A heavy smog hung over the cities–blanketing skyscrapers and apartment buildings while people coughed and wheezed an the streets. But in 1970 congress enacted a pivotal environmental legislation that cleared America’s skylines. Decades later, scientists are still discovering ways that the Clean Air Act has helped protect mother nature.
Researchers have proved that the Clean Air Act has helped forest ecosystems recover from long-term acid rain. In a four year study of eastern red cedar trees (Juniperus virginiana) in the Central Appalachian Mountains of West Virginia, scientists found that the trees have improved in growth since 1970.
The scientists collected data from eastern red cedar trees between 100 and 500 years old to look at the trees’ growth response to acidic deposition. Their analysis showed that in the years after the Clean Air Act, the trees had increased growth and recovery from decades of sulfur and acid rain pollution.
“There is a clear shift in the growth, reflecting the impact of key environmental legislation,” said Jesse Nippert, associate professor of biology at Kansas State University.
Cedar trees were prime for this historical study because they rely on surface soil moisture, making them sensitive to environmental variability. Scientists can compare hundreds of years of growth in a single tree because they contain centuries of data.
The scientists began their analysis on tree rings from the early 1900’s, the time when sulfur dioxide deposition began to increase in the Ohio River Valley. By taking the isotopic signature in each tree ring, the research team could compare growth patterns in the lifetime of the tree. Physiological changes in the tree rings indicated fluctuations in atmospheric chemistry.
Despite an increase in carbon dioxide (which increases plant growth) through the 20th century, tree growth still declined throughout the 1900’s. This was from the high amounts of acidic pollution during this time. Then, around 1980, something changed.
It took about 10 years for the environmental legislation to effectively reduce sulfur dioxide emissions to a point that trees began to recover. “Our data clearly shows a break in 1982, where the entire growth patterns of the trees in this forest started on a different trajectory,” said Nippert.
Besides reducing acid rain, the Clean Air Act has reduced the amount of particulate pollution Americans breath, preventing thousands of respiratory-related diseases and deaths. The Clean Air Act also prompted innovation in clean technologies that are used in vehicles, energy plants, and even home devices. Environmental legislation is important because it goes beyond economic benefits, but can also be directly tied to increased public health and quality of life Americans experience.
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