Sunday Long Read: Buggin' Out

This week's Sunday Long Read comes from The Guardian's Oliver Milman, with a story on how the effects of climate change are already showing up in insect populations in 2022, with more aggressive species of invasive insects migrating to new homes and causing major problems with the ecology.

The climate crisis is set to profoundly alter the world around us. Humans will not be the only species to suffer from the calamity. Huge waves of die-offs will be triggered across the animal kingdom as coral reefs turn ghostly white and tropical rainforests collapse. For a period, some researchers suspected that insects may be less affected, or at least more adaptable, than mammals, birds and other groups of creatures. With their large, elastic populations and their defiance of previous mass extinction events, surely insects will do better than most in the teeth of the climate emergency?

Sadly not. At 3.2C of warming, which many scientists still fear the world will get close to by the end of this century (although a flurry of promises at Cop26 have brought the expected temperature increase down to 2.4C), half of all insect species will lose more than half of their current habitable range. This is about double the proportion of vertebrates and higher even than for plants, which lack wings or legs to quickly relocate themselves. This huge contraction in livable space is being heaped on to the existing woes faced by insects from habitat loss and pesticide use. “The insects that are still hanging in there are going to get hit by climate change as well,” says Rachel Warren, a biologist at the University of East Anglia, who in 2018 published research into what combinations of temperature, rainfall and other climatic conditions each species can tolerate.

Some insects, such as dragonflies, are nimble enough to cope with the creeping change. Unfortunately, most are not. Butterflies and moths are also often quite mobile, but in different stages of their life cycle they rely on certain terrestrial conditions and particular plant foods, and so many are still vulnerable. Pollinators such as bees and flies can generally move only short distances, exacerbating an emerging food security crisis where farmers will struggle to grow certain foods not just due to a lack of pollination but because, beyond an increase of 3C or so, vast swaths of land simply becomes unsuitable for many crops. The area available to grow abundant coffee and chocolate, for example, is expected to shrivel as tropical regions surge to temperatures unseen in human history.

The climate crisis interlocks with so many other maladies – poverty, racism, social unrest, inequality, the crushing of wildlife – that it can be easy to overlook how it has viciously ensnared insects. The problem also feels more intractable. “Climate change is tricky because it’s hard to combat,” says Matt Forister, a professor of biology at the University of Nevada. “Pesticides are relatively straightforward by comparison but climate change can alter the water table, affect the predators, affect the plants. It’s multifaceted.”

Insects are under fire from the poles to the tropics. The Arctic bumblebee, Bombus polaris, is found in the northern extremities of Alaska, Canada, Scandinavia and Russia. It is able to survive near-freezing temperatures due to dense hair that traps heat and its ability to use conical flowers, like the Arctic poppy, to magnify the sun’s rays to warm itself up. Rocketing temperatures in the Arctic, however, mean the bee is likely to become extinct by 2050. Species of alpine butterflies, dependent on just one or two high-altitude plants, are also facing severe declines as their environment transforms around them.

Further south, in the UK, glowworm numbers have collapsed by three-quarters since 2001, research has found, with the climate crisis considered the primary culprit. The larvae of the insects feed on snails that thrive in damp conditions, but a string of hot and dry summers has left the glowworms critically short of prey.

These sort of losses in Europe have challenged previous assumptions that insects in temperate climates would be able to cope with a few degrees of extra heat, unlike the mass of species crowded at the world’s tropics that are already at the upper limits of their temperature tolerance. A team of researchers from Sweden and Spain have pointed out that the vast majority of insects in temperate zones are inactive during cold periods. When just the warmer, active, months of insects’ lives were considered by the scientists, they found that species in temperate areas are also starting to bump into the ceiling of livable temperature. As Frank Johansson, an academic at Sweden’s Uppsala University, glumly puts it: “Insects in temperate zones might be as threatened by climate change as those in the tropics.”

 

We're already starting to see the complete reshuffling of insect populations worldwide, and those species that can adapt to climate change will not only survive, but thrive. But those species left behind, facing imminent extinction, could take all kinds of flowers, crops, fruits and vegetables with them as pollination becomes more and more difficult. 

As goes the insect world, so goes us.