By DAVID GREEN
Everyone’s talking about the early spring and the record-setting temperatures it brought along, but a slowly advancing spring is not a new phenomena. This year’s exceptionally warm March only brought it to the forefront.
The science of studying plant and animal cycles—when the redbud blooms, when carp spawn, etc.—is called phenology. The entire season is considered. Scientists aren’t only interested in when something appears in the spring, but also in late-blooming plants of the fall. Researchers often look at the relationship between those cycles and climate.
The timing of seasonal events is important in the natural world in many ways. For example, if a particular caterpillar emerges, it needs food to survive. When a bird chick hatches, it might need that caterpillar to eat.
Phenology is also important to agriculture for determining planting times and for pest control. For many people, it’s a matter of pollen release and allergies.
This year’s odd spring could have an effect in many areas.
Few people take careful note of when a particular plant flowers every year, but scientists do consult the record of amateur phenologists including Henry David Thoreau.
Starting in 1851, Thoreau began keeping meticulous journal records of when plants bloomed in the woods near Concord, Mass. By comparing Thoreau’s records to contemporary data, scientists have discovered an advance of about seven days for 43 of the most common plants. That study ended in 2006. Since then, researchers have continued to update the study and now see a change of 10 days since Thoreau lived by Walden Pond.
Similarly, Wisconsin conservationist Aldo Leopold provided a decade of careful observations from 1935-45, and his daughter resumed the work in the 1970s and many changes have been observed. For example, the compass plant used to bloom in mid-July, but now flowers in late June.
Not all plants change their flowering time to match the climate, and an inability to change can have serious consequences. Plants with inflexible flowering times are disappearing. An example comes from Thoreau’s records. In his time, 21 species of orchids grew in the area. Now there are only six.
Few complaints were heard about the four days of 80°-plus weather last week—surely someone groused that it was too hot—but many complaints could follow with regard to allergies and mosquitoes.
Physicians are seeing allergy patients earlier this season since trees flowered so much earlier. In addition, a mild winter means a higher rate of bud survival, so there’s likely to be more pollen in the air.
Another trade-off from a mild winter will likely come from the insect world.
December, January and February resulted in 67 days below 25° here in 2010-11. By contrast, the past winter produced only 28 days below 25° and that means more insects survived the cold.
It’s likely that more ticks will be crawling around this summer and mosquitoes will get an early start. Some people have already observed ants in their homes.
Growers of certain plants might be accustomed to fungicide treatments at this time of year, but instead they might have to move directly to insecticides.
Although some people are quick to see the recent odd weather in terms of climate change, meteorologists aren’t so quick to make that jump.
There’s no question among the vast majority of climate scientists that global climate change is underway, but there will always be deviations—both in heat and cold—along with some very dramatic departures such as what went on in March. Overall, the heat waves are becoming more dramatic and cold waves weaker.
Although the recent months’ weather may not be a direct result of climate change, climate models suggest that odd weather is more likely to happen.
• Sources: National Phenology Network; LiveScience by Wynne Parry; NPR’s Diane Rehm show; NPR’s All Things Considered; Climate Wisconsin.