In "Living on the Edge," reporter Martin Smith shares some devastating field notes from the melting Himalayas, drought-stricken Africa and the warming waters of the South East Atlantic. Smith came across these stories while working on Heat, a two-hour FRONTLINE documentary on climate change to air this fall on PBS. Visit the site and watch a preview.

When reporter Martin Smith set out to investigate climate change a year and a half ago, he’d heard a lot about polar bears and melting ice shelves in the Antarctic but less about the earth’s third pole, the Himalayas.

Traveling to the world’s highest point, Smith’s guide is American mountaineer David Breashears. Breashears has climbed Everest five times but this time he is returning on a special mission. He’s going to climb to 19,000 feet, to the place where British explorer George Mallory took a photograph in 1921, to see just how much the landscape has changed.

Eight hours later, with Mallory’s image in hand, Breashears looks across at the Rongbuk Glacier, a frozen river of ice that flows from the north side of the mountain. “I know this place," Breashears says. The mountaineer was last here in 1996.  “Look at the glacier here in 1921,” he says pointing to Mallory’s black and white photo. “To look at it out there now, the glacier’s just gone.”

Scientists report that glaciers are disappearing at an alarming rate across the Himalayas. The Intergovernmental Panel on Climate Change estimates that 80 percent of all Himalayan glacier ice will be gone by 2035.

Before his journey to the Himalayas, Smith visited one of the world’s foremost glacier labs in Columbus, Ohio, where ice cores taken from across the planet are analyzed.

The lab’s founder and director Dr. Lonnie Thompson is said to have spent more time at high altitude than any other scientist in the world.

When Smith asks Thompson how important glaciers are to those living on either side of the Himalayas, Thompson explains that glaciers are the world's natural water towers.“They kind of store water in the wet season and they disperse it during the dry season. And they do that for free,” he says.  But he also points out that the valleys that lie beneath this great mountain range are really dry parts of the world that rely on the water from these glaciers.

For now, the melting glaciers are bringing more water to these slopes. But it’s a short-term boon and a mixed blessing. More water has attracted more farmers and that’s straining the environment.

In the stunning foothills, a Nepali man tells Smith that an increasing population has meant more deforestation and so cattle are producing less milk. “If temperatures continue rising like this, there will be a crisis," he says.

These climate changes will have consequences far beyond the Nepalese foothills.

“You hear people talk about, ‘Oh, we’ve had these huge climate changes in the past.’  Yeah, that’s true,” says Thompson. “But we’ve never had 6.5 billion people.”

Half of the global population, Smith reports, depends on the rivers that originate in the Himalayas. Among them, the Ganges, the Indus, the Mekong, the Brahmaputra, the Irrawaddy, the Yangtze, and the Yellow rivers. The IPCC predicts that in the near future, some will no longer flow year round.

Dr. Rajendra Pachauri, chairman of the IPCC, says that 500 million people on the Asian subcontinent -- 250 million people in China alone -- will suffer from water scarcity as a result of melting glaciers. “In terms of the impact on the lives and livelihoods of people,” he tells Smith, “we’re turning thousands of years of human history around and perhaps, leaving people with no choice now.” Vast parts of China are already water stretched, making conflicts with neighboring countries over water rights inevitable.

A continent away, those conflicts have already begun.

Next, Smith travels to northwestern Kenya, near the Sudanese border, where the Turkana tribespeople live on the edge of poverty.

When he arrives, they have just had their first rain in months and the landscape has turned a rich green.

The people here have always lived with droughts. But they used to come every decade. Now severe droughts are hitting the Turkana every few years and lasting longer.  The worst in living memory began in 1999 and lasted six years.

Smith meets some of the tribespeople who are gathered for a wedding feast. But the mood is subdued.  Many men here are unable to pay a bride price and have to go into debt in order to get married.

One woman explains to Smith that in the past men had enough cattle to afford many wives. “Now,” she says, “even paying for one wife is difficult. No one can afford to marry.”

