Kassie Siegel, 36

Environmental law

Siegel continues leading the charge in a landmark legal battle to gain protections for the polar bear under the Endangered Species Act due to impacts from global warming. Last year, the polar bear became the first mammal to be listed under the act, primarily due to threats from climate change, but the decision has met with fierce opposition from oil and gas producers. Siegel is not only fighting off an industry challenge to overturn the polar bear listing, but she is seeking even stricter legal protections for the bear. Now head of the environmental group’s new Climate Law Institute, Siegel is also focusing her energy on pushing for stringent federal climate change legislation.