Honey Bee Population: Overview

Introduction

In 2006, beekeepers from apiaries across the United States sounded the alarm about a mysterious honeybee die-off, the first scattered signs of which had begun to emerge two years earlier. Everywhere the pattern was the same: without warning, in a move highly uncharacteristic of normal bee behavior, mature worker bees were abandoning their hives in droves, leaving behind the queen, the immature bees, and listless adult bees who mostly refused to either accept feed or forage for nectar. The worker bees that left the hive simply vanished without a trace; it was assumed that they were dying in fields. The remaining bees were insufficient to sustain the hive. By the end of winter 2006–7, 32 percent of all bee colonies in the United States had been lost, according to the US Department of Agriculture (USDA).

Although large-scale bee losses have been documented in the past, the speed, severity, and geographic scope of the 2006 die-off disturbed scientists. They named the phenomenon “colony collapse disorder,” or CCD, and began scrambling to identify its cause. The urgency of their work stemmed from worries that CCD could potentially spell trouble for the human population. According to a Cornell University study, in the United States the cultivation of $14 billion worth of more than ninety common vegetables, fruits, and nuts depends on pollination by honeybees. Any large-scale disruption of this pollination could ultimately threaten the food supply.

Understanding the Discussion

Apiary: A place where beekeepers, also called apiarists, keep bees and beehives, often for the purpose of producing honey and increasingly for pollinating crops as well. The term is derived from the Latin word apis (bee).

Bee Colony: A social unit consisting of worker bees, drones, a queen, and immature bees living together in a hive or other shelter. A colony may consist of as many as twenty thousand bees in the winter and sixty thousand bees in the summer. Many commercial beekeepers maintain thousands of colonies.

Colony Collapse Disorder (CCD): A disorder characterized by the mass abandonment of hives by worker bees, who presumably then die off, leaving behind only a queen, immature bees, and a small number of listless adult bees. The die-off generally occurs within a time frame of one to three weeks, leaving no accumulation of dead worker bees either in the hive or near its entrance.

Israeli Acute Paralysis Virus (IAPV): A honeybee virus identified in 2002 by an Israeli plant virologist. Bees afflicted by the virus typically display neurological symptoms, such as shivering wings and paralysis, before dying.

Pollination: The process of transferring pollen from one plant to another, thus making plant reproduction possible. Honeybees indirectly pollinate crops and trees in the course of feeding themselves. When bees gather nectar from flowers, the pollen sticks to their bodies, then rubs off on other flowers that the bee comes in contact with. In the United States, commercial migratory beekeepers travel cross-country to provide pollination services to farmers.

Worker Bees: Sterile female honeybees that carry out all the tasks necessary for a bee colony’s survival, with the exception of egg laying. One of their most important functions is to pollinate flowers.

History

Honeybees were first introduced to the United States from Europe in the early seventeenth century by some of the earliest settlers. American apiarists have periodically recorded large die-offs of their honeybee colonies since the nineteenth century. Heavy losses were reported in 1869, 1891, 1896, 1915, and 1917, as well as sporadically throughout the 1970s. Over the decades, beekeepers and scientists have assigned a variety of names to the affliction, such as autumn collapse, May disease, spring dwindle, disappearing disease, and fall dwindle disease, and blamed a wide variety of causes, among them microorganisms, inadequate pollen, excessive pollen, toxic honey or nectar, pesticide contamination, severe weather conditions, and pest infestations.

In 1984, the arrival of a new parasite, the tracheal mite, began to devastate both wild and commercial honeybees throughout the United States. In 1987, American beekeepers experienced some of their heaviest losses on record when a second newly arrived parasitic mite, the aptly named Varroa destructor, spread quickly from a honeybee colony in Wisconsin to bee stocks across the nation. The tiny, vampiric mites deliver a double blow to bee populations: not only do they have a taste for honeybee blood, but in the act of biting, they also create open wounds and transmit to bees devastating viruses that can lead to deformed wings and acute paralysis. Within seven years of the varroa mite’s appearance, all but 2 percent of feral, or wild, honeybees throughout the United States had disappeared, and the number of colonies managed by commercial apiarists had declined by half.

After another round of heavy bee losses in the mid-1990s, researchers invoked the usual list of suspected causes. They also began to consider two additional culprits: poor bee-colony management practices and breeding-induced genetic weaknesses. Honeybees, some scientists speculated, had never been given the opportunity to evolve a natural resistance to the deadly varroa mite. A vicious cycle was born: under pressure from the agricultural industry to deliver an ever-increasing volume of pollination services, commercial beekeepers relied on ever-more-potent doses of pesticides and antibiotics to keep their bees free of the effects of increasingly pesticide- and antibiotics-resistant pests and microbes.

