An earlier thaw can trim winter logging.

Global warming, rather than increasing opportunities for development in cold northern regions, can detrimentally affect a region's economy. In New Hampshire, for example, the trend toward earlier spring thaws has significantly lowered logging revenues, a new study suggests.

During the past 4 decades, winter temperatures in New England have risen about 2[degrees]C, says Jennifer B. Wurtzel, a climatologist at the University of Michigan in Ann Arbor. That warmer winter weather, in turn, has reduced the number of days on which unimproved roads are frozen and therefore able to support the weight of a truck loaded with fresh-cut timber.

New Hampshire is the second-most forested state in the nation, after Maine. To assess the effect of a warming climate on the state's logging industry, Wurtzel and colleague Cameron P. Wake, a climatologist at the University of New Hampshire in Durham, used weather data to estimate the change in the number of frozen-road days each year between 1970 and 2007. Towns in northern New Hampshire, where logging in the state is most prevalent, now have on average 9 fewer frozen-road days each winter than they did in 1970. Over the same period, towns in central New Hampshire have lost about 10 frozen-road days, the researchers found.

Data from previous studies suggest that a loss of 9 frozen-road days each year, about 10 percent of the logging season, translates into a loss of $1 million in logging fees paid to landowners.