In the first broad-scale estimate of air pollution removal by trees nationwide, U.S. Forest Service scientists and collaborators calculated that trees are saving more than 850 human lives a year and preventing 670,000 incidents of acute respiratory symptoms.While trees’ pollution removal equated to an average air quality improvement of less than 1 percent, the impacts of that improvement are substantial. Researchers valued the human health effects of the reduced air pollution at nearly $7 billion every year in a study published recently in the journal Environmental Pollution.The study by Dave Nowak and Eric Greenfield of the U.S. Forest Service’s Northern Research Station and Satoshi Hirabayashi and Allison Bodine of the Davey Institute is unique in that it directly links the removal of air pollution with improved human health effects and associated health values. The scientists found that pollution removal is substantially higher in rural areas than urban areas, however the effects on human health are substantially greater in urban areas than rural areas.”With more than 80 percent of Americans living in urban area, this research underscores how truly essential urban forests are to people across the nation,” said Michael T. Rains, Director of the Forest Service’s Northern Research Station and the Forest Products Laboratory. “Information and tools developed by Forest Service research are contributing to communities valuing and managing the 138 million acres of trees and forests that grace the nation’s cities, towns and communities.”The study considered four pollutants for which the U.S. EPA has established air quality standards: nitrogen dioxide, ozone, sulfur dioxide, and particulate matter less than 2.5 microns (PM2.5) in aerodynamic diameter. Health effects related to air pollution include impacts on pulmonary, cardiac, vascular, and neurological systems. In the United States, approximately 130,000 PM2.5-related deaths and 4,700 ozone-related deaths in 2005 were attributed to air pollution.Trees’ benefits vary with tree cover across the nation. …Read more
Aug. 30, 2013 — In the 1970s, red spruce was the forest equivalent of a canary in the coal mine, signaling that acid rain was damaging forests and that some species, especially red spruce, were particularly sensitive to this human induced damage. In the course of studying the lingering effects of acid rain and whether trees stored less carbon as a result of winter injury, U.S. Forest Service and University of Vermont scientists came up with a surprising result — three decades later, the canary is feeling much better.Decline in red spruce has been attributed to damage that trees sustain in winter, when foliage predisposed to injury by exposure to acid rain experiences freezing injury and dies. Paul Schaberg, a research plant physiologist with the U.S. Forest Service’s Northern Research Station in Burlington, Vt., and partners studied red spruce trees in Vermont, New Hampshire and Massachusetts. They found that the influence of a single damaging winter injury event in 2003 continued to slow tree growth in New England for 3 years, longer than had been expected, and had a significant impact on carbon storage.They also found something they did not expect.”The shocking thing is that these trees are doing remarkably well now,” said Schaberg, a co-author on the study. Researchers found that diameter growth is now the highest ever recorded for red spruce, indicating that it is now growing at levels almost two times the average for the last 100 years, a growth rate never before achieved by the trees examined. “It raises the question ‘why?'” Schaberg said.The theories that Schaberg and his colleagues are eager to test include whether the red spruce turn-around can be credited to reductions in pollution made possible by the Clean Air Act of 1990, which helped reduce sulfur and nitrogen pollution. Another possibility is that red spruce may be one of nature’s winners in the face of climate change. …Read more
July 25, 2013 — U.S. Forest Service researchers have identified what may be a key to unraveling some of the mysteries of White Nose Syndrome: the closest known non-disease causing relatives of the fungus that causes WNS. These fungi, many of them still without formal Latin names, live in bat hibernation sites and even directly on bats, but they do not cause the devastating disease that has killed millions of bats in the eastern United States. Researchers hope to use these fungi to understand why one fungus can be deadly to bats while its close relatives are benign.The study by Andrew Minnis and Daniel Lindner, both with the U.S. Forest Service’s Northern Research Station in Madison, Wis., outlines research on the evolution of species related to the fungus causing WNS. The study is available online from the journal Fungal Biology.”Identification of the closest known relatives of this fungus makes it possible to move forward with genetic work to examine the molecular toolbox this fungus uses to kill bats,” according to Lindner, a research plant pathologist. “Ultimately, we hope to use this information to be able to interrupt the ability of this fungus to cause disease.”The study is an important step toward treating WNS, according to Mylea Bayless, Bat Conservation International’s director of conservation programs in the U.S. and Canada. “This research increases our confidence that this disease-causing fungus is, in fact, an invasive species,” Bayless said, “Its presence among bats in Europe, where it does not cause mass mortality, could suggest hope for bats suffering from this devastating wildlife disease. Time will tell.”White Nose Syndrome was first observed in 2006 in a cave in Upstate New York. …Read more
May 9, 2013 — The loss of eastern hemlock from forests in the Southern Appalachian region of the United States could permanently change the area’s hydrologic cycle, reports a new study by U.S. Forest Service scientists at the Coweeta Hydrologic Laboratory (Coweeta) located in Otto, North Carolina, published online in the journal Ecological Applications and available now in preprint format.
“The hemlock woolly adelgid, an exotic invasive insect, has caused widespread hemlock mortality,” says Steven Brantley, a post-doctoral researcher at Coweeta and lead author of the paper. “Hemlock decline is expected to have a major impact on forest processes, including transpiration.”
Transpiration describes the loss of water from plant leaves or needles. Coweeta researchers estimated changes in transpiration at the forest-level since hemlock woolly adelgid infestation by monitoring tree water use and changes in forest composition from 2004 to 2011. The four studied stands were once dominated by eastern hemlock trees, and are located in the Coweeta watersheds.
Because of its dense evergreen foliage and dominance in riparian and cove habitats, eastern hemlock plays an important role in the area’s water cycle, regulating stream flow year round. The loss of hemlock from southern Appalachian forests can be compared to the loss of American chestnut from eastern forests, which became functionally extinct after the introduction of an exotic fungus in the early 20th century. Changes in local forest hydrology from the loss of eastern hemlock will largely depend on which species replace it.
Rhododendron, a woody evergreen shrub common in southern Appalachian forests, is one of the species replacing eastern hemlock trees. Although rhododendron is evergreen, it has lower leaf area than hemlock, and thus transpiration in rhododendron-dominated forest stands is lower than in previously-healthy hemlock forests. Most of the other species replacing eastern hemlock trees are deciduous, such as sweet birch, which unlike the evergreen rhododendron and eastern hemlock, do not transpire during the winter. Sweet birch trees also have a much higher transpiration rate than eastern hemlock trees during the growing season.
“The cumulative effect of these species changes will probably mean permanent changes in seasonal transpiration patterns,” says Brantley. “In the growing season, transpiration rates will likely rise, leading to lower stream flow in the summer. However, transpiration rates in the winter will be reduced, which could cause increased winter stream discharge.” Whatever species eventually replace eastern hemlock, there will be important long-term implications for riparian habitats beyond stream discharge. Without the shade provided by eastern hemlock, stream temperatures could rise, threatening aquatic animals like eastern brook trout that require cold water for survival. The loss of eastern hemlock will not only affect the animal and plant communities in riparian habitats, but ecosystem function throughout these areas.
The study was conducted at the U.S. Forest Service Coweeta Hydrologic Laboratory, in the Nantahala Mountains of western North Carolina. Coweeta is one of the oldest continuous environmental studies in North America. Since 1934, precipitation, temperature, and stream flow have been continuously recorded at Coweeta, a U.S. Forest Service Southern Research Station facility.Read more