The effects of agricultural pesticides on UK wildlife

Blog Post by Catherine Miller 05 August 2015

The UK is dominated by agriculture, occupying around 71% of the country's land. The country's population depends on agriculture for its food security and economic growth. Because of this, efforts are often made to increase yield and reduce pest numbers, but what effect is this having on native wildlife?

Agricultural chemicals fit into two main groups – pesticides and fertilisers. Pesticide is a broad term that covers a range of products used to control pests, which include:

  • Insecticides – insect killers
  • Fungicides – mould and fungi killers
  • Herbicides – weed killers
  • Molluscicides – slug and snail killers
  • Rodenticides – rat and mouse killers

These pesticides have specific groups of species which they target, although many other species can be exposed to them. With over 98% of sprayed insecticides and 95% of herbicides reaching non-target areas, it is relatively easy for wildlife to come into contact with pesticides either in crops, field boundaries and even watercourses due to run-off.

Pesticides can eliminate some animals’ essential food sources, causing the animals to relocate, change their diet, or starve. Pesticides affect wildlife far beyond the field boundaries with birds, amphibians and even aquatic life being affected. Residues can also travel up the food chain; for example, birds can be harmed when they eat insects that have consumed pesticides.

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Modern pesticides are generally less harmful to non-target species than they have been in the past. During the 1960s and 70s, DDT, an extremely harmful insecticide, resulted in the loss of millions of birds, in particular raptors, as it caused significant egg shell thinning. DDT has now been banned in the UK and all pesticides must be robustly assessed to ensure their safety to both humans and biodiversity.

Despite these robust assessments, non-target wildlife is still being affected by the legal use of pesticides.  Rodenticides, used to control rat and mouse numbers, are commonly used in rural areas in the UK. The vast majority of rodenticides used are highly toxic ‘Second Generation Anticoagulant Rodenticides’ (SGARs), such as bromadiolone and difenacoum, which disrupt the recycling of vitamin K and prevent blood from clotting. Due to increasing resistance to the poison, more accumulation is occurring in non-target species, putting their lives in danger, for example research has found traces of SGAR poison in 93% of tested spawrrowhawks, 48% of tested buzzards, 35% of tested peregrine falcons and 57% of tested hedgehogs.

There’s currently concern over a group of insecticides called neonicontinoids. In 2013 the European Commission restricted the use of three pesticides belonging to this group – clothianidin, imidacloprid and theiametoxam. Neonics are systemic pesticides, unlike contact pesticides which stay on the plant surface, systemics are taken up by the plant and transported to all the tissues i.e. leaves, flowers and roots. The restriction was issued as the pesticides posed a “high acute risk” for bees and other pollinators, being referred to as the “new DDT”. The pesticide is known to cause disruption to foraging behaviour, homing ability, communication and larval development, as well as disrupting bees’ immune systems, making them susceptible to viral infections to which they are normally resistant.

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On 23rd July 2015, a decision was made to lift the ban on neonicontinoids for 4 counties in the UK; Suffolk, Cambridgeshire, Bedfordshire and Hertfordshire. Two of the neonicotinoid pesticides can now be used for 120 days on around 5% of England’s oilseed rape crop to prevent damage from pests – primarily the cabbage stem flea beetle. Recent studies have indicated that the areas where the ban has been lifted could lose two-thirds of their wild bumblebee colonies by winter of 2016/17.

Although pesticides are known to cause problems with non-target species there’s no doubt that their use will continue into the foreseeable future and potentially causing further decline or even extinction of some of the UKs native species.


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