The keepers also turned to intensive selective breeding designed to enhance the bees’ most lucrative trait: their ability to pollinate. However, the artificially narrowed gene pool also reduced the overall hardiness of the bees. When scientists completed sequencing the honeybee genome in 2006, they discovered that in comparison with other insects, honeybees possess more genes related to scent detection and nectar and pollen processing—the precise characteristic that has made honeybees the preferred species for large-scale agricultural pollination. However, honeybees also have relatively fewer genes for the production of autoimmune defenses or the clearing of systemic toxins—only half as many as the common fruit fly or the mosquito, for example—which accounts for their reduced ability to fight off disease.

Commercial beehive-management practices created conditions that substantially worsened this artificially induced vulnerability to pathogens and toxins. Each year, commercial apiarists, in search of pollination contracts, transport billions of bees across the United States. Dozens of commercial hives, each roughly the size of a small stove and containing between fifteen thousand and thirty thousand honeybees, are stacked in large trucks for months at a time. Some researchers believe that the physical stress of this unnatural confinement further degrades the bees’ already-weakened immune systems. They also theorize that the inability of ailing, confined bees to remove themselves from the colony—as normally occurs in the wild, where sick bees almost never die in the hive—ensures the rapid circulation of diseases among captive, closely quartered populations.

The definitive cause of CCD continues to elude researchers. Many scientists believe that some type of pathogen is most likely responsible for the latest round of devastation. Bolstering this theory are experiments that have shown that bees will refuse to recolonize an empty hive whose previous inhabitants have been wiped out by CCD. They will, however, unhesitatingly take over such a hive after it is sterilized via irradiation, a process that removes all traces of any lingering infectious agents.

The completion of the decoding of the honeybee genome in 2006 enabled researchers to recognize and screen out any bee-related genetic material and search for alien genetic material that would indicate the presence of a pathogen in infected bees. Thanks to these advances in genetic knowledge and sequencing tools, in 2007, a team of scientists found what may be an important piece of the puzzle. In this study, reported in the journal Science, the researchers identified a striking association between CCD-devastated colonies and the Israeli acute paralysis virus (IAPV), which is commonly carried by Australian honeybees. When the scientists compared the genetic sequences of bees from thirty American colonies that had succumbed to CCD with the sequences of bees from twenty-one healthy colonies, they discovered that the IAPV virus was present in the genetic material of more than 96 percent of the sick bees.

Noting that CCD first emerged in 2004—the same year American apiarists began large-scale importation of Australian bees, who suffer no ill effects from being carriers—the researchers have argued that the virus is likely one of a constellation of factors driving the spread of CCD. This idea remains controversial, however; other studies of CCD-affected hives found no evidence of IAPV prevalence, and Australia itself has experienced no incidence of CCD. Many scientists, including the USDA’s Agricultural Research Service, believe that rather than a single disease being at fault, CCD may be the result of an overall increase in the total load of several different honeybee pathogens, IAPV being just one of many.

Another suspected contributor is Nosema apis (and other members of the Nosema genus), a parasitic fungus that mainly affects worker bees during or after bad winters. Nosema, as well as deformed wing virus, also appears to be infecting bumblebee populations, according to a 2014 Nature study by M. A. Fürst et al. This suggests that honeybees may be transmitting contagious conditions to the wild population as well—a trend that indicates CCD may not be confined to commercial honeybees but wild bees as well. More than four thousand wild bee species inhabit the United States. However, it is difficult to assess the health of wild populations.

Research published in Nature in May 2015 pointed to the addictiveness and neurological impacts of neonicotinoids, a class of insecticide commonly used to protect crop plants, as another potential culprit in bee deaths. Sébastien Kessler and his colleagues found that neonicotinoids were tasteless to bees but changed neural patterns such that bees chose to frequent plants with neonicotinoids more often than those without. Kessler et al. argued that this meant the bees could not control or prevent their exposure to the pesticides.

Still other research suggests CCD is caused not by any single factor but rather by multiple factors. A study by Dave Goulson et al., published in the March 2015 issue of Science, hypothesized the cause to be the combination of neonicotinoid exposure, varroa mite infestation (which may itself be exacerbated by neonicotinoids increasing the bees' susceptibility to the mite), and the single-crop diet to which commercial honeybees are subject as they are rotated from one industrial farm to the next. These findings support the view that pesticides must be reduced and that large-scale agribusiness, with its plant monoculture, is harmful to the environment. In another study released that same month in Proceedings of the National Academy of Sciences, Clint J. Perry and his colleagues found that under stress, immature worker bees that leave the hive early to forage are cannot collect as much nectar, are more likely to die while foraging, and may cause colony collapse as the population of workers declines.

