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Truth Behind the Headlines: The Clean Air Act saved 1.5 billion birds

The Clean Air Act saved 1.5 billion birds claims one news report. They state that bird populations in North America have declined by nearly 3 billion birds since 1970 and claim this study shows that without the regulations and ozone-reduction efforts of the Clean Air Act 1970, a further 1.5 billion birds may have been lost accounting for nearly 20% of birdlife in the United States today.  

Using our recommended five tips, Global Action Plan reviewed the study:


Questions to ask to get to the truth Our response
1. Does the article refer to a report to back up its claims?

The article refers to the study Conservation cobenefits from air pollution regulation: Evidence from birds published in Proceedings of the National Academy of Sciences. 

2. Who is behind the study it refers to?

Researchers were based at Cornell University, New York. 

3. How fantastical and radical is the claim that is being made?

The researchers used a database of 11 million birding trip reports – adjusted to account for things like birding preferences – to estimate the bird population over time.  


They used U.S. Environmental Protection Agency’s Air Quality System database for their air quality data, specifically looking at ozone.  


Finally the researchers accounted for season and changes in weather so they could determine the impact of air pollution alone on bird population.  


4. What geographical region does the claim refer to?


5. What is the sample size of the study?

Researchers tracked the monthly changes in bird abundance, air quality and regulation in over 3,000 U.S counties over a 15-year period. 


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