plant-pollinator mutualisms

Climate change affects nectar collection patterns

A few days ago I wrote about the need for citizen scientists to collect data on wild bee species. Well, here’s another interesting project—one that deals with climate change and nectar collection.

Wayne Esaias, a biological oceanographer and beekeeper from Maryland, has been tracking the dates of nectar collection by his bees for 15 years. One day he realized they were collecting nectar earlier and earlier every year. He compared his data to climate data collected by satellite and found that it correlated. As spring came earlier, the bees collected earlier.

To confirm his theory, Esaias collected data from two other Maryland beekeepers who also had been weighing their hives. They found that the spring nectar flow in Maryland is now 26 days earlier than it was in 1970.

The problem with this, as Esaias sees it, is that there may be some limitation on the bees and plants changing in synchrony with each other. David Inouye, a professor of pollination biology and plant phenology, put it this way, “If spring is arriving earlier and air temperatures are warming up sooner, then the bees are likely to be responding. But they may be more sensitive or less sensitive to the temperature change than the plants are.” At some point, plants and bees may get out of sync.

Armed with this theory, Esaias organized a group of backyard beekeepers called HoneyBeeNet. These citizen scientists agree to keep a scale hive (a hive mounted on a commercial-size scale) and record hive weights every day during the nectar season and submit their data to the network. Since satellite data is hard to interpret, the colony weight data adds an important dimension to the study of climate change.

The cumulative data will help scientists predict how climate change will affect the relationship between plants and pollinators, and will help food producers devise ways to manage their farms in the future. If you are interested in knowing more about this project, visit

In the meantime, here’s a climate change tidbit to wrap your mind around:

Satellite data in combination with HoneyBeeNet data have revealed that although spring comes earlier in the northeastern United States, it is coming later in the southeastern states. Say what? It turns out that many trees and plants need a certain number of chilling days to enter dormancy. In the south, those chilling days are coming later and later in the fall. The result is a delay in dormancy and a commensurate delay in spring greening.



  • To accomplish your goal, you need only collect high/low temperature data, and calculate the growing degree days accumulated at a specific site. You can then compare to historical growing degree days accumulated by the same day of the year in prior years.

    The article Be A Budding Genius, Not A Blooming Idiot (Bee Culture Feb 2002) covers the issue. The number of growing degree days required for each specific plant to bloom is not neatly listed in a single textbook, but one can pick a few common reference plants, and use them as sentinels for the study.

    To date, I have NOT noticed earlier blooms, as the small changes caused by Global Warming have not been enough to change bloom dates significantly.

    • It’s that easy? I didn’t realize the intricacies of climate change as it affects plant/pollinator mutualisms could be discerned with a simple thermometer. By all means, contact NASA directly and let them in on the secret. You could save U.S. taxpayers billions of dollars and many years of frustration. Again, that website is Wayne Esaias, the NASA official in charge of the project, can be reached at

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