The Everest industry is suffering from a dangerous shortage of its most important resource: experienced Sherpa guides.
Ethnic Sherpas from the valleys around Everest have become synonymous with high altitude climbing.
With their unique ability to work in a low-oxygen, high altitude atmosphere, they are the backbone of the industry, hauling clients and equipment to the top of the 8,848-metre (29,029-foot) mountain.
The number of Everest climbers has more than doubled in two decades, however, and the Sherpa supply has not kept pace. Raw recruits are now being used to reach the top and it has already taken a toll.
Dawa Sange Sherpa, 20, summited Mount Everest last year -- a first for him and the climber he was with.
On the way down, the cold, lack of oxygen and exhaustion took hold. The pair collapsed just below the summit and were found hours later, barely alive.
"My friend said to me, 'He's done'. But I found a small pulse in him," said guide Ang Tshering Lama, who found Sange.
- Everest victim -
Lama dragged the unconscious Sange back down the mountain while others helped his client.
Both had severe frostbite. Sange lost all of his fingers, spelling the end of his short career on Everest.
Sange was not meant to be guiding that year. He was planned to be carrying equipment up the mountain, a job many young Sherpa do before graduating to become guide.
"I was in the second team, in which untrained Sherpa usually carry the equipment and food from the base camp to camp two, three and four," Sange said.
But his employer, Seven Summit Treks, the largest Nepal-based expedition operator, had more than 60 clients on Everest and needed someone to take a paying climber to the top.
Head of Seven Summit Treks Mingma Sherpa said Sange was ready to be a guide and had previously summited Everest. Sange said he had not.
Nine other Sherpa from Seven Summit Treks were rescued on Everest that year, but Mingma denied there were any problems.
"A Sherpa can summit five times, eight times but sometimes he gets a problem. That's the body," he said.
With the climbing season barely started, so far this year at least four Sherpas from Seven Summit Treks have already sustained frostbite, according to base camp sources.
- 'Risky business' -
No qualifications are needed to work on Everest. Some expedition operators require staff to do one of two short courses for mountain workers. Others do not.
Mingma dismissed the Nepal Mountaineering Association courses as worthless, saying everything could be learned on the mountain.
"My Sherpa don't have any training with NMA. NMA training for us is not enough, we should do our own training on the mountain," he said.
Dawa Steven Sherpa of Asian Trekking requires all staff to have done the NMA course. He said that budget expedition operators hire inexperienced Sherpa to cut costs.
"As long as his name is Sherpa," he quipped of the recruitment criteria.
Experienced Sherpa guides can make up to $10,000 in the April to May climbing season, more than 14 times Nepal's average annual income. The lowest paid will barely scrape together $1,000 for two months' risky work.
"It's the fault of the clients as well if they just close their eyes and go cheap," said Lama, who rescued Sange.
Seven Summit Treks -- which charges about $20,000 to climb Everest, less than a third of other operators -- blames rivals for the shortage, accusing them of not investing in the next generation of Sherpa guides.
"They take only experienced Sherpas. They don't want to spend extra money to train new Sherpas," Mingma said.
Phurba Tashi Sherpa, head Sherpa with the Himalayan Experience company, who has summited Everest 21 times, said it was becoming more difficult to find experienced Sherpa for his team.
"The young Sherpa are very strong and they think they can do everything, but actually they can't. The older Sherpa go slow and steady," he said.
Sherpa have been helping Everest climbers since the first British teams set their sights on the summit in the 1920s.
Their unique physiology, adapted over thousands of years of living at high altitudes, has made them essential since. A recent British study found that Sherpas use oxygen more efficiently than lowlanders.
But climbing Sherpa have arguably become a victim of their own success, and the community is now at a generational turning point.
Many experienced Sherpa who started working for the first commercial expeditions in the 1990s are retiring. Others have left Nepal for rival mountaineering countries buoyed by their reputation for being strong and dedicated.
They have earned enough money to educate their children in Kathmandu, or even in India and the United States.
"They are educated so they can find other jobs," said Kami Rita Sherpa, who has been guiding on Everest since 1994 and admits he would never allow his son to work in such a "risky business".
"If the old climbing guides don't bring their kids into this sector, the number of climbing Sherpas will definitely decline," he continued.
"Those from the next generation won't join this field."
Sherpa Ang Tshering Lama -- one of Everest's dying breed of experienced guides -- at the mountain's base camp
The number of Everest climbers has more than doubled in two decades but the Sherpa supply has not kept pace
Mountaineers walk from Camp 3 to Camp 4 as they push for the summit of Mount Everest
Summit route on Mount Everest. The Everest industry is suffering from a dangerous shortage of its most important resource: experienced Sherpa guides.
A climber walks through base camp below Everest, which is suffering from a dangerous shortage of its most important resource: experienced Sherpa guides
Tents at Everest base camp. No qualifications are needed to work on the mountain and although some expedition operators require staff to do a short course for mountain workers, others do not