A blog by Advocacy and Social Change Manager, David Smith.
From the sightings of praying mantids in Cornwall to the suspected sound of cicadas on London streets, reports of non-native invertebrates appearing across Great Britain are becoming increasingly common. These discoveries can be exciting, offering a glimpse of new species in the UK. But they also raise an important question: should we celebrate these exotic invertebrates, or be concerned about how they appeared and what impact they may have on our native wildlife?
In some cases, human-caused climate change may be helping species expand their natural ranges. Warmer temperatures and milder winters can make the environment more suitable for insects and other invertebrates that previously struggled to survive here. A changing climate could allow some species to establish populations, particularly in the south of the country and other areas with favourable conditions, such as large urban areas.
Milder winters can be a significant factor – frost will kill off the adults, eggs and young of many species from warmer climes – meaning that, even though they may arrive, they are unable to establish here as viable populations. Take away the frost and that climatic insurance policy against new species is lost.
Not every new arrival is the result of natural range expansion. Many pathways into the UK are created by people, with species unable to jump the sea to get here. Invertebrates can travel in imported plants, soil, timber, cargo, vehicles and horticultural materials. Global trade and tourism provide countless opportunities for species to cross natural barriers and reach new environments. And enthusiasts might be tempted to keep exotic species as pets, which in turn might escape.
The arrival of a non-native species is not automatically a problem. Many introduced species are harmless and may live alongside native wildlife without causing significant disruption. The concern lies with those that become invasive, organisms that spread rapidly and cause ecological, economic or social damage.
Invasive species can compete with native animals for food and habitat, introduce diseases, damage crops or alter entire ecosystems. Some impacts may be difficult, or even impossible, to reverse. We are already experiencing the consequences of introduced species such as invasive flatworms, North American Signal Crayfish (Pacifastacus leniusculus) and Yellow-legged Hornets (Vespa velutina). These examples demonstrate how quickly human-assisted introductions can become challenging to manage.
That is why each new sighting matters. We need to understand whether a species has arrived through climate-driven range expansion, accidental human transport or deliberate release. We also need information about its habitat, behaviour, diet and ability to reproduce. Early identification can make prevention and control far more effective.
The recent discovery of praying mantis nymphs may be exciting, and we are glad to see the interest in these fascinating invertebrates, but it should also prompt careful investigation. Rather than celebrating every new species or treating every sighting as a crisis, we need a balanced, evidence-based approach.
Understanding how these species reached us is essential. More importantly, we must improve biosecurity and avoid repeating the mistakes that allowed damaging invasive species to become established in the first place.
If you spot a species in the UK which you think might be non-native, please report it to the GB Non-native Species Secretariat: www.nonnativespecies.org/non-native-species/recording
All non-native species records are useful and help us to identify and track the risk of invasive species across the country.
Main image Credit: Yellow-legged Hornet (Vespa velutina) © Vespa-Watch, no rights reserved (CC0)