A_Dead_carpenter_bee_(Xylocopa_pubescens)

Pollinator decline is the reduction in abundance of

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 ...

and other animal pollinators in many

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 worldwide that began being recorded at the end of the 20th century. Multiple lines of evidence exist for the reduction of wild pollinator populations at the regional level, especially within Europe and North America. Similar findings from studies in South America, China and Japan make it reasonable to suggest that declines are occurring around the globe. The majority of studies focus on bees, particularly

honeybee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...

and

bumblebee A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related genera ...

species, with a smaller number involving hoverflies and lepidopterans. The picture for domesticated pollinator species is less clear. Although the number of managed honey bee colonies in Europe and North America declined by 25% and 59% between 1985-2005 and 1947-2005 respectively, overall global stocks increased due to major hive number increases in countries such as China and Argentina. Nevertheless, in the time managed honeybee hives increased by 45% demand for animal pollinated crops tripled, highlighting the danger of relying on domesticated populations for pollination services. Pollinators participate in the sexual reproduction of many plants by ensuring

cross-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, bird ...

, essential for some species and a major factor in ensuring genetic diversity for others. Since plants are the primary food source for animals, the possible reduction or disappearance of pollinators has been referred to as an "armageddon" by some journalists.

Evidence

The declines in abundance and diversity of insect pollinators over the twentieth century have been documented in highly industrialized regions of the world, particularly northwestern Europe and eastern North America.

Colony collapse disorder Colony collapse disorder (CCD) is an abnormal phenomenon that occurs when the majority of worker bees in a honey bee colony disappear, leaving behind a queen, plenty of food, and a few nurse bees to care for the remaining immature bees. While s ...

has attracted much public attention. According to a 2013 blog the winter losses of beehives had increased in recent years in Europe and the United States, with a hive failure rate up to 50%. A 2017 German study, using 1,500 samples from 63 sites, indicated that the biomass of flying insects in that area had declined by three-quarters in the previous 25 years. One 2009 study stated that while the bee population had increased by 45% over the past 50 years, the amount of crops which use bees had increased by 300%; although there is absolutely no evidence this has caused any problems, the authors propose it might cause "future pollination problems". In mathematical models of the networks linking different plants and their many pollinators, such a network can continue to function very well under increasingly harsh conditions, but when conditions become extremely harsh, the entire network fails simultaneously. A 2021 study described as the "first long-term assessment of global bee decline", which analyzed GBIF-data of over a century, found that the number of bee species declined steeply worldwide after the 1990s, shrinking by a quarter in 2006–2015 compared to before 1990.

Possible explanations

Although the existence of pollinator decline can be difficult to determine, a number of possible reasons for the theoretical concept have been proposed, such as exposure to pathogens, parasites, and pesticides;

habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

;

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

; market forces; intra- and interspecific competition with native and invasive species; and genetic alterations. Honey bees are an invasive species throughout most of the world where they have been introduced, and the constant growth in the amount of these pollinators may possibly cause a decrease in native species. Light pollution has been suggested a number of times as a possible reason for the possible decline in flying insects. One study found that

air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different typ ...

, such as from cars, has been inhibiting the ability of pollinators such as bees and butterflies to find the fragrances of flowers. Pollutants such as

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

, and nitrate radicals bond quickly with volatile scent molecules of flowers, which consequently travel shorter distances intact. Pollinators must thus travel longer distances to find flowers. Pollinators may also face an increased risk of extinction because of

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

due to alterations in the seasonal behaviour of species. Climate change can cause bees to emerge at times in the year when flowering plants were not available.Gosden Emily (29 March 2014
Bees and the crops they pollinate are at risk from climate change, IPCC report to warn
The Daily Telegraph, Retrieved 30 March 2014

Consequences

Seven out of the ten most important crops in the world, in terms of volume, are pollinated by wind (maize, rice and wheat) or have vegetative propagation (banana, sugar cane, potato, beet, and cassava) and thus do not require animal pollinators for food production. Additionally crops such as sugar beet, spinach and onions are self-pollinating and do not require insects. Nonetheless, an estimated 87.5% of the world's flowering plant species are animal-pollinated, and 60% of crop plant species use animal pollinators. This includes the majority of

fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...

s, many

vegetable Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers, fruits, stems, ...

