The insects of the world are incredibly numerous, diverse, critical to the web of life, and disappearing in alarming numbers. In my last post I mentioned the concept of shifting baselines syndrome and gave my own observational example of how, when I was much younger, I recalled the numerous bug splats on your car windshield that needed to be cleaned off every time you filled the gas tank, yet now it is rare to even get a single bug splat on your windshield. While doing research for this post, I found that this is a well-known observation and has been dubbed “the windshield effect”. In this post, I would like to explore this further and provide some insights on why we need to care about and protect the insect world. It’s a huge topic but I will work to keep it digestible by providing some specific examples.
If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed ten thousand years ago. If insects were to vanish, the environment would collapse into chaos. — E. O. Wilson
- Biotic homogenization: The process by which ecosystems lose their biological uniqueness. This is an emerging, yet pervasive, threat in the ongoing biodiversity crisis. This phenomenon stems primarily from two sources: extinctions of native species and invasion of nonnative species. While this process pre-dates human civilization, as evidenced by the fossil record, and still occurs due to natural impacts, it has recently been accelerated due human-caused pressures.
- Taxonomy: a hierarchical scheme of classification in which things are organized into groups or types based on shared characteristics. Today we still use an expanded version of the system developed by Carl Linnaeus in the 18th century. The categories, from broadest to most specific, are: Domain – Kingdom – Phylum – Class – Order – Family – Genus – Species.
- Neonicotinoid pesticides: a class of chemical insecticides that act by causing neurotoxic effects on nicotinic acetylcholine receptors in the nerve synapse. This chemical is very toxic to invertebrates. Nicotinic acetylcholine receptors are also present in the nervous systems of mammals. There is concern that neonicotinoids may impact animals other than their insect targets (including humans). Neonicotinoids are known to have sub-lethal effects on bees’ foraging and colony performance.
To start, let’s be clear about just what insects are. Insects belong to the Kingdom Animalia, Phylum Arthropoda, Class Insecta. There are at least 28 different Orders of insects; the pictures below show the 5 orders that include at least 100,000 species each —greater than the number of all known species of fish, reptiles, mammals, amphibians, and birds combined. WOW — Half of all known living organisms are insects! All insects have a chitinous exoskeleton, a 3-part body, 3 pairs of jointed legs, compound eyes, and one pair of antennae. They live in nearly all environments (including the ocean). Insects do NOT include centipedes, scorpions, spiders, woodlice, mites, and ticks.
Selected orders shown in the slideshow below: 1. Lepidoptera (butterflies and moths, 2. Coleoptera (beetles), 3. Hymenoptera (bees, wasps, hornets, sawflies, ants), 4. Hemiptera (cicadas, aphids, plant hoppers, bed bugs, sheild bugs), 5. Diptera (flies).
Insect Diversity and Biomass
The class Insecta originated on Earth about 480 million years ago, about the same time as terrestrial plants. Until recently, insects have had very low extinction rates; in one group of beetles studied (Polyphaga), there have been no extinctions in its entire evolutionary history, even during the mass extinction event at the end of the Cretaceous period (~66 million years ago).
Roughly 10 quintillion individual insects exist on the planet at any given moment. They make up about 80% of all the known animal kingdom species. About a million insect species have been discovered but it’s generally agreed that, by some estimates, about four million more have yet to be discovered. If you look at the food webs of any species habitat, you’ll find insects playing a role. To understand the importance of each species within a given web, see my previous posts. Although any individual insect species within a given food web may not be considered a keystone species, the larger group of insects are clearly vital to life on land.
Crucial Insect Ecological Contributions
Every insect on the planet is playing a role in the ecological machine. Each individual effort adds up to colossal benefits for life on Earth. Along with these insect *”services” provided, there are also insect “disservices”, for example, pest damage to agriculture, spread of diseases, negative actions as an invasive species, etc. As presented to the general public, these negative affects associated with insects are given far greater coverage than the benefits of insects. Often the insects negative affects in an ecosystem are due to imbalances in nature that were caused by humans.
*Note: I’m not a fan of the terms ecological “services” — if you do much reading about ecology you’re sure to come across the term. Whether it is meant this way or not, it smacks to me of “how does [something found in nature] contribute to improving humans’ life on earth”. We need to stop holding this warped view that all of nature is simply available to “serve” our needs and wants. We need to recognize the importance of the roles that each living thing on earth plays in keeping all of nature in balance so all can be well.
PROVIDERS: Insects are the meal of choice for many larger animals such as birds, bats, amphibians, and fish. These animals are in turn the meal of choice for even larger predators. The decline in insect populations is suspected to be the leading cause of recent declines in bird populations. Insect eating reptiles include geckos, anoles, and skinks. Insect eating mammals include tree shrews and anteaters.
