Climate Crisis Is Killing Off Key Insects and Spreading Insect-Borne Diseases

We love them or hate them, but we still need insects. From declining Monarch butterflies in North America to disappearing BumblebeesIn Europe, evidence is mounting that insects are on the verge of extinction. This should concern us all as insects are so important. They are food for many larger creatures like birds and bats, control pests, recycle nutrients and help keep the soil healthy. They also pollinate three-quarters the crops we grow. Without insects, life would be impossible.

There are many factors that contribute to the decline of insects, including habitat loss and the loss of food. Global farming is being industrializedThe rise in pesticide use, the decline of invasive species and increasing light pollution are some of the factors that have helped to lead the way. Populations of many insects are now much reduced compared to the past, and most now exist in habitat “islands” — fragments of their favored habitat surrounded by inhospitable terrain.

Unfortunately, climate change may prove to be the end for many. Although the climate has changed many times in the past, insects have survived. Although many species were lost, insects have survived the five previous mass extinction events. This time, however, is different. Climate change used to be more gradual in the past. Species could shift towards the poles when the climate warmed, and then return to the equator when it cooled. It was possible to move across large areas of habitat. To move pole-wards, insects must traverse roads, landscapes populated with polluting factories and arable fields spray with insecticides, as well as housing estates and other alien, man-made landscapes.

Insects cannot live alone. They rely on certain plants to provide food and nectar for their larvae. If these plants haven’t travelled ahead of them — for example via seeds blown on the wild — then they cannot survive, so entire communities of organisms need to make this journey. They seem to be failing to do this. The bumblebees of North America and Europe are disappearing from their southern ranges as the climate warms. However, their northern ranges are not moving northwards as one might expect. It has been described as a climate “vice,” the ranges of the bees being gradually squashed from the south. Some mountain-dwelling bumblebees from Colorado and Spain have responded positively to climate warming by moving higher up the mountains. But eventually, they will run out mountain and find nowhere else.

These mountain bees’ studies have also shown that climate change can affect the seasons in subtle, but important ways. Many insects plan their life cycles carefully to ensure that the availability of vital resources coincides with times of activity. As the climate warms, different organisms might use different cues in order to time their lives. This can lead into mismatches. Some mountain plants in Colorado, for example, are now starting to flower before the bumblebees who feed on them emerge from hibernation. This means that they are not pollinated and have few seeds.

Bumblebees are sensitive to heat because they live in cool, temperate environments. Their large size and furry fur coats are adaptations to keeping cool in cool conditions. They can literally overheat in hot temperatures. Most bumblebees are unable maintain long-term activity above 30oC (30°C). The recent heat waves that afflicted much of Europe’s temperatures (even in the U.K.) exceeded 40oC, leaving bumblebees unable to gather food for extended periods.

Are bumblebees the exception? Many other insects are more “thermophilic” — warmth loving — and thrive in hot climates. We might expect warmer climates to be beneficial for many butterflies, which are found at the northern edges of their range in Britain. To test this, the charity Butterfly Conservation analyzed changes in the populations of 46 butterfly species that all reach the northern edge of their range in the U.K. — the species we would expect to be enjoying warming. Between 1970 and 2000 three-quarters of these species declined significantly. The pattern differs between sedentary ecosystem specialists (fussy, low-mobility species, comprising 28 species) as well as the generalist, highly mobile species (18). Only 89 percent of habitat specialists had declined, while only half the generalists had declined. A few species, including pest species were still thriving. This provides a clue about why climate warming has not yet benefited even warmth-loving butterfly species. Mobile generalists are more able to move in response to climate warming and are more likely find somewhere they can survive once they reach there.

Climate change isn’t just about slight temperature increases. Climate change is likely to have a greater impact on wildlife due to the increasing frequency of extreme weather events like droughts, heat waves and wildfires. These events are likely will become more frequent and more severe in the future. Although we don’t know what these will do to insects, it is likely that very few will be beneficial. Fires will kill insects. However, some ecosystems might benefit from the flush of new blooms that follows fires. Summer storms are likely a to batter delicate adult insects like butterflies and flash floods will likely destroy underground nests of creature such as bumblebees. Drought can cause water-stressed plants not to produce nectar in their flowers, which can harm pollinators. In prolonged droughts, plants wilt and become unpalatable for caterpillars — for example, in the hot British summer of 1976, many caterpillars of the Adonis blue butterfly died as their food plant, horseshoe vetch, shriveled in the heat. The following year, the number of adults was much lower and some populations died. It is likely that 2023 will be a particularly poor year for butterflies, given the U.K.’s current drought.

While climate change is undoubtedly bad for many insects, it is clear that some insects are thriving. These insects are often undesirable from a human point of view. These species, which are adaptable and mobile and can thrive in urban settings, such as houseflies or mosquitoes, have been on the rise. The yellow fever mosquito (Aedes aegyptiThe ) seems to have adapted well in urbanization and thrives within cities. They breed in blocked gutters and discarded tires, barrels and buckets, as well as any other human waste that traps water in puddles. It is a vector for many nasty diseases such as yellow fever, chikungunya and Zika fever.

The Anopheles The spread of humans is also helping the mosquito, which is the main transmitter, of malaria. Because the mosquito prefers to breed in sunlit ditches and puddles, it is more likely to contract malaria in areas where forests have been cleared for agriculture. Climate predictions indicate that malaria will spread to higher elevations in the tropics, such as Kenya, Colombia, and Ethiopia. These areas are densely populated because they have been largely malaria-free for a long time. The southern states of the U.S., southeastern Europe, parts of China and the densely populated areas surrounding São Paulo and Rio de Janeiro in Brazil are all likely to become suitable for malaria by 2050. Dengue fever is also predicted to increase in North America and as far south as Canada.

These problems are not easy to solve. We must make tackling climate change a top priority for humanity, for both the protection of our amazing biodiversity and our own well-being. Insects and other wildlife can cope by preserving as much of the habitat that is natural as possible and linking habitat patches together.