A new study in Bioscience “casts new light on the classic controversy about acid rain — and contains some other welcome dicta about the treatment of skeptics.
According to the study’s media release:
During the 1970s and 1980s, researchers and policymakers became increasingly worried about multiple consequences of acidic emissions of sulfur dioxide and nitrogen oxides from the stacks of power stations, and eventually they were controlled. In Europe, there was much concern about the effects on Sweden’s many lakes, which were found to be in some cases strikingly acidic. The Swedish government instituted a program of countering the acidification by adding thousands of tonnes of lime to the lakes.
The link between emissions and acidification of lakes was never universally accepted, however. A new study of the role of dissolved organic carbon, which comes from living organisms and can also make lakes acidic, suggests that power station emissions may have played less of a role than previously thought. Martin Erlandsson of the University of Reading, United Kingdom, and his colleagues wondered whether it was possible to distinguish the historical effects of organic acids and power station emissions by assessing findings during the 20 years since lake acidification started to decrease in Sweden. They describe their results in the August issue of BioScience.
Although there are few measurements of the amount of dissolved organic carbon in Swedish lakes before the 1980s, the amount of dissolved organic carbon in them has continued to increase despite the stabilization of power station emissions around 1990. The reason is unknown, but the increase supports the idea that as power station emissions increased during the 20th century they may have partly suppressed organic acidity in lakes that was present in pre-industrial times—at higher levels than when it was assessed in 1990. Erlandsson and colleagues estimated the pre-industrial acidity of 66 lakes under different assumptions about the amount of dissolved organic carbon in them, and found that the assumptions had a large effect on estimates of how much the lakes had been affected by power station emissions. Studies of sediments in some of the lakes seem to bear out the idea that preindustrial organic carbon levels were at least as high as they are today—and considerably higher than they were in 1990. That in turn means the power station emissions did not contribute as much to lake acidification as was thought when liming programs were instigated. [Emphasis added]
Imagine: Mother Nature may have had a compensatory mechanism that offset the much-dreaded “acid rain.”
The researchers concluded their study with the following important observations:
More generally, when turning to acidification as a textbook example for how environmental science can support policy, it should be remembered that the handling of natural organic acidity was a poor example of how to treat dissenting scientific views. The failure to account for organic acidity contributed to a false dichotomy between natural and anthropogenic acidification, when in fact they coexisted. The difficulty of resolving opposing viewpoints is a challenge for all policy relevant science. Although science can indeed support the policy process, there is a peril in not seriously and respectfully considering dissenting viewpoints and alternative hypotheses with controversial policy implications. With respect to acid rain, such dissenting voices contributed to advancing the clarity of the understanding of a complex environmental issue, despite these alternative viewpoints’ being eschewed by some at the time. This shortcoming in the handling of organic acidity has contributed to mistakes in Swedish remediation measures (Bishop 1997) but might be a salutary example that will help avoid mistakes with other environmental issues. [Emphasis added]