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Running Head: EFFECT OF GLOBAL CLIMATE CHANGE ON HONEY BEE

Effect of Global Climate Change on our Natural Pollinators, Specifically Bee’s

Matthew Bettin

Rowan University

In today’s world we are facing an anthropogenic crisis that is having a detrimental effect

on the world’s biodiversity, land production, food surplus, and the pollinators who have

been keeping the machine running for millions of years. As our global average

temperatures continue to rise there is no doubt that there will be negative effects felt by

the populations of our main pollinators, the honey bee. In this paper I attempt to shed

light on what these problems may actually be and the magnitude of this apparent crisis

that is hitting us as humans at this exact moment of time. It may seem like a problem for

future generations, but this paper is to assure you that we are living in a time of crisis

and something must be done in order to sustain the Earth for future generations and a

wealth of biodiversity.

Key words: Biodiversity, pollinators, anthropogenic, global climate change, entomophily

EFFECT OF GLOBAL CLIMATE CHANGE ON HONEY BEE 2

Introduction

The European Honey Bee is an important pollinator for the crops of the world both in the

wild and those that are cultivated by Humans. They have a wide range of habitats while their

behavior seems to be highly affected by the temperature fluctuations of a region. As the

temperature of regions continue to shift it is expected that honey bees will begin to migrate to

foreign areas. This migration would open them up to brand new predators, parasites and diseases

which could in turn have a detrimental effect on the honey bee population (Conte & Navajas,

2008).

The interaction of pollinators with flowering plants increases biodiversity which benefits

the earth as a whole as well as us, as humans, directly (Hegland, Nielson, Lazaro, Bjerknes, &

Totland, 2008). Since there is a mutualistic relationship between plants and pollinators, all the

species above producers on the food pyramid are directly influenced by this relationship. The

pollinators induce plant reproduction, the plants feed the first tier consumers, and first tier

consumers provide food for the second tier consumers, and so on and so forth. This mutualistic

relationship may possibly be altered by the anthropogenic global climate change that had been

taking place since the start of the industrial revolution.

Biodiversity has been hypothesized to have a positive effect on both the function and

variance of that specified function within ecosystems, and multiple studies have been conducted

that have shown support towards this idea. This hypothesis has come to be known as the

biodiversity insurance hypothesis (Bartomeus, Park, Gibbs, Danforth, Lakso, & Winfree, 2013).

That being said, it is important for us to monitor the populations of our pollinators. Specifically


Honey Bees since they promote and boost biodiversity in ecosystems. This leads to not only a

positive effect on the environment, but also our economic industries such as agriculture.

Pollination of Flowering Plants

There are multiple ways in which flowering plants may be pollinated. These include by

wind (anemophily), by pollinators such as birds, bats, mice, and water, or most importantly by

insects (entomophily). Some of the insects that are considered to be pollinators are butterflies,

flies, beetles, and bees. The Bee is thought to be the most efficient in the completion of

pollination within species of plants due to their nature of nectar/pollen collection (O’Toole,

2013, p. 107). Approximately 80 percent of the plant species that are pollinated by insects

(entomophily) are hermaphrodites, in other words they contain both male and female

reproduction organs within the same flower. Although many plants have both reproductive

organs, most species require pollen grains that have been gathered from a different individual of

the same species (O’Toole, 2013, p. 107). Again, due to the bee nature of nectar collection they

venture deep into a flower, as they do this pollen sticks to their furry bodies and then is able to be

transported to other plants through the flight of the bee. This is a process referred to as cross-

pollination (O’Toole, 2013, p. 107). The pollen transport that is induced by the bee populations

ultimately leads to genetic diversity and a stronger ecosystem. Plant species have evolved

multiple functions that have increased the chances that their flowers will be pollinated by bees.

One example of this comes in the form of Evergreen shrubs (Mahonia). They actively move

pollen from their anther (pollen bearing structure) to the head of the bee by closing in when

landed upon (O’Toole, 2013, p. 107). With this slight mutation plants that had this function

increased their fitness thus passing on this trait and therefore evolution occurred over

generations. There are many other examples of morphological traits possessed by species of


flowering plants to increase their rate of pollination, but for the sake of this paper they will not

be discussed in full detail. The importance of the bee pollinators are so great:

The bee- plant mutualism is much more complex and ecologically important than this.

