How Ice Storms May Shape the Future of Forests

In order to study the effects of an ice storm on tree growth, susceptibility to pests and pathogens, changes in habitat for wildlife, a team of researchers created an ice storm at Hubbard Brook Experimental Forest in New Hampshire.

By the Cary Institute of Ecosystem Studies

A team of scientists in New Hampshire recently succeeded in capturing one of nature's most destructive forces - ice - and corralling it in two large research plots on the Hubbard Brook Experimental Forest.
 
Scientists from the USDA Forest Service, Syracuse University, the Cary Institute of Ecosystem Studies, Cornell University, University of Vermont, and the Hubbard Brook Research Foundation created an experimental ice storm that will improve understanding of short- and long-term effects of ice on northern forests.

Ice storms are a big deal in a changing world. Ice storms are expected to become more frequent and severe in the northeastern United States and eastern Canada as long term climate continues to warm while short term weather patterns still bring blasts of arctic air into the region.

Large Ice storms disrupt lives and damage infrastructure in towns and cities in northern New England, resulting in billions of dollars in damage. Ice storms also literally reshape forests. Heavy ice loads break branches and topple whole trees, resulting in reduced tree growth in ensuing years, increased susceptibility to pests and pathogens, changes in habitat for wildlife, and alterations in how nutrients like carbon and nitrogen cycle in the forest.

"Science is critical to our understanding of how climate change may shape forests in the future," said Tony Ferguson, acting director of the Northern Research Station and the Forest Products Laboratory. "Creating an ice storm is a very unique experiment that would not be possible without all of our partners and funding from the National Science Foundation."

While ice storms are a powerful force in forests, they are also inherently difficult to study because scientists, like citizens, have little lead time on when and where these storms are going to occur. Scientists at the Hubbard Brook Experimental Forest are changing that equation, and instead of waiting for the next big storm to hit, they are creating their own artificial ice storms using high-pressure firefighting pumps and hoses to spray water high up into the forest canopy during a cold snap. They are measuring the obvious and immediate downing of limbs and trees, as well as subtler longer term growth responses, interactions with invasive species, and impacts on forest nutrient cycling.

"This research will provide the scientific community, land managers and the concerned public greater insight on the impacts of these powerful, frightening, and curiously aesthetic extreme winter weather events on ecosystem dynamics in northern hardwood forests," said Lindsey Rustad, team leader at Hubbard Brook Experimental Forest and an investigator on the ice storm experiment.

"Ice storms are a great example of extreme weather events with complex outcomes. The experimental ice storm is part of a comprehensive study of ice storms and their effects at Hubbard Brook, which also includes examining forest recovery from a severe ice storm in 1998, developing and applying models to depict the climate conditions that result in ice storms and forest ecosystem effects, and associated outreach and education," said Charles Driscoll, a professor at Syracuse University and investigator for the Hubbard Brook ice storm experiment.

In addition to Rustad and Driscoll, investigators in the experiment include John Campbell and Paul Schaberg of the USDA Forest Service; Katharine Hayhoe of Texas Tech University, and Sarah Garlick of the Hubbard Brook Research Foundation. Partners include Peter Groffman of the Cary Institute of Ecosystem Studies, Timothy Fahey of Cornell University, and Robert Sanford and Joe Staples of the University of Southern Maine.

The Hubbard Brook Ice Storm Experiment is funded by a grant from the National Science Foundation (DEB-1457675 - Collaborative Research: Understanding the Impacts of Ice Storms on Forest Ecosystems of the Northeastern United States).

The mission of the Forest Service's Northern Research Station is to improve people's lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.

The mission of the Forest Service, part of the U.S. Department of Agriculture, is to sustain the health, diversity, and productivity of the Nation's forests and grasslands to meet the needs of present and future generations. The agency manages 193 million acres of public land, provides assistance to state and private landowners, and maintains the largest forestry research organization in the world.

Public lands the Forest Service manages contribute more than $13 billion to the economy each year through visitor spending alone. Those same lands provide 20 percent of the nation's clean water supply, a value estimated at $7.2 billion per year. The agency has either a direct or indirect role in stewardship of about 80 percent of the 850 million forested acres within the U.S., of which 100 million acres are urban forests where most Americans live.

How Ice Storms May Shape the Future of Forests

Unregulated, Agricultural Ammonia Threatens U.S. National Parks' Ecology

Foggy Tremont River, Great Smoky Mountains National Park. In Great Smoky Mountains National Park, the deposition of nitrogen compounds from pollution far exceeds a critical threshold for ecological damage.

(Credit: © Dave Allen / Fotolia)

Thirty-eight U.S. national parks are experiencing "accidental fertilization" at or above a critical threshold for ecological damage, according to a study published in the journal Atmospheric Chemistry and Physics and led by Harvard University researchers. Unless significant controls on ammonia emissions are introduced at a national level, they say, little improvement is likely between now and 2050.
    

