SPIEGEL: You keep track of expeditions to the Himalayas from Kathmandu, the Nepalese capital. Earlier this month four climbers lost their lives on Mount Everest. Among them was a 61-year-old German man. What happened?
Bierling: The German climber is thought to have died from cerebral edema. The others were trapped on the Hillary Step, a bottleneck at 8,760 meters (28,740 feet). One of them is thought to have become snow blind. This year the conditions on Everest are bad; there has been a lot of falling rock.
SPIEGEL: On the weekend before last, 200 climbers began making their way to the summit at the same time. Isn't such a situation ripe for catastrophe.
Bierling: The climbing route is marked by a fixed rope, it is like a highway to the top. Sometimes up to 20 climbers are clipped on to a single rope, which is only anchored to the ice with a couple of screws. The climbers can barely pass each other because it would cost too much energy at such an altitude. Delays are inevitable. Climbers get cold while waiting and they can become short on oxygen.
SPIEGEL: Mr. Everest is attracting more climbers than ever. Why?
Bierling: Business is booming; Everest opens many doors. There are people who begin their climb as mechanics or hairdressers and fly back as authors or motivational coaches. They want to use their climb as a calling card and as a result they come up with some bizarre ideas.
SPIEGEL: Like what?
Bierling: This year, one climber wanted to take his bicycle with him to the top of Everest. A few years ago a Dutch man tried to climb to the top wearing only underpants. He got to 7,400 meters (24,300 feet). There's too much bravadó now and people are losing respect for the mountain.
SPIEGEL: Why doesn't anyone restrict the number of people climbing Everest?
Bierling: Those wishing to climb the mountain must pay the Nepalese authorities $10,000 (7,963). Nepal is one of the poorest countries in the world and the climbing indutsry is an important source of revenue.