Insect biodiversity accounts for a large proportion of all
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
on the planet—over half of the estimated 1.5 million organism
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
described are classified as
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
s.
Species diversity
Estimates of the total number of insect species or those within specific
orders are often highly variable. Globally, averages of these predictions estimate there are around 1.5 million beetle species and 5.5 million insect species with around 1 million insect species currently found and described.
Between 950,000–1,000,000 of all described species are insects, so over 50% of all described eukaryotes (1.8 million) are insects (see illustration). With only 950,000 known non-insects, if the actual number of insects is 5.5 million, they may represent over 80% of the total, and with only about 20,000 new species of all organisms being described each year, most insect species likely will remain undescribed, unless species descriptions greatly increase in rate. Of the 24 orders of insects, four dominate in terms of numbers of described species, with at least 670,000 species included in
Coleoptera,
Diptera,
Hymenoptera and
Lepidoptera.
The fossil record concerning insects stretches back for hundreds of millions of years. It suggests there are ongoing background levels of both
new species appearing and
extinctions. Very occasionally, the record also appears to show mass extinctions of insects. The
Permian–Triassic extinction event
The Permian–Triassic (P–T, P–Tr) extinction event, also known as the Latest Permian extinction event, the End-Permian Extinction and colloquially as the Great Dying, formed the boundary between the Permian and Triassic geologic periods, as ...
saw the greatest level of
insect extinction, with the
Cretaceous–Paleogene being the second highest. Insect diversity has recovered after past mass extinctions, due to periods where new species originate with increased frequency, though the recovery can take millions of years.
In the Holocene
Several studies seemed to indicate that some insect populations are in decline in the late 20th and early 21st centuries, and has also been popularized as the
windshield phenomenon. For many studies, factors such as abundance, biomass, and species richness are often found to be declining for some, but not all locations in many studies; some species are in decline while others are not.
Every species is affected in different ways by changes in the environment, and it cannot be inferred that there is a consistent decrease across different insect groups. When conditions change, some species easily adapt to the change while others struggle to survive.
Concerns of
declines in insect abundance in the holocene have been attributed to habitat loss from land use changes such as urbanization or agricultural use,
pesticide use,
invasive species, and artificial lighting.
The use of increased quantities of
insecticides and
herbicides on crops have affected not only non-target insect species, but also the plants on which they feed. Climate change and the introduction of exotic species that compete with the
indigenous
Indigenous may refer to:
*Indigenous peoples
*Indigenous (ecology), presence in a region as the result of only natural processes, with no human intervention
*Indigenous (band), an American blues-rock band
*Indigenous (horse), a Hong Kong racehorse ...
ones put the native species under stress, and as a result they are more likely to succumb to pathogens and parasites.
[
As of 2017, at least 66 insect species extinctions had been recorded in the previous 500 years, which generally occurred on oceanic islands.] For 203 insect species that had IUCN-documented population trends in 2013, 33% were in decline with variation in documented species across orders. Most scientific and public attention has been focused on the conservation of larger, charismatic vertebrates, and relatively fewer studies have been done on insect groups, especially Diptera, Orthoptera and Hemiptera. Data from the past from which to calculate trends is largely unavailable, and what does exist is mostly related to Western Europe and North America. Insect population assessments that have been undertaken were largely concentrated on the more popular insect groups, butterflies and moths, bees, dragonflies and beetles.
Some studies have suggested a large proportion of insect species (up to a third of the known species) are threatened with extinction in the 21st century, such as a 2019 review by Sánchez-Bayo and Wyckhuys, though ecologist Manu Sanders notes that many of these findings are often biased limited to specific geographic areas and specific groups of species. The methodology of the Sánchez-Bayo & Wyckhuys study has been questioned; the search string used to sift through the scientific literature was "(insect* + decline* + survey)". This meant that the authors identified studies finding insect declines, but may have missed those that found increases in insect populations or stability. In assessing the study methodology, an editorial in Global Change Biology
''Global Change Biology'' is a biweekly peer-reviewed scientific journal covering research on the interface between biological systems and all aspects of environmental change that affect a substantial part of the globe including climate change, glo ...
stated, "An unbiased review of the literature would still find declines, but estimates based on this 'unidirectional' methodology are not credible. However, according to the authors of that review "more than half of the surveys were obtained from references cited in other reports" and "the 73 insect surveys cover all species in a particular taxon – irrespective of them exhibiting declines, stable or increasing trends in their distribution or abundance". Entomology professor Simon Leather suggested that media reports of an "Ecological Armageddon" may be exaggerated and advocated for more funding to allow better collection of long term data on the decline.
