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MYTH #49: Spring isn’t arriving sooner


How can we be warming? Spring gets here the same time every year.


It's not your imagination: Spring is coming sooner than it used to.

There is mounting evidence that as temperatures rise, winters are getting shorter and spring is coming sooner. For example, the peak spring runoff is happening more than 20 days earlier in rivers and streams across the American West. In the U.K., the average first flowering date of more than 400 plant species occurred earlier in the last 25 years than in any other period since 1760. Migratory birds are arriving earlier in their summer breeding grounds in Australia, Europe, Asia, and North America. This is known as “season creep.”

More info from the Union of Concerned Scientists

Climate scientists projected that human-induced global warming would make spring arrive earlier than normal, and it is — about 10 days earlier so far. It is not that difficult for people to adjust, but "spring creep" already is posing a significant threat to plants and animals across the country.

Plant and animal cycles out of sync

Spring creep can create "mismatches" when some plants bud earlier and the animals that depend on them have not adjusted their internal clocks. For example, bees might fly to an area that provides habitat for plants they historically pollinate only to find those plants already have bloomed.

In 2009, researchers at the University of Alberta published a study on the decline of North American caribou herds. The researchers believe the problem is at least partly due to the fact that pregnant caribou need to eat new leaves when they are the most nutritious. The leaves are now coming out earlier, but the caribou's migration schedule has not changed, so the herds are arriving after the leaves are past their peak.

Likewise, many insects, including caterpillars, are emerging earlier, but some migratory birds have maintained their traditional migratory schedule. As a result, the birds are arriving after the insects have metamorphosed into butterflies or other inedible bugs.

Invasive plants "winners," native plants "losers" in New England

Charles Davis, an assistant professor of evolutionary biology at Harvard University, has discovered that in Concord, Massachusetts, climate change is especially harmful for certain groups of native plants linked by common ancestry. Using data collected by Henry David Thoreau, Davis published a study in 2008 that found native plants that have maintained their historic flowering schedule tended to be the "losers" to climate change. These groups include many of the area's most "charismatic" wildflowers: orchids, roses, lilies and dogwoods. Davis said about 30 percent of the native species Thoreau documented in the 1850s are extinct in the area. Another 30 percent are so scarce that they likely will disappear.

Davis published a follow-up study that found invasive, nonnative plants in Concord that are flowering earlier with the early arrival of spring are, by and large, the "winners" in climate change. Davis believes the fact that they can adjust their flowering time to changing temperatures may give them an edge to flourish and spread at the expense of native plants.

More large fires in Western states

Anthony Westerling, an assistant professor of environmental engineering and geography at the University of California-Merced, published a paper in 2006 showing rising temperatures combined with early snowmelt are contributing to a dramatic increase in the number and size of forest fires in Western states. Westerling explains that spring creep means a longer summer season and a more flammable fuel supply for fires due to drier vegetation.

Westerling found that there are now about 10 times more large fires in the northern Rockies than there were in the 1970s and early 1980s, and today's fires burn 30 times more land than fires did decades ago. The increase was so dramatic because there were very few large fires prior to the mid-1980s.

The largest fires occurred in years with early springs. Conversely, very few fires occurred in years with late springs. Climate change will continue to speed up spring's arrival, and that will mean more large wildfires.

The lesson of spring creep

Global warming emissions already are causing significant changes in our environment, just one of which is the early arrival of spring. Some species are able to respond to these changes, while others are not. According to the UN Intergovernmental Panel on Climate Change, a 3 degree to 7 degree Fahrenheit increase in the average global temperature could result in the loss of 30 percent of the world's species.

Even if we were able to stop all global warming emissions today, the planet would still experience more climate changes because carbon dioxide and other heat-trapping gases remain in the atmosphere for decades. Our near-term choices about energy, transportation and land use will not stop climate change, but they will determine its extent and severity.