Much of the visual impact of a wide range of habitats is the direct result of the pollination

services of bees, which play keystone roles in the creation and maintenance of habitats

that support a myriad of other species, including our own. (O’Toole, 2013, p. 113)

Without this mutualism there would be massive declination to both of species of flowering plants

and bees who rely so much on one another for survival. This quote is stressing the importance of

the mutualism due to it being the driving force in the sustainability of ecosystems.


Figure 1: This is an image of a European Honey Bee extracting nectar from a flowering plant.

Pollen is attached to its legs in this action. (Photo taken by John Severns)

Honey Bee Economic Value

It can be stated that the European Honey Bee is the most economically valuable

pollinator in the world for agricultural crops. Due to this fact along with many others the

Honey Bee is an extremely important and versatile organism that is used worldwide for

the pollination of crops. In the United States alone it has been estimated that the honey

bee contributes to approximately $117 billion annually in agricultural crops (Conte &

Navajas, p. 500). This high economic value comes due to 35% of all agricultural crops

being dependent on their pollination through the honey bee and another 84% being

related to the activity of the bees. With their contribution to the economy and food

production of the world alone it should be clear that a negative impact to the populations

or behavior of this species would induce a range of major complications to both the

economy and human well-being.


Figure 2: This is a map showing the distribution of the European Honey Bee throughout Europe

and Asia. The bee populations are also found in North America. (Map from Conte & Navajas

“Climate change: impact on honey bee populations and disease”)

Climate Change Effect on Pollinators

Plants have reacted to the anthropogenic increase to global temperatures over the recent

decades by having their onset of flowering occur earlier in the season over the past 20 to 50

years. It is thought that these flowering plants have thermal-sensitive phenologies. This means

that their genetics are such that their flowering is related to the mean temperatures of either the

month that flowering occurs or the months prior to the action of flowering (Hegland, Nielson,

Lazaro, Bjerknes, & Totland, 2008). Those plants species that are pollinated entomophily seem

to be more sensitive to fluctuations in temperature than those that are pollinated anemophily.

The thermal-sensitive relationship between temperature and flowering within species of plants is

not yet fully known. For example, it is not known if this relationship is linear (as the temperature

continues to rise the flowering will occur earlier) or if the relationship will follow some other

sort of change. An example of this can be seen in figure 2 (below).

Figure 3: This is a graph that shows the

linear relationship that has been observed today based on the few available studies of the temperature


increase and its effect on the day of appearance in both flowering plants and pollinators. The slope of the line

represents the magnitude of the effect (steeper slope, more effect on the species). The future responses shows

different possible ways that the species will be altered in the future, the larger the line between pollinators

and plants would lead to a greater decrease in their mutualism (Figure from Hegland et al., 2008).

If the slopes of the lines for plant first appearance and pollinator first appearance were to

veer too far off course this could cause a massive reduction in the amount of pollination possible.

This is due to the fact that these plants have a limited flowering season, and within the time that

they are in bloom they must be germinated in order to reproduce. If pollinators arrive too far

after the first appearance of flowering plants then they will have missed the prime period for

collecting pollen and nectar. Not only would this lead to a reduction in both population and

diversity of plant life, but also a reduction in the population of pollinators due to the lack of food

presence.

Most pollinators are insects; these are small organisms that are considered to be

poikilothermic, meaning that their internal body temperatures vary significantly and is highly

affected by the temperature of the environment in which they are located (Hegland et al., 2008).

Due to their body temperature being so highly variable it is likely that both their life cycle

development and activity patterns will be dependent on the outside temperature:

Butterflies are appealing organisms frequently attracting public attention. As a result,

long-term butterfly monitoring programs exist in several countries and studies based on

such data have document a close positive relationship between first appearance date and

temperature (Roy & Sparks 2000; Forister & Shapiro 2003). Across climatic zone in

Europe, the date of first emergence of butterflies is strongly correlated with temperatures

in the month of, or previous to, appearance (Roy & Sparks 2000; Gordo & Sanz 2006).

(Hegland et al., 2008).


