Understanding the Buzz on Honey Bee Population Decline

Arianna Wills [NRC Wildlife] Emily Mann [Pre-Veterinary Science] Valovia Costa [Environmental Science]

Understanding the Buzz on Honey Bee Population Decline

      In the 1940s the pesticide DDT was developed and used with great success to combat deadly insect borne diseases like malaria and typhus. DDT was sprayed on everything, including: crops, livestock farms, lakes, parks, homes, and gardens (Environmental Protection Agency, 2015). It was relatively cheap, extremely effective, and began to be used around the globe. However, in the 1960s, evidence showed that DDT was having unforeseen environmental consequences (EPA, 2015). DDT proved toxic to nontarget species, like birds and fish because this chemical does not break down naturally in the environment and accumulates in the fatty tissues of wildlife (EPA, 2015). DDT began to significantly impact bald eagles because they ate contaminated fish and this chemical began building up in the birds (U.S. Fish & Wildlife, 2007). DDT interfered with the eagles ability to produce proper eggshells, so the eggs were crushed during incubation or otherwise simply never hatched (U.S. Fish & Wildlife, 2007). The bald eagle population crashed (U.S. Fish & Wildlife, 2007). Once the Environmental Protection Agency banned the use of DDT in the U.S., bald eagle populations slowly began to bounce back (U.S. Fish & Wildlife, 2007). Impressively, the ban lead to the removal of the bald eagles from the endangered species list (U.S. Fish & Wildlife, 2007). The environmental repercussions of DDT were realized and caught in time to save bald eagles from extinction.

      Now, a similar threat is faced by an even more important species: the honey bee. In the spring of 2007, commercial beekeepers, who loan their bees out to help farmers pollinate their crops, began to see more and more cases of what became known as colony collapse disorder (CCD) (Turner, 2014). Beekeepers were discovering hives that were completely abandoned by worker bees, leaving only immature bees and the queen bee (EPA, 2016a). Some bees are found dead near the colony but most die far enough away from the hive that they are never seen again (EPA, 2016a). A hive cannot sustain itself without worker bees and their absence eventually leads to the death of the entire hive (EPA, 2016a). There is substantial evidence linking colony collapse disorder and the use of common pesticides.

Research shows that the widespread use of neonicotinoid based pesticides are, partially, at fault for colony collapse disorder. Once applied, neonicotinoids are absorbed by the plant and the plant itself becomes poisonous for potential pests as the toxin spreads to the roots, leaves, stems, and pollen (BBC, 2013). Neonicotinoids are much more toxic to invertebrates, such as insects, than they are to mammals, birds and other higher organisms, which makes them very popular among farmers concerning pest control (BBC, 2013). As neonicotinoid spread through the plant into the pollen, they pose a threat to pollinators such as honeybees (BBC, 2013).  Exposure to neonicotinoids may not directly kill honeybees, however exposure may work synergistically with other factors such as habitat loss and parasitic infections, leading to widespread population decline. Colony collapse disorder is a serious threat to honey bee populations and precautionary measures need to be taken in order preserve this economically and ecologically important species.

Honey bees are an essential part of the agricultural economy and provide pollination services around the world. Honeybees are a crucial pollinator for a wide range of crops such as fruits, vegetables and nuts which are all essential for a diverse, flavourful and nutritious diet (Agriculture Research Service, 2015). In particular, almond crops rely fully on honeybee pollination in order to produce nuts. In California, the almond industry demands the use of 1.4 million honeybee colonies, which is about 60 percent of all managed honeybee colonies in the United States (Agriculture Research Service, 2015). USDA Agriculture Secretary, Tom Vilsack, stated that more than 130 fruits and vegetables that make up a nutritious diet are pollinated by honeybees (Hagopian, 2016). Commercial bees are responsible for pollination of an estimated 80 percent of all food crops in the United States (Hagopian, 2016). To put this all in perspective, every third bite of food we eat comes as the result of bees and other pollinators (Hagopian, 2016).

The dramatic honey bee decline is an enormous problem affecting not only farmers but also consumers and companies worldwide. Honey bee population decline around the globe is at an all time high. In the last five years, over 30 percent of the national bee population vanished and nearly a third of all the bee colonies in the U.S. collapsed (Hagopian, 2016, para. 5). The normal annual loss of honeybee colonies is approximately 10 percent each year but has now increased to over 30 percent in the past few years, with some beekeepers seeing a dramatic 80 percent population loss annually (Turner, 2014, “Colony Collapse Disorder Takes Hold”). Colony collapse disorder is a serious problem that has detrimental consequences to our food supply and economy. With so much at stake, there has been a mad scramble to try and figure out what is causing CCD. The majority of scientific research agrees that habitat loss, neonicotinoid based pesticides, and parasites are working together to cause CCD events and honey bee decline.

