Don: Time to go again to the A Moment of Science mailbag. A listener writes:

 

Dear A Moment of Science,

 

During the 2008 presidential election, I read about how Sarah Palin opposed the federal government declaring polar bears a threatened species. And it made me wonder: Who decides if a species is threatened? How does that work?

 

Yaël: Great question. And the answer lies in the Endangered Species Act of 1973. Five basic criteria are used to determine if a species is threatened or endangered: 1) if its habitat or range is being destroyed or significantly modified; 2) if the species is being  overused for commercial, scientific or other purposes; 3) the extent of disease or  predation; 4) laws already in place that don't provide adequate protection; and 5) other factors threatening the specie's existence.

 

D: As you can tell, these criteria are vague. So the federal government needs to rely on the best available scientific data to make decisions. And as you can imagine, the process can get very political. But once a species has been defined as threatened or endangered, it comes under the protection of the U.S. Fish & Wildlife Service.

 

Y: In the case of polar bears, Sarah Palin based her case on studies paid for by natural gas and oil companies. Siding with these businesses, she argued that protecting polar bears and their habitat would hurt Alaska's economy. But the federal government sided with the bears. They were listed as a threatened species in May of 2008.