As research continues, growers are searching for alternative pollination methods. Researchers are trying to breed specialized traits into other insects, such as the blue orchard bee, so that farmers will no longer have to rely almost exclusively on honeybees to pollinate their crops. However, skeptics argue that without the implementation of meaningful apiary management reform, such measures will ultimately prove futile. According to this view, it is essential for beekeepers to increase honeybee genetic diversity and to limit the geographic scope of their pollination contracts. Both moves could cut significantly into beekeeping profit margins. Critics warn that without such changes, it will only be a matter of time before any newly domesticated pollinating species fall prey to the same cycle of problems currently decimating the American honeybee population.

By 2014, the number of beehives had reached 2.7 million, a twenty-year record, though more than 40 percent of colonies were lost between 2014 and 2015. Data from the nonprofit Bee Informed Partnership show that for the year 2017–18, US beekeepers lost over 700,000 colonies to all causes, and the loss rates varied by state, ranging from 23 percent in Colorado to 78 percent in Arizona. Indeed, despite the prevalence of CCD, beekeepers have been able to continue breeding their remaining bees, through tactics such as re-queening or splitting the hive. This has convinced some that the danger of CCD is not the extinction of the honeybee but that of the commercial beekeeper, as costs associated with lost colonies become too much to bear and younger generations choose other occupations.

In 2014 President Barack Obama called for government agencies to develop and implement protections for bees, monarch butterflies, and other pollinators. Critics pointed out that neither the USDA nor the Environmental Protection Agency (EPA) had cited the role of pesticides in bee declines. However, in January 2016, in a preliminary risk assessment, the EPA found that at least one neonicotinoid pesticide, known as imidacloprid, does in fact pose a threat to bees when used on certain types of crops, such as cotton and citrus. Preliminary risk assessments for three other neonicotinoids, clothianidin, thiamethoxam, and dinotefuran, were released in January 2017. The EPA asserted that they too were dangerous only when sprayed on certain crops. Some scientists have questioned the government's methods in making those determinations, while pesticide manufacturers have felt vindicated.

In August 2016, the governor of Minnesota issued an executive order banning farmers from spraying neonicotinoids unless they can demonstrate it is necessary to prevent "an imminent threat of significant crop loss"—the broadest state restriction passed to date. That same year, the Maryland legislature passed a bill that banned all consumer use of neonicotinoids, although it still allowed usage by farmers, veterinarians, and certified pesticide applicators. The law became the first in the country to ban that class of pesticides and took effect on January 1, 2018.

In September 2016, news that seven species of bees had been added to the US endangered species list for the first time raised concerns among the public that the honeybee population was still in trouble. However, the seven species were yellow-faced bees native to Hawaii, members of the Hylaeus genus rather than Apis, the genus to which all honeybee species belong. While the threat of disappearing honeybees had received significant publicity, scientists were concerned that the plight of wild bees, such as the yellow-faced bees, had not received sufficient attention because fewer species of wild bees engage in crop pollination. Scientists and conservationists alike heralded the bees' addition to the list, and the attendant protections it will provide, as good news for the species in question.

Further research and theories on why bees continue to weaken, die, or disappear continue to proliferate. Preliminary research from the University of Texas, published in a 2018 PNAS article, suggested that the commonly used pesticide glyphosate may harm bees' immune systems. The maker of the glyphosate product RoundUp disputed that claim. Other research has pointed to climate change shifting the timing of bloom and shrinking wildflower habitat as crop production expands. Still other investigators are looking into parasites' effects.

Honeybee Population Today

By 2023, the EPA reported that CCD had declined substantially between the 2006–7 and 2014–15, and suggested that it no longer posed a major long-term threat to honey bees. The agency also noted that bee colony collapses were not necessarily attributable to CCD, and stated that some acute pesticide poisoning incidents had been mischaracterized by the media as being related to CCD.

At the same time, the debate shifted its focus away from CCD's impact on honey bees to a broader consideration of how best to protect bees and other pollinators, biodiversity, ecosystems, and agriculture. While some advocates remained focused on protecting honey bee populations, others argued that more efforts should be made to protect native bee species and their habitats, citing their superior efficiency as pollinators of both native plants and essential crops as well as the competition for pollen and nectar that native bees face from honey bees.

These essays and any opinions, information or representations contained therein are the creation of the particular author and do not necessarily reflect the opinion of EBSCO Information Services.

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