Pacific

World Health Organization and UNICEF has found that the world is on track to surpass the Millennium Development Goal for drinking water access, but will fall short by one billion people for sanitation if current trends continue.

A look at what is commonly considered the greatest Karst landscape on earth, and its secret waters that flow underneath.

KUNMING — The ground quakes with a blast as the limestone fragments are blown from their roots, like giant white teeth shattered and unmoored. Nearby, a worker prepares his drill to place another stick of dynamite deep within the rock. He stops for a moment, places his foot high on the rubble and surveys the vast construction landscape that will soon become China's fourth largest airport.

Scientists who study caves and karst landscapes are like all researchers. They look for data that addresses the broadest and most significant questions possible. It turns out that caves do a good job of providing significant answers. Those that contain animal fossils and records of ancient humans, for example, have been shown to have great value for understanding climate change and past environmental conditions.