Very high birthrates in places like Niger mean the country's own limited resources must be shared among more people - a particular problem as climate change disrupts farming and herding, threatening food supplies.
Pope Francis warned that climate change risked destroying humanity on Saturday and called on energy leaders to help the world to convert to clean fuels to avert catastrophe.
Seventy percent of Americans now accept that climate change is happening, outnumbering those who don't by a 5 to 1 ratio, according to a new survey by the Yale Program on Climate Change Communication.