In the last drought, the tribe lost half its cattle.  Since then, food aid has been keeping them alive.

When Smith asks the tribe who is responsible for these changes, one tribesman responds, “First, I have to blame God, because God gives out the rain and can refuse at any time. But I also blame the white man. Since he left, there has been no rain. And that’s why the droughts are so frequent.”

Many men have already left Turkana to look for work in the crowded slums of provincial towns.

Professor Jeffrey Sachs, Director of the Earth Institute at Columbia University, tells Smith that pastoralist communities in Northern Kenya, Somalia and Sudan are living at the edge of survival.  “Those places are experiencing a significant, long term decline in precipitation and the effects have been devastating,” he tells Smith. “They've contributed to the massive conflicts in Darfur.  They've contributed to the instability in Somalia. They become security threats for the world, in fact, as well as devastating shocks to these societies themselves.”

In some places, climate change may be causing whole economies to collapse.  

To see this firsthand, Smith travels to the beautiful and remote Skeleton Coast, along the shores of Namibia.

Namibia’s sardine or pilchard fishing industry used to be one of the richest in the world.  Fishing made up 60 percent of the nation’s economy.

The industry was built around the Benguela Current, where cold waters streamed up to the surface full of rich nutrients, spawning millions of fish year after year.  But decades of overfishing and shifting currents that scientists believe are due to a rise in ocean temperatures, have left the industry in steep decline.

On a tour of the fishing harbor in Walvis Bay, veteran fisherman David Narburgh tells Smith that catches are down 90 percent from the good days.

Twenty years ago, Narburgh tells the reporter, there were 44 active fishing boats, which have dwindled to 10 at most today.  As the boat moves across the harbor, the scene is like a graveyard filled with boats that have been junked.

Onshore, the picture is no brighter. Nearly all the canneries have been driven out of business.

“The pelagic [or seafood] industry was the biggest industry in its heyday,” Willem Pronk, Managing Director of the United Fishing Enterprises, tells Smith, as they tour one of the few canneries still operating.

“ I don’t know about the rest of the world. I do know what’s going on out here. Something has changed. What it is exactly, I don’t know,” Pronk says.

Just outside the cannery gates, unemployed young men line up hoping for a day’s pay. Thousands of jobs have been lost since the fishing industry collapsed.

Sixty-five percent of the region’s economy once relied on the fishing industry, now it’s down to less than half that amount, says Daniel Imbili, President of the Namibian Fishing Workers Union.

They are all victims of what is happening now,”says Imbili, pointing to groups of men.“With this climate change, there is less hope."

To restore pilchard stocks, the government has imposed strict quotas on fishermen, but the fish stocks have not rebounded.

Although this community and many others across Africa have seen more dramatic environmental changes in recent years, climate expert Joseph Romm says it’s unlikely that global warming is the only cause of what they are seeing.  But, he says,  “It adds such a terrible stress on over-fished lands so [that] you cross a threshold and you get a collapse. Unfortunately, once you've changed the climate, it becomes very hard to un-collapse,” Romm says.  “It may be that some of these changes are irreversible.”

Across the world, pilchard, salmon, cod, Atlantic blue fin tuna, and anchovy have all suffered serious collapses, reports Smith – all have been struck by the double blows of overfishing and warming oceans.

As the oceans continue to heat up, scientists expect the long-term decline in fisheries to worsen, which will place the billions of people who depend on the seas for their food and income under increasing pressure.

It’s not an easy fix says Romm, "The problem with the way a lot of people look at global warming is they think the climate will change to a new state and that we will adapt to it.” But the big fear, Romm says, is that “the climate just keeps changing and changing and changing, and adaptation is going be exceedingly difficult.”

After reporting on climate change across the world, Smith reflects on what the real story has become -- how the world will deal with global warming. “It’s become a story about the future and the inconveniences we may face," he says.

And for the people he has met in Asia and Africa, the effects of climate change are already far too real.