Pesticides 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 – and globally their use is a major contributor to the biodiversity crisis.
That is the finding of the first study assessing the impacts of pesticides across all types of species in land and water habitats, carried out by an international research team that included the UK Centre for Ecology & Hydrology (UKCEH) and the University of Sussex.
Multiple negative impacts
The scientists analysed over 1,700 existing lab and field studies of the impacts of 471 different pesticide types – either insecticides, fungicides or herbicides – in agricultural, commercial or domestic use.
Wide-ranging negative effects 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.
These negative effects can result in the premature death of wild organisms and reduce populations.
The international study, led by East China University of Science and Technology, has been published in Nature Communications.
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.
Necessary option
"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. However, our findings highlight the need for policies and practices to reduce their use. 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."
Alternatives
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. Farms in the UK, for example, are currently encouraged to carry out an Integrated Pest Management assessment which emphasises reduced pesticide use and natural pest control. In the European Union, over 10% of land under agricultural production is organic, using no synthetic pesticides.
Alternative options for farmers include planting wildflowers and beetle banks to support species that eat pests, allowing them to reduce spraying when there are high numbers of these natural predators present. Other measures include adjusting the timing of planting to avoid pests and rotating crops to break the species' life cycles and reduce their numbers.
Gardeners can do their bit to reduce the use of chemicals. Options for natural pest control include introducing nematodes, ladybirds or mites, which can be bought online, and encouraging other natural predators such as frogs, birds and hedgehogs with wildlife-friendly gardening. Physical barriers such as netting can prevent caterpillar and bird damage.
Future developments
New monitoring work by UKCEH, working with Defra, is currently using honeybee colonies to monitor pesticide risks across England to act as an early warning of emerging problems.
Dr Woodcock pointed out there was a lot of scope in the future for developing agricultural methods to be more responsive to our natural pest controllers, such as AI monitoring of both pests and predators using high-tech cameras.
