At the Mohonk Mountain Preserve in New York’s Shawangunk Mountains, naturalists have been collecting data on weather, spring migrants, plant life, and seasonal milestones for almost 90 years. What started as simple record keeping has become important data for those studying global climate change.
The record-keeping can be traced back to Daniel Smiley, whose relatives owned and operated the famous Mohonk Mountain House resort. Daniel started taking almost daily records of plant blooms, tree frog populations, bird populations, and other natural phenomena in 1925 and continued until his death in 1989. In all, he left about 100,000 observations, all indexed on handwritten 3-x-5-inch note cards.
Today, Shanan Smiley, a conservation biologist and collections manager at the Daniel Smiley Research center (and the wife of one of Daniel’s grandsons) and colleagues carry on Daniel’s work, though now they use field computers. Twice a week, they sample water from the property, record what plants are blooming and which insects, amphibians, and reptiles are out. “Wherever we are, we’re taking notes on what we see,” said Smiley.
A look back on the Preserve’s records provides an eye-opening overview of changes in the region’s ecological happenings. By plotting the data on a graph, Smiley and her cohorts have created “lines of best fit” to indicate trends in the data. (Statisticians call this a linear regression analysis.) The chart above shows Smiley’s data on rubythroated hummingbird arrival times, and gives some sense of the strengths and weaknesses of this kind of data analysis. Year-to-year variations are large; the first hummer in 1945 wasn’t seen until May 25, and just five years later, one showed up on April 22. But when the data from 90 years are analyzed, the line of best fit indicates that the hummingbird’s arrival is now seven days earlier than in 1925.
Smiley says that it’s clear that the trend is towards warming temperatures, earlier bloom times, and earlier animal arrival dates. Consider the data for when the Mohonk Lake freezes and thaws. The dates, of course, vary from year to year, but the trend line shows that the lake’s average freeze date is two-and-a-half weeks later than it was 80 years ago and its average melt date a full week earlier.
There are some significant differences in bird spring arrival times, too. While any birder anxiously awaiting her favorite warbler can tell you a bird’s first appearance in spring may vary widely from year to year, the trend is toward earlier arrivals. At Mohonk Mountain, northern flicker arrival dates are averaging three weeks earlier than they did in the 1920s, those of the red-eyed vireo about a week earlier, and those of the eastern towhee a week and a half earlier.
Overall, amphibians are coming out of hibernation earlier. On average, the northern gray tree frog is three weeks earlier than in 1931, the wood frog is two weeks earlier than in 1932, and the northern spring peeper is nine days earlier than in 1931.
So, can we attribute the shifts in animal schedules to human CO2 emissions and global climate change?
“I’m really careful not to say the causes and effects,” Smiley said. “What we’ve been careful to do so far is to just present the facts, the data.”
When asked if 90 years was a long enough timespan for the data collected to show definitively that the planet is warming, Smiley said, “90 years is good enough to at least show the trend."