Juanita Browne: Pesticides harm more than the weeds and pests they’re designed to kill
One To Of Using Of Environmental Widescale Lot Ways Chemicals Accidentally We Our In By Is Problems The A Add Gardens Which In
Sometimes we don’t realise the broader environmental impacts of the chemicals we use at home.
It seems obvious to say that gardeners love the outdoors, and because they find great joy in nature, they would never want to cause environmental harm.
But sometimes we can be unaware of how something we do within the confines of our own property can actually have knock-on effects on environments and wildlife elsewhere. One of the ways in which we accidentally add to widescale environmental problems is by using a lot of chemicals in our gardens.
A pesticide is a biocide designed to kill a pest, e.g. a pest of crops, lawns, cereals, fruits or vegetables. The term ‘pesticide’ covers herbicides, insecticides, fungicides, molluscicides (such as slug pellets), rodenticides, etc.
- Insecticides, of course, are designed to kill insects that damage crops. Unfortunately, insecticides also harm ‘valuable’ insects, such as pollinators. Another negative effect of using insecticides is that it results in less availability of insects in the environment to feed animals higher up the food chain, such as birds and mammals.
- Herbicides are designed to kill weeds that reduce crop yields or productivity, but they also kill off wildflowers that feed our insects and again affect the whole food chain. Another common problem with herbicides is run-off - when they run off the land and get into our streams and rivers, they cause water plants to die, removing oxygen, which can suffocate fish.
- Rodenticides or rat poison doesn’t just kill mice and rats. It is designed to be slow-acting, only killing the animal after a few days. In the meantime, they can be caught by predators such as Barn Owls, where the toxins they carry accumulate over time. Bird Watch Ireland research has shown that over 88% of Irish barn owls have rodenticides in their systems.
- Slug pellets also contain dangerous poisons that build up in the systems of hedgehogs and birds which prey on slugs and snails. Pesticides in soil can also affect soil diversity including earthworms, which become food for so many mammals and birds.
But when considering the effects of pesticides on wildlife, it’s really important to remember that animals aren’t just being exposed to a single pesticide, they are now coming into contact with a ‘cocktail’ of chemicals - in their foods, water and in soil — a combination of many different pesticides that are pervasive in our environment.
Even when a pesticide doesn’t kill an animal, the ‘cocktail effect’ or repeated exposure can cause non-lethal effects that reduces their ability to forage, make nests or reproduce and thus causes population declines. These non-lethal effects have been shown in both bees and fish.
Many plants now contain systemic pesticides that contain active chemicals in every part of the growing plant, including the pollen, nectar and leaves. Pesticide residues are found in most of our fruits and vegetables.
Pesticides have been found all over the planet — in the high Arctic, in the bodies of predators such as polar bears, beluga whales, and even in studies looking at human breast milk.
Pesticides are also turning up in our drinking water. In Ireland, our drinking water is abstracted from approximately 290 surface water catchments and 960 groundwater catchments.
In the EPA’s Water Quality in Ireland 2013-2018 Report, published in 2019, the herbicide MCPA was detected in over half of the 144 rivers that were monitored. MCPA (2-methyl-4-chlorophenoxyacetic acid) is used to treat rushes, docks and thistles and is also found in ‘Round Up for Lawns’.
Conventional water treatment plants are not designed to remove pesticides from raw water. In 2020, Irish Water found that 36 public water supplies exceeded the EU Drinking Water Directive standards for pesticides on one or more occasions.
57% of these exceedances related to MCPA; and the next pesticides with the most exceedances were 2,4-D and glyphosate — all three are ingredients of pesticides regularly used in gardens.
But isn’t this large-scale pesticide use all down to Agriculture, Transport, Forestry, Local Authorities or other large sectors?
Perhaps not.
“I don’t like weeds or long grass around my trees, so I just spray around them…”
“I don’t want moss in my lawn, so I spray it…”
“I don’t like to mow my road verge so I spray it off once a year… I like my garden neat. What harm am I doing?”
According to 2018 stats, 17% of total pesticides sold in Ireland were for use in gardens! Professionals in the agriculture and horticulture industries have to undergo training in order to use pesticides, and they have to keep records of how these chemicals were used and stored.
But If you walk into any hardware store in Ireland, you will find long shelves piled high with chemical herbicides, insecticides and fungicides. You won’t be given guidance, you won’t have to keep any records, and you can buy the same amount of pesticide for your garden that might be used on a whole field.
Like so many environmental challenges, it’s difficult to grasp that what is happening in your small garden can have cumulative effects elsewhere. These seem like simple small decisions. It’s personal too, and ‘no one is going to tell me what to do in my garden’.
I also think there’s an assumption that the pesticides on sale in garden centres must somehow be ‘weaker’ and ‘less dangerous’ than industrial products, but think about it… if it was any weaker, it wouldn’t kill your plants.
The first thing you should ask yourself is ‘do I really need to spray or could I try something else?’ Where possible, you could try strimming, hand-weeding or mulching. Look into alternatives to chemicals, such as vinegar or hot water.
If you must use chemicals, use spot-spraying instead of spraying wide areas. Do follow the instructions carefully. Don’t spray in windy conditions. Don’t use pesticides near drains, wells or water courses, such as rivers, streams or lakes. Don’t apply pesticides if it’s raining, if the area is wet, or if rain is forecast.
Remember that when we use pesticides in our gardens, we’re just adding more and more chemicals into our environment, into the air, our soils and ultimately into our watercourses. The EU Biodiversity Strategy aims to reduce by 50% the overall use of chemical pesticides by 2030.
Could domestic sales of pesticides be the first thing we could reduce?
Useful tips and alternatives to pesticides
- Juanita Browne has written a number of wildlife books, including and .
CLIMATE & SUSTAINABILITY HUB