Insects at Greatest Risk in Face of the Sixth Mass Extinction

Life on Earth has always been ever-changing, a survival of the fittest, where those species who are not fit enough to survive simply go extinct. This basal rate of extinction resulting from normal evolutionary processes is known as the “background extinction rate.” Occasionally though, Earth’s background rate of extinction is dramatically exceeded, leading to the loss of 75% or more of the world’s species within a relatively short period of geological time (typically within 2.8 million years). This is known as a mass extinction event.

A monarch caterpillar (Danaus plexippus) feeding on its exclusive host plant, milkweed. Milkweed plants are toxic, but these caterpillars have evolved to not only be unaffected by this defense, but incorporate its toxins into their own bodies to become toxic themselves.

Unfortunately, most scientists now agree that human activity has plunged us into Earth’s sixth mass extinction event, deemed the Holocene or Anthropocene extinction. Current extinction rates are a staggering 100 to 10,000 times higher than pre-human background rates, with approximately 0.01 to 0.1% of species being lost each year and over 134,400 species on the IUCN Red List of Threatened Species. If we continue to treat our environment as we have been, we will lose well over 75% of Earth’s species before 2.8 million years pass.

While these statistics are very real, they have largely failed to incorporate the most biodiverse, and arguably the most ecologically important group of animals on Earth: insects. Despite representing approximately 80% of all species on Earth, the Red List of Threatened Species contains evaluations for less than 1% of all described insect species compared to 91% of mammals and 100% of birds. At the same time, recent studies on insect populations indicate that around 40% of insect species are declining, with extinction rates eight times higher than that of mammals, birds, and reptiles. One might still wonder why we should care about these creatures that typically elicit fear and disgust from people; to some of the more insect-averse folks, a high extinction rate for insects may even sound like a relief.

However, the reality is that we simply could not exist without insects. Insects are integral to the functioning of virtually every ecosystem on Earth. This is due in part to their unmatched biodiversity and abundance, but it is also due to their extensive, influential evolutionary history. The oldest insect fossils appear around 479 million years ago, closely following the emergence of the first terrestrial plants some 500 million years ago. Preceding tetrapods and virtually all other terrestrial animal life besides protozoa, it should come as no surprise that insects and their diversification has significantly shaped terrestrial ecosystems as we know it, and thus insects are vital to their very functioning. In such ecosystems, they often serve irreplaceable, basal roles such as major pollinators, recyclers of nutrients, population control, and being sources of food for other creatures.

A common lagoon fly (Eristalinus aeneus) feeding on the nectar of a flower. Like many other flies, their larvae are aquatic, and thus these flies are often found around freshwater ecosystems such as coastal lagoons, ponds, and streams.

As insect populations decline, these ecosystems will spiral out of balance and eventually collapse. Decaying material will build up without detritivorous insects to recycle it, and topsoil will erode without insects driving its creation and aeration. At the same time, countless birds, reptiles, amphibians and fish that eat insects will face starvation. All of the organisms engaged in niche mutualistic relationships with insects will die out, and other unforeseen consequences will surely arise. So why are these organisms that have very successfully diversified through nearly 480 million years of Earth’s changeable climate suffering so heavily today? In short, the rapidly shifting patterns of climate today in combination with other anthropogenic stressors such as habitat destruction and degradation, insecticides, herbicides, and invasive species exert unprecedented pressure on these species, and they cannot adapt quickly enough.

In order to mitigate the destruction of insects, and more broadly of the countless organisms intertwined with insects, we must take immediate, multifaceted action to preserve insect diversity. We must adjust societal attitudes towards insects, shifting away from insect aversion and towards insect appreciation, or, at the very least tolerance and acknowledgement of their ecological importance. On a more concrete level, the world must change the way it uses land. Industrialized agriculture drives a large portion of the world’s habitat destruction and usually entails the heavy use of herbicides and pesticides, making these habitats hostile to insects. One possible avenue for mitigating the damage done by food production could be organic farming, as organic farms have been observed to host significantly more insects. Similarly, we must also learn to more sustainably integrate insects into human life, as urbanization leaves little room for insects to survive.

An unidentified species of sweat bees (Halictidae), which are non-aggressive, highly important native pollinators in the United States. Their brilliant green color appears metallic and highly iridescent in the sun.

In order to mitigate the destruction of insects, and more broadly of the countless organisms intertwined with insects, we must take immediate, multifaceted action to preserve insect diversity. We must adjust societal attitudes towards insects, shifting away from insect aversion and towards insect appreciation, or, at the very least tolerance and acknowledgement of their ecological importance. On a more concrete level, the world must change the way it uses land. Industrialized agriculture drives a large portion of the world’s habitat destruction and usually entails the heavy use of herbicides and pesticides, making these habitats hostile to insects. One possible avenue for mitigating the damage done by food production could be organic farming, as organic farms have been observed to host significantly more insects. Similarly, we must also learn to more sustainably integrate insects into human life, as urbanization leaves little room for insects to survive.

An ailanthus webworm moth (Atteva aurea), which unlike most other moths, is a diurnal, nectar-eating species of moth. The range of these moths was historically from South America to the southernmost parts of North America until the introduction of invasive species like the tree-of-heaven to North America allowed their populations to expand farther north.

Individually, people can fight this by building insect hotels, planting native pollinator plants, and advocating for environmental legislation that protects natural areas, reduces the use of harmful chemicals, and so on.

No matter your feelings towards insects, there is no denying the impressive evolutionary history, biodiversity, and ecological impact of insects. As an insect-enthusiast myself, I hope that holding more positive discourse about insects may de-stigmatize them enough to where people can realize their beauty and value more fully.

A suspected chinese mantis (Tenodera sinensis), which is invasive to North America. Chinese mantises look incredibly similar to European mantises (another invasive species) and Carolina mantises (a native species of the United States). They are commonly distinguished by wing length, size, body and head shape, and the presence or absence of stripes on the face.