In 1983, a young Australian driving along a sandy track in the wilds of Niger in west Africa stumbled on a revelation that would transform his life and the fortunes of millions of Africans. Tony Rinaudo had spent three exhausting and dispiriting years trying to bring God and sustainable agriculture to poor, famine-plagued village communities on the southern fringes of the Sahara Desert. His efforts to help replant forests in one of the harshest climates on earth had been met with suspicion, hostility and failure. Then came what many of Rinaudo's faith would count a miracle, or at least a road to Damascus moment, in the desert. Stopping briefly before heading into a particularly rough section of track, Rinaudo paused and, while pondering his misfortune, gazed at some small shrubs growing nearby.

"I had a trailerload of trees in the ute and I stopped to let pressure out of the tyres to go through the sandy track better," he recalls. "It dawned on me how useless it all was. In every direction there were no trees. And here I was with this piddly little trailerload of trees and I knew the farmers weren't going to look after them and most of them would die. But these shrubs caught my eye and I saw very quickly that this was the same leaf structure as some of the existing trees. I suddenly realised this wasn't a shrub but a tree trying to regrow."

It is not just about tree-hugging. It is actually crucial for survival.  

Bauhinia reticulata is a tough hardwood mostly used for firewood. Fast-growing, it produces abundant foliage for fuel and fodder, enhances soil fertility and crop yields, and allows farmers to plant crops right up to the trees' trunks. What Rinaudo realised that day was that Bauhinia reticulata and many other native tree species had not, as people thought, vanished over the decades after being relentlessly felled for firewood or to make way for agriculture, torched by marauding herdsman and ostensibly killed off by the extremes of climate. Instead, many of the trees were simply dormant beneath the ground, their vast root systems still alive - in some cases a century or more after the trees had gone.

What was needed to bring back the forest vegetation of Niger was not replanting but regeneration - protecting the first regrowth from the old root systems, from grazing livestock and from human plunder, then carefully pruning to encourage growth and guarding the reborn trees from premature harvesting. The methods Tony Rinaudo pioneered to achieve that end become known as Farmer-Managed Natural Regeneration (FMNR).

Three decades on, FMNR is transforming the landscape not only of Niger but also vast areas of Africa and Asia. More than five million hectares, or half Niger's farmland, has been regenerated through FMNR, and substantial tree regeneration has also been achieved in Ethiopia, Ghana, Senegal, Burkina Faso and Mali. Rinaudo, who joined World Vision Australia after returning from Niger in 1999, is now driving FMNR programs in 11 African and five Asian countries, including East Timor, and is about to start work in Haiti. Chris Reij, a senior fellow with the non-profit World Resources Institute, has described it as "probably the largest positive environmental transformation" in all of Africa.

Tony Rinaudo grew up in Myrtleford, northern Victoria - once the tobacco-growing capital of Australia - one of six children in a devout Catholic family. The environmentally-destructive farming practices of the 1950s and '60s had a powerful impact on the boy. "At that time they were using planes to spray the crop," he remembers. "It would kill fish in the stream. They would clear-fell the native bush, which I loved, and replace it with a monoculture of pines. I would see little kids in India or Africa going hungry and it didn't add up that we were putting so much effort into these things that seemed to be destructive, and children over there just needed food. Something clicked in my heart."

After studying agricultural science at the University of New England in Armidale in northern NSW, where he met his wife, Liz, Rinaudo joined Serving in Mission, a missionary society with a substantial presence in Africa. He wanted to go to English-speaking Nigeria or Ghana, but Serving in Mission had other ideas and sent him to Francophone Niger, one of the poorest and most environmentally-challenged nations in west Africa.

The southern third of Niger was once covered with dense dryland forest teeming with elephants, giraffe and buffalo. "For generations the trees had served all of the people's needs; it was their pharmacy, their supermarket, their hardware store," says Rinaudo. That began to change radically around the 1970s, when severe drought hit the Sahel, the semi-arid region that spans sub-Saharan Africa from the Atlantic to the Red Sea. Niger, once home to more than 50 species of trees, saw massive deforestation and the disappearance of most forest diversity. Successive droughts killed many trees and resulted in many more being cut down by people desperate for income from firewood.