The temperature change that Earth is experiencing now is already beginning to

have an adverse effect on specific populations of butterflies. Due to the high quantity of

studies revolving around Butterflies and their times of appearance it can be theorized and

their first appearance in a season is in direct relationship with the temperatures that an

environment has experienced over a specific period of time. This study specifically

focused on Butterflies, but this could have an overarching reach into all species of

pollinators since they are still all poikilothermic. Roy and Sparks found in 2000 that the

warming period which occurred from 1976 to 1998 lead to an earlier appearance of

Butterflies along with longer flight durations (Hegland et al., 2008). Both of these factors

seem to have an influence on the mutualism that is experienced between pollinators and

plants in healthy environments.

As mentioned previously, it is believed that Bees are the most important

pollinators for both wild and domestic plant growth. A long term study of the Honey Bee

which took place over a time period of over 50 years collected data that shows a direct

relationship between the first appearances of the bee and temperatures of the early Spring

(Hegland et al., 2008). From 2001 to 2007 it has been shown by the Natures Calendar

Project that bumble bees have increased their flight times by approximately 2 weeks in

the spring (Hegland et al., 2008). It is clear that the honey bee’s natural clock is being

altered by the anthropogenic temperature changes that are being experienced by the

Earth. Although this alteration may seem slight now, it is sure to increase as global

temperatures rise perpetually. As the timing of insect appearance and flowering

appearance continue to become more distant there will be negative impacts on both

populations since they are so mutually dependent on one another.


Aforementioned, species interactions are important in maintaining a healthy and

productive ecosystem. With the recent global warming that has been occurring these

interactions have been observed to be mismatched, particularly in the plant-insect

interaction (Schweiger, Biesmeijer, Bommarco, Hickler, Hulme, Klotz, Kuhn, Moora,

Nielsen, Ohlemuller, Petanidou, Potts, Pysek, Stout, Sykes, Tscheulin, Vila, Walther,

Westphal, Winter, Zobel, & Settele, 2010). Climate warming is causing alterations to the

patterns of flowering and flight times, this becomes an issue since the insect and plant

phenology may not respond equally to the environmental cues that are being emitted by

the changing climate. If this is the case then we would see a reduction in interaction

between the pollinators and plants. The system of balance between the mutual interaction

of plants and insects has stood the test of time, through multiple cycles of climatic

change, but this cycle seems to be occurring at a much faster rate than experienced in the

past. With the more rapid change in global temperatures it is not fully known if the

synchronization of the interaction will deviate (Schweiger et al., 2010).

When the mutual interaction that should naturally occur is changed this is known

as mismatches between plants and pollinators. A mismatch could be considered to be

any condition that reduces the amount of time or space that is shared by both plants and

their pollinators which leads to a breakdown of their mutualistic nature. There is two

known ways that they mismatch can be caused and they are through either phenological

or distrubutional alterations (Hegland et al., 2008). The phenological or temporal

changes can be caused in plant species due to how the climate is changing. This change

in temperature, moisture, and weather patterns in general can have an impact on the

natural selection that acts on populations of plants, thus having their populations evolve


unnatural phenotype percentages that would have not been present if not for climate

change. Studies conducted by Memmott:

Simulated how global warming might affect a highly resolved plant-pollinator

network. They found that, depending on the phenological shifts applied, between

17 and 50% of all pollinator species suffer from disruption of food supply due to

temporal mismatch. They showed that specialized pollinators were most likely to

be left with no food plants, but that generalist pollinators could also experience

considerable diet reductions following phenological shifts. The variation across

species in phenological responses to climate warming may also uncouple many

plant-pollinator interactions because the pollinators cannot track all their ancestral

hosts, if some flower earlier and some later (e.g., Menzel et al. 2006; Memmott et

al. 2007). (Hegland et al., 2008).

The temporal shifts that are possible have shown to have a profound effect on the

populations of both pollinators and plants. By disrupting the food supply as the

simulation has shown that this shift has causes it would lead to a reduction in both

populations since the pollinators wouldn’t have as much food available for them to

sustain themselves and the plants themselves will not be able to reproduce at such a high

frequency.

A study conducted by Gordo and Sanz in 2005 found that plants and pollinators

alike both show phenological responses to increased ecosystem temperatures. Their

study was focused in the Iberian Peninsula. Here they found that the herbivorous insects

that they were studying had hastened their activity period to be earlier than that of their


main plant resource (Hegland et al., 2008). In their specific study the pollinators had a

greater phenological shift than the pollinators and this resulted in a temporal mismatch

and less food availability.