The environmental scientists, experts in air quality, atmospheric chemistry, and ecology, have been studying the fate of nitrogen-based compounds that are blown into natural areas from power plants, automobile exhaust, and -- increasingly -- industrial agriculture. Nitrogen that finds its way into natural ecosystems can disrupt the cycling of nutrients in soil, promote algal overgrowth and lower the pH of water in aquatic environments, and ultimately decrease the number of species that can survive.

"The vast majority, 85 percent, of nitrogen deposition originates with human activities," explains principal investigator Daniel J. Jacob, Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at the Harvard School of Engineering and Applied Sciences (SEAS). "It is fully within our power as a nation to reduce our impact."

Existing air quality regulations and trends in clean energy technology are expected to reduce the amount of harmful nitrogen oxides (NO_x) emitted by coal plants and cars over time. However, no government regulations currently limit the amount of ammonia (NH₃) that enters the atmosphere through agricultural fertilization or manure from animal husbandry, which are now responsible for one-third of the anthropogenic nitrogen carried on air currents and deposited on land.

"Ammonia's pretty volatile," says Jacob. "When we apply fertilizer in the United States, only about 10 percent of the nitrogen makes it into the food. All the rest escapes, and most of it escapes through the atmosphere." The team of scientists -- comprising researchers from Harvard SEAS, the National Park Service, the USDA Forest Service, the U.S. Environmental Protection Agency, and the University of California, Irvine -- presents evidence that unchecked increases in nitrogen deposition are already threatening the ecology of federally protected natural areas.

In many previous studies, environmental scientists have identified the nitrogen levels that would be ecologically harmful in various settings. The new Harvard-led study uses a high-resolution atmospheric model called GEOS-Chem to calculate nitrogen deposition rates across the contiguous United States, and compares those rates to the critical loads.

The findings suggest that many parks may already be suffering. In Eastern temperate forests, like those in Great Smoky Mountains National Park, the most sensitive elements of the ecosystem are the hardwood trees, which start to suffer when nitrogen deposition reaches approximately 3 to 8 kilograms per hectare, per year. According to the new study, the actual rate of deposition -- 13.6 kg/ha/yr -- far exceeds that threshold. In the forests of Mount Rainier National Park, it's the lichens that suffer first; their critical load is between 2.5 and 7.1 kg/ha/yr, and the deposition rate there is at a troubling 6.7 kg/ha/yr.

"The lichens might not be noticed or particularly valued by someone walking around a national park, but they're integral for everything else that's dependent on them," explains lead author Raluca A. Ellis, who conducted the research as a postdoctoral fellow at Harvard SEAS. She now directs the Climate and Urban Systems Partnership at the Franklin Institute.

Jacob, Ellis, and their collaborators predict that NO_x emissions from the United States will decrease significantly by 2050 (globally, those decreases may be offset to some extent by increases in industrialization overseas). But for ammonia, the story is different. The team predicts significant increases in the amount and density of agricultural land in the Midwest and the West -- to feed a growing population and to meet an anticipated demand for biofuels -- requiring more and more fertilizer.

"Even if anthropogenic NO_x emissions were globally zero, avoiding [critical load] exceedance at all national parks would require a 55% reduction of anthropogenic NH₃ emissions," their report states. How such a reduction would be achieved is a matter for further study. "Air quality regulations in the United States have always focused on public health, because air pollution leads to premature deaths, and that's something you can quantify very well. When you try to write regulations to protect ecosystems, however, the damage is much harder to quantify," says Jacob. "At least in the national parks you can say, 'There's a legal obligation here.'"

The project was funded by the NASA Applied Sciences Program through the Air Quality Applied Sciences Team, which is led by Jacob at Harvard and includes 23 researchers from numerous institutions. The National Park Service has been studying nitrogen deposition for some time now, typically in focused studies such as those at Rocky Mountain National Park and Grand Teton National Park. The new collaboration has enabled many different research teams to unify their efforts and benefit from shared resources like the GEOS-Chem model, which was first developed at Harvard and has become an international standard for modeling atmospheric chemistry over time. Actual levels of future nitrogen deposition will depend on a complex interplay of economic, legal, and environmental factors.

"The point is, in the decades ahead, the problem in our national parks is not going to be solved by the reduction of NO_x emissions alone," explains Ellis. "It will require a targeted effort to control ammonia."

"It's a national issue, and I think that's why having the national perspective was so important," Jacob adds. "We've shown that most of the nitrogen deposition to parks in the United States is coming from domestic sources. It's not coming from China; it's not coming from Canada -- it's something we can deal with, but we need to deal with it at the national level."

http://www.sciencedaily.com/releases/2013/10/131010205144.htm

Urban Trees Save Lives

A recent study by urban forestry guru David Nowak and other researchers at U.S. Forest Service and The Davey Institute found that urban trees save at least one life per year in most cities and up to 8 people per year in large metropolises like New York City.

