Pollinator decline
Pollinator decline is the reduction in abundance of
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.[13][14][15] 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.[15]
Pollinators participate in the sexual reproduction of many plants by ensuring
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.[16][17][18]
Colony collapse disorder 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%.[19]
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.[20] 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".[21]
In mathematical models of the networks linking different plants and their many pollinators,[22] such a network can continue to function very well under increasingly harsh conditions, but when conditions become extremely harsh, the entire network fails simultaneously.[23]
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.[24][25]
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; climate change; market forces; intra- and interspecific competition with native and invasive species; and genetic alterations.[26][27]
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.
Pollinators may also face an increased risk of extinction because of
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.[34] Additionally crops such as sugar beet, spinach and onions are self-pollinating and do not require insects.[35] Nonetheless, an estimated 87.5% of the world's flowering plant species are animal-pollinated,[36] and 60% of crop plant species[37] use animal pollinators. This includes the majority of fruits, many vegetables, and also fodder.[38] According to the USDA 80% of insect crop pollination in the US is due to honey bees.[39]
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.[40]
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.[41] 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.[34] A 2000 study about the economic effects of the honey bee on US food crops calculated that it helped to produce US$14.6 billion in monetary value.[42] In 2009 another study calculated the worldwide value of the 100 crops that need pollinators at €153 billion (not including production costs).[43] 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.[44]
Possible nutritional consequences
A 2015 study looked at the nutritional consequences of pollinator decline. It investigated if four
More studies also identified vitamin A as the most pollinator-dependent nutrient.[46][47] 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.[48]
One study estimated that 70% of dietary vitamin A worldwide is found in crops that are animal pollinated, as well as 55% of folate. 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.[47]
Solutions
Several scholars have called for application of the precautionary principle.[27][49]
Efforts are being made to sustain pollinator diversity in agricultural and natural ecosystems by some
Some international initiatives highlight the need for public participation and awareness of pollinator conservation.[52] 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 enacted legislation in those states addresses five specific areas relating to pollinator decline: awareness, research, pesticides, habitat protection and beekeeping.[53]
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".[54]
See also
- Bees and toxic chemicals, Pesticide toxicity to bees
- Biodiversity loss
- Defaunation
- Insect biodiversity
- Decline in insect populations
References
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It is difficult to determine whether North American pollinator species are declining, and no less challenging is determining the causes of putative declines or local extirpations. Many explanations have been invoked to account for declines in pollinator populations in North America, including, among others, exposure to pathogens, parasites, and pesticides; habitat fragmentation and loss; climate change; market forces; intra- and inter-specific competition with native and invasive species; and genetic alterations. Careful evaluation of the literature allows some causes to be assigned, but explanations are ambiguous or elusive for other species losses. ... The best evidence of specific pollinator decline is seen in the western honey bee, Apis mellifera L., the primary commercial pollinator of agricultural crops in North America and the most widely used, actively managed pollinator in the world. The population losses among honey bees are elucidated in a large body of literature...
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[To] know whether or not a wholesale decline in flying pollinators ... is occurring across the world is very difficult, due to an insufficiency of geographically widespread and long-term data. Bees, as the best documented species, can be seen to be suffering from chronic exposure to a range of stressors, which include: a loss of abundance and diversity of flowers, and a decline in suitable habitat for them to build nests; long-term exposure to agrochemicals, including pesticides such as neonicotinoids; and infection by parasites and pathogens, many inadvertently spread by the actions of humans. [Climate] change may impact further on particular pollinators... Moreover, the co-operative element of various different stress factors should be noted; thus, for example, exposure to pesticides is known to diminish detoxification mechanisms and also immune responses, hence lowering the resistance of bees to parasitic infections. [For] wild non-bee insects – principally moths and butterflies – where data are available, the picture is also one of significant population losses. Alarmingly, a recent study in Germany indicated that a decline in the biomass of flying insects had occurred by 76% in less than three decades, as sampled in nature reserves across the country. Accordingly, to fully answer the question ... 'pollinator decline - an ecological calamity in the making?' will require many more detailed, more geographically encompassing, more species-inclusive, and longer-term studies, but the available evidence points to a clear 'probably', and the precautionary principle would suggest this is not a prospect we can afford to ignore.
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Environmentalists hailed a 'victory for bees' today after the European Union voted for a ban on the nerve-agent pesticides blamed for the dramatic decline global bee populations. ... Dr Lynn Dicks, a research associate at the University of Cambridge, said that despite the contradictory studies, the EU was right to err on the side of caution. 'This is a victory for the precautionary principle, which is supposed to underlie environmental regulation,' she said.
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Further reading
- Pollination, the Forgotten Agricultural Input, Malcolm Sanford, Proceedings of the Florida Agricultural Conference and Trade Show, Lakeland, FL, September 29–30, 1998, J. Ferguson, et al. eds., pp. 45–47.
- The International Initiative for the Conservation and Sustainable use of Pollinators: A proposal for a plan of action Convention on biological diversity, Montreal, 12–16 November 2001,
- Pollinator biodiversity a co-ordinated global approach, Eardley, C. 2001. Acta Hort. (ISHS) 561:331-332(FAO) VIII International Symposium on Pollination; Pollination: Integrator of Crops and Native Plant Systems
- The Economic Impacts of Pollinator Declines: An Approach to Assessing the Consequences, Peter G. Kevan and Truman P. Phillips, Conservation Ecologyv.5, i.1 June 2001
- Brazilian Pollinators Initiative, Vera Lucia Imperatriz Fonseca; Braulio Ferreira Souza Dias, accessed March 2004
External links
- Pollinators U.S. Fish and Wildlife Service, retrieved 31 August 2015
- The North America Pollinator Protection Campaign by the Coevolution InstituteUS; retrieved 31 August 2015
- The Bumblebee Conservation Trust Great Britain; retrieved 31 August 2015