Pining for Clean Air

Students have helped monitor and document the health of white pine as part of the UNH Forest Watch program. Photo courtesy of the UNH Forest Watch

Since 2010, many white pine trees in northern New England have become infected with one of several fungal diseases that have caused yellow and brown discoloration of one year old needles, particularly in wet areas and during wet years. But the news isn’t all bad. According to a University of New Hampshire professor, white pines throughout New England have actually been getting healthier over the last 20 years, and he attributes it to the lower smog levels in the region. Ground-level ozone (smog) levels reached their peak in 1991, a year after passage of the federal Clean Air Act. Since then, smog levels have steadily decreased and tree health has correspondingly improved.

These results are borne out by the UNH Forest Watch program, a hands-on science program that trained students in grades K-12 to recognize the characteristic symptoms of ozone damage on pine needles. (The program began monitoring tree health in 1991 and continued this mission until early 2014, when a loss of federal funding brought it to an end.)

According to Barrett Rock, founding director of Forest Watch, white pines are particularly sensitive to ground-level ozone. Exposure to high levels of smog causes browning of the ends of the needles, a symptom called tip necrosis, as well as chlorotic mottle or yellow spots on the needles. “There isn’t really anything other than ozone that causes those symptoms on white pines,” Rock said. “And it’s easy to train a third grader to recognize it and measure its extent.” Students collect pine needles, measure their length, and measure the amount of mottle or necrosis to get a percentage. Half of the needles the students collect are sent to Rock to verify their results with a spectrometer.

Rock said that white pines across New England were in ill health in the early and mid-1990s, but needle health improved dramatically soon after the Clean Air Act. “Ozone levels made a significant drop from 1997 to 1999, and that’s when we also saw the tremendous jump in the health of pine needles,” said Rock. “Further [regulatory] modifications improving ambient air quality standards have been made more recently, and with each improvement in air quality we see an improvement in the state of health of pine trees.”

“The lesson here,” he added, “is that stronger environmental policy changes have had a dramatic, positive impact on air quality and white pine health. And from my perspective, this good news story needs to be told because it comes at a time when there are growing efforts to trim back on EPA regulations, which are considered to be too restrictive on business and industry.”

Data from the Forest Watch program covers all of New England and the Adirondacks, as well as Long Island. Since there are no corresponding programs measuring white pine health in other regions of the country, it is impossible to know whether similar improvements are happening elsewhere. But since most of the smog produced by coal-fired power plants in the Midwest flows directly to New England, Rock said that white pines elsewhere probably did not experience the same smog-related declines in health. He also speculates that other tree species are getting healthier due to improved air quality, but it’s harder to measure improvements in species that are not as sensitive to smog as white pines.


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