“Trees growing in cities help clean the air of fine particulate air pollution — soot, smoke, dust, dirt — that can lodge in human lungs and cause health problems,” Grist explains. As an example, “trees clear 71 tons” of air particulate matter 2.5 micrometers in diameter (PM2.5) from Atlanta’s air each year.

Urban particulate air pollution kills as many as 2.5 million people each year. PM 2.5 has a drastic effect on human health, including premature mortality. Researchers noted that larger particles between particulates 2.5 to 10 micrometers in diameter—also called coarse dust particles or PM10—are removed by trees at a substantially higher rate. However, the health benefits of PM2.5 removal is 30 to 350 times more valuable.

What happens to our health when those trees die from natural causes en masse? Apparently, as another recent study claims, people die, too. This study showed that the “loss of trees to the emerald ash borer increased mortality related to cardiovascular and lower-respiratory-tract illness. This finding adds to the growing evidence that the natural environment provides major public health benefits.” Untrammeled development would then also have the same negative health impacts at the ash borer.

Of course, the health benefits are not restricted to our lungs and heart, but also our minds. As can be seen in a new UK-wide study, parks, gardens, and even street trees in urban areas improve the mood and mental well-being of the surrounding residents.

The value of trees goes well beyond their immediate air quality-reducing properties, too. According to one recent U.S. Forest Service study, “urban forests are responsible for storing 708 million tons of carbon—a service valued at $50 billion.”

Not to ignore the financial side of better health, the Nowak study also claims that “the average health benefits value per hectare of tree cover was about $1,600, but varied [from city to city].”
The study concludes that “trees can produce substantial health improvements and values in cities.” Although more research is needed to improve these estimates, this study also leaves room for new research that explores the local effects of tree-filled landscapes in cities.

http://dirt.asla.org/2013/08/06/urban-trees-save-lives/

U.S. Urban Trees Store Carbon, Provide Billions in Economic Value

From New York City's Central Park to Golden Gate Park in San Francisco, America's urban forests store an estimated 708 million tons of carbon, an environmental service with an estimated value of $50 billion, according to a recent U.S. Forest Service study.

 

Annual net carbon uptake by these trees is estimated at 21 million tons and $1.5 billion in economic benefit.
In the study published recently in the journal Environmental Pollution, Dave Nowak, a research forester with the U.S. Forest Service's Northern Research Station, and his colleagues used urban tree field data from 28 cities and six states and national tree cover data to estimate total carbon storage in the nation's urban areas.
"With expanding urbanization, city trees and forests are becoming increasingly important to sustain the health and well-being of our environment and our communities," said U.S. Forest Service Chief Tom Tidwell.

"Carbon storage is just one of the many benefits provided by the hardest working trees in America. I hope this study will encourage people to look at their neighborhood trees a little differently, and start thinking about ways they can help care for their own urban forests."

Tens of thousands of people volunteered to plant and care for trees for Earth Day and Arbor Day this year, but there are opportunities all year long. To learn about volunteer opportunities near your home, visit the Arbor Day Foundation. The Forest Service partners with organizations like the Arbor Day Foundation and participates in programs like Tree City USA to recognize and inspire cities in their efforts to improve their urban forests. Additionally the Forest Service is active in more than 7,000 communities across the U.S., helping them to better plan and manage their urban forests.

Nationally, carbon storage by trees in forestlands was estimated at 22.3 billion tons in a 2008 Forest Service study; additional carbon storage by urban trees bumps that to an estimated 22.7 billion tons. Carbon storage and sequestration rates vary among states based on the amount of urban tree cover and growing conditions. States in forested regions typically have the highest percentage of urban tree cover. States with the greatest amount of carbon stored by trees in urban areas are Texas (49.8 million tons), Florida (47.3 million tons), Georgia (42.4 million tons), Massachusetts (39.6 million tons) and North Carolina (37.5 million tons).

The total amount of carbon stored and sequestered in urban areas could increase in the future as urban land expands. Urban areas in the continental U.S. increased from 2.5 percent of land area in 1990 to 3.1 percent in 2000, an increase equivalent to the area of Vermont and New Hampshire combined. If that growth pattern continues, U.S. urban land could expand by an area greater than the state of Montana by 2050.
The study is not the first to estimate carbon storage and sequestration by U.S. urban forests, however it provides more refined statistical analyses for national carbon estimates that can be used to assess the actual and potential role of urban forests in reducing atmospheric carbon dioxide.

More urbanization does not necessarily translate to more urban trees. Last year, Nowak and Eric Greenfield, a forester with the Northern Research Station and another study co-author, found that urban tree cover is declining nationwide at a rate of about 20,000 acres per year, or 4 million trees per year.

http://www.sciencedaily.com/releases/2013/05/130507195815.htm