Around the world local people are restoring forests, boosting their incomes and sucking carbon from the atmosphere
"A decade ago this land was dismissed as lost to the desert," said ecologist Mamadou Diakite. He was smiling beneath the shade of a tree, one of hundreds growing vigorously all around him on land previously abandoned by local millet farmers.
The growth of these trees, and hundreds of millions more in a remote region of West Africa on the edge of the Sahara desert, is the result of local farmers abandoning long-standing advice from government experts to uproot trees on their fields - and to nurture them instead.
What is today called "Farmer-Managed Natural Regeneration" is thought to have begun in the mid-1980s in Dan Saga, a village in the Maradi region of Niger, which suffered hugely from Sahel droughts in the 1970s.
The story is that some young men returned to their fields late in the season after working abroad. In a rush, they planted their crops without first clearing their land of woody plants. To their surprise, their grain yields were better than in neighbouring fields that had been cleared. When the same thing happened the next year, the village got the message: Trees were good for their crops.
So from then on, when preparing their land for planting, farmers cultivated stems growing from stumps in their fields. The resulting trees fixed nitrogen, stabilised soils and dropped leaves that maintained soil moisture.
And before long, the trees were providing firewood, animal fodder and other products, as well as shading crops and villages from wind and sun. The message spread. "It was slow to take off, but now they all want to do it," Diakite said. "The land is coming back into production."
This version of agroforestry has now extended across 5 million hectares of Niger. The 200 million extra trees benefit yields of millet and sorghum on more than a million farms, which typically gain an income of about $1,000 per year from selling products such as wood, fodder, fruit, pods and leaves.
And there is another, less immediately tangible benefit: The trees capture an estimated 30 million tonnes of carbon from the atmosphere.
Niger's grassroots revolution - which for a long time was invisible to outsiders - is not an isolated example of people bringing back diverse forests, but has been replicated in different forms in different corners of the globe - from once denuded farmlands in Costa Rica to the foothills of the Himalayas, from the remote Scottish coast to the Xingu basin in the Amazon, and elsewhere.
In all these places people are doing this as much for their own good as for the good of nature. And the evidence is growing that with the right assistance, such forest restoration could start happening on an even grander scale. If so, it will have profound implications for the fight against climate change.
Intergovernmental Panel on Climate Change (IPCC) author Joeri Rogelj has calculated that to achieve the Paris Agreement's aim of keeping global warming to 1.5 degrees Celsius, total future emissions of carbon dioxide (CO2) will probably need to be limited to less than 300 billion tonnes.
Bringing CO2 emissions to net zero by the middle of this century would fall far short of that target; it would allow total emissions of around 800 billion tonnes. So we will need to suck CO2 back out of the air. On Rogelj's estimates, those so-called "negative emissions" would have to amount to between 450 billion and 1,000 billion tonnes.
The world's forests still store the equivalent of almost a trillion tonnes of carbon. Adding 500 billion tonnes of CO2 equivalent or 136 billion tonnes of carbon to that store would require a 14 percent increase in forest cover.
Although it has so far received remarkably little attention from the climate community, restoring natural biologically diverse forests and nurturing trees on agricultural land could help achieve this.
It is however, clearly a huge task, and the prospect of dedicating large areas of land to absorbing atmospheric CO2 raises fears of a massive land grab. So to succeed, forest restoration will need to be in harmony with local customary land needs and rights.
The good news is that this can be achieved. There is considerable potential to restore biodiversity and tree cover within existing forests in a way that is socially and economically useful for the communities who currently occupy the land, and does not infringe on their land rights.
In fact, restored forests can and often should be managed by the people who live in and around them. This is not a trade-off, but a win-win. There is growing evidence that community and indigenous management of forests is better for the forests, their biodiversity and their carbon storage than much state or commercial management.
But forest restoration alone will not save the climate.
An excessive reliance on its benefits to soak up CO2 would be both unjust and unsustainable. Moreover, negative emissions are a one-off gain, and eventually the growth of forests slows down.
So, however great the potential drawdown of CO2 from the air from restoring the planet's forests, it emphatically does not offer an alternative to stopping forest destruction and bringing CO2 emissions from fossil fuels and land-use to zero as soon as possible.
That said, the climate gains from forest restoration would be real - and could head off the worst impacts of climate change while delivering great social and ecological benefits.
Fred Pearce's report, "Return of the Trees, How restoring natural forests can stem climate change and revive rural communities", is published by forests and rights NGOs, Fern and Rainforest Foundation Norway.
Fred Pearce is an author and journalist who has reported on science, development and environmental issues from 67 countries. He won a lifetime achievement award for his journalism from the Association of British Science Writers in 2011, and was voted UK Environment Journalist of the Year in 2001.
Any views expressed in this article are those of the author and not of Thomson Reuters Foundation.