LAGOS, Nigeria (AP) — The United Nations says the world’s population is reaching the 8 billion mark on Tuesday. The projection came in a U.N. report released in July that said much of the growth expected between now and 2050 is coming from just eight countries. Half of those are in sub-Saharan Africa: Nigeria, Congo, Ethiopia and Tanzania. The U.N. says that populations in the region are growing at 2.5% — more than three times the global average. Still, experts say the bigger threat to the environment is consumption, which is highest in developed countries not undergoing big population increases. The report also said that India is expected to overtake China next year as the world’s most populous country.