Environmentalists tend to tread carefully around the subject of population.
In a planet of finite resources and no place to throw things "away," overpopulation could devastate the Earth.
Philip Cafaro has been talking for years about the intersection between environmentalism and population studies.
In his latest book, "," Cafaro narrows the focus on immigration into the United States... and makes a rare progressive (not conservative) argument for reducing it.
He joins us to explain.
