residues on the food that we want to export, that’s going to be an issue.
“This is a really key moment for New Zealand with the review of pesticide regulations underway. But we put it at risk by not investing adequate resources to hire more staff at the EPA, and by not funding monitoring programs to know where pesticides are applied and what their levels are in our water and soil. We are the only country in the OECD not keeping track of what pesticides are used in our country. That’s really shocking. This study just gives us another motivation to do something about it.
“Agriculture is responsible for most of the pesticide use in New Zealand. But this may also make individuals think twice before they use chemicals in their garden. It would be good if people at the personal, domestic level would realise that taking the synthetic pesticide path has impacts, not only in their own garden and their own health, but also beyond.”
Alternatives
David Wright, a Science Team Leader – Microbial Solutions at AgResearch, says the article highlights the wide-ranging potential for negative impacts from synthetic pesticide use, and the urgency in which we need to adopt alternative practices that reduce those impacts.
“There is increasing interest and use of microbial technologies to complement, or provide alternatives to, synthetic chemistry. Bioprotectants containing live micro-organisms or derivatives such as peptides are considered safer alternatives as they are generally more specific to target pests and have a significantly shorter environmental residue.
“There are some excellent examples of microbial biopesticides under development, including AgResearch-developed AgR96X that contains a natural pathogen specific to the New Zealand grass grub and Manuka beetle. AgR96X has shown equivalence to registered synthetic products in field trials.
“While biopesticides offer promising alternatives, sometimes several products may be required to target multiple pests that are currently controlled by a single broad-spectrum agrichemical. Research is needed to incorporate these into production systems and a step change in thinking from the current reactive silver-bullet approach.
“We need to move to more integrated systems that incorporate an increased understanding of the pest/disease lifecycle and monitoring to predict outbreaks, along with the use of multiple technologies that include breeding for improved animal/plant genetics with resistance to pests and disease, changes to farm management practices, digital tools to identify areas of risk, and a move from broadacre treatment to targeted delivery of biopesticides and where necessary agrichemicals at significantly reduced volume.”
Necessary option
The findings highlight the need for policies and practices to reduce their use says Dr Woodcock. This could include bottom-up initiatives led by farmers such as regenerative agriculture, as well as government policies such as Defra’s Sustainable Farming Incentive, which pays farmers to reduce insecticide use on crops.”
Professor Dave Goulson of the University of Sussex, who was also part of the research, added: “It is often assumed that pesticides are toxic primarily to the target pest and closely related organisms, but this is clearly not true.
“Concerningly, we found pervasive negative impacts across plants, animals, fungi and microbes, threatening the integrity of ecosystems,” he says
Future developments
Dr Andrea Byrom Andrea is an independent consultant and a former member of the EPA Board and chaired its Hazardous Substances and New Organisms (HSNO) Committee from 2021 to 2024. She is also a member of the Board of Manaaki Whenua Landcare Research.
“In a 2022 report on the fate of chemicals in the environment, the Parliamentary Commissioner for the Environment (PCE) noted that Aotearoa New Zealand has approved approximately 150,000 substances for use, made up of about 30,000 chemicals. So here in Aotearoa we should be very interested in the findings in this global meta-analysis: that there are strong negative effects of three classes of pesticides (insecticides, fungicides and herbicides) on the environment and on ecosystems, with potential consequences for biodiversity loss.
“Any global meta-analysis such as this is potentially useful. To me, however, this one stood out for several reasons. First, the authors were able to demonstrate significant effects on growth, reproduction and (in the case of animals) behaviour across a number of non-target plants and animals.
“These physiological effects potentially have far-reaching consequences for individual species and most likely add to a suite of threatening processes (others being the impact of invasive species or climate change) that put pressure on our native organisms, primary production sectors, and natural environments.
“Second, the authors tested whether their findings held for experimental field studies, not just studies under laboratory conditions. This is important, because what we really need to know is the impacts that pesticides might cause in the real world, not just in a lab. They found the same negative effects of pesticides on a range of species in the real world, which should be of concern both for our natural and primary production systems here in Aotearoa.
“Third, the authors went even further and tested whether their findings held for the sub-set of studies that investigated use of chemical pesticides under ‘field-realistic’ application rates. This is important too, because – despite the usually good intentions of those who use chemical pesticides – not all users adhere to recommended use or dosage conditions. This study demonstrates that even adhering to the recommended dosages and application rates still caused negative effects in non-target organisms in the field, which is again concerning.
“This study is a demonstration of just why the PCE’s recommendations back in 2022 – to help strengthen Aotearoa’s regulatory system so that we can understand the environmental fate of chemicals and their potential impacts – is so important.
“This study highlights that better surveillance, monitoring and reporting on the presence and quantity of chemicals such as pesticides in our environment would help us take a more holistic and systemic approach to the approval and use of chemicals in Aotearoa New Zealand,” she says.
