insects are at the heart of every food web, they pollinate the large majority of plant species, keep the soil healthy, recycle nutrients, control pests, and much more. Love them or loathe them, we humans cannot survive without insects.
Plummeting insect numbers ‘threaten collapse of nature’
The world’s insects are hurtling down the path to extinction, threatening a “catastrophic collapse of nature’s ecosystems”, according to the first global scientific review.
More than 40% of insect species are declining and a third are endangered, the analysis found. The rate of extinction is eight times faster than that of mammals, birds and reptiles. The total mass of insects is falling by a precipitous 2.5% a year, according to the best data available, suggesting they could vanish within a century.
The planet is at the start of a sixth mass extinction in its history, with huge losses already reported in larger animals that are easier to study. But insects are by far the most varied and abundant animals, outweighing humanity by 17 times. They are “essential” for the proper functioning of all ecosystems, the researchers say, as food for other creatures, pollinators and recyclers of nutrients.
Insect population collapses have recently been reported in Germany and Puerto Rico, but the review strongly indicates the crisis is global. The researchers set out their conclusions in unusually forceful terms for a peer-reviewed scientific paper: “The [insect] trends confirm that the sixth major extinction event is profoundly impacting [on] life forms on our planet.
“Unless we change our ways of producing food, insects as a whole will go down the path of extinction in a few decades,” they write. “The repercussions this will have for the planet’s ecosystems are catastrophic to say the least.”
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Insect collapse: the red flags
Butterflies and moths
There has been a “severe reduction” in butterflies and moths in the Kullaberg nature reserve in Sweden compared with 50 years ago. Scientists found more than a quarter of the 600 species once found had been lost. Butterflies were hardest hit, losing almost a half of species, including the large tortoiseshell and scarce copper. In England, two-thirds of 340 moth species declined from 1968-2003.
Bumblebees
Museum records enabled scientists to assess the fate of 16 species of bumblebees in the US midwest from 1900 to 2007. They found four had completely died out, while eight were declining in number, and blamed intensive agriculture and pesticides.
Dragonflies
Red dragonfly populations have fallen sharply in Japan since the mid-1990s, which scientists link to insecticides in rice paddies that stop the water-living nymphs emerging into adults. In the US, recent surveys across California and Nevada found 65% of dragonflies and damselflies had declined in the 100 years since 1914.
Leafhoppers
Leafhoppers and planthoppers often make up a large proportion of the flying insects in European grasslands. But scientists found their abundance in Germany plunged by 66% in the 50 years to 2010. Soil acidification, partly due to heavy fertiliser use, was the main cause.
Ground beetles
In the UK, dramatic declines in ground beetles have been seen in almost three-quarters of the 68 carabid species studied from 1994-2008. A few species increased, but overall one in six of all the beetles was lost in that time.
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The analysis, published in the journal Biological Conservation, says intensive agriculture is the main driver of the declines, particularly the heavy use of pesticides. Urbanisation and climate change are also significant factors.
“If insect species losses cannot be halted, this will have catastrophic consequences for both the planet’s ecosystems and for the survival of mankind,” said Francisco Sánchez-Bayo, at the University of Sydney, Australia, who wrote the review with Kris Wyckhuys at the China Academy of Agricultural Sciences in Beijing.
The 2.5% rate of annual loss over the last 25-30 years is “shocking”, Sánchez-Bayo told the Guardian: “It is very rapid. In 10 years you will have a quarter less, in 50 years only half left and in 100 years you will have none.”
One of the biggest impacts of insect loss is on the many birds, reptiles, amphibians and fish that eat insects. “If this food source is taken away, all these animals starve to death,” he said. Such cascading effects have already been seen in Puerto Rico, where a recent study revealed a 98% fall in ground insects over 35 years.
The new analysis selected the 73 best studies done to date to assess the insect decline. Butterflies and moths are among the worst hit. For example, the number of widespread butterfly species fell by 58% on farmed land in England between 2000 and 2009. The UK has suffered the biggest recorded insect falls overall, though that is probably a result of being more intensely studied than most places.
Bees have also been seriously affected, with only half of the bumblebee species found in Oklahoma in the US in 1949 being present in 2013. The number of honeybee colonies in the US was 6 million in 1947, but 3.5 million have been lost since.
