Phenological Issues

 Climate Change and Shifting Spring Phenology: 

Potential for Trophic Mismatch between Bees and the Flowers they Pollinate 

     Climate change has caused temperatures to increase around the world. This temperature change has translated, in many regions, to the spring season shifting earlier and earlier [18]. As spring is normally a season where warmer temperatures begin to appear, it makes sense that, as the earth warms, we would expect the warmer seasons to arrive sooner and sooner. The following map (from Climate Central's website), provides a visual representation of how spring shift has manifested in the United States:

CLICK on the image to go to an interactive map from Climate Central!

     As one might guess, plants take their cues for flowering from the changing of the seasons, the shift to spring being one of utmost importance. Honey Bees and Bumble Bees are among the most crucial pollinators of flowering plants [14]. There is a notable difference between Honey and Bumble Bees however, primarily that Honey Bees, of which a large number are domesticated species, are perennial (the adults are active in winter), while Bumble Bees and other Bee species tend to exhibit a dormant larval stage until they emerge in the spring [11].  Spring is, however, a crucial time which all bee species use to gather and store nectar.

     Regardless of their species, the concept of "trophic mismatch" still applies. A "trophic level" is basically a step up the food chain. Flowers provide food for bees, so, generally speaking, flowers exist on the trophic level beneath bees. As you may realize next, it's very important that the two trophic levels (the species eating and the species providing food) exist in the same space at the same time. If for some reason the timing is thrown off, for example, if one species emerges later than the other, then the interaction between trophic levels may not be as long as it ought to be, and a trophic mismatch could occur.

    Given the extended seasonal activity of Honey Bees as opposed to other bee species, when discussing the potential for trophic mismatching, it would seem that Honey Bees are at a slightly lower risk for being affected by phenological shifts. "Phenology" can be loosely defined as the timing of biological events, in this case, the coming of spring [17]. When we say trophic mismatch now, we mean a discrepancy in the time when flowers are blooming and ready to be pollinated, and the time when bees are present to do the pollinating [8, 12, 13].

Studying the effects of climate change through nectar flow monitoring:

   The term "nectar flow" refers to the amount of nectar that bees are able to consume in a given season, which typically translates into a similar level of honey production. In other words, higher nectar flow should result in heavier hives, due to greater amounts of honey. Beekeepers have been tracking nectar flow patterns using this hive-weight method [6]. The results of these experiments are still largely preliminary, but they point to a fairly strong correlation between climate warming and reduced nectar flow. Nectar flow patterns are indicative not only of phenological changes, but also bee fitness and food availability [6].

Watch a 3 minute video from NASA explaining this issue!

The video below from NASA's Earth Science division provides a clear and concise explanation of the interplay between honey bees and climate change: