Insects – Cabot Institute for the Environment blog

Insects will struggle to keep pace with global temperature rise – which could be bad news for humans

Posted on October 4, 2022March 29, 2023 by janet.crompton

Animals can only endure temperatures within a given range. The upper and lower temperatures of this range are called its critical thermal limits. As these limits are exceeded, an animal must either adjust or migrate to a cooler climate.

However, temperatures are rising across the world at a rapid pace. The record-breaking heatwaves experienced across Europe this summer are indicative of this. Heatwaves such as these can cause temperatures to regularly surpass critical thermal limits, endangering many species.

In a new study, my colleagues and I assessed how well 102 species of insect can adjust their critical thermal limits to survive temperature extremes. We found that insects have a weak capacity to do so, making them particularly vulnerable to climate change.

The impact of climate change on insects could have profound consequences for human life. Many insect species serve important ecological functions while the movement of others can disrupt the balance of ecosystems.

How do animals adjust to temperature extremes?

An animal can extend its critical thermal limits through either acclimation or adaptation.

Acclimation occurs within an animal’s lifetime (often within hours). It’s the process by which previous exposure helps give an animal or insect protection against later environmental stress. Humans acclimate to intense UV exposure through gradual tanning which later protects skin against harmful UV rays.

One way insects acclimate is by producing heat shock proteins in response to heat exposure. This prevents cells dying under temperature extremes.

A ladybird drinking a speck of water on a narrow leaf. — Insects in warmer environments develop fewer spots to reduce heat retention.
mehmetkrc/Shutterstock

Some insects can also use colour to acclimate. Ladybirds that develop in warm environments emerge from the pupal stage with less spots than insects that develop in the cold. As darker spots absorb heat, having fewer spots keeps the insect cooler.

Adaptation occurs when useful genes are passed through generations via evolution. There are multiple examples of animals evolving in response to climate change.

Over the past 150 years, some Australian parrot species such as gang-gang cockatoos and red-rumped parrots have evolved larger beaks. As a greater quantity of blood can be diverted to a larger beak, more heat can be lost into the surrounding environment.

A colourful red-rumped parrot perched on a branch. — The red-rumped parrot has evolved a larger beak to cope with higher temperatures.
Alamin-Khan/Shutterstock

But evolution occurs over a longer period than acclimation and may not allow critical thermal limits to adjust in line with the current pace of global temperature rise. Upper thermal limits are particularly slow to evolve, which may be due to the large genetic changes required for greater heat tolerance.

Research into how acclimation might help animals survive exceptional temperature rise has therefore become an area of growing scientific interest.

A weak ability to adjust to temperature extremes

When exposed to a 1℃ change in temperature, we found that insects could only modify their upper thermal limit by around 10% and their lower limit by around 15% on average. In comparison, a separate study found that fish and crustaceans could modify their limits by around 30%.

But we found that there are windows during development where an insect has a greater tolerance towards heat. As juvenile insects are less mobile than adults, they are less able to use their behaviour to modify their temperature. A caterpillar in its cocoon stage, for example, cannot move into the shade to escape the heat.

Exposed to greater temperature variations, this immobile life stage has faced strong evolutionary pressure to develop mechanisms to withstand temperature stress. Juvenile insects generally had a greater capacity for acclimating to rising temperatures than adult insects. Juveniles were able to modify their upper thermal limit by 11% on average, compared to 7% for adults.

But given that their capacity to acclimate is still relatively weak and may fall as an insect leaves this life stage, the impact is likely to be limited for adjusting to future climate change.

What does this mean for the future?

A weak ability to adjust to higher temperatures will mean many insects will need to migrate to cooler climates in order to survive. The movement of insects into new environments could upset the delicate balance of ecosystems.

Insect pests account for the loss of 40% of global crop production. As their geographical distribution changes, pests could further threaten food security. A UN report from 2021 concluded that fall armyworm populations, which feed on crops such as maize, have already expanded their range due to climate change.

A damaged corn crop following an attack by fall armyworms. — The fall armyworm is a damaging crop pest which is spreading due to climate change.
Alchemist from India/Shutterstock

Insect migration may also carry profound impacts on human health. Many of the major diseases affecting humans, including malaria, are transmitted by insects. The movement of insects over time increases the possibility of introducing infectious diseases to higher latitudes.

There have been over 770 cases of West Nile virus recorded in Europe this year. Italy’s Veneto region, where the majority of the cases originate, has emerged as an ideal habitat for Culex mosquitoes, which can host and transmit the virus. Earlier this year, scientists found that the number of mosquitoes in the region had increased by 27%.

Insect species incapable of migrating may also become extinct. This is of concern because many insects perform important ecological functions. Three quarters of the crops produced globally are fertilised by pollinators. Their loss could cause a sharp reduction in global food production.

The vulnerability of insects to temperature extremes means that we face an uncertain and worrying future if we cannot curb the pace of climate change. A clear way of protecting these species is to slow the pace of climate change by reducing fossil fuel consumption. On a smaller scale, the creation of shady habitats, which contain cooler microclimates, could provide essential respite for insects facing rising temperatures.