There are more than 350,000 species of beetle and many are thought to have declined, especially dung beetles. But there are also big gaps in knowledge, with very little known about many flies, ants, aphids, shield bugs and crickets. Experts say there is no reason to think they are faring any better than the studied species.
A small number of adaptable species are increasing in number, but not nearly enough to outweigh the big losses. “There are always some species that take advantage of vacuum left by the extinction of other species,” said Sanchez-Bayo. In the US, the common eastern bumblebee is increasing due to its tolerance of pesticides.
Most of the studies analysed were done in western Europe and the US, with a few ranging from Australia to China and Brazil to South Africa, but very few exist elsewhere.
“The main cause of the decline is agricultural intensification,” Sánchez-Bayo said. “That means the elimination of all trees and shrubs that normally surround the fields, so there are plain, bare fields that are treated with synthetic fertilisers and pesticides.” He said the demise of insects appears to have started at the dawn of the 20th century, accelerated during the 1950s and 1960s and reached “alarming proportions” over the last two decades.
The world must change the way it produces food, Sánchez-Bayo said, noting that organic farms had more insects and that occasional pesticide use in the past did not cause the level of decline seen in recent decades.
“Industrial-scale, intensive agriculture is the one that is killing the ecosystems,” he said.
In the tropics, where industrial agriculture is often not yet present, the rising temperatures due to climate change are thought to be a significant factor in the decline. The species there have adapted to very stable conditions and have little ability to change, as seen in Puerto Rico.
Sánchez-Bayo said the unusually strong language used in the review was not alarmist. “We wanted to really wake people up” and the reviewers and editor agreed, he said. “When you consider 80% of biomass of insects has disappeared in 25-30 years, it is a big concern.”
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Insects pollinate more than 75% of global crops, a service valued at up to $577 billion per year, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) says.
The collapse of insects
The most diverse group of organisms on the planet are in trouble, with recent research suggesting insect populations are declining at an unprecedented rate.
Source: https://www.reuters.com/graphics/GLOBAL-ENVIRONMENT/INSECT-APOCALYPSE/egpbykdxjvq/
As a boy in the 1960s, David Wagner would run around his family’s Missouri farm with a glass jar clutched in his hand, scooping flickering fireflies out of the sky.
“We could fill it up and put it by our bedside at night,” says Wagner, now an entomologist.
That’s all gone, the family farm now paved over with new homes and manicured lawns. And Wagner’s beloved fireflies – like so many insects worldwide – have largely vanished in what scientists are calling the global Insect Apocalypse.
As human activities rapidly transform the planet, the global insect population is declining at an unprecedented rate of up to 2% per year. Amid deforestation, pesticide use, artificial light pollution and climate change, these critters are struggling — along with the crops, flowers and other animals that rely on them to survive.
“Insects are the food that make all the birds and make all the fish,” said Wagner, who works at the University of Connecticut. “They’re the fabric tethering together every freshwater and terrestrial ecosystem across the planet.”
[see image in article – Diagram shows an example of a North American food chain with insects feeding small- and medium-sized animals.]
The tree of life
It’s easy to think insects are doing OK. After all, they’re nearly everywhere — crawling through rainforest canopy, burrowing into soil, skimming freshwater ponds or, of course, flitting through the air.
On the biological “tree of life” — which classifies organisms to describe their evolutionary and genetic relationship to one another — insects fall under the branch, or phylum, called Arthropods, one of the 40 branches of the Animal Kingdom.
In terms of diversity, insects are unrivaled, representing two-thirds of the world’s more than 1.5 million documented animal species with millions more bugs likely still undiscovered, scientists say. By comparison, there are roughly 73,000 vertebrates, or animals with a backbone from humans to birds and fish — these represent less than 5% of the known Animal Kingdom, according to the International Union for Conservation of Nature (IUCN).
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The demise of insects can’t be attributed to any single cause. Populations are facing simultaneous threats, from habitat loss and industrial farming to climate change. Nitrogen overloading from sewage and fertilizers has turned wetlands into dead zones; artificial light is flooding out nighttime skies; and the growth of urban areas has led to concrete sprawl.
