UNITED NATIONS (AP) — The outgoing U.N. humanitarian chief is warning that the explosion in people needing humanitarian assistance in recent years will keep getting worse until major powers tackle the root causes of hunger and desperation — conflicts, extremism, climate change, poor governance, corruption and violence, to name a few. Mark Lowcock, who steps down Friday after four years, told The Associated Press that unfortunately the world has been dealing with symptoms. He pointed to people displaced by fighting and natural disasters or at risk of famine, which is now stalking Ethiopia’s embattled Tigray region and Yemen. He called for a much bigger effort to help poorer countries out of the pandemic, and said the G-7 should do more than just donating vaccines.