s, and also fodder. According to the USDA 80% of insect crop pollination in the US is due to honey bees. A study which examined how fifteen plant species said to be dependent on animals for pollination would be impacted by pollinator decline, by excluding pollinators from them with domes, found that while most species do not suffer any impacts from decline in terms of reduced fertilization rates (seed set), three species did. The expected direct reduction in total agricultural production in the US in the absence of animal pollination is expected to be 3 to 8%, with smaller impacts on agricultural production diversity. Of all the possible consequences, the most important effect of pollinator decline for humans in Brazil, according to one 2016 study, would be the drop in income from high-value cash crops, and would impact the agricultural sector the most. A 2000 study about the economic effects of the

honey bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...

on US food crops calculated that it helped to produce US$14.6 billion in monetary value. In 2009 another study calculated the worldwide value of the 100 crops that need pollinators at €153 billion (not including production costs). Despite the dire predictions, the theorised decline in pollinators has had no effect on food production, with yields of both animal-pollinated and non-animal-pollinated crops increasing at the same rate, over the period of supposed pollinator decline.

Possible nutritional consequences

A 2015 study looked at the nutritional consequences of pollinator decline. It investigated if four

third world The term "Third World" arose during the Cold War to define countries that remained non-aligned with either NATO or the Warsaw Pact. The United States, Canada, Japan, South Korea, Western European nations and their allies represented the " First ...

populations might in the future potentially be at possible risk of malnutrition, assuming humans did not change their diet or have access to supplements, but concluded that this cannot be reliably predicted. According to their model, the size of the effect that pollinator decline had on a population depends on the local diet, and vitamin A is the most likely nutrient to become deficient, as it is already deficient. More studies also identified vitamin A as the most pollinator-dependent nutrient. Another 2015 study also modeled what would happen should 100% of pollinators die off. In that scenario, 71 million people in low-income countries would become deficient in vitamin A, and the vitamin A intake of 2.2 billion people who are already consuming less than the recommended amount would further decline. Similarly, 173 million people would become deficient in folate, and 1.23 million people would further lessen their intake. Additionally, the global fruit supply would decrease by 22.9%, the global vegetable supply would decrease by 16.3%, and the global supply of nuts and seeds would decrease by 22.1%. This would lead to 1.42 million additional deaths each year from diseases, as well as 27 million disability-adjusted life years. In a less extreme scenario wherein only 50% of pollinators die off, 700,000 additional deaths would occur each year, as well as 13.2 million disability-adjusted years. Melon plant

One study estimated that 70% of dietary vitamin A worldwide is found in crops that are animal pollinated, as well as 55% of

folate Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing an ...

. At present, eating plants which are pollinated by animals is responsible for only 9%, 20%, and 29% of calcium, fluoride, and iron intake, respectively, with most coming from meat and dairy. 74% of all globally produced lipids are found in oils from plants that are animal pollinated, as well as 98% of vitamin C.

Solutions

Several scholars have called for application of the

precautionary principle The precautionary principle (or precautionary approach) is a broad epistemological, philosophical and legal approach to innovations with potential for causing harm when extensive scientific knowledge on the matter is lacking. It emphasizes caut ...

. Efforts are being made to sustain pollinator diversity in agricultural and natural ecosystems by some environmental groups. In 2014 the Obama administration published "the Economic Challenge Posed by Declining Pollinator Populations" fact sheet, which stated that the 2015 budget proposal recommended congress appropriate approximately $50 million for pollinator habitat maintenance and to double the area in the Conservation Reserve Program dedicated to pollinator health, as well as recommending to "increase funding for surveys to determine the impacts on pollinator losses". Some international initiatives highlight the need for public participation and awareness of pollinator conservation. Pollinators and their health have become growing concerns for the public. Around 18 states within America have responded to these concerns by creating legislation to address the issue. According to the

National Conference of State Legislatures The National Conference of State Legislatures (NCSL), established in 1975, is a "nonpartisan public officials’ association composed of sitting state legislators" from the states, territories and commonwealths of the United States. Background ...

, the enacted legislation in those states addresses five specific areas relating to pollinator decline: awareness, research, pesticides, habitat protection and beekeeping. A 2021 global assessment of the drivers of pollinator decline found that "global policy responses should focus on reducing pressure from changes in land cover and configuration, land management and pesticides, as these were considered very important drivers in most regions".

References

External links

Pollinators
U.S. Fish and Wildlife Service, retrieved 31 August 2015
The North America Pollinator Protection Campaign
by the Coevolution Institute US; retrieved 31 August 2015
The Bumblebee Conservation Trust
Great Britain; retrieved 31 August 2015 {{DEFAULTSORT:Pollinator Decline Bee ecology Beekeeping Pollination Environmental issues