A recent study by two University professors shows that global climate change is causing some animals to genetically evolve and alter their seasonal behavior patterns, and the two researchers are receiving national media attention for their conclusions.
Dr. William Bradshaw and Dr. Christina Holzapfel, whose work was published in a June issue of Science journal, have compiled their data of mosquito seasonal dormancy behaviors, climate change and response to day length since 1972.
Their study finds that mosquitoes, which typically use day length as a cue for when to go dormant in preparation for winter, are now waiting longer to do so because of global warming. In some cases, Bradshaw and Holzapfel found that the mosquitoes they studied had evolved and changed their behavior in as short a time period as five years.
“That is evolution at break-neck speed,” Bradshaw said.
Holzapfel was equally amazed, saying she would have been skeptical of the data had they not collected so much evidence with extremely large population sizes that all showed the same results.
“We were just totally stunned,” Holzapfel said.
Bradshaw said mosquitoes need to anticipate winter to be able to survive. If they waited for it to come, he said, they wouldn’t make it.
“You don’t wait for winter to come and sock you in the chops; you use day length to predict when winter will be coming in the future, and therefore you can prepare for it,” Bradshaw said. “You can go dormant, or you can migrate before winter comes.”
But because winter is arriving later and later because of climate change, Bradshaw and Holzapfel found that between 1972 and 1996, mosquitoes began waiting longer than usual to prepare for it.
“In all cases, the same population was now using a shorter, more southern-like day length to determine when it should make its important life history decision to go dormant,” Holzapfel said.
Holzapfel said she and Bradshaw didn’t intend to study climate change when they first started collecting data, but that they only wanted to observe evolutionary adaptation in the temperate zone. She said one night they decided to compare
the data they had collected from 30 years ago to today’s, and it led them to the conclusions they are now making.
Bradshaw said global warming is more prevalent in the northern latitudes than closer to the equator. He also said a common misconception is that climate change is more noticeable in the summer months, when in fact the temperature difference is more substantial in winter.
According to data in the study, the average temperature in many northern hemisphere locations during the winter months of December, January and February saw an increase of one degree Celsius between 1976 and 2000.
This, Bradshaw said, is what leads to the longer seasons that caused the mosquitoes to alter their behavior.
“There’s quite convincing evidence that the Earth is warmer now than it’s been in a century,” said environmental studies professor Scott Bridgham.
The reasons for this are more ambiguous, he said, but greenhouse gasses likely accounted for some of it.
Patrick Phillips, a University biology professor, said people should not downplay what they think is an insignificant change in global temperature.
“A half of a degree might mean several weeks’ worth of seasonal change,” he said. “I think that’s a very important point.”
Holzapfel said there are still other effects of climate change to be researched. Fertile agriculture belts, for example, could possibly shift north into Canada over time, she said. Holzapfel also said knowledge of genes could change that and allow farmers to adapt their crops.
Holzapfel said organisms with small sizes and large populations could actually benefit from the climate change.
“Things with long generation times and relatively small population sizes are definitely going to take it in the shorts,” she said.
Phillips said the exposure the two professors’ work is getting is good for both the University and the rest of the science community because it brings important research on climate change to the forefront. He said people outside the science community will have to be the ones to realize its importance and decide what to do about it.
“Those are not scientific questions,” Phillips said. “Those are cultural questions.”
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