United Arab Emirates ? The rampant growth of urban slums around the world and weather extremes linked to climate change have sharply increased the risks from “megadisasters” such as devastating floods and cyclones, a U.N. report said Sunday.

The study — which examines natural disaster trends and strategies to reduce potential catastrophes — also noted that millions of people in rural areas are at higher risk from disasters such as landslides where forests have been stripped away or crippling droughts blamed on shifting rainfall patterns.

Much of nearly 200-page report restates warnings from previous studies about unchecked urban growth and shortsighted rural planning. But it also seeks to sharpen the apparent link between climate change and the severity and frequency of major natural disasters including severe droughts and epic storms.

At least 900 million people now live in shantytowns and other makeshift settlements in cities vulnerable to disasters such as cyclones, flooding or earthquakes, the report said. Those populations are growing at a rate of about 25 million a year, it said.