In the lead up to the 26th UN Climate Change Conference of the Parties (COP26) in November of this year, we are writing a series of articles looking at some of the toughest global climate crisis challenges that we are currently facing. This post looks at the evidence for and challenges posed by a global decline in insects.

What is the evidence for a global insect armageddon?
One of the first meta-analyses of insect population decline was published in 2014 by Dirzo et al. in Science under the title ‘Defaunation in the Anthropocene’. This seminal paper reported that 67% of monitored invertebrate populations showed 45% mean abundance decline and warned that ‘such animal declines will cascade onto ecosystem functioning and human well-being’. Three years later, Hallmann et al. (2017) published the results from 27 years of malaise trap monitoring in 63 natural protection areas in Germany, and concluded that insect biomass had declined by more than 75% during this time. This paper in particular was widely reported in the media, creating widespread concern among the public of an impending insect armageddon, or ‘insectageddon’.
Since then, several other reports have continued to draw attention to declines in insect abundance, biomass and diversity around the world (for excellent reviews see Wagner (2020) and Sánchez-Bayo & Wyckhuys (2019)). However, many of these studies have been restricted to well-populated areas of the US and Europe and there is little information available to assess how these patterns compare with other less well studied regions.
Despite the abundance of data suggesting a pattern of global insect decline, many studies show conflicting results, with datasets from a similar area often reporting different patterns. There is also evidence that some insects are faring well, particularly in temperate areas which are now experiencing milder winters. Species that benefit from an association with humans, such as the European honeybee, may also be experiencing an advantage, along with certain freshwater insects that have benefited from efforts to reduce pollution in inland water bodies.
What are the challenges in assessing and predicting insect population trends?
In comparison to vertebrate groups, comprehensive long-term datasets are rare for invertebrates. This is primarily down to the fact that invertebrates are incredibly species rich and so, even for those that have been formally identified and described, a considerable amount of skill and knowledge is required for reliable identification. In addition to this high level of expertise is the need for large amounts of field equipment, which means that long-term, comprehensive studies can be expensive and difficult to fund.
Both historical and current invertebrate monitoring data tends to come from a small number of wealthy and well-populated countries (usually the US and western Europe), and there are comparatively few datasets available from tropical and less developed areas. Unfortunately, these understudied countries and regions tend to be the areas where we might expect to find the most diverse and species rich populations of invertebrates.
Other challenges relate to the way that data is collected. Using total insect biomass as a measure provides a useful large-scale perspective and provides information relevant to ecosystem function. It also minimises the problems involved with taxonomy and identification. However, using this measure means that species-level trends are completely overlooked.

What are the main stressors affecting insect populations globally?
Studies suggest that the main stressors impacting invertebrates are changes in land-use (particularly deforestation), climate change, agriculture, introduced and invasive species, and increased nitrification and pollution. However, it is rare that a single factor is found to be responsible for monitored declines and the situation has been described as being akin to ‘death by a thousand cuts’.
In a recent special edition of PNAS, that looked in depth at the available research and literature on insect decline in the Anthropocene, climate change, habitat loss/degradation and agriculture emerged as the three most important stressors.
Where do we go from here?
Traditionally, conservation has focused on rare and endangered species. However, with mass extinctions and large scale invertebrate loss, which include declines in formerly abundant species, a different approach is required. Invertebrates form an important link between primary producers and the rest of the food chain, and play a key role in most ecosystems. They provide numerous ecosystem services such as pollination, weed and pest control, decomposition, soil formation and water purification, and so their fate is of both environmental and economic importance.
There are several things to be positive about within the realms of invertebrate conservation: over the past decade, funding to support insect conservation has been growing and, in many countries, there are now substantial grants allocated to monitoring and mitigation projects. The EU and US have seen widescale banning of certain pesticides following research demonstrating their impacts on both economically important pollinators and other fauna. Finally, citizen science projects to study invertebrate populations are becoming both numerous and successful, greatly increasing the amount of comprehensive, long-term data that is available to inform conservation decisions.
Despite this, much more long-term data on invertebrate populations is required, particularly from regions outside of Europe and the US, such as tropical areas of the Americas, Africa and Asia. Attention to factors such as the standardisation of survey techniques and improved data storage and accessibility are also important, as well as the utilisation of new methods including automated sampling/counting equipment and molecular techniques. Using the information available, evidence-based plans for mitigating and reversing declines are desperately required.
All of this takes time however, and we need to act now. Even without comprehensive species-level data, we know that a biodiversity crisis is occurring at a rate serious enough for it to have been termed the ‘6th Mass Extinction’. Individual, group, nationwide and global action will all be required to combat this. Widescale change in societal attitudes to insects will undoubtedly need to play a role in this process, alongside global efforts to slow climate change and develop insect-friendly methods of agriculture.

