How could intelligent beings seek to control a few unwanted species by a method that contaminated the entire environment and brought the threat of disease and death even to their own kind.” – Rachel Carson, Silent Spring.

Pesticides are used extensively across the world, especially in agriculture. In the 60 years since Rachel Carson highlighted the risks of pesticide use to wildlife and people in her hugely influential book, Silent Spring, we have sleepwalked into a situation where pesticides have become the norm in terms of the way we manage land.

But what does this really mean for wildlife? This week, RSPB has released a report called ‘Pesticides and Wildlife’ – a comprehensive review of studies looking at the harmful effect of pesticides on wildlife and setting out why the current risk assessments are  failing to protect nature.

Evidence reveals significant knowledge gaps

RSPB scientists undertook a comprehensive search of the published evidence reviews that looked at impacts of pesticides on wildlife. They also looked specifically for papers on impacts on wildlife of the top 30 most commonly used pesticides in GB.  By doing so they discovered something worrying: 70% of published papers focussed on just four substances: the herbicide glyphosate, and three insecticides.

Given the large number of pesticides routinely applied to the UK’s farmland (at least 150 active substances in 2020), and the fact that these studies mostly do not take into account cumulative or cocktail effects of multiple substances being used on the same parcel of land, this demonstrates a very worrying lack of research available for the impacts of the vast majority of chemicals.

Despite this lack of research, what we do know is very worrying. The report highlights a number of studies demonstrating population level impacts on wildlife (including grey partridge and bees) and we know also that unintended negative impacts of pesticides on wildlife are inevitable because of the way they work.

  • Pesticides are rarely specific to their target pest species or groups.
  • Pesticides typically persist in the environment for weeks, months or even years, and their breakdown products may also be harmful.
  • Pesticides are rarely contained within the area where they are applied, and they can drift or drain away, contaminating nearby habitats, including water.

But surely they are safe if they are approved for use?

Pesticides, especially in the EU and the UK, undergo an assessment process before they are licenced for use. So why have these assessments failed to prevent such widespread environmental damage?

The pesticide approvals process has many glaring omissions in terms of the wildlife impacts considered and some examples are set out here. Firstly, testing on pesticide toxicity is mainly restricted to short-term, lethal effects. The vast majority of assessments do not test for any chronic or long-term effects or sub-lethal effects such as impacting the behaviour of an animal (such as the infamous impact of neonicotinoids on bees’ ability to navigate). Long lasting and cumulative effects are ignored.

Testing is only conducted on a very restricted range of ecologically inappropriate species and very little direct testing takes place under real-world field conditions. This means that these tests do not reflect real-world conditions and do not take account of other pressures affecting wildlife such as food availability, disease, climate change and, importantly, other chemicals.

Toxicity testing is restricted to a single active substance and does not consider potential interactive ‘cocktail effects’ of exposure to multiple active substances, or the ‘co-formulants’ (the non-active substances in each pesticide products) which are now showing as potentially as harmful as the active substances. None of the tests account for indirect effects on the food chain, such as removing seed food or insect food for birds. Approval also relies on unrealistic assumptions about how the pesticide is used – such as the supposed burying of neonicotinoid coated seeds.

This alarming combination of gaps means that important detrimental impacts on wildlife have gone unnoticed at the time the chemicals are approved for general usage. Some of these impacts may never be detected or understood, and even where impacts are detected there is often a lag between the evidence coming to light and any changes to the approval status of a chemical.

One example of this is neonicotinoids. Evidence now shows how harmful they are to a wide variety of wildlife, but as much of this is not immediately lethal, it was missed by the approved process. Neonicotinoids affects the ability of honeybees to navigate, and the ability of bumblebees to grow and produce queens.


The report highlights a wealth of evidence of the harm to wildlife, but also significant gaps in our understanding. Although it is important to use science to try and increase some of this understanding, instead of spending endless time and money trying to clarify every impact of every chemical on every species or ecosystem, we could realistically assume that chemicals designed to kill things, must be used minimally if we are to avoid damaging our world, and recover nature.

What can be done?

In agriculture, more and more farmers are choosing to move away from chemical pesticides, by finding non-chemical solutions. Many of these solutions rely on nature, such as providing habitats for pest predators such as hoverflies and ladybirds. Martin Lines – an arable farmer from Cambridgeshire – has not used insecticides since 2013 and has noticed that crop yields are 5-20% greater next to the wildflower habitat strips that he has created.

A recent study from the United States demonstrated that by improving pollinator conservation, insecticide use could be reduced by 95% with no change, or even increases, in crop yield. And a study in France showed 59% of farms could reduce the number of pesticide applications by an average of 42% without impacting either productivity or profitability.

Creating habitat for pest predators, along with actions such as ensuring diversity of crops and monitoring pest thresholds, are important parts of an Integrated Pest Management approach to managing pests and diseases – where chemical pesticides are only used as a last resort.

In England, the Government has committed to paying farmers for IPM in the new Sustainable Farming Incentive, and it is vital that this is ambitious and really helps to drive a reduction in reliance on pesticides.

Outside of agriculture, people can make their own contribution by gardening organically and asking their local councils to go pesticide free in towns and cities.

The UK Government also needs to invest in more research into non-chemical alternatives and set an ambitious pesticide reduction target which will clearly set the direction of travel and drive innovation.

And we must make sure, that when pesticides are approved and must be used, the real-world impacts are better understood and managed, to better protect people and wildlife.

Photo credit: Kevin Sawford