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This blog is written by Hester Weaving, PhD Candidate in Entomology, University of Bristol. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Hester Weaving

“Between the Insect Hordes and Ourselves”: Imaginaries of insect declines from the 1960s onwards

Posted on December 11, 2020April 4, 2023 by janet.crompton

A still from Bee Movie (2007), directed by Simon J. Smith and Steven Hickner

‘According to all known laws of aviation, there is no way a bee should be able to fly. Its wings are too small to get its fat little body off the ground. The bee, of course, flies anyway because bees don’t care what humans think is impossible.’ You might recognise these words as the opening from the animated film Bee Movie (2007). The film is as known for its memes as its compulsive heteronormativity. If you are unaware: not only are there many happy nuclear bee families, the star of the film, Barry, is a male worker bee. On top of that, the human woman with whom Barry takes on the honey industry and fights for equal bee rights appears to develop some warm feelings for him. Needless to say, Bee Movie is fun but not a cinematographic masterpiece.

Jokes aside, the 2007 film is a good indicator of an influx of documentaries, memoirs, novels, and poetry collections starring the Western or European honeybee. Perhaps I’m being too critical here. This influx does excite me in a way, as it shows that insect life and decline has become part of a broader conversation. But, with this awareness of insect decline in our cultural imagination comes a sting in the tale. In this case, the sting is an almost obsessive focus on the European honeybee in an age of overall insect decline and what Elizabeth Kolbert (2014) popularised as the sixth extinction. There are thousands of known species of bees all over the world—not to mention other bugs—and yet a select group of people continue to talk, write, film, draw and campaign for the European honeybee. (Are you familiar with the concept of bee-washing?)

In response to these stories, I started thinking about the following: why is there so much creative work on the honeybee? Insects make up the most biodiverse and largest class of described (and estimated) species in the animal kingdom. And while many of these—not all—are indeed facing decline or even extinction, the European honeybee is not one of them.

What started out as a general interest, quickly evolved—metamorphosed!—into my doctoral project on insect decline. Inspired by Ursula Heise’s (2016) work on the cultural side of extinction, I started asking the following: what kind of narratives do people create when talking about insect decline, and how do they tie in with other and older insect stories, our broader cultural memory? Is there an explanation to be found for this honeybee hyperfocus when it comes to narratives of insect decline? Thinking about these questions, I kept returning to Donna Haraway, who wrote that ‘it matters what stories we tell to tell other stories with … It matters what stories make worlds, what worlds make stories.’ (12) Haraway’s keen (if not overcited) observation also applies to the case of insect decline. When looking at creative storytelling—of which there is a lot—we’re not just considering entertainment or aesthetics. Even with something as seemingly banal as Bee Movie, it does matter what stories we tell to tell the story of insect decline. So why do people contribute to this, for lack of a better word, honeybee extravaganza?

An assortment of contemporary honeybee stories

My project become more than a chance to get deep into the problem with honeybees and other charismatic microfauna. Thinking about tiny critters (instead of charismatic megafauna) created the opportunity to engage with and tease out some of the broader questions in the fields of critical animal and extinction studies. Between all the reading and writing and talking and plotting out of the work that needs to be done, theories and ideas and random shower thoughts keep falling into place, and I have a red thread or two running through the different chapters of my thesis. Watch this space.

For now, I do want to say that one of the more rewarding elements of my research so far has been the deep dive into care ethics. My understanding of the concept has both expanded and gained new focus, and my deep dive into care and conservation has opened my eyes to the possibility of care as a violent practice (Salazar Parreñas 2018). One of my current challenges is to see how care, understood as ‘a vital affective state, an ethical obligation and a practical labour’ (Puig de la Bellacasa), is reflected in the poetics of insect decline. What does a poetics of care look like when we let ourselves become subject to, as Haraway (2008) phrased it, the ‘unsettling obligation of curiosity, which requires knowing more at the end of the day than at the beginning’ (36). What happens when we allow ourselves to pay careful attention to the other-than-human life around us and start to care?

Assorted Coleoptera in the University of Texas Insect Collection

Another thread is that of the different (temporal and spatial) scales of extinction and the limits of our empathy for other-than-human animals. As Ursula Heise (2016) and Dolly Jørgensen (2019) so effectively argue in their monographs on the topic, extinctions come to matter once they reflect upon our own (human) pasts, presents, and futures and we can emotionally engage with them. And like these different pasts, presents, and futures, extinction isn’t singular. It is easy—and to a certain extent even useful—to put it all under the label of the sixth extinction. Still, I am increasingly convinced that such labels obscure the differences and intricacies people need to be aware of in the face of the sixth extinction—or rather, extinctions.

