Imogen Davenport, Dorset Wildlife Trust
The UK has over 20,000 species of insect, but their numbers are declining sharply. In Dorset over 8,000 species have been recorded over time – no doubt an under-estimate but some 20% of these are now under various categories of threat, are rare, protected or indeed extinct. Some of our best-known groups of insects show even starker figures – some 51% of Dorset’s 219 bee species, 42% butterfly and wasp species and 27% of beetles are in this concerning state.
But why should we care about insects any more than the rest of nature? The drastic decline of insects we have witnessed over the last 100 years affects us all – and the decline in insects is more stark than in some of the more endearing wildlife. The decline in insects tells us something about the state of our natural food chains and the resilience of the environment. We cannot afford to ignore this any longer. That’s why I got involved in encouraging ‘Action for Insects’ a year ago through my work with Dorset Wildlife Trust.
Insects, along with other invertebrates, have some of the least glamorous but most important roles in making sure nature functions properly and keeps us all alive. Just a few examples are below:
Around 80% of UK plants are pollinated by insects, including a large number of our crops. It has been estimated that the value of insect-pollinated fruits and vegetables grown in the UK is about £220m a year. Those showy wild and garden flowers we love – all insect pollinated, the biological point of a flashy flower is to attract insects not to please our eye. The relationships between plants and insects are sometimes incredibly complex. Several orchids are adapted to be pollinated only by specific bee species. Some plants provide incentives such as sweet nectar to attract ant colonies – which then guard against other insects which might want to nibble on them.
One of the important and unnoticed roles that insects play is to break down and decompose organic matter. They feed on dead plant tissues, dead animals, and the excrement of other animals. For example saproxylic beetles feed on dead and decaying wood. By ‘tidying’ dead wood away we remove these beetles’ habitat and don’t allow for the key recycling of nutrients into the soil. A messier environment is a healthier one.
Our decomposers are unsung heroes of recycling, turning dead organic matter and waste back into usable forms. Their actions help give us healthy, fertile soil. From this we get the food we eat, our landscapes and habitats, the ability to hold and filter rainwater and the capture of carbon – some 94% of UK biocarbon stock is in soil rather than vegetation, and without a healthy soil this process is broken.
As pivotal parts of the food web, all insects are food for other insects, or something bigger, and this can be of real use to humans too. Biological control of pests is big business, estimated to be worth $4.5bn a year in the USA alone. The conservation of natural enemies is probably the most important biological control practice available to growers and means that the use of damaging and expensive chemical pesticides can be reduced and ultimately avoided. Insect predators and parasitoids have perfected their merciless seek and destroy skills over millions of years, but pesticides take out both the target and, either directly or indirectly, the natural control as well. The pest species tend to rebound first, while rebuilding biological control, once lost, takes a little longer – in effect an addiction to pesticides is the result – effort is needed to break this dependence and provide a less sterile and hostile environment.
The much maligned common wasp feeds for most of the year on aphids, it’s actually a gardener’s friend……
Numerous UK birds, mammals and fish are insectivorous, including all our native bat species – pipistrelles bat species are thought to eat around 3,000 small insects such as gnats and midges every night. Some of the most dramatic declines in British birds are amongst the insect-eaters – for example spotted flycatchers, cuckoos and nightingales.
Insect species are highly susceptible to changes in the environment. This sadly makes them vulnerable to habitat degradation and climate change, but it also makes them very useful as bio-indicators. By carefully monitoring changes in insect populations, ecologists can measure the impact of disturbance and take steps to mitigate changes that may not have been initially apparent within other species.
Butterflies are recognised as valuable environmental indicators, and representatives for the diversity and responses of other wildlife. Many aquatic invertebrates, such as caddisflies, are also important indicators of the quality of our waterways and for this reason Dorset Wildlife Trust has been hosting a local Riverfly Monitoring programme. This programme was featured as ‘Citizen Science at its best’ in July’s Reversing Insect Declines report.
If no one is paying attention to insects the clues will be missed and we’ll carry on heading in the wrong direction. There is good news though – many people ARE paying attention – some 4,000 people signed up to take action for pollinators in their homes or gardens and Get Dorset Buzzing in 2019, for example. And in many cases insects, having short life cycles, can rebound quickly if we help them – so the message is that it is worth everyone doing something now, no matter how small.
There are many inspiring examples and ideas about what you can do, whether you run a home, school, farm, community group or local authority, through the Action for Insects campaign.
With thanks to Science Communicator David Urry and The Wildlife Trusts’ Action For Insects campaign.
Data on species in Dorset provided by Dorset Environmental Records Centre.
- Early bumblebee – Jon Hawkins (Surrey Hills Photography)
- Community gardening – Paul Harris (2020Vision)