In particular, habitat loss is a major component of colony collapse disorder. As open land such as natural grassland, meadows, and forest edges, are developed the bees lose crucial food supply. Not only does this mean the bees must fly further from the hive to find food, but less available food leads to nutritional stress. Bees that must fly further from the hive on less energy are less likely to make it back to the hives, especially if they are also fighting a parasite. Studies show that there is a correlation between the number of colonies lost and the open land cover. This means that states with the most open land report the fewest cases of colony collapse disorder and states with the least amount of open land experienced the greatest number of cases (Naug 2009). This correlation also held true for honey production; states with more open land show higher honey yields (Naug 2009). In short, more habitat means more bees and more honey. However, it is not enough to simply acquire open land, the type of open land matters too. Colonies near farmland, especially those planting monoculture crops, and livestock pasture contained less protein in their food stores, while colonies near grassland and forests consisted of much higher levels of protein (Donkersley, Rhodes, Pickup, Jones, & Wilson. 2014). A food store with high nutrition is key, especially for overwintering survival. The study found that there was significant correlation between nutrition in the food stores and the type of plant species accessible to the honey bees (Donkersley et al., 2014). Nutritional stress can lead to immune system deficiency in the bees, the same way eating poorly affects our immune systems. Bees with lowered immune systems are more likely to catch a parasite which combined with nutritional stress can make them less likely to return to the hive.  It should come as no surprise that bees with access to a wider range of habitat with a higher nutritional value are healthier than bees exposed to a limited amount of habitat with a limited variety of low nutrition plants. Unhealthy bees have a tougher time fighting off parasites and other pathogens which can in turn lead to a greater number of colony collapse events. It is extremely important that a wide variety of flowering plants close to the hive are accessible to the bees in order to maintain proper nutrition throughout the year. The bees can fight off most parasites with a healthy immune system but when weakened by poor nutrition the bees become more susceptible and are more likely to succumb to a parasite.

Along with habitat loss, studies also linked exposure to pesticides to immune deficiency in honey bees. Neonicotinoids are a widely used agricultural pesticide that are linked to colony collapse disorder. Bees exposed to neonicotinoids, even at levels known to not cause effects on the lifespan or foraging ability of adult bees, are more likely to become infected with gut parasites such as Nosema apis and Nosema ceranae (Pettis, Dively, Johnson, and van Engelsdorp 2012). Neonicotinoids are indirectly lethal. They subvert the bees’ immune system and make them more susceptible to the gut parasites which in turn makes the bees even more weak (Pettis et al., 2012). Furthermore, parasites such as Nosema ceranae are known to cause a decrease in the normal functioning of the immune system of infected bees (Farooqui, 2013), which creates a cyclical pattern of weakened immune system defense and disease. Honey bees weakened by parasites become too weak to return to their colony after a foraging trip (Farooqui, 2013).

Specifically the parasite Nosema, places a substantial energy demand on the bees leading to increased hunger and foraging frequency (Mayack and Dhruba, 2008). Since honey bees are social insects, foraging rates are determined by the colony’s energy demand and the honeybee’s individual hunger (Mayack and Dhruba, 2008). Infected honey bees show increased foraging rates compared to uninfected honey bees because they acquire an overall higher energy demand (Mayack and Dhruba, 2008). Infected honey bees demand higher metabolic needs that cannot be met without habitat availability. The parasites combined with habitat loss create greater nutritional stress. Longer and more frequent trips from the hive also reduce the likelihood of the bees returning to their colony. The honey bees are required to forage more frequently and for longer periods of time because of the scarcity of nutritional plant species caused by habitat loss.

Not only does habitat matter but the quality of the habitat matters because not all plant species provide the same amount of nutrition. Therefore, the availability of a vast variety of plant species is key to the nutritional health of honeybees (Donkersley et al., 2014). Honey bee friendly plants would include a variety of native flowering trees, shrubs and wildflowers that bloom throughout the year (Moisset & Buchmann, 2011). When coupled with habitat loss and the increasing scarcity of viable resources, returning and survival rates of infected bees decreases as trips became longer and more frequent.

Individually, habitat loss, pesticide exposure, and parasites would not cause massive decline in honey bee populations. Working together habitat loss, pesticide exposure, and parasites create a vicious cycle and heavily impact the bees. Each cause feeds into the next resulting in huge impacts. Habitat loss and pesticide exposure both weaken the bee’s immune system which makes them more susceptible to parasites which makes them even more hungry and even more weak until inevitably they perish.

Bees are dying at unprecedented rates and one way to halt the problem is to ban the use of neonicotinoids. The majority of scientific research found a relationship between the use of neonicotinoids and their adverse effects on bees. Furthermore, recent findings show that neonicotinoids may adversely affect birds, aquatic invertebrates, and other insects (European Environment Agency, 2013). As with DDT we are finding that neonicotinoids have a broader range of environmental impacts than previously thought.

