A new global scientific study has found that invasive alien species are playing a far greater role in the worldwide decline of insects than previously recognised, contributing to sharp losses in both insect numbers and diversity across continents.
Published in the journal Nature Communications the research was conducted by scientists from the UK Centre for Ecology & Hydrology and the University of Cambridge. The findings add a crucial dimension to the ongoing debate on insect decline, which has largely focused on habitat loss, climate change and pollution.
Invasive species linked to major global losses
According to the study, regions affected by invasive plants and animals recorded an average 31 per cent decline in terrestrial insect abundance and a 26 per cent drop in species richness. Researchers analysed ecological data from six continents, examining how insect populations changed following the introduction of non-native species.
Rather than focusing on isolated case studies, the team searched for patterns across different ecosystems and geographies. The results revealed a consistent global signal: invasive species are significantly undermining native insect populations.
Invasive animals often reduce insect numbers by preying on them or competing for resources, while invasive plants replace native vegetation that insects rely on for food, shelter and reproduction.
Some insect groups hit harder than others
The study found that not all insect groups were equally affected. True bugs, known as Hemiptera, experienced the steepest decline, with populations falling by an average of 58 per cent. Hymenoptera which include bees, ants and wasps declined by 37 per cent, while grasshoppers and crickets dropped by 27 per cent.
Beetles were comparatively less affected, showing an average decline of 12 per cent.
Grace Skinner, lead author of the study and a data scientist at UKCEH, said identifying which insect groups are most vulnerable could help prioritise conservation efforts. She noted that such information is especially valuable when resources for biodiversity protection are limited.
Although invasive species are recognised globally as a major cause of biodiversity loss, their specific impact on insects has received far less attention than other threats such as urbanisation or agricultural pollution.
The researchers say this study helps close that gap by showing that biological invasions are affecting insects worldwide, not just in isolated regions.
Skinner stressed that insects should not only be seen as invaders but also as victims of invasion, warning that continued declines could threaten essential ecosystem services such as pollination, nutrient cycling and soil health.
Climate change and global trade amplifying the threat
The authors point out that invasive species do not act alone. Increased global trade and transportation have made it easier for non-native species to spread across borders, while rising temperatures are allowing many invaders to survive in regions that were once unsuitable.
Co-author Dr Joseph Millard of the University of Cambridge said the interaction between climate change and biological invasions could further intensify pressures on insect populations, calling for more research into how these threats reinforce each other.
A problem that can still be managed
Despite the scale of the impact, the researchers say invasive species remain a manageable threat if addressed early. They emphasise the importance of stronger biosecurity measures, better monitoring and international cooperation to prevent new invasions.
Individuals can also play a role by choosing native plants in gardens and following biosecurity practices such as cleaning equipment used in fishing, boating or forestry to avoid unintentionally spreading invasive species.
The study’s authors argue that recognising invasive species as a central driver of insect decline is critical if conservation strategies are to be effective in slowing or reversing one of the most alarming biodiversity crises of the modern era.
Writer-Vaishali Verma