Australia’s wildfires have illuminated a growing global concern over water quality. That’s because forests, grasslands and other natural areas that supply drinking water to millions of people are increasingly vulnerable to fire in a hotter, drier world.
More than 60% of the water for the world’s 100 largest cities originates in fire-prone watersheds. And countless smaller communities also rely on surface water. But storms can dump far more water in a shorter period than in the past.
That means ash, sediment and debris from burned areas can quickly wash into waterways. Affected areas include the Western U.S., where 65% of water supplies originate in forested watersheds. Experts say communities need to prepare for more impacts.