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New England drought
Dry winter puts wildlife and wildflowers at risk

By Tim Stoddard

The snowstorm that arrived on the first day of spring was what many hope will be an auspicious start to a soggy season. But even as April showers bring welcome rainfall to Boston, New England remains in one of the worst droughts on record. According to the National Climatic Data Center, the period from September 2001 to February 2002 has been the warmest and driest in Massachusetts in 107 years.

Since July 2001, urban areas in the Northeast have seen the worst precipitation deficits (inches below normal) in over a century. Image courtesy of the Northeast Regional Climate Center, Cornell University

For Bruce Anderson, a CAS assistant professor of geography, the lack of snowfall and balmy temperatures this winter suggest that something's amiss up north. The unusually warm and dry weather, he says, is probably linked to a climate pattern called the Arctic Oscillation.

Described by scientists in July 2001, the Arctic Oscillation is a strengthening and weakening of winds that circulate counterclockwise around the Arctic at about 55 degrees north latitude, roughly in line with Moscow and Copenhagen. When they are blowing steadily, these winds become a dam that keeps cold Arctic air from spilling down to mid-latitudes. During a normal winter, the winds slow down periodically, allowing fingers of cold air to reach down over North America, where they cause winter storms.

"My guess is that over the winter the winds were particularly strong," Anderson says, "which means that there weren't many excursions of cold polar air to the southern latitudes." Anderson, who studies the weather patterns that cause mini-monsoons in the southwestern United States, says that the jury is still out on the causes of this year's drought in the Northeast.
"Almost all of the [scientific] commentary on the drought at present is really just descriptive --as in what's occurring as opposed to why it's occurring," he says.

The National Weather Service reports that since July, the amount of precipitation in southern New England has been 10 to 17 inches below normal. Massachusetts remains in an official drought watch, but as water consumption increases this summer, that designation may escalate to warning or emergency.

Reservoirs outside of Boston offer some of the most alarming evidence of the drought. While the Quabbin and Wachusett reservoirs are at 83.5 percent capacity, well within the normal range for this time of year, the Worcester reservoir is only 57 percent full. Water managers in the western suburbs now say that water restrictions are almost inevitable this summer.
Humans won't be the only ones affected by the water shortages. As ponds shrink and streams disappear, beavers are expected to dam waterways more aggressively, says CGS Professor Peter Busher.

"If the drought continues through the spring and summer," he says,
"I think we'll hear a lot more about beaver-human conflicts in the suburbs, where beavers are simply trying to maintain their own toehold on the water supply and are plugging things up."

Busher, who is chairman of the division of natural sciences at CGS, adds that the toothy mammals may also help recharge local aquifers.

"I think it's very positive to have beavers doing this because it slows down runoff," Busher says. "When you've got a beaver pond, the water will sit there and will percolate down into the soil and into the groundwater. It doesn't just run right off to the big rivers."

But many New England wetlands are also shrinking in the dry weather. Lisa Sorenson, a CAS adjunct assistant professor of biology, says that the drought may disrupt the breeding of many waterfowl in May and June. "Ducks need water," she says. "If ponds are dry, the birds will either go elsewhere looking for water, they'll stick around and try to breed, but less successfully, or they won't even attempt to breed."

For endangered species of water birds that are already threatened by loss of habitat, the dry conditions could be particularly challenging. "If drought becomes more common because of climate change," Sorenson says, "it is going to exacerbate the problems that these rare species already face."
Rare plant populations on Cape Cod may also decline if the drought continues this spring. Wildflowers, such as the Plymouth gentian and the golden club, that live next to small ponds on the Cape are particularly at risk, says Richard Primack, a CAS professor of biology. "A lot of these ponds are already being threatened by the water table being drawn down too much," he says. "If we have a really dry year, these plants are going to dry up completely."

Primack adds that this winter's warm, dry weather may harm endangered plants found only at the summits of New England's highest peaks. Rare species such as Potentilla robbinsiana, a mountain cinquefoil that looks like a buttercup, thrive in the extremely cold, wet conditions on top of Mt. Washington and Mt. Katahdin. "The combination of changing weather patterns, milder winters, and warmer summers is really going to have a profound impact on plant and animal populations in this area," Primack says.

For more information on New England's drought, visit http://lwf.ncdc.noaa.gov/oa/climate/research/2002/feb/drought-regional-overview.html
http://lwf.ncdc.noaa.gov/oa/climate/research/prelim/US/US_prelim.html.

12 April 2002
Boston University
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