There are local extinctions, global extinctions, extinctions completely missed or forgotten (by human eyes), even desired extinctions. Communities respond to and engage with different species and local and global extinctions in different ways. Especially when something tricky like shifting baseline syndrome ensures that some communities aren’t aware of local extinctions or declines in the first place, while passionate campaigns for charismatic megafauna put certain species on the global agenda and in the public eye. I’m not saying this is always a bad thing (I’m just as passionate about the survival of the Malayan and Sumatran tiger as the next person).

I am, however, saying that it is worth researching how attention and care are directed and, ideally, can be redirected in times of need. And insects—in all their creeping and crawling diversity, with important ecosystem functions such as pollination, prey, and waste disposal—have turned out to be an excellent group to consider these questions.

Sources

Haraway, Donna J. Staying with the Trouble: Making Kin in the Chthulucene. Duke UP, 2016.
—. When Species Meet. U of Minneapolis P, 2008.
Heise, Ursula K. Imagining Extinctions: The Cultural Meanings of Endangered Species. U of Chicago P, 2016.
Jørgensen, Dolly. Recovering Lost Species in the Modern Age: Histories of Longing and Belonging. MIT Press, 2019.
Kolbert, Elizabeth. The Sixth Extinction: An Unnatural History. Bloomsbury, 2014.
Puig de la Bellacasa, María. Matters of Care: Speculative Ethics in More Than Human Worlds. U of Minnesota P, 2017. Salazar Parreñas, Juno. Decolonizing Extinction: The Work of Care in Orangutan Rehabilitation. Duke UP, 2018

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This blog is written by Cabot Institute member Eline D. Tabak, PhD researcher in English (University of Bristol) and Environmental Humanities (BSU). This blog outlines her SWW DTP-funded project. You can follow Eline on twitter @elinetabak and see more of her writing and work at www.elinedtabak.com. This blog was reposted with kind permission from the Centre for Environmental Humanities. View the original blog.

Eline D. Tabak

Sowing the seeds of collaborations to tackle African food insecurity

Posted on June 28, 2019April 3, 2023 by janet.crompton

A group of early career researchers from 11 African countries got together in Bristol, UK, this month for a two-week training event. Nothing so unusual about that, you may think.

Yet this course, run by the Community Network for African Vector-Borne Plant Viruses (CONNECTED), broke important new ground.

The training brought together an unusual blend of researchers: plant virologists and entomologists studying insects which transmit plant diseases, as an important part of the CONNECTED project’s work to find new solutions to the devastation of many food crops in Sub-Saharan African countries.

The CONNECTED niche focus on vector-borne plant disease is the reason for bringing together insect and plant pathology experts, and plant breeders too. The event helped forge exciting new collaborations in the fight against African poverty, malnutrition and food insecurity.

‘V4’ – Virus Vector Vice Versa – was a fully-funded residential course which attracted great demand when it was advertised. Places were awarded by competitive application, with funding awarded to cover travel, accommodation, subsistence and all training costs. For every delegate who attended, five applicants were unsuccessful.

The comprehensive programme combined: scientific talks; general lab training skills; specific virology and entomology lecture and practical work; workshops; field visits, career development, mentoring, and desk-based projects.

Across the fortnight delegates received plenty of peer mentoring and team-building input, as well as an afternoon focused on ‘communicating your science.’

New
collaborations will influence African agriculture for years to come

There’s little doubt that the June event, hosted by The University of Bristol, base of CONNECTED Network Director Professor Gary Foster, has sown seeds of new alliances and partnerships that can have global impact on vector-borne plant disease in Sub-Saharan Africa for many years to come.

CONNECTED network membership has grown in its 18 months to a point where it’s approaching 1,000 researchers, from over 70 countries. The project, which derived its funding from the Global Challenges Research Fund, is actively looking at still more training events.

The V4 training course follows two successful calls for pump-prime research funding, leading to nine projects now operating in seven different countries, and still many more to come. Earlier in the year CONNECTED ran a successful virus diagnostics training event in Kenya, in close partnership with BecA-ILRI Hub. One result of that training was that its 19 delegates were set to share their new knowledge and expertise with a staggering 350 colleagues right across the continent.

Project background

Plant diseases significantly limit the ability of many of Sub-Saharan African countries to produce enough staple and cash crops such as cassava, sweet potato, maize and yam. Farmers face failing harvests and are often unable to feed their local communities as a result. The diseases ultimately hinder the countries’ economic and social development, sometimes leading to migration as communities look for better lives elsewhere.

The CONNECTED network project is funded by a £2 million grant from the UK government’s Global Challenges Research Fund, which supports research on global issues that affect developing countries. It is co-ordinated by Prof. Foster from the University of Bristol School of Biological Sciences, long recognised as world-leading in plant virology and vector-transmitted diseases, with Professor Neil Boonham, from Newcastle University its Co-Director. The funding is being used to build a sustainable network of scientists and researchers to address the challenges. The University of Bristol’s Cabot Institute, of which Prof. Foster is a member, also provides input and expertise.

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This blog is written by Richard Wyatt, Communications Officer for the CONNECTED network.