Summary
• Numerous studies have reported large-scale declines in insect populations, with several estimating a loss of approximately 1–2% of species each year.
• The availability of high-quality and long-term datasets is a limiting factor in assessing population trends. Furthermore, available data tends to be from well-populated and historically wealthy areas such as the US and western Europe, with the diverse and species-rich tropics severely under-researched.
• The main stressors thought to be impacting insect populations globally are climate change, habitat loss/degradation and agriculture. In most, if not all of these cases, a combination of these and other factors are likely to play a role.
• Although there are some aspects of insect conservation to be positive about, much work still needs to be done. Further monitoring and recording are required, particularly in poorly studies areas, in order to inform conservation decisions. Simultaneously, local and global efforts must be made to slow climate change, halt the destruction of ecologically important habitats and develop nature-compatible methods of agriculture.
References and further reading
• Jarvis, B. (2018) The Insect Apocalypse is Here. The New York Times
• Dirzo, R. et al. (2014) Defaunation in the Anthropocene. Science 345: 401–406
• Hallmann, C. A. et al. (2017) More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS One 12: e0185809
• Wagner, D. L. (2020) Insect declines in the Anthropocene. Annu. Rev. Entomol. 65: 457–480
• Sánchez-Bayo, F. & Wyckhuys, K. A. G. (2019) Worldwide decline of the entomofauna: A review of its drivers. Biol. Conserv. 232: 8–27
• Wagner, D. L. et al. (2021) Insect decline in the Anthropocene: Death by a thousand cuts. Proceedings of the National Academy of Sciences. 118(2): e2023989118
Silent Earth: Averting the Insect Apocalypse
Eye-opening, inspiring and riveting, Silent Earth is part love letter to the insect world, part elegy, part rousing manifesto for a greener planet. It is a call to arms for profound change at every level – in government policy, agriculture, industry and in our own homes and gardens, to prevent insect decline. Read our extended review.
The Insect Crisis: The Fall of the Tiny Empires that Run the World
In a compelling global investigation, Milman speaks to those studying this catastrophe and asks why these extraordinary creatures are disappearing. Part warning, part celebration of the incredible variety of insects, The Insect Crisis highlights why we need to wake up to this impending environmental disaster.
Climate Change and British Wildlife
In this latest volume in the British Wildlife Collection, Trevor Beebee examines the story so far for our species and their ecosystems, and considers how they may respond in the future. Check out our interview with Beebee, where we discuss the background of this book, his thoughts on conservation and his hopes for the future.
Rebugging the Planet: The Remarkable Things that Insects (and Other Invertebrates) Do – Any Why We Need to Love Them More
Environmental campaigner Vicki Hird demonstrates how insects and other invertebrates, such as worms and spiders, are the cornerstone of our ecosystems and argues passionately that we must turn the tide on this dramatic bug decline.
The Last Butterflies: A Scientist’s Quest to Save a Rare and Vanishing Creature
Weaving a vivid and personal narrative, Haddad illustrates the race against time to reverse the decline of six butterfly species. A moving account of extinction, recovery, and hope, The Last Butterflies demonstrates the great value of these beautiful insects to science, conservation, and people.
Why Every Fly Counts: Values and Endangerment of Insects
Hans-Dietrich Reckhaus discusses the beneficial and harmful effects of insects and explains their development and significance for biodiversity. This second, fully reviewed and enlarged edition provides new insights into the value of species seen as pests, insect development and their decline in different regions in the world.












