Environmental issues are increasingly central to aspects of human society, whether it’s how we will feed the world’s growing population or what sort of extreme weather events. But even as it becomes clear how critical these questions are, Americans are becoming more divided over how they perceive these problems, and what needs to be done about them. After failing to enact a bill that would cap greenhouse gas emissions in the United States, the Obama administration pushed to promote renewable energy through the federal loan guarantee program. But this initiative, along with a slew of others, came under fire from Republican lawmakers. And even as the nation’s most important elected officials bickered over whether to develop clean energy, massive fossil-fuel projects such as the Keystone XL pipeline mobilized activists on the left and the right.