In contrast to the study above, Kudo in 2004 conducted an experiment in Japan

that found flowering plants budding earlier than usual when experiencing a warm spring.

During this same time interval the emergence of the bumble bee queens had seem to be

unaffected, leading to less possible plant-pollinator interactions in the populations

(Hegland et al., 2008).

Based on the finding of the two studies previously mentioned it can be denounced

that the mismatches that occur within populations of plants and pollinators are greatly

variable from one to the other (Hegland et al., 2008). . This highlights the fact that us, as

humans, are altering a system that we know little to nothing about and basically there is

no honest predictions that we can create based on the climate change that is being caused

on Earth today.

Buffers

While it has been found that mismatches between pollinators and plants are

created by climate change it has also been found that the relationship between them can

be extremely robust. Many species of pollinators are included in generalist pollination

networks rather than specialized networks. This means that in nature it is rare to find a

one to one relationship, such that one species of pollinator is responsible for pollinating

only one species of plant (Hegland et al., 2008). A specialized network such as this

would be fragile and unsustainable. On the other hand a generalized relationship to


pollination provides both plants and pollinators alike with a figurative safety net. This

tendency may in itself help for species to endure through the mismatches that are

naturally created by climate change (Hegland et al., 2008).

Another buffer that has been naturally set into place by selection is the asymmetry

of pollination interactions. Meaning that plants that are extremely important to the

survival of a species of pollinator (high number of visits occur at this particular plant)

will have a low dependence on that specified pollinator (low percentage of visits to plant

are from that pollinator) (Hegland et al., 2008). These buffers together have been shown

to work in synchronization to help to stabilize the system and make this more adaptable

to species extinction.

Geographic Distribution of Invasive Species

As climate change occurs it will pave the way for both areas of hospitality and

inhospitality for species of Honey Bee. For instance, specific areas that become more

prone to drought due to climate change will be abandoned by bees since they no longer

would be able to survive and thrive. They will migrate to the edges of these areas where

they would eventually be able to find a new environment that better suits their needs

(Conte & Navajas, p. 506). The act of moving from one area to another creates a large

amount of competition between both native and invasive species of bees.

An example of this comes in the form of the Africanized Honey Bee. The

Africanized Honey Bee is an extremely aggressive and invasive species of bee that is able

to out compete the European Honey Bee due to its insusceptibility of a parasite called the

Varroa mite (Conte & Navajas, p. 506). Afranized Honey Bee colonies are not docile or


domestic meaning that they cannot be farmed and cultivated as done with European

colonies. The explosion to their population would decimate agriculture in the United

States by lessening the fertilization ability of farmers. Presently the geographic

distribution of this species ranges from Argentina to the southern part of the United States

(Conte & Navajas, p. 506). However, this distribution has been halted due to the climate

being too cold for their survival in the Northern areas of the United States. As climate

change continues to have an impact on our

environment it is likely that new niches will

open up to this species of bee as the temperature

rises in the north regions (Conte & Navajas, p.

506).

Figure 4: This is a map showing the migration and invasion of the Africanized Honey Bee colonies over the

years. The latest date shown on the map is from 1998; here it was found that the populations have halted

their migration, likely due to climatic factors. (Figure published as Benjamin Cummings from uTexas.edu).


Another invasive species that has a negative effect on the overall population of

honey bees is the Bee-eater. This is a species of bird that are originally inhabitants of the

Mediterranean regions, but again, as the temperature becomes warmer in northern areas

they are able to migrate and thrive in a new area. In present times the Bee-eater has had a

miniscule effect on bee populations, but their distribution has extended slightly north into

France and could possibly have an impact in the future (Conte & Navajas, p. 507).

There are still more invasive species that will prove to be a hazard to the

populations of both honey bees and pollinators as a whole if climate change continues in

the direction that it is. Beekeepers will have to take actions in order to protect their

colonies from these potential risks in the future (Conte & Navajas, p. 506).