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VIDEOS
Insect decline and UK food security
https://committees.parliament.uk/work/7381/insect-decline-and-uk-food-security/
After giving written and oral evidence, the Royal Entomological Society responds to the House of Commons – Science, Innovation and Technology Committee report on insect decline and UK food security.
https://www.royensoc.co.uk/news/insect-decline-food-security/
On Thursday 7 March 2024 the House of Commons Science, Innovation and Technology Committee published its report on insect decline and UK food security.
The RES published its Grand Challenges in Entomology paper in 2023 which reflects the conclusions of the committee report. This highlights the need for better societal engagement and public communication around insects. The public is frequently made aware of ‘charismatic’ insects, such as bumblebees or butterflies but there are over 27,000 species of insect in the UK, and huge gaps in both knowledge and expertise about most insect populations.
The RES is committed to closing this gap through its education and public engagement programmes and takes part in a number of events each year to improve the communication and perception of insect science including the RHS Chelsea Flower Show in 2023[1], its annual Insect Week, The Big Bang Fair, and annual photography and art competitions.
In response to the report, Professor Jane Hill, President of the Royal Entomological Society (RES) said:
“We welcome the committee’s call for further research, long term monitoring of insect decline together with a nationwide approach to insect conservation. We are in agreement with the wider scientific community that there is an urgent requirement for more investment and funding to facilitate our thorough understanding of insect population trends. A far more cohesive and integrated approach across all government departments is required to reach vital targets, enable progress and halt population declines before it is too late.
“The committee’s findings confirm there is a worrying decrease in naturalist skills in the UK and we are encouraged by the report’s reference to the RES Grand Challenges paper[2] to enhance entomological skills at all educational levels from schools to further education. There is an urgent need for more entomological career paths with both academic and vocational applications. We are delighted to see the committee’s backing of the new Natural History GCSE course, which RES is helping steer and which will further foster an appreciation for insect science in secondary education and enhance the UK’s skills base. The RES brings together global experts to share cutting-edge research, offers guest lectureships, school outreach, grants, bursaries, regular publication of journals and scientific papers, and an extensive library and archive resources in support of its educational engagement programmes.”
In the UK, 70% of land is used for farming and agricultural practices. This has a significant effect on insect populations. In light of the mounting evidence of insect decline the RES supports the committee’s call for the Government to increase support for the development and regulation of pesticide alternatives. The UK has pledged to reduce pesticides use by at least half by 2030, and set targets to halt and reverse species extinctions and decline by 2042. The RES emphasises the need for more funding and a long-term cross departmental approach to understand the effects of pesticides. We also highlight the urgency of greater engagement with farmers and landowners to adopt research into alternatives in order to make these targets achievable.
Pollinators have a crucial impact on our food security, and addressing concerns about insect decline and food production is essential. The UK Government should use the findings of this report to advocate for insect science on a global scale. This will positively impact the reversal of trends in insect decline and contribute to ensuring our future food security.
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Agriculture and climate change are reshaping insect biodiversity worldwide
Source: https://www.nature.com/articles/s41586-022-04644-x?fromPaywallRec=false
Abstract
Several previous studies have investigated changes in insect biodiversity, with some highlighting declines and others showing turnover in species composition without net declines1,2,3,4,5. Although research has shown that biodiversity changes are driven primarily by land-use change and increasingly by climate change6,7, the potential for interaction between these drivers and insect biodiversity on the global scale remains unclear. Here we show that the interaction between indices of historical climate warming and intensive agricultural land use is associated with reductions of almost 50% in the abundance and 27% in the number of species within insect assemblages relative to those in less-disturbed habitats with lower rates of historical climate warming. These patterns are particularly evident in the tropical realm, whereas some positive responses of biodiversity to climate change occur in non-tropical regions in natural habitats. A high availability of nearby natural habitat often mitigates reductions in insect abundance and richness associated with agricultural land use and substantial climate warming but only in low-intensity agricultural systems. In such systems, in which high levels (75% cover) of natural habitat are available, abundance and richness were reduced by 7% and 5%, respectively, compared with reductions of 63% and 61% in places where less natural habitat is present (25% cover). Our results show that insect biodiversity will probably benefit from mitigating climate change, preserving natural habitat within landscapes and reducing the intensity of agriculture.