Claims of pending mass insect extinctions or "insect apocalypse" based on a subset of studies have been popularized in news reports, but often make claims extrapolated beyond the study data or hyperbolize study findings. The Entomological Society of America has stated there are not sufficient data to predict an imminent mass extinction of insects. For some insect groups such as some butterflies, bees, and beetles, declines in abundance and diversity have been documented in European studies. Other areas have shown increases in some insect species, although trends in most regions are currently unknown. It is difficult to assess long-term trends in insect abundance or diversity because historical measurements are generally not known for many species. Robust data to assess at-risk areas or species is especially lacking for arctic and tropical regions and a majority of the southern hemisphere.
Conservation
While biodiversity loss
Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, de ...
is a global problem, conserving habitat for species of insects is uncommon and generally of low priority, although there are exceptions. More commonly insect conservation occurs indirectly, either through the setting aside of large portions of land using "wilderness preservation" as the motive, or through protection of "charismatic vertebrates". Some studies estimate that global insect populations are in rapid decline, perhaps by as much as 80% in recent decades. The windshield phenomenon describes people noticing vastly fewer insects flying into the path of their cars after long drives, and this may reflect worldwide loss of insect abundance.
Single-species insect conservation can preserve other species indirectly; this preservation-by-default is referred to as the umbrella effect. Showy insects such as butterflies or large, colourful beetles serve as flagship species
In conservation biology, a flagship species is a species chosen to raise support for biodiversity conservation in a given place or social context. Definitions have varied, but they have tended to focus on the strategic goals and the socio-economi ...
, and can expand public awareness and financial contributions for conservation efforts. Wealthy nations such as the United States do list species of concern, and occasionally insects are placed on its Endangered Species List. In 2017 this list had classified over 80 insects as endangered species, the majority of them beetles or butterflies; a significant percentage of these listed insects are native only to the Hawaiian Islands. Migratory species, such as the well-known monarch butterfly (''Danaus plexippus
The monarch butterfly or simply monarch (''Danaus plexippus'') is a milkweed butterfly (subfamily Danainae) in the family Nymphalidae. Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown. I ...
''), are in need of special conservation methods. One species may require several habitat locations, even across international boundaries, for the different periods of their migratory patterns.
Insect conservation has been labelled in the past as a concern only for the affluent. The developing country of Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
has a "happily ever after" ending in their attempts to preserve the world's largest butterfly, Queen Alexandra's birdwing
''Ornithoptera alexandrae'', the Queen Alexandra's birdwing, is the largest species of butterfly in the world, with females reaching wingspans slightly in excess of 25 cm to 28 cm (9.8 inches to 11 inches). This birdwing is restricted to the ...
(''Ornithoptera alexandrae''). This species is restricted to a very small range of habitat due to specificity in their diet. In the international market of insect collecting, the butterfly can retrieve up to US$2000. In 1978, the government of Papua New Guinea set up the Insect Farming and Trading Agency (IFTA) to regulate the exploitation and conservation of Queen Alexandra's birdwing and other valuable butterflies.
Agriculture
In agricultural ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s, biodiversity is important for the production of food and for ecological services such as the recycling of nutrients, regulation of microclimate
A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few squ ...
and local hydrological processes, and biological control
Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also i ...
of pests.
In the United States alone, pollination
Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...
by bees accounts for over US$
The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
9 billion of economic revenue
In accounting, revenue is the total amount of income generated by the sale of goods and services related to the primary operations of the business.
Commercial revenue may also be referred to as sales or as turnover. Some companies receive reven ...
. According to some estimates, over ⅓ of the human diet can be traced directly or indirectly to bee pollination. Losses of key pollinators have been reported in at least one region or country on every continent except Antarctica, which has no pollinators. The Millennium Ecosystem Assessment
The Millennium Ecosystem Assessment (MA) is a major assessment of the human impact on the environment, called for by the United Nations Secretary-General Kofi Annan in 2000, launched in 2001 and published in 2005 with more than $14 million of g ...
concluded that with the global decline in the amount of pollinators, there is not a complete loss of fruit or seeds, but a significant decrease in quantity and viability in fruits, and a lower number of seeds.
See also
*Insect ecology
Insect ecology is the scientific study of how insects, individually or as a community, interact with the surrounding environment or ecosystem.
Insects play significant roles in the ecology of the world due to their vast diversity of form, functio ...
*Defaunation
Defaunation is the global, local or functional extinction of animal populations or species from ecological communities. The Human overpopulation, growth of the human population, combined with advances in harvesting technologies, has led to more int ...
*List of prehistoric insects
References
{{DEFAULTSORT:Insect Biodiversity
Biodiversity
Biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...