In 1960 Niger's population had been about four million. By 1980 it had doubled and has now redoubled to about 16 million. "As the population grew, so did the cities," says Rinaudo. "There was a significant market for wood for fuel and timber. In the past, famine might strike in west Africa every 50 or 70 years. In the 1970s they started to occur more frequently and more recently; big famines have been happening about every five years."

That reality confronted Tony and Liz Rinaudo when they arrived in Niger in 1980 with their six-month-old son, Ben. They would stay for nearly two decades, raising another son and two daughters. The mission station they were assigned was a farm school in a village near Maradi, Niger's second largest city. Rinaudo was tasked with running a project planting windbreaks and woodlots. "It had been born out of the 1975 famine. There was a little money left over and the missionaries asked to use that for tree planting. Most community members weren't interested at all. Everything was so hard: the climate, the people, the work, and I thought, 'Why on earth am I here?' "

By 1983, Rinaudo began experimenting with FMNR. Well aware that Australian gum trees coppiced when cut (a process whereby the stumps regenerate with new shoots and stems), Rinaudo says he had been blind to that possibility in Africa. "Other organisations - USAID, World Bank-funded projects, the Niger government - were planting trees, so there was a certain mindset: have desert, will plant. Even in the face of failure, you just worked harder. And it still didn't work."

Even after Rinaudo realised the potential to regenerate the forests, he struggled to persuade the village farmers. "People's hearts weren't in it. They were more concerned to earn money or grow food and not many people saw the link between deforestation and declining soil fertility and crop yields."

The turning point came in 1984, when another devastating drought swept the Sahel. In Niger there was almost no rain and total crop failure, which triggered one of the worst famines recorded. Official estimates were that 100,000 people died across the Sahel but Rinaudo believes the toll was higher. "Suddenly people started to think that maybe there was something wrong with cutting all the trees down," he says.

Rinaudo turned his limited famine relief funds into a food-for-work program that pressed villagers into compulsory tree-management projects. Over 12 months his mission raised about $500,000, purchased 1800 tonnes of grain and helped 50,000 people - provided they agreed to manage the regenerating trees.

"But at the end of the famine," he says, "when their crops came in and we discontinued the food aid, of the 500,000 trees that were pruned and on our books, two-thirds were immediately cut down for fuel or cash. Many people were ticked off that I had required them to protect the trees on their own land when they were not convinced of the benefits, but one-third of the farmers said, 'No, Tony's not completely mad. We still got a crop and, in fact, the crop did very well and we had some extra firewood that we wouldn't have had before and there's fodder, so we are going to try this.'

"Before the famine, the project had been working in just 10 villages. It intensified and expanded during the famine to 100 villages, then would have scaled back a bit after that, but the message was the same: food or no food, this is a good thing to do, the right thing to do economically, biologically and environmentally. People who had lost hope and were leaving for the cities were content to stay. They started to dream."

And the word spread. "We trained some of the Care International people and other non-government organisations and we sent farmers to other parts of the country to show them what we were doing." In search of hardier species to withstand the droughts, Rinaudo also promoted some species of Australian acacias, a traditional food source for Aborigines. "The nutritional profile is quite astounding. The seed contains about 20 per cent protein, 40 per cent carbohydrate and 6 per cent fats. Many of these species thrived under the conditions in west Africa."

World Vision Australia is exploring the food and fodder potential of about 40 species of acacia. But Rinaudo - and many Africans - are already convinced. "There are villagers in Niger who love that food. They have dances and songs about it. The guys tell me, 'If you eat this stuff you can see further and you are stronger, you can work harder, and you are better in bed as well.' "

It wasn't until he was back in Australia in 2004, five years after he returned from Niger, that Rinaudo discovered how profound the impact of FMNR had been. Now with World Vision Australia, he returned to Niger to explore a new resource management project. There he met Chris Reij, a human geographer then working at Vrije University in the Netherlands who had just completed a national forestry survey.