In his latest book,
shapes, forms and colours of the birds. They were so very different to the birds I was used to seeing in the Somerset countryside around our home. After that, every now and again I’d see footage of hummingbirds on wildlife documentaries, and began to appreciate further just how remarkable they were – what Tim Dee described as ‘strange birds: not quite birds or somehow more than birds, birds 2.0, perhaps’.
There were plenty of other moments that I’ll hold in my heart, and they don’t all involve the iconic, rare species. One such was watching Golden-tailed Sapphires, a hummingbird that looks as if it’s been dipped in rainbows, feeding in a clearing in the immediate aftermath of a heavy rain shower. As the sun broke through the dripping vegetation and steaming air we were suddenly surrounded by myriad small rainbows through which the birds were flying. That moment was ephemeral, over almost as soon as it began, but it’s etched in my memory forever.
I found myself asking myself that very question as my journey into their world unfolded… Hummingbirds certainly seem to touch something deep inside us. They featured in the mythology of the Aztecs; inspired the most dramatic of all of the immense geoglyphs carved into the desert floor by the Nazca; appear in renowned art and literature; and, to this day, are singled out for particular love by those whose gardens they frequent, people who would not necessarily identify themselves as birders.
Inevitably there were some logistical challenges to contend with, not least having to reacquaint myself with horse-riding after a decades-long and deliberate avoidance of it! There were a couple of close encounters with large predators that were, in hindsight, more alarming than they felt at the time – as a naturalist, I was thrilled to get (very) close views of a puma… But perhaps the most challenging moment of all was landing in Bolivia at the very moment the country was taking to the streets to protest the outcome of a recent presidential election. There was an incident at a roadblock manned by armed men that was genuinely scary, with an outcome that hung in the balance for a terrifying instant, and could easily have ended badly.
I sometimes think there’s almost too much optimism expressed when talking about conservation challenges anywhere in the world – a narrative that suggests “if we only care enough, the [insert iconic species name here] can be saved”. And to a degree, that’s good – we’ve got to have hope, as the alternative is too dreadful to countenance – but given our impact to date, and in an uncertain future where the effects of climate change are still unfolding and will continue for many decades to come, to name just the biggest of the mounting pressures on the natural world, I’m not sure that I do feel terribly optimistic, least of all for those hummingbird species that have very localized populations, or depend upon very specific habitats. They’re undeniably vulnerable. But like Fox Mulder,
As recently featured on
photographing and surveying insects. I learned about the insects, watched them and counted the sheer number of species, and realised that no one else had actually surveyed a small urban park extensively. The book came about as I wanted to show people what was living in the bushes and to put Peckham on the entomological map!
and usually open 24 hours – but there is no reason why we can’t include habitats for our wildlife. A simple solution would be to leave areas un-mowed to grow wild. In the parks of my local area in London, large swathes of grasses and flowers have been left to mature and people have been really receptive to it. I think we are finally moving away from the Victorian ideal of neat and tidy!




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And most importantly – just go out there and watch mammals. I may be biased, but for me there is nothing better than being out in the countryside early on a spring morning watching the hares chasing around and knocking seven bells out of each other. You might like to stay up late watching badgers or bats, or enjoy the crazy antics of a squirrel on a bird feeder. It’s important that we engage with nature and encourage our children to do the same. If we don’t see and understand wildlife, we won’t fight for it. And, trust me, we need to fight for it.

slow I would be overtaken by very old people on Zimmer frames. It seemed as though I’d hit 97 five decades prematurely.


To the casual observer, global summits and the resolutions they produce can seem frustratingly ineffective – repeating cycles of targets set, missed and reset, with no obvious progress. Yet despite the apparent inertia, when used to good effect these processes can be powerful tools for positive change.
It’s hugely important. Not only do these treaties establish some of the most important conservation objectives, but they provide a means of learning from other experience. Typically, international treaties set a broad goal – such as ‘the wise use of wetlands’ in the case of the Ramsar Convention – but are much less prescriptive as to exactly how this will be delivered nationally. Accordingly, there is much to learn from the broad diversity of other national conservation experience in implementing treaty obligations. Such comparative experiences make these treaties fascinating and their study valuable.
Following on from the previous question, this book highlights the role and importance of NGOs (and a number of the authors themselves have been or are currently involved with NGOs). Do you think NGOs should have more involvement in environmental policy, both within the UK and on a global scale?
James Lowen is an award-winning writer whose work is regularly featured in The Telegraph, BBC Wildlife and Nature’s Home, among other publications. He is also an editor, lecturer, consultant and keen photographer.
fragile creatures flying a thousand-plus miles). There’s wackiness too: china-mark moths, whose caterpillars live underwater; Sandhill Rustic, whose adults can swim underwater; Scarce Silver-lines, which sings from oak trees; various moths that are engaged in an evolutionary arms race with bats; Indian Meal Moth and Wax Moth, whose caterpillars can digest polyethylene and polypropylene (perhaps conceivably hinting at a solution to the global plastics problem?); and even one New World moth whose cells have proved critical for producing the Novavax COVID vaccine.
sun-loving, day-flying moth. I guess the other thing to emphasise is that whereas moth-trapping in your garden makes for gloriously lazy wildlife-watching, simply flick the switch and let the insects come to you, surveying moths in remote places is contrastingly hard work. After a long drive, often on the back of little sleep, you need to lug heavy generators and a fleet of moth traps up steep slopes or across difficult terrain. And then you need to stay alert all night to make sure you don’t miss anything. I didn’t get much sleep that year…
intrepid endeavours to safeguard