Fall Foliage Delayed: Studies Link Late Autumn And Early Spring To Climate Change
If it seems like autumn is coming a bit later every year you're probably right, according to several studies, including one announced Friday that used sateillte images to track leaf color.
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"There is much speculation about whether our seasons are changing and if so, whether this is linked to climate change," said lead study author Peter Atkinson, a geologist at the University of Southampton, in a statement. "Our study is another significant piece in the puzzle, which may ultimately answer this question." His paper appeared this month in the journal Remote Sensing of Environment.
Phenology — the seasonal cycles of Earth's plants and animals, such as hibernation and leaf shed — is seen as a great indicator for climate scientists because the cycles are influenced by things like temperature and precipitation. Consequently, a multitude of climate change research has focused on fall foliage and springtime buds. Atkinson is not the first scientist to say his study "answers the question."
One of the first big studies was published in 2006 by a team of 31 scientists from all around Europe. They picked through 29 years worth of phenological data, from leaf fall to flowering, across 21 European countries in an effort to produce the most all-encompassing study to date. They discovered that spring was arriving, on average, three days sooner by 2000 than it had in 1971. "The timing change is clear, very clear," a co-author said at the time.
Since then, more scientists have attempted even more comprehensive studies that use technology to help them acquire even more objective data. At Harvard Forest, researchers have set up cameras above five forests in New England. Every 30 minutes, the cameras take a picture and post them online in real time (click here to see what Waltham, Mass., looks like right now). In one study, they tested how closely leaf color change related to temperatures and found that trees were extremely sensitive: the warmer the summer, the later the autumn. That, they said, could affect everything from ecology to "billions of dollars" in eco-tourism.
In the new research, Atkinson and his colleagues attempted an even more comprehensive and objective study. They used satellite images covering the entire northern hemisphere over 25 years leading up to 2006. "Previous studies have reported trends in the start of spring and end of autumn," Atkinson said. "But we have studied a longer time period and controlled for forest loss and vegetation type, making our study more rigorous and with a greater degree of accuracy."
It turned out that the delay of autumn leaf changes is greater than the earlier onset of spring, though each had shifted in some forests by as much as a day per year. Atkinson says the delay could have consequences for the health of the plants and the animals that depend on them for food or shelter. In the long run, he said, these climate-induced changes could in turn affect the climate because of shifts in the carbon cycle.
Above photo courtesy of Shutterstock
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