As any experienced mountaineer will tell you, ascending Mount Everest demands skill, experience and a deep knowledge of the mountain and your own limitations.

The climb is so perilous that the vast majority of those who attempt it fail to achieve their objective.

Worse, the bodies of those who could not descend in time, who made a crucial mistake or simply suffered bad luck remain littered across Everest's treacherous path, a grim warning to others who would aspire to reach its peak.

As Sandra Leduc, a climber following the same route as her ill-fated fellow Canadian, Shriya Shah-Klorfine, tweeted, the path was strewn with "lots of dead or dying bodies," adding, "Thought I was in a morgue."

While fatalities can occur because of accidents and falls, many lose their lives in what is called "the death zone," the area of the mountain that stretches higher than 8,000 metres above sea level.

The low oxygen levels at that height can cause a sense of deep fatigue, lulling the inexperienced into a sleep that they never emerge from.

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Alan Arnette, a well-known mountaineer and blogger from Fort Collins, Colo., has completed the challenge of the seven summits – climbing the tallest mountains on each of the seven continents. (Courtesy of Alan Arnette/The Coloradoan/Associated Press)

Alan Arnette is a well-known mountaineer from Fort Collins, Colo., who has managed to complete the challenge of the seven summits — climbing the tallest mountains on each of the seven continents.

He successfully summited Everest in May 2011, following three failed attempts over the previous decade. He spoke to CBC News about the dangers of the mountain and of reclaiming the bodies of those who have died on its slopes.

CBC News: How many bodies are still on the mountain?

Alan Arnette: You know, you'll never get a 100% accurate number for that.

Last year I was climbing it, one of our climbers died, and his body was removed.

The best number I have is that approximately 233 people have died and of those, my wild guess is that 200 bodies are still there.

What is the process for removing bodies from the mountain?

It's very complicated. First off, it depends on where the person dies. If they're at base camp or at the icefall, then it's a matter of taking their body back down to base camp where Fishtail Air, with those high-altitude helicopters, can get to them.

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Mount Everest, at 8,448 m, rises above Everest Base camp in Nepal on May 26, 2003. (Gurinder Osan/Associated Press)

If they climb where the Canadian [Shriya Shah-Klorfine] and the other three people who died did, above the South Col, above 8,000 metres, the difficulty goes up exponentially.

It's expensive and it's risky, and it's incredibly dangerous for the Sherpas. What they have to do is reach the body, then they typically put it in some type of a rigging, sometimes a sled but often it's just a piece of fabric. They tie ropes onto that, and then they do a controlled slip of the body in the sled, for lack of a better term, down to the next camp.

In Shriya's case I guess it would be down the South Col from the balcony, and then they have to go down the Lohtse Face, which is another 5,000 feet [1,500 metres] from the South Col at 26,000 [8,000 metres] down to 21,000 [6,500 metres] to be at a point where the helicopter can come in.

All of this takes anywhere from six to 10 Sherpas a good part of a day to do a controlled slide of the body. They're letting the body use its own momentum to go down the mountain, but sometimes there are little undulations where they'll kind of have to pull it up.

They've occasionally got to cross crevasses or wide cracks, so it requires having to pick up the body. But most of the time the body is just slipping on its own momentum or being pulled along the ice.

Once it gets down to the Camp 2, that's at the top of the Western Cwm, at the base of the Lohtse Face, that's about as high as the helicopters will go, land, pick up a load, and be able to take off again.

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The body of Japanese climber Takashi Ozaki is carried out of a helicopter after it was transported from Mount Everest to Kathmandu May 23, 2011. Ozaki died 11 days earlier, just several hundred metres from the summit. (Navesh Chitrakar/Reuters)

They are able to fly all the way up to the summit of Everest. About six years ago, they actually landed a skid on the summit for just a few seconds. But helicopters do not land above Camp 2 and then load and take back off. That's just the operating limits that they have today.

So it requires multiple Sherpas, they're putting their lives at risk because bad weather could move in, and one of those guys could slip while, not to use the wrong term, while carrying what's truly dead weight. It's just incredibly physical.

The reason that I'm pretty accurate about all of this is that I helped to bury a teammate on another 8,000-metre mountain earlier in my career, so I have first-hand experience in moving a body across ice. And in this case we buried him in a crevasse.

Do the Sherpas cremate any of the bodies they find on the mountain?

Not on the mountain. You'd have to take them all the way back to Kathmandu or one of the lower villages. There's no wood or enough stove fuel to do a proper cremation.

A lot of times when you go climb these mountains you sign what's called a body disposal form. You specify to the operator that if you do die on the mountain — and typically you have your spouse sign this, so think about that conversation — you say leave me on the mountain, or get me back to Kathmandu and cremate, or try to get me back to my home country.

And all of those are either impossible or expensive. It can be $30,000 US just to get a body all the way back to their home country.

Where are the bodies generally found?

They're all over the place. There are people that have fallen into crevasses on the icefall. There are almost no bodies in the Western Cwm and there are none on the Lhotse Face because they just simply slide down into the crevasses.

There are none at the South Col, but then you start to get more above between the South Col and the balcony along the southeast ridge, and then from the south summit to the summit.

But honestly I didn't actually see a body on the mountain last year. Most of them have either been pulled off to the side, or they've been covered up with snow, or covered up by rocks or something by other climbers.

So they're not used as landmarks anywhere?

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'Green Boots,' an Indian climber who died in a small rock alcove on Mount Everest in 1996. Arnette says he is called a landmark, something he considers 'very disrespectful.' In 2006, the year this photo was taken, British climber David Sharp collapsed and died in the same alcove. (Dave Watson/Associated Press)

There is a dead climber on the north side who is referenced by his green boots, and it's very disrespectful. But he is called a landmark, and he is right there next to the trail.

Some experts have said that the overcrowding has contributed to the dangers that climbers face.

That's what happened last weekend. There was a very narrow weather window, we didn't know if there would be a second window — which is happening right now — so you had 200 or 300 people that all got on the mountain at the same time.

There were slow climbers and slow teams and it's almost impossible to pass on the higher sections of the mountain, so you end up getting stuck behind them and you're using your oxygen up and the clock is ticking and people aren't moving and you're getting cold.

It's a recipe for disaster.

Were there any close calls on your last run?

We had an individual who died right below Camp 3. He literally was on the fixed ropes going up to Camp 3 at 23,500 feet [7,200 metres] and he collapsed on the rope and never recovered.

What motivated you to become a mountaineer?

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Alan Arnette talks to his wife Cathy in Fort Collins, Colo. from the summit of Mount Everest on May 21, 2011. His climb was part of his effort to raise awareness of Alzheimer's disease. (Courtesy of Alan Arnette/The Coloradoan/Associated Press)

I'm 55 years old and I started climbing really late compared to a lot of people, at age 38.

My first climb was Mount Blanc in France and Switzerland and I just fell in love with the sport. One thing led to another and I've done 30 major expeditions over the last 17 years.

I just completed a project where I climbed the so-called Seven Summits, the highest mountains on each of the seven continents. I did it in a year, which is almost unheard of. Only about 10 people have ever even attempted it. And I did it to raise money and awareness for Alzheimer's.

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Canadian Shriya Shah-Klorfine died just below the summit of Mount Everest on May 19, 2012. The guide company she climbed with plans to remove her body and return it to her family. (CBC)