Among the general population, many insects – such as moths and beetles – are seen as an irritant, requiring their removal from homes and properties where they live in abundance. Some other insects – such as butterflies – are prized for their beauty and fragility the world over. But both categories of insects have one dire factor in common: their populations are in decline. With volatile environmental conditions and the brutal reality of climate change, the current decline was practically inevitable.

On its face, fewer insects sound like a net positive for human, leading to a decrease in their pestering intrusions over time. But beneath the surface, these dramatic declines in insect population are a considerable hazard to the health of the worldwide environment. If these declines are left unchecked and unaddressed, these declines could severely affect the planet’s ecosystems and trickle down to affect humans negatively in turn. This is why efforts for biological conservation have ramped up recently.

These population declines haven’t been isolated to one geographical region. Unfortunately, native insect populations everywhere from North America to Europe have seen declines indicative of severe underlying causes. These causes are numerous and, in some cases, reversible through a concerted effort by the general population.

These troubling insect declines are not a foregone conclusion. Through careful planning and interpretation of existing trend data, individuals and groups with influential power may be able to mitigate this harmful decline and restore a stable insect population to the effect regions worldwide.

Declines by Geographical Region

Due to scalability, a great deal of the existing research on insect population decline has focused on regional decreases in localized insect biomass. As such, much of the research on this topic should be disseminated regionally before being applied globally. Taken together, these regional declines point to a larger, more harmful trend that stands to hurt the global environment in both the short and long term.

Worldwide

In so many words, the worldwide insect population is declining today and has been in a state of decline for at least the past several decades, according to current research.

While studies covering this phenomenon have been available for decades, one of the most noteworthy (due to its widespread media coverage) bodies of knowledge on this topic derives from a 2017 study re-published in the German publication PLoS ONE. In this study, researchers extrapolated nearly 27 years of direct testing to discover that nearly 75% of their region’s flying insect biomass had declined during the testing period.

Headlines carrying titles such as “Insect Apocalypse” appeared in popular newspapers and magazines around the world, with a particular focus on the acute impacts these declines would have on food sources and habitats. While this study was designed to only account for Germany and the European region originally, its broad appearance in global media caused a fresh appraisal of global insect population declines.

This renewed focus on insect population declines has already brought new evidence to the forefront, even on the global scale where widespread trends take an extended period of time to evaluate. One such piece of global analysis came in the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services’ 2019 assessment on global biodiversity.

While this assessment did not commit to any specific worldwide causes or cross-regional declines in insect population, the authors did assert that well-documented regional declines in everything from butterflies to bees gives credence to a larger underlying problem. The assessment called the prospect of extinction among effected insect populations a “key uncertainty”, but still estimated a tentative 10% decrease if nothing is done to correct the decline.

North America

North America (and specifically, the United States) has an active history with insect population declines that dates back to the region’s long history with ecosystem modification to meet the needs of human civilizations. A February 2019 article from National Geographic points to this, as it cites the rapid extinction of the Rocky Mountain locust as a prime example of Great Plains settlers eliminating a multi-billion population in just around 27 years.

Scientific American covered a similar, and more recent trend, in its evaluation of another recent study demonstrating a decades-old decline in insect and arthropod populations in the US and Mexico. While this study also elicited hyperbolic conclusions indicating an incoming “insect Armageddon”, researchers in the field have quickly clarified that the decrease in biomass and diversity may quickly impact the ecosystems in this region.

Certain “desirable” insect species have also received the star treatment among researchers, perhaps due to their noticeable absence in certain parts of the US. For example, a 2018 study of monarch butterflies shows that their population is in decline. This news has come as a surprise to researchers in California, where some subspecies spend their winter, and in Illinois, where the monarch butterfly is the official state insect.

Overall, the North American region has a fair amount to worry about when it comes to insect population declines. With some $57 billion in productive services provided by insects in the US annually, researchers in this region have fair cause to further evaluate how these rapid decreases can be halted.

Europe

European nations, and the European region as a whole, have conducted the majority of useful studies into insect population declines at this point, likely due the region’s ongoing commitment to finding ecologically sustainable growth models. Findings from these several studies all point to the conclusion that both regular and so-called “linchpin” species are threatened under the presently harmful hegemony.

