Joe Biden’s climate plan promises to put the U.S. on a path to 100% clean energy and net-zero carbon emissions “no later than 2050.” It also vows that greening the U.S. economy will create millions of good-paying jobs, many of them in unions. With this plan, the Democratic nominee for president has achieved an extraordinary feat: winning over both environmental activists and organized labor. But keeping those often-opposed constituencies happy inside the Democratic Party’s big tent will get tougher if the former vice president manages to get elected in November and has to choose between them.

The two kinds of green—dollars and nature—don’t go that well together, Stavins says. And he’s not alone in this opinion. Measures to fight climate change tend to destroy some jobs while creating others, says David Popp, an economist at the Maxwell School of Syracuse University. “The literature that looks at employment effects says it’s mainly about reallocating jobs from one sector to another,” he adds. Fewer coal miners, more solar installers.

It’s understandable that Biden emphasizes jobs in his platform, a sales pitch for his candidacy. It’s essential to counter President Trump, who called the Environmental Protection Agency under President Obama “one of the biggest job killers” and in August withdrew limits on oil and gas companies’ emissions of methane, a greenhouse gas many times more potent than carbon dioxide.