Supporting biodiversity by reducing chemical use on your garden or allotment
07/30/2025
Chemicals have traditionally been used in gardens and allotments to eliminate pests and accelerate crop growth. But in recent years, there has been growing concern about the impact of chemical pesticides and synthetic fertilisers on the environment and biodiversity.
Some experts – such as award-winning garden designer Zoe Claymore, go as far as to say that the use of chemicals undermines other well-meaning efforts to support biodiversity, such as introducing ponds and native hedges.
Why avoid chemicals in allotments and gardens?
Chemicals can present a variety of risks and hazards that need to be understood and carefully managed. These can include risks to human health – for example, burns, corrosive injuries or sickness as a result of incorrect handling or storage.
Chemicals can also have a negative impact on biodiversity. One of the main reasons to cut down on chemical use in allotments is to reduce the risk of harm to wildlife other than the ‘pests’ that such chemical products are often intended to eradicate - such as aphids, caterpillars and slugs. Few pesticides are specific in what they kill, so their use can also endanger all sorts of plants and animal life.
For example:
- Spraying pesticides on or near flowers can put bees, butterflies and other pollinators at risk
- If pesticides get into water courses, for example through run-off from hard surfaces or as a result of being flushed down drains, they can pose a significant risk to fish and other marine animals
- Other garden chemicals, for example synthetic fertilisers, can pose a risk to larger animals, such as cats and dogs, either through direct ingestion, or as a result of eating or chewing grass and plants which have been treated with such chemicals.
Even when chemical pesticides are effective in killing their intended targets, many experts believe their use is not necessary. The Royal Horticultural Society (RHS) discourages the use of the term ‘pest’ altogether. It points out that many of these creatures play an important role in biodiversity. It has produced a guide to some of the most useful insects and bugs you may find on your garden or allotment.
Alternatives to chemical pesticides
One of the things the RHS recommends is a change of mindset – to avoid thinking about eradicating unwanted creatures altogether, and to instead try to reduce their numbers to tolerable levels, as many plants will be able to tolerate some damage from feeding or disease.
There are a number of ways to do this that don’t involve using chemicals. One is to find alternative ways of protecting plants, for example using mesh or the top half of large drinks bottles. Inspecting your allotments or garden plants regularly will allow you to assess the level of damage caused by insects or other animals, and work out if this is within a tolerable level for the plants to survive. It will also enable you to spot and remove unwanted creatures mechanically, e.g. removing caterpillars and slugs by hand, or using a hose to wash off aphids and other unwanted insects.
In addition, it’s a good idea to consider ways to encourage (or simply buy) natural predators to keep pest populations in check. For example, you can introduce hoverflies to prey on aphids, or build a pond to encourage frogs and toads, which feast on slugs and snails.
Companion planting – creating areas of plants that provide benefits to each other – is also a great way to attract beneficial insects and repel the unwanted ones. Chives, onions and garlic, for example, are often said to have a repellent effect on many insects. Alternatively, some plants can simply be used as a sacrifice to lure insects away from precious vegetables.
Chemicals are also used frequently in allotments and gardens to reduce the risk of disease to plants. However, these risks can often be reduced or mitigated in other ways. Inspecting a plot regularly will enable you to remove decaying plants, leaves and other debris early to reduce the spread of disease. Rotating crops on your allotment or vegetable plot can also help, by preventing reinfection of vegetables of the same family (by starving out soil-borne diseases).
Alternatives to chemical fertilisers
Synthetic fertilisers are typically quicker to stimulate plant growth than organic alternatives, but their effects generally don’t last as long, and unlike organic fertilisers, synthetic fertilisers only support the crop, not the surrounding soil ecosystem. Perhaps the biggest reason to ditch synthetic fertilisers is their potentially harmful impact on biodiversity, for example through pollution as a result of chemical run-off into waterways.
The first thing to consider is the quality of your soil and whether it’s actually necessary to use fertilisers at all. Soil quality can be improved and maintained by applying organic matter, either as a soil conditioner dug into the soil, or as mulch (a layer of material applied to the soil surface in the late autumn/winter months). Mulch can take the form of well-rotted garden compost and manure, chipped bark, gravel, grit, or slate chippings.
See the RHS’s guide to fertilisers and advice on how to use organic matter.
Risk and insurance considerations if you are using chemicals
Use of chemicals in a garden or allotment can also potentially pose a risk to humans – particularly if the chemicals are not stored, handled, labelled, or disposed of correctly.
These risks can include burns, fire hazards, or pollution of waterways.
If you are using garden chemicals, then in order to keep your staff/volunteers and members of the public safe, it is important you understand what chemicals you are using and how to deal with different scenarios.
For example, in the event of a spill, do you have protective gloves and safety goggles to hand?
How Zurich Municipal can help
For more on the risk and insurance considerations of using chemicals, see our article:
To find out more about some of the services we offer to help our customers better manage their risks, visit our Zurich Resilience Solutions page.
Or, if you’ve got any questions about the content of this article, get in touch.
- Give us a call on: 0121 697 9131
- Emails us: zrs.enquiries@uk.zurich.com