Potential of Adaptation

It has been found that the species of honey bees have great variability when it

comes to their ability to adapt to their changing surroundings and different climates. One

specific species that has been found to have a large adaptive capacity is the European

Honey Bee (Conte & Navajas, p. 506). This species can be found most places around the

world and has had a long history interacting with humans. The first populations of

European Honey Bees were brought to the Americas by colonists. Their populations

have therefore been artificially evolved with humans and were able to spread throughout

the continent. This evolution of new phenotypes and adaptations to various climates can

be seen as a positive since their high biodiversity and genetic variability will help in

adaptation to changing climate (Conte & Navajas, p. 506). As previously mentioned

though, the Africanized Honey Bee presents a formidable threat based on competition for


resources as the temperature rises to meet their needs. But, it is feasible to be optimistic

that the European Honey Bee will be able to adapt to the changing climate since again,

their populations have an extremely large phenotype pool which makes adaptation more

likely and a more stable organism.

What can be done?

It is clear that us, as humans, and as stewards in a way to the land in which we

reside have to focus on the task at hand of protecting the populations of our pollinators.

When looking at the honey bee specifically this protection can be gained by investing

resources in education, the eradication of invasive species, and an increase in beekeeping.

Education is always a main factor is dealing with an issue that is having a negative effect

on the world as a whole (Conte & Navajas, p. 507). If enough people are informed on the

facts that we are facing climate change today and we can indeed act to fix it than that’s

when change comes about. As previously stated invasive species are having a large

impact on the populations of pollinators throughout the world, and this impact is ever

increasing as climate change continues to perpetuate the migration of species northward.

There are ways to stop or slow this movement, but it may take a large amount of

resources along with the creation of many jobs. Beekeepers are able to adapt their bee

colonies to the specific climate change of their area through breeding. Since the colony

has an economic impact on the beekeeper themselves they have a reason to protect and


sustain the bees. They can aid their bee populations with the introduction of medicines

and other control methods (Conte & Navajas, p. 507).

An important issue that we will have to face as not only a nation, but as a global

community is getting away from fossil fuels and unstable production of energy. There

are many alternatives to our fossil fueled economy; it’s just a matter of investing in the

technology. By investing in “green energy” we strive towards a brighter tomorrow and

also pursue a future where we keep moving forward as humanity, instead of getting stuck

in a rut.

Conclusion

The survival of the European Honey Bee is important to the survival of Humans,

biodiversity, and our world as a whole. Not only do they have a large impact on our

environments but also our economic stability and agricultural food supply. Although this

species of bee seems to have a wide range of habitats, their behavior has been seen to be

greatly affected by temperature fluctuations that are occurring in their geographic range.

These climate shifts are expected to lead to large migrations of colonies.

Although there are buffers set in place by natural selection over generations

within ecosystems it is yet to be seen if these can withstand the rapid rate of climate

change that is occurring today. The mutualistic relationship that is active between plants

and pollinators may be being altered by our anthropogenic causes of climate change.

We need to understand that we are causing a catastrophic impact on the climate of

the Earth at a rate that has never before been recorded in the history of the Earth. Our


way of life is not sustainable and if we don’t act soon than we will reach a point of no

return.

Works Cited

Bartomeus, I., Park, M. G., Gibbs, J., Danforth, B. N., Lasko, A. N., & Winfree, R. (2013). Biodiversity ensures plant–pollinator phenological synchrony against climate change. Ecology Letters

Hegland, S. J., Nielson, A., Lazaro, A., Bjerknes, A., & Totland, O. (2009). How does climate warming affect plant-pollinator interactions? Ecology Letters, 12(2), 184-195. Retrieved February 9, 2016,

Le Conte, Y., & Navajas, M. (2008). Climate Change: Impact on honey bee populations and diseases. Scientific and Technical Review of the Office International Des Epizooties, 27(2), 499-510. Retrieved February 9, 2016,

O'Toole, C., & Ross, E. S. (n.d.). Bees: A natural history.

Schweiger, O., Biesmeijer, J. C., Bommarco, R., Hickler, T., Hulme, P. E., Klotz, S., . . . Settele, J. (2010, February 23). Multiple stressors on biotic interactions: How climate change and alien species interact to affect pollination. Retrieved February 9, 2016

Severns, J. (Photographer, 2006). European Honey Bee Extract Nectar [Digital image]. Retrieved from (https://commons.wikimedia.org/wiki/File:European_honey_bee_extracts_nectar.jpg)

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