Yesterday, TIME published the news that the Sierra Club had taken more than $25 million dollars from the natural gas industry — specifically, from employees and subsidiaries of Chesapeake Energy, one of the largest natural gas companies around. The donations came at a time when the environmental movement was rallying behind natural gas as a “bridge fuel” — an energy source cleaner than coal that could lead to a renewable energy future.

But in 2010, the Sierra Club’s new executive director, Michael Brune, decided to end the financial relationship, forgoing an additional $30 million in funding — an amount equal to a quarter year’s budget for the club. By then, issues with hydrofracking had become more apparent, and as Brune told TIME, “We need to be unrestrained in our advocacy … The first rule of advocacy is that you shouldn’t take money from industries and companies you’re trying to change.”

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That Brune is talking about this now shows a real shift in how environmental groups are thinking about clean and renewable energy. In a post on the Sierra Club’s own blog, Brune wrote, “It’s time to stop thinking of natural gas as a ‘kinder, gentler’ energy source … as we phase out coal, we need to leapfrog over gas whenever possible in favor of truly clean energy.”

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