DECOMPOSERS: Waste-eating insects, such as springtails, termites, beetles, etc, recycle nutrients back into the earth for plants to absorb and grow that would otherwise stagnate in dung, dead plants, and carrion. Without insects, dead organic matter would being to pile up. Insects are also used in sewage treatment plants to help decompose and filter matter along with neutralizing toxins.
PEST CONTROLLERS: Insects such as ladybirds, hoverflies, and wasps that eat other crop-threatening insects play the role of pesticides without chemicals, reducing costs to farmers and increasing yields. In addition to killing unwanted insects or weeds, pesticides and herbicides can be toxic to a host of other organisms including birds, fish, beneficial insects, and non-target plants. Surface and groundwater pollution due to pesticides is a worldwide problem. According to the soil scientist Dr. Elaine Ingham, “If we lose both bacteria and fungi, then the soil degrades. Overuse of chemical fertilizers and pesticides have effects on the soil organisms that are similar to human overuse of antibiotics. Indiscriminate use of chemicals might work for a few years, but after awhile, there aren’t enough beneficial soil organisms to hold onto the nutrients”. Pesticides are often considered a quick, easy, and inexpensive solution for controlling weeds and insect pests in urban landscapes. However, pesticide use comes at a significant cost. Weed killers can be especially problematic because they are used in relatively large volumes. The best way to reduce pesticide contamination (and the harm it causes) in our environment is for all of us to do our part to use safer, non-chemical pest control and weed control methods.
POLLINATORS: Nearly 90% of flowering plant species and 75% of crop species depend on pollination by animals — mostly insects. Overall, one out of every three bites of food humans eat relies on animal pollination. Insects also play a critical role in seed dispersal. For example, the seeds of many plants have structures (elaiosomes) that are packed with fats and other nutrition. Ants will carry off the seed, eat only the elaiosome, and leave the rest to sprout.
SOIL ENGINEERS: Termites and ants transform soil through their tunneling which aerates hard ground, helping it retain water and adding nutrients. In some regions of the world, introduction of termites has turned infertile land into cropland within a year.
In the late 1980’s, a researcher launched a project to find out how insects were faring in different types of protected areas in Germany. He collected insects from 63 areas over the course of 20 years. In 2013, entomologists returned to two sites that were first sampled in 1989. The mass of trapped insects was just a fraction of what it had been 24 years earlier. The team that sifted through all this data found that between 1989 and 2016, flying insect biomass in these protected areas of Germany declined by 76%. Insect biomass studies conducted in other areas have shown similar results: a protected forest in New Hampshire found the number of beetles had decreased by more than 80% and the beetles diversity decreased by almost 40%. A study of butterflies in the Netherlands found their numbers had declined by almost 85% since the end of the 19th century. A study of mayflies in the upper Midwestern U..S. found their populations dropped by more than half just since 2012. A research station in the tropics of Costa Rica has found a 40% decrease in caterpillar diversity since 1997, and a drop in parasitoid diversity of about 55%. This data is particularly significant given that about 80% of all insect species live in the tropics. The geographic extent and magnitude of insect declines remain largely unknown — there is an urgent need for monitoring efforts, especially across ecological gradients, which will help to identify important causal factors in declines.
Earth is clearly in a biodiversity crisis, not surprisingly when you consider how much of the planet we humans have altered by mowing down forests, plowing up grasslands, planting monocultures, and pouring pollutants into our waters and the air. The rate of insect loss is significantly faster than other animal groups. It is not clear why this would be. Pesticide use would seem a logical culprit, however many of the places where steep declines have been reported are pristine landscapes where pesticide use is minimal. Climate change is suspected to be a major driving factor.
The Culprits and Potential Solutions
In a recent study, questions were posed to expert entomologists on the root causes of potential insect declines worldwide, 413 expert opinions were summarized regarding the relevance of threats to insects as follows (in order of importance):
- Agriculture (causing habitat loss and biotic homogenization)
- Climate change
- Pollution (includes pesticide use, the number one stressor for freshwater invertebrates)
- Natural system modifications
- Invasive species
- Residential and commercial development
The above list refers to all insects worldwide. The main stressors that affect any given insect family may vary and are dependent on their habitat and species. Insects — the most diverse class of animal organisms on the planet — are still severely understudied.
Climate change is believed to be one of the main drivers of insect population decline. Many insect species are very susceptible to extreme weather conditions — they are just not adapted to large fluctuations.. In the words of one researcher, “…the insects run out of food, they run out of cues, everything just falls apart.” Pesticide use and habitat loss are thought to be another main contributing factor in insect decline. The European Union has banned most neonicotinoid pesticides which several studies have linked to insect and bird decline. The German government had adopted an “action program for insect protection”, which includes restoring insect habitat, banning the use of insecticides in certain areas, and phasing out glyphosate (a commonly used herbicide). A group of more than 50 scientists from around the world have proposed a roadmap for insect conservation. It recommends taking aggressive action to reduce greenhouse gas emissions, preserving more natural areas, imposing stricter controls on exotic species, and reducing the application of synthetic pesticides and fertilizers.
