Address Air Pollution at its Roots
California Forests magazine interviews Dr. Gabriele Pfister on how managed forestland can help clear the air.
Scientists know that when forests burn, air quality suffers. The summer of 2004 provided a unique opportunity to see just how badly.
That year, particularly intense wildfires blazed through Alaska and Canada, driven by unusually warm and dry weather. For more than two months, wildfires burned more than 11 million acres and spewed as much carbon monoxide into the air as all the cars and factories in the continental United States combined in those same months.
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The same wildfires increased ground-level ozone by up to an estimated 25 percent in parts of the northern United States and 10 percent as far away as Europe during intense burning.
Poor air quality aggravates asthma and leads to other ailments. Carbon monoxide can cause nervous system and brain damage. Ozone irritates the eyes, nose and respiratory systems and may increase the risk of heart attack.
If we really want cleaner air, we must understand where pollutants come from and how they interact with our atmosphere, then address air quality threats at the source.
Capitalizing on a scientific opportunity
The International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) study conducted during the time of the Alaskan and Canadian wildfires captured uniquely comprehensive measurements of the effect of catastrophic wildfires on air quality. Using satellite, air- and land-based monitoring technology, this campaign traced wildfire plumes throughout North America and all the way to Western Europe. Those efforts are helping researchers to distinguish wildfire pollutants from other pollutants and study the impact these fires had on atmospheric composition.
Human activities like burning fossil fuels account for major contributions to the elevated pollutant levels in the atmosphere, and reducing fossil-fuel emissions is a necessary step toward better air.
Wildfire smoke releases similar pollutants as automobile tailpipes, and millions of acres of forestland burn every year in North America. With wildfires, reducing pollution at the source is feasible and can have doubly positive effects on atmospheric carbon concentrations. When a forest isn't burning, it's helping to clean the air.
Forest vegetation removes carbon dioxide from the air through photosynthesis. Trees store the carbon as wood fiber and release oxygen to the air. Trees also capture trace elements of other gases that if left in the atmosphere can contribute to poor air quality.
Whereas a healthy forest stores carbon, wildfires release carbon. When the forest burns, all of the carbon that was trapped in the wood is released in one massive outburst. Chemical reactions in the smoke trigger ozone production, and ash can fill the sky for hundreds, even thousands of miles.
Eventually, the carbon released in wildfires will be offset by the up-take during forest re-growth. But in the near term, the massive release of carbon in a fire can throw natural systems out of balance - an effect made worse because many unmanaged forests in the West have become overcrowded. Human fire suppression efforts have put out natural fires that would have thinned the forest for a century. That extra forest fuel contains extra carbon.
Hands-on approach can help air quality
Managing a forest can reduce fuel loads and the frequency of catastrophic fires. It simultaneously prevents the mass-release of carbon and accelerates the absorption of carbon from the air by growing trees and producing wood products that store carbon long-term.
Not managing forests, leaving them to grow overcrowded, invites short and long-term air quality degradation. Here's why: Catastrophic wildfires can pour thousands of tons of trace gases and particulate matter into the air. Carbon dioxide and other gases emitted by fires (e.g. methane) or produced from fire emissions (e.g. ozone) are greenhouse gases and contribute to an increase in global temperatures, which, in turn, could lead to more droughts, thus increasing the incident of wildfires in boreal forests.
Actions after a fire can have an impact on air quality. Private forestland managers replant after fires to accelerate the return of a healthy forest. Much charred public forestland goes without reforestation. According to a 2005 survey by The Forest Foundation, only 28 percent of California's severely burned national forestland in 2001 has been replanted, and only 43 percent will ever be replanted. Replanting a burned forest prevents the landscape from turning to brush fields or rangeland, both of which store far less carbon than a thriving forest.
While we look for ways to reduce emissions from our freeways and factories, as we must to conserve a healthy environment, we might also want to consider ways to neutralize the impact of similar emissions from wildfires. Managing forestland so it stores carbon rather than mass-releases it, so trees grow rather than burn, could help us all breath a little easier.
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Gabriele Pfister, Ph.D. is a postdoctoral scientist with the Atmospheric Chemistry Division of the National Center for Atmospheric Research (NCAR) in Boulder, CO. NCAR is operated by the University Corporation for Atmospheric Research under the sponsorship of the National Science Foundation.