A prime example can be seen the aforementioned 2017 study out of the UK covering the regions so-called “ecological Armageddon”. Specifically, this study found that the “less charismatic” insects studied in the United Kingdom in recent decades had shown moderate signs of decline, with some room for interpretation based upon habitat and other extenuating factors.

A 2006 study in Great Britain lead to similar conclusion, with the light-based traps in that study drawing in far fewer moths than would be expected based on previous population counts. As described above, a 2017 study out of Germany even found a ¾ decline in insect biomass across 63 unique regions of Germany between 1989 and 2016.

As it stands, Europe is as threatened by insect populations as any other part of the world. As fresh research continues to enter the public record, government and private entities are expected to take more interest in understanding the causes of these declines as well as an interest in working to mitigate their deleterious effect on the environment.

Declines by Insect-Type and Species

A fair volume of the current research into insect population decline has been conducted by insect type or species. Though the information gathered from these studies cannot be used to make wide-reaching conclusions about “insects” as a whole, this area of data analysis can provide insight into which species are most acutely affected by the various causes of insect population decline.

Bees

Simply put, bees have received a great deal of attention from media and researchers alike, likely due to their keystone role as pollinators in nearly every ecosystem worldwide. This intense attention is justified, given that ongoing decreases among bees may lead to collapses in agricultural norms in all corners of the world.

One article from the Yale School of Forestry and Environmental Studies put the bee population decreases in stark terms, with US-based beekeepers experiencing up to 50% hive die-offs during the winter of 2013. This article highlights that these massive declines may be chalked up to a wide variety of converging factors, including the use of certain classes of pesticides and the well-documented colony collapse disorder.

Even in Europe, the situation for bees has become notably troubling. By population, there are some 25% fewer bees in Europe since 1985, with an even sharper 45% decline since 2010. Without these crucial bees, the world’s food supply – which relies on bee-based pollination – may be in serious danger.

Butterflies

Butterflies are one notably fragile insect species that have not escaped the general trend of population decline. Monarch butterflies, in particular, have been studied extensively because of their broad enjoyment by populations in the United States and Mexico.

Sadly, monarch butterflies have faced some of the most sporadic decreases in recent years. While a 2016 count found their population to have risen up to 150 million, this population increase came on the tails of a devasting 2015 count at just 42 million. Even this 2016 figure showed a dramatic decrease from the 20-year average, with a decrease of 68% telling the grim tale.

European butterflies are similarly endangered in terms of their total population. A 2019 study from Statistics Netherlands and the Dutch Butterfly Conservation found that the butterfly population in the Netherlands between 1890 and 2017 had dropped a shocking 84%.

Because butterflies additionally act as pollinators, their population decline goes to further exacerbate the agricultural strain presented by mass bee die-offs. Though some species, such as the monarch, have gained special protected status with regulators such as the US Environmental Protection Agency, there is no promise that their population decreases will abate without direct intervention.

“Less Charismatic” Insects

One UK researcher in 2017 used this blanket term to refer to all of the insects that are affected by population declines but are generally seen as less desirable for one reason or another. While research into these insects has been less focused on any one species, this class tends to include recognizable insects such as moths, beetles, dragonflies, and certain aphids.

Arthropods are one interesting case study worth noting, given their recent population decreases in Puerto Rico’s Luquillo rainforest. In a 2018 study at that location, researchers found that the biomass of arthropods had decreased between 10 to 60 times over. At the same time, researchers correlated this population decrease with decreases in other interconnected species (mostly predators), including several types of lizards, frogs, and birds.

In certain parts of Europe, these miscellaneous insects are facing similar threats to their population count. A 2019 study from the Swiss Academy of Natural Sciences pointed to this conclusion, with researcher analysis isolating nearly 60% of the studied insect species as deserving an “at risk” status.

Potential Causes

Across the current body of knowledge regarding insect population decline, there stands broad agreement that the causes of this harmful phenomena are numerous and, in many cases, overlapping. David Wagner, an ecologist at the University of Connecticut, sees the matter as a “death by a thousand cuts.” As such, each individual cause should be taken as a cog in larger system that is rapidly widdling down the world’s insect-based biodiversity.

That being said, the causes of insect population decline are beginning to come into focus as researchers dig deeper into the broader implications of a century of industrialization and urbanization. While these two broad causes are often offered up in popular media sources, there is far more complexity in these two causes that should be examined in order to attain an actionable understanding of the underlying issues.

