By Shannon McNeeley
Ah, spring. From ancient civilizations on, what poet hasn’t greeted the season of longer days, increasing warmth, melting snow, and blooming flowers? But today’s poets may have to revise their odes.
Many signs of spring have shifted earlier and earlier, out of sync with the lengthening days. Warmer weather, snowmelt, and flowers, for example, are now arriving during what used to be winter in many parts of the globe. Evidence is growing that some animals and insects aren’t adapting fast enough to the changes in timing of the seasonal signs, and that the consequences of that failure can be disastrous.
Legislators have also greeted the seasons, typically with regulations governing water use, hunting, grazing on public lands, and other seasonal activities. And like other creatures, people are beginning to feel the effects of the increasing disconnect between the permanent dates written into these laws and the changing seasons.
It’s taken scientists a while to respond to the issue—sometimes referred to as seasonal asynchrony—which has a distinct set of consequences beyond those of more commonly recognized indicators of global climate change. Specific populations are being put at risk, including migratory animals and people governed by date-specific laws that no longer match reality.
Biologists only began researching the effects on vulnerable animal populations in the early 2000s. A few social scientists have recently begun looking at how human populations are also being affected, particularly in Alaska, one of the fastest-warming places on Earth. And just within the last decade, experts in environmental law have began questioning the consequences of outdated policies on agriculture and water supplies.
This area of study is so new, according to NCAR postdoctoral researcher Shannon McNeeley, that it’s suffering from a lack of a comprehensive view.
“Some people focus on changing seasonality from either a biological or a climate point of view, and a small but growing community study the links between changing seasonality and policies,” McNeeley says. “There aren’t many yet who do truly comprehensive social and natural science research from a systems point of view by integrating social science, climatology, and ecology to understand how this affects vulnerable livelihoods on the ground.”
Here’s a brief overview of research emerging on the effects of seasonal mistiming.
EVIDENCE FROM THE NATURAL WORLD
Warmth governs the ability of seeds to germinate, the dates of snowmelt, and other triggers of the growing season.
There’s copious documentation that plant growth is shifting earlier in response to a warmer climate. The U.K.’s Royal Botanic Gardens, Kew, has been tracking first flowering dates for some 100 species since the 1950s; snowdrops are now flowering 10 days earlier on average, and spring narcissus almost two weeks earlier. In the United States, the flowering date for winter wheat, a major crop of the High Plains, has advanced by one to two weeks since World War II, marching forward 0.8–1.8 days per decade over the last 70 years.
Among animals and insects, however, the situation isn’t so straightforward. Researchers have been aware for some time that warming is changing the geographic range of species. For example, a 1996 study by Camille Parmesan (University of Texas) noted the range shift of a California butterfly northward and to higher altitudes.
Migratory and hibernating animals may take their cues to move from increasing or decreasing sunlight or from temperature changes in their current habitat (spring warming in their wintering grounds, for example). In either case, the migrators may arrive at their destination habitat to find that it’s out of sync with their needs if climate change is producing different results there. When that happens, the consequences ripple through entire ecosystems.
The full extent to which the seasonal drift is putting plants and animals at risk is not yet known. One of the first studies of multiple species was a 2005 paper by Dutch ecologists. Searching for long-term datasets covering both vulnerable species and their food sources, the authors found adequate information for only 11 species. In this small sample, however, 8 species—including birds, insects, and zooplankton—had changed their behavior either too little or too much, so they were out of sync with their food sources. Only 3 species were adapting in sync.
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