The Xerces Society for Invertebrate Conservation based here in Portland, Oregon is one of the few organizations in the world that is specifically devoted to invertebrate conservation. As a science-based organization, they both conduct their own research and rely upon the most up-to-date information to guide their conservation work. Their key program areas are: pollinator conservation, endangered species conservation, and reducing pesticide use and impacts. I highly recommend you take a look at their website to learn more about this great organization: https://xerces.org/. Their introductory video is worth watching:
A Few (kinda interesting) Insect Facts
- Globe mallow bees don’t make hives; the females sleep in ground nests and males curl up inside the globe mallow flowers. If all the blooms are booked, a male bee will nestled alongside another bee and convert the single room to a double.
- While many invertebrates fill the seas, and a small fraction of insect species live at the edges the ocean or in the intertidal zones, there is only one insect that lives on the surface of the open ocean: the sea strider (Halobates). This carnivorous insect sprints on the water surface looking for prey that has fallen onto the water, such as zoo- plankton, fish eggs, larvae and dead jellyfish. In turn, it provides a source of food for sea birds and surface feeding fish.
- Researchers have observed chimpanzees catching insects and putting them into wounds on themselves or other chimps. They catch the insect, squeeze it between their lips to immobilize it, then place it on the wound moving it around with their fingertips, and finally removing it with their fingers or mouths. Sometimes the insect would be put in and out of the wound several times. At the least, it’s interesting behavior. Yet it seems quite possible that they are in some way treating the would….chimp TEK (Traditional Ecological Knowledge)!
- Some insects have evolved into remarkably specialized roles within their habitats. The moth caterpillar (Ceratophaga vicinella) scavenges only on the tough keratin shells of dead gopher tortoises. You can see how the extinction of these specialized insects can unravel the balance in an ecosystem.
- Dragonflies move each of their four wings independently, flapping each up and down and rotating them forward and back. They can move straight up and down, fly backward, hover and stop, and make hairpin turns at full speed or in slow motion. They can fly at speeds up to 30 mph. AND they can eat up to 100 mosquitos per day.
- Many insects live off other insects — most parasitic wasps lay their eggs in the bodies of caterpillars, using their hosts as a source of nutrients. Other insects, known as hyperparasitoids, lay their eggs in or on the bodies of parasitoids. There are even insects that parasitize hyperparasitoids!
- Fireflies have dedicated light organs under their abdomens that they use for finding mates. They do this by combining oxygen and a substance called luciferin they hold in special cells. This light produces no heat. Fireflies flash in patterns that are unique to different species. Some species synchronize their lighting — coordinating their flashes into bursts that ripple through the entire group of insects.
MAKING THE CONNECTION
I started writing this post with the vague notion that I now observe far fewer insects in the environment than I remember from decades ago, along with some sneaking suspicions about what some of the causes of this decline could be. During my research phase, I was particularly alarmed to discover just how widespread and drastic global insect die-off has occurred, and in such an incredibly short period of time. I hope, given the content I’ve included here, that you have also been able to make these connections: incredible diversity and overall biomass of the class Insecta, what they contribute to the overall balance of nature along with the importance of these contributions, and the causes for their decline (both proven and suspected by experts in the field).
It’s time for ALL people on this planet to change their relationship with nature, which requires some radical changes in how we live our lives. The damage we are currently causing to the planet is quite simply not sustainable. I suspect that on some level everyone knows this and many are afraid to acknowledge it because they do not want to give up their current way of life. There is often a push to “live in the moment”, which can be comforting and soothing, but we also must be disciplined in preparing for our future. We need to develop a new relationship, based on respect and gratitude, with the our incredible, miraculous home — earth. There are so many organizations and individuals around the world that are already engaged in this work. Some of the business sector is even recognizing the need for change and moving in the right direction. I encourage everyone to continue learning and take whatever actions you feel called to take to help support these efforts. It is only by the participation of everyone who calls the earth “home” that we can continue to live in comfort and harmony with nature.
- Kolbert, E., & Liittschwager, D, & Bittel, J (May 2020) Where Have All the Insects Gone? National Geographic, pp. 45-65.
- Wagner, D. (2020), Insect Decline in the Anthropocene, Annual Review of Entomology, 65, 457-480. https://www.annualreviews.org/doi/abs/10.1146/annurev-ento-011019-025151,
- Milicic, M., et.al, Insect Threats and Conservation through the Lens of Global Experts, Conservation Letters, July/Aug 2021, https://conbio.onlinelibrary.wiley.com/doi/full/10.1111/conl.12814
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