Also, each region faces different types and different degrees of the following primary causes. Research into the following three categories is merely designed to show common trends that have been demonstrated to negatively affect insect populations around the globe.

Habitat Destruction

When urbanization and industrialization are brought into the conversation about insect population decreases, often the twin broad terms are being used to euphemistically refer to the larger threat of habitat loss & destruction. While this phenomenon is not new, with human civilizations significantly modifier the environment for several centuries, this threat has regained renewed focus as verdant forests and prairies become ever scarcer.

Deforestation and agricultural practices are perhaps the most obvious source of habitat destruction, given the manner in which they dramatically deserve self-contained ecosystems. One National Geographic article even points to the decrease in small scale “family farms,” with their open pastures and hedgerows, as a recent development contributing to habitat destruction overall.

Even for these recent changes, entomologists such as S.R. Leather are quick to note that these habitat changes and their damaging effects on native insect populations have been observed for over a century. Leather quotes one source from 1909, which describes the oncoming damage to modified ecosystems as follows:

“Men all around were clearing available land. The trees fell wherever corn would grow. The swamp was broken by several gravel roads…Wherever the trees fell the moisture dried, the creeks ceased to flow, the river ran low, and at times the bed was dry…Big pursy caterpillars could not be picked from their favorite bushes, where there were no bushes. Dragonflies could not hover over dry places and butterflies became scare in proportion to the flowers.”

While some efforts are being made to combat this ongoing threat (as described below), more will certainly need to be done in order combat threats to native insect species in parts of the developing world. These global changes will require time and practice, as well as concerted effort by both public and private entities to care for the remaining areas where insect live thrives.

Insecticides and other Chemical Deterrents

As expected, researchers have also been able to conclusively point to a further increase in insecticide use by farmers as a cause of insect population decreases. This does not come as a dramatic surprise, in research terms, given that this kind of biomass destruction is the intended effect of these chemical pesticides.

A 2018 study from the journal Environmental Pollution points out that this relationship is not strictly “linear.” In other, there mere presence of heightened levels of pesticides alone does not account for the ongoing thinning among insect populations. Instead, these researchers assert factors including metapopulation can cause ongoing harm to sensitive insect species. The use of pesticides is not the main issue here.

In particular, these researchers identified butterflies as being distinctly vulnerable to insecticides. Because of their ecological fragility, butterflies in particularly likely to take hard population hits in areas where insecticides are regularly applied. This harm can come from direct contact through the air and through food sources, as well as in decreased survival rates in effected larvae.

Of note also, the rise of mid-sized and large scale farming operations in parts of the developing world – including South America and Africa – may be further adding fuel to this chemical-induced fire. As farmers in these regions begin to compete globally, they are expected to further harm their native insect populations as they dial up their insecticide use to industrial levels.

Invasive Insect Species

While this factor is often overlooking, the threat posed by non-native invasive insect species may be more long lasting than current popular commentators understand. Invasive species of all types – from kudzu in the Southern United States to Asian carp in the Mississippi River – have a tendency to crowd out their native competitors due to their lack of natural predator.

This, in turn, causes these introduced species to flourish beyond reasonable control, further crowding out native species for living space and food resources. This phenomenon can be seen even among insects, who are often threatened by the likes of invasive plants, non-native grazers, and so-called social insects such as ants.

While this threat is wholly apparent in both mainland forests and prairies, researchers such as David Wagner and Roy Van Driesche have clarified that the threat posed by invasive species is particularly acute in isolated locations, such as islands frequented by tourists.

These researchers have additionally posited the belief that these small struggles for resources can further “cascade” into ecosystem-wide problems, such as changes in hydrology, nutrient cycles, soil chemistry, fire susceptibility, and light availability. Each of these harmful after effects run the risk of further decreasing an already dwindling insect population.

Effects on the Environment

As to be expected, declines in insect numbers around the world are currently causing noteworthy effects on the environment. While these effects have immediate effects on their adjacent ecosystems, some of these negative effects are able to trickle down into vulnerable human systems.

What’s more, these effects are not just centered around the present. Instead, the vast majority of effect-based predictions put out by researchers today indicate future environmental effects that future generations will need to deal with if nothing is done to remedy the present problems. The following listed effects, though, are not exhaustive by any means.

