Red cedars recover from acid rain

Thanks to the Clean Air Act, red cedars in the eastern US have bounced back from acid rain pollution.

Starting around the mid-1800s, the burning of fossil fuels sent atmospheric carbon dioxide and sulfur dioxide (SO2) levels soaring. But the Clean Air Act reversed part of that trend. Since the legislation passed in 1970, SO2 levels have dropped.

Researchers studied eastern red cedars in the Central Appalachian Mountains, which suffered from heavy acid rain caused by SO2 emissions from nearby coal-fired plants. The trees’ growth has increased since 1970, the team reports in Proceedings of the National Academy of Sciences. And the rate of photosynthesis rose by 27 percent after 1980.

Detailed analyses of the trees’ carbon and sulfur content “provide evidence for a distinct physiological response to changes in atmospheric SO2 emissions since ~1980 and signify the positive impacts of landmark environmental legislation,” the authors write. Roberta Kwok | 3 September 2013

Source: Thomas, R.B. et al. 2013. Evidence of recovery of Juniperus virginiana trees from sulfur pollution after the Clean Air Act. Proceedings of the National Academy of Sciences doi: 10.1073/pnas.1308115110.

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