The European Commission banned the use of three neonicotinoids that posed the highest risk in 2013 (European Environment Agency, 2013). The ban prevents the use of the three neonicotinoids on crops that are attractive to bees, prohibits seeds to be treated with the neonicotinoids, and outright bans all neonicotinoids from the hands of amatuer growers in the United Kingdom (BBC, 2013). France, Germany, Italy and Slovenia have all set restrictions on the use of neonicotinoid pesticides (BBC, 2013). All of these countries found correlations between the use of the neonicotinoid pesticides and honey bee decline. While scientists cannot say with complete and definite certainty that neonicotinoid pesticides are killing all the honeybees, significant scientific evidence indicates that the pesticides are at least part of the problem. These countries decided to take a precautionary approach to the situation in order to avoid the possibility of an irreversible disaster.

Here in the United States, the Oregon Department of Agriculture (ODA) banned the use of neonicotinoids on all species of Linden tree, a favorite of honey bees, in 2015 (Oregon Department of Agriculture, 2015). The ODA states that the ban was implemented to protect pollinators, specifically mentioning honey bees as an area of concern (Oregon Department of Agriculture, 2015). This ban is very selective, only preventing a specific species of tree from being sprayed with the pesticide. However, the ODA sets a precedent by acknowledging the adverse effects of the pesticide and issuing a ban at the state level.

The United States should follow the examples set by other countries and the state of Oregon, and take a precautionary approach toward the use of neonicotinoid based pesticides. The evidence shows that neonicotinoids are having negative effects on the bees and there are other possible consequences to using the pesticides. We should learn from the precedent set by the use and eventual ban of the pesticide DDT and federally ban the use of neonicotinoid pesticides.


Even though scientists have evidence of honey bee population decline, the general public is still skeptical (Debate.org, 2016). Some people believe that if we discontinue the use of pesticides to not kill the bees, then it will affect farmers and pests will destroy their crops (Debate.org, 2016). Neonicotinoids are popular and widely used but they are not the only pesticides on the market. One set of pesticides that could be used instead of neonicotinoids are Bacillus thuringiensis (Bt) based pesticides (National Pesticide Information Center, 2015). Bt containing pesticides are used on crops and ornamental plants to make toxins that target insect larvae when ingested by the insect (National Pesticide Information Center, 2015). There are multiple strains of Bt, each one being specific to the target insect such as caterpillars, beetles, mosquitoes, black flies and moths (National Pesticide Information Center, 2015). Bt based pesticides are proven to be safer for honey bees and humans alike (National Pesticide Information Center, 2015).

Other possible alternative pesticides to neonicotinoids are biopesticides. Biopesticides are based on naturally occurring substances like pheramones or plant extracts, or involve the use of microorganisms, or plants that are genetically altered to resist pests (EPA, 2016b). Biopesticides are less toxic than conventional commercial pesticides, they do not build up in the environment, they decompose quickly, and they only affect the target species (EPA, 2016b).

Along with the availability of an alternative pesticides, the U.N. Food and Agriculture Organization stated that honey bees pollinate a shocking 71 percent of the world’s most widely-consumed crops (Valentine, 2013, para. 5). Honey bee decline is more of a concern for farmers than using an alternate pesticide since without honey bees there won’t be very many crops left to farm.

Honey bees are necessary for the pollination of about 70-80 percent of the world’s most widely used crops (National Resources Defense Council, 2011). However, the honey bee population has considerably declined in the last half decade (Hagopian, 2016, para. 5). There are three major causes for the dramatic honey bee population decrease: as more open land is developed, and more infrastructure is built, honey bee habitats are destroyed which results in a severely diminished food supply (Naug 2009). Also, as honey bees are exposed to the neonicotinoids farmers spray on their crops, they lose their ability to fight off deadly parasites that render them physically unable to return to their colonies (Farooqui, 2013). These parasites force the honey bees into a much higher energy demand than normal honey bees, increasing the foraging frequency(Mayack and Dhruba, 2008). So, as pesticides cause the honey bees to be more susceptible to parasites, who ultimately increase their necessary food intake, habitat loss restricts them from acquiring the nutrients they need and they end up dying (Mayack and Dhruba, 2008). Our solution to ban neonicotinoids is very similar to the ban on DDT that was set to regrow the eagle population. We propose that the ban of neonicotinoids will help rebuild honey bee populations by safeguarding their immune system while lowering the bees susceptibility to parasites and making them able to forage efficiently. Humans need to pursue this problem with the same intensity they did with the eagles, because while the honey bee may not be as majestic as the eagle, they are crucial to our survival.


























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