A 2019 global review was very frank when it came to the prospective effects of further insect population declines. In short, these researchers hypothesized that catastrophic, grassroots-level impacts are bound to hit many of the Earth’s ecosystems in the immediate future if decisive action is not taken. In other words, these effects are not to be taken lightly.

Agriculture and the Food Supply

In a human-centric world view, environmental impacts on the food supply resulting from declining insect populations may well be the most immediate concern. While this concern may feel abstract – as if there could never be a large enough pollinator die-off to effect agriculture – the reality is that these types of effects are already being felt in industries reliant on bees.

In concrete terms, the world’s food crops wouldn’t be immediately impacted by a continual decline in pollinating insects, such as honey bees. Instead, current intensive agriculture practices would not be able to keep the production pace due to a lack of pollinators. This, in turn, would cause food shortages, especially in the most vulnerable regions where artificial pollination is unavailable.

Overall, these impacts may be one of the most difficult to identify, given the industrialized world’s ability to obscure weaknesses in its production cycle through artificial abundance. That being said, the potential for food supply interruptions and agricultural breakdowns are two of the most immediately concern effects that will come to pass if insects (and specifically bees) are not better protected going forward.

Decreased Biodiversity

In basic terms, biodiversity refers to the practical and intrinsic value of varied plant and animal species in a given ecosystem. As a function of time, most ecosystems are able to create their own biodiversity such that nearly every plant and animal in a region serves a niche function for the larger ecosystem. Biodiversity can be interrupted, though, especially when an important species is eliminated substantially.

Such is the case in regions where insects – both “charismatic” and “non-charismatic” – have begun to this out population-wise. Depending on their precise role in that ecosystem, this growing absence can cause a direct interruption of nutrient cycles and ecosystem services (such as natural waste recycling).

Once such interruptions are initiated, it becomes difficult to stop them from “cascading.” As David Wagner and Roy Van Driesche describe in a 2010 study, these decreases in biodiversity can eventually “alter basic ecosystem properties” including changes to nutrient cycles, soil chemistry, and fire susceptibility (among others).

In so many words, the removal of any insect species – whether it is perceived as important or not – through population thinning can result in unforeseen consequences for their host ecosystem. Maintaining biodiversity, then, is of key importance when it comes to addressing the threats faced by insect population declines.

Efforts to Prevent Further Declines

Despite all of the gloomy predictions presented by current research into insect population declines, there is some hope on the horizon when it comes to addressing these mounting problems. In some countries and regions, government organizations have even taken up the torch in order to protect vulnerable insect populations and the ecosystems that rely on them.

One such international-level response has come from the United Nation, with the years 2011 through 2020 being internally dubbed the “Decade on Biodiversity.” This title has come with a variety of ecologically-sound implications, all of which are designed to help support the UN’s broader Sustainable Development Goals. All in all, the UN’s efforts have spurned a greater international response to the issues described above, rather than relying on individual countries to act.

Of course, some countries have still redoubled their efforts to fight ecosystem degradation, especially regarding the noteworthy decreases in insect populations. One such country is Germany, whose Federal Ministry for the Environment, Nature Conservation, and Nuclear Safety started an “Action Programme for Insect Protection” following the landmark 2017 study by Krefeld, et al. This program is specifically geared at preserving existing insect habitats as well as moderating insect pollutants, both toxic and physiological. Nature reserves are great for maintaining biodiversity across the globe.

Of course, all of the efforts to help improve the plight of insect populations has not been left to large government agencies alone. In fact, some groups such as the Xerces Society provide several “civilian scientist” opportunities to increase awareness and understanding of insect-related problems.

One such program implores average citizens to take part in the annual Western Monarch Count, which helps quantify how many of the colorful species are surviving year to year. In the same vein, the Xerces Society runs a program wherein citizens can submit information on local milkweed patches. This information is critical, given that monarch butterflies use milkweed plants for procreational purposes.

The Last Word

In short, the plight of insect populations is dire today and growing worse with each year that passes with minimal action. As these insect populations continue to decline, the environmental impacts will continue to ravage ecosystems, leading to eventual impacts on human-centric systems.

This matter need not be taken sitting down, though. You can play a part in preserving insect populations by advocating for insect-friendly policies in your community and state, as well as taking part in a citizen scientist program to keep track of insect population health.

The time to act is now in order to turn the page and become more actionably conscious of the critical role these insects and their declining populations play in the global environment.

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