Climate change causing collapse in insect numbers: Study

Insects are critical to the future of our planet. They help to keep pest species under control and break down dead material to release nutrients into the soil. Flying insects are also key pollinators of many major food crops, including fruits, spices and importantly for chocolate lovers - cocoa.

The growing number of reports suggesting insect numbers are in steep decline is therefore of urgent concern. Loss of insect biodiversity could put these vital ecological functions at risk, threatening human livelihoods and food security in the process. Yet across large swathes of the world, there are gaps in our knowledge about the true scale and nature of insect declines.

Most of what we do know comes from data collected in the planet's more temperate regions, especially Europe and North America. For example, widespread losses of pollinators have been identified in Great Britain, butterflies have experienced declines in numbers of between 30 and 50% across Europe, and a 76% reduction in the

biomass of flying insects has been reported in Germany.

Information on insect species numbers and their abundance in the tropics (the regions either side of the Equator including the Amazon rainforest, all of Brazil, and much of Africa, India and Southeast Asia) is far more scarce. Yet the majority of the world's estimated 5.5 million insect species are thought to live in these tropical regions - meaning the planet's greatest abundances of insect life may be suffering calamitous collapses without us even realising.

The largest of the 29 major insect groups are butterflies/moths, beetles, bees/wasps/ants and flies. Each of these groups is thought to contain more than one million species. Not only is it near-impossible to monitor such a vast number, but as many as 80% of insects may not have been discovered yet - of which many are tropical species.

Responding to these knowledge gaps, researchers at UCL's Centre for Biodiversity and Environment Research have conducted one of the largest-ever assessments of insect biodiversity change. Some three-quarters of a million samples from around 6,000 sites worldwide were analysed in our study, adding up to nearly 20,000 different species in all.

Insects are facing an unprecedented threat due to the "twin horsemen" of climate change and habitat loss.

Understanding what is causing insect declines is key for preventing even greater losses in the future, and for safeguarding the valuable functions that insects perform. Climate change and biodiversity loss are major global crises that are two sides of the same coin. Their combined effects on food production mean the health, wellbeing and livelihoods of many people in the tropics and beyond are hanging in the balance. Insect biodiversity losses are a crucial, but as yet understudied, part of this story.