Climate scientists have projected human-induced global warming would make spring arrive earlier than normal, and it is—by about 10 days so far. And while most people are only too happy to say goodbye to winter, “spring creep” is posing a significant threat to plants and animals across the country.
I recently moderated a press conference with scientists who are studying the effects of spring creep. Jake Weltzin, the executive director of the U.S.A. National Phenology Network and an ecologist at the U.S. Geological Survey, found an earlier spring creates “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.
Spring creep also may be taking a toll on North American caribou herds. Last year, University of Alberta researchers published a study on herd decline. They know pregnant caribou need to eat new leaves when they are the most nutritious. But the leaves are now coming out earlier, and the caribou’s migration schedule has not changed, so the herds are arriving after the leaves are past their peak. This may partly explain the declining numbers of caribou.
Weltzin says many insects, including caterpillars, are emerging earlier, too, but some birds have maintained their traditional migratory schedule. As a result, birds are arriving after the insects have metamorphosed into butterflies or other inedible forms.
Sometimes these spring mismatches can be fatal. In a number of states, caterpillars, which in the past were eaten by migratory birds, are now falling to the ground before the birds show up.
That is not only bad news for the birds. A recent study by a scientist in Kentucky found thousands of grazing pregnant mares in the Ohio River Valley were ingesting the caterpillars, which causes them to abort their fetuses.
Other scientists are finding that spring creep is affecting vegetation in New England. Charles Davis, an assistant professor of evolutionary biology at Harvard University, together with researchers at Boston University, discovered that in Concord, Mass., climate change is especially harmful to certain groups of native plants linked by common ancestry.
Using data taken by Henry David Thoreau, Davis and his colleagues published a study in 2008 that found native plants that have maintained their historic flowering schedule tend to be the “losers.” These groups include many of the area’s most “charismatic” wildflowers: orchids, roses, lilies and dogwoods. Dr. Davis said about 30 per cent of the native species Thoreau documented in the 1850s are extinct in the area. Another 30 per cent are so scarce they likely will disappear.
Davis and his co-authors published a followup study in January that found invasive plants that flower earlier with the early arrival of spring are, by and large, the “winners.” Davis believes the fact they can adjust their flowering time to changing temperatures may give them an edge, allowing them to flourish and spread at the expense of native plants.
These findings are significant given that damages from invasive species total more than $100 billion a year.
Spring creep also has a direct link to forest fires. Another scientist at our press event, Anthony Westerling, 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, an assistant professor of environmental engineering and geography at the University of California-Merced, explained spring creep means a longer summer season and drier vegetation, which provides a more flammable fuel supply.
Westerling found 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 acreage than they did decades ago. This increase was so pronounced, he said, because there were very few large fires prior to the mid-1980s.
These are just some of a number of examples of how global warming emissions already are causing significant changes in our environment. Some species are adapting to these changes, but a significant number of others are not, and that spells trouble. According to the UN Intergovernmental Panel on Climate Change, a three-degree to seven-degree Fahrenheit increase in the average global temperature could result in the loss of as much as a third of the world’s species.
If we exceed seven degrees Fahrenheit warming, more than half of all species could become extinct.
So what can we do about this problem? Unfortunately, even if we were able to stop all global warming emissions today, the climate would still continue to change because carbon dioxide and other heat-trapping gases remain in the atmosphere for decades. But we can avoid the worst potential consequences of climate change by dramatically reducing our emissions. It’s time to spring into action, the earlier the better.
Melanie Fitzpatrick is a climate scientist at the Union of Concerned Scientists.
Republished from the Winnipeg Free Press print edition May 11, 2010 A10