"He said, 'There is something amazing happening here.' He did a back-of-the-envelope calculation and said there had been more than a million hectares of regeneration. He banged his pen down and said, 'It's time to stop researching. This story needs to get out.' "

Reij helped to persuade the Dutch government to commit €40 million to FMNR projects in Africa. "Now the Dutch are talking about this being a pilot," says Rinaudo. "Can you imagine how big the mother will be?" He says there's at least a doubling in crop yields in areas where FMNR is being practised, with regenerating trees providing shade for crops, retaining moisture in the land and fodder for livestock that enrich the soil with their waste. "We have had this depressing story about the Sahara encroaching south into the Sahel and now, against the odds, satellite images are showing the opposite, not just in Niger, but in Mali, Burkina Faso and now in Senegal."

The forests of East Timor saved Manuel da Silva's life. Now he is their champion and guardian. "In the past it was just slash and burn," he says. "Now if I see people doing this I will call the police and I will fight them myself, if necessary, to make them stop. We have seen what happened in Africa and we don't want to see the same thing here."

Da Silva once was a soldier, a member of the Falantil guerrilla movement led by Xanana Gusmão that resisted Indonesia's 25-year occupation of East Timor. "For four years I lived in the forests. We didn't burn them. The forests protected us. They saved us."

After East Timor won its independence in 1999, Da Silva returned to the farming district of his birth near the town of Aileu in the hill country behind Dili. Now, with his wife and 12 children, he is building a garden oasis, an instinctive pioneer of the principles of FMNR. Thousands of trees once clear-felled are now regenerating around groves of coffee, pineapple and cinnamon. A nursery provides seedlings to other farmers keen to restore their environment.

"Before, there was nothing here, just red soil and the stumps of old trees," Da Silva says. "There were landslips and severe erosion. Now the trees are coming back and many other types of plants are regenerating and the soil is more fertile. At first people thought I was crazy. Now everyone wants to do what I am doing."

East Timor is a new frontier in FMNR. One of the poorest countries in south-east Asia, it also has one of the most degraded natural environments, having lost most of its native forest cover. The Portuguese colonists stripped most of the valuable timbers, the sandalwood, mahogany and teak, unravelling the traditional code of tara bandu, which carefully guarded and managed the forest resource. During World War II, both the Japanese and Allied forces used fire to try to flush out the enemy. After the Indonesians invaded in 1974, what remained of the native timber was plundered.

"There are whole valleys and hills with just stumps left," says Rinaudo. "This would once have been a country of dense tropical rainforest." Rinaudo sees regenerating the forests of East Timor as crucial to the task of improving the lives of the predominantly rural population. "They won the battle for independence but they have still to win the battle over poverty."

There is a strong commitment by the Timorese government to conserve and protect forests. The rules of tara bandu were reimposed about three years ago, halting seasonal burning in rural areas.

"Already we are seeing a reduction in the amount of flooding and landslides, which is a great saving to the economy," says Rinaudo. "As the trees recover, there will be more biodiversity, so more options for people to earn income and to harvest different kinds of food.

"At the moment, they rely on rice and maize. If the forest comes back, we can have honey, a very valuable commodity. We can sell wood. There might be high-value fruits and spices that people can plant in among the regenerating trees."

Tony Rinaudo's experience has also convinced him that FMNR offers a powerful weapon in fighting the impacts of climate change. "It is not just about tree-hugging. It is actually crucial for survival."

Over the past 25 years, west Africa has seen a 20 per cent drop in rainfall, he says. And there are predictions that inland temperatures will rise by between five and 10 degrees in the coming years. But he is convinced FMNR is helping change that grim outlook.

"You are affecting rainfall patterns, and what rain does fall is more effective with FMNR because wind speeds are lower, evaporation is less, more soaks into the ground and is held there in organic matter."

With carbon dioxide emissions from agriculture making up about 25 per cent of total emissions globally, Rinaudo sees great potential for FMNR. "Imagine if agriculture changed from being a net emitter of carbon dioxide to a net sequester, locking in more than it is emitting? When farmers plough the soil, organic matter is oxidising, emitting more carbon dioxide, so the combination of this type of agri-forestry and conservation agriculture where you leave the crop residues on the surface can reduce emissions.

"The trees will actually absorb carbon dioxide out of the atmosphere. The potential, if this becomes a global movement, is enormous."

Mark Baker and Angela Wylie visited East Timor as guests of World Vision Australia.