Bremner was speaking Tuesday at an event hosted by the Woodrow Wilson Center, which has formed a working group of scientists and officials working on climate change and family planning to try to cross the gap between the two. Even as the population passes 7.2 billion and is projected by the United Nations to reach 10.9 billion by the end of the century, policymakers have been unable—or unwilling—to discuss population in tandem with climate change.

But there’s been little or no funding for such programs, and the discussions tend to stall before getting into meaty policy. And despite the United Nations holding a special session on population and development a day before its September climate-change summit, academics lamented a lack of cross talk.

Why? Talking about population control requires walking a tightrope: There’s nuance between encouraging access to birth control and a China-style one-child policy, but that doesn’t always translate in the retelling, and it can all too easily sound like a developed world leader telling people in the developing world that they should stop having children—especially because much of the population boom is coming from regions like sub-Saharan Africa.