Earth out of sync: Rising temperatures throwing off seasonal timing

By Janet Larsen
March 25, 2010 …With global average temperatures up 0.5 degrees Celsius since the 1970s, springtime warming is coming earlier across the earth’s temperate regions. A number of organisms have responded to the warming temperatures by altering the timing of key life-cycle events. The problem, however, is that not all species are adjusting at the same rate or in the same direction, thus disrupting the dance that connects predator and prey, butterfly and blossom, fish and phytoplankton, and the entire web of life.

The timing of seasonal biological events, otherwise known as phenology, has been tracked in some places for centuries. Japan’s much-feted cherry tree blossoming has been carefully recorded since before 1400. The trees showed no clear trend in timing until the early 20th century, when they began to bloom earlier, with a marked advancement since around 1950. The meticulous records of Henry David Thoreau help us gauge how spring has changed in Concord, Massachusetts, since the mid-1800s. Comparing his notes on over 500 species and subspecies of plants with modern surveys and records in between, researchers found that springtime blooming advanced by an average of one week over the past 150 years as local springtime temperatures rose. … Exactly how these changing plant communities will interact with pollinators and foragers that may or may not be changing at the same pace remains unanswered. Members of the animal kingdom are responding to warming in different ways. A quintessential early bird, the American robin, now sometimes makes an even earlier springtime debut. In the Colorado Rocky Mountains, where robin migration is not just south-to-north but also up to higher elevations, the birds have responded to warming in their wintering grounds by traveling to their high-altitude summer breeding grounds two weeks earlier in 2009 compared to the early 1980s. In some years the robins arrive long before the snow has melted—making it far more difficult for this early bird to catch the worm. For pied flycatchers that breed in the Netherlands, migration timing from their West African wintering grounds has not changed, but earlier spring warming has caused the birds to breed about as soon after their arrival as possible. Unfortunately, their caterpillar food has been able to respond even more strongly, advancing hatching in one woodland by an average of 15 days over two decades, while the birds only advanced by 10 days. At sites where the caterpillar populations still peak somewhat late, flycatcher populations have dropped by 10 percent, but where the caterpillars have advanced hatching the most, flycatcher populations have plummeted about 90 percent. Across Europe as a whole, populations of birds that did not advance their migration time along with earlier spring warming have shrunk since 1990. Short-distance migrants seem to be faring better than those traveling long ways. …

Earth Out of Sync – Rising Temperatures Throwing off Seasonal Timing