Think back on a hot summer day when you’re laughing and having a good time with some friends at a cook out by the pool. Suddenly, after hearing a feint buzzing sound in your ear and you find yourself writhing in pain and your fun in the sun is ruined. Because of times like this, a typical observer would probably think of bumble bees as little other than a nuisance or pest. A more typical opinion would probably be to wish they did not exist. However, if you wish this you probably never took into consideration the consequences of their disappearance, or knew these consequences could be quite severe. Bumble bees are so commonly found in the world that nearly all of us take their existence for granted.
Could you imagine an increase in world hunger due to scarcity of food? What if the price of agricultural resources, like food or cotton, doubled? What if the last pair of sneakers you bought cost $160 instead of $80? Without worldwide pollinators such as bumble bees, all of these things could happen. Bumble bees make great contributions to the environment and play a vital role in increasing the efficiency of pollen transfer in million dollar crops, such as tomatoes and berries. These little creatures help our nation agriculturally, economically, and environmentally. Unfortunately, there have been observations that reveal the bumble bee population in North America is slowly decreasing.
In the article “Patterns of widespread decline in North American bumble bees,” scientists came up with two possible reasons for the decrease of bumble bees. One factor is Nosema bombi, a parasite which lives inside cells. This parasite is found commonly in bumble bees and is a pathogen, which is an infectious germ. Scientists investigated the relationship between patterns in population decline and levels of infection. They examined 6,708 specimens for presence of parasites and found a significantly higher amount of N. bombi in the fast declining species of bumble bees. The trend for other slower declining species was less strong. However, there is still additional need to study other known bumble bee infections and possible viruses that could contribute to the observed species that are decreasing in numbers.
The other factor that affects the decline of bumble bees is lower range-wide genetics caused by inbreeding between smaller populations. The study of the two types of bumble bees B. occidentalis and B. pensylvanicusshows that they may typically live in smaller colonies than other species that live together, which could play a role in declining population. Since these two types of bumble bees have small populations, there is a higher chance of inbreeding and genetic drift, both of which make the bumble bees more vulnerable to infectious agents like N. bombi. Genetic drift means a random change in allele frequencies that can lead to loss of genetic diversity. An easy way to understand this concept is to pretend alleles are last names. If a family had the last name Brown and everyone in the family had daughters, none of their children would have the last name Brown. Therefore, this last name would be gone in this family. Genetic drifts are more likely to happen in small populations. It may be easier for bumble bees from small colonies to lose the genes that help them resist these parasites.
Although there have been observations of declining bumble bee populations, there is not concrete evidence to support that this is truly happening. Due to survey protocols and limited geographic scope of studies, scientists can only obtain limited sampling and cannot draw conclusions about the general population of bumble bees. For example, you want to determine whether or not all the oranges on an island are juicy and sweet, but the master of the tribe living on the island only allows you to take sample oranges from the trees on the northeast side. The northeast side happens to be the side with the least sun and water; therefore the oranges in this area will most likely be less sweet than the oranges on the rest of the island. These sample oranges will not be able to represent all the oranges on the island. In relation to bumble bees, limited sampling of the bumble bees may cause skewed results.
In order to overcome the problem of limited sampling and test the validity of the declining of bumble bee population, scientists compared historical collection records with those from current field surveys from 2007 to 2009. It is found that the species of bumble bees are less abundant across the nation than they used to be. As figure 1 illustrates, the bumble bee species B. occidentalis that was once among the broadest geographic ranges of any bumble bee species in North America are now only abundant throughout the intermountain west and Rocky Mountains. Although many species of these bees are less abundant on current studies than historical records, there are still some species that remain relatively abundant and widespread, such as B. bifarius, B. vosnesenskii, B. bimacultatus, and B. impatiens.
Figure 1. The relative abundance of different kinds of bumble bee species
Understanding the connection between pathogen infection levels and population genetic factors will be a promising possibility for future research to explore species and the relationship between population-specific genetic differences and N. bombi infection. This would provide an important test of the hypothesis that the N. bombi infection is causing the population decline. By doing this, we may be able to discover a way to prevent the declining of bumble bees.
Why is preventing the declining of bumble bee populations such an important global concern for us? The loss of pollinator diversity may have wide-range effects on both natural and agricultural systems. The decline of bumble bee populations has raised many concerns over impacts on global food production, stability of pollination services, and disruption of plant–pollinator networks. This has become a worldwide issue that we must work to come up with a solution for. Having bumble bees around are like having an annoying little brother; although they can be annoying sometimes, we cannot live without them.
Sources:
Cameron, Sydney A. “Patterns of widespread decline in North America bumble bees”. Proceedings of the National Academy of Science 108 (Jan. 2011): 662-667. Web. 18 Mar. 2011.
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