Nearly 15 years ago I wrote a story for the New York Times science section about the Champion Tree Project, an effort by a Michigan shade tree farmer and his sons to clone the largest tree of every species in the United States.

A year later that farmer, David Milarch, showed up at my office in Helena, Montana, and told me the backstory. The genesis of his tree project was a near-death experience or NDE he'd had, and that light beings on the "other side" had told him that life on the planet was in trouble and that trees, especially old growth trees, were more important than we know. I was dumbfounded. I'd never heard of an NDE before and wasn't sure what to think.

A couple of years later nearly every Ponderosa pine tree on my 15 acres, some of them two or three centuries old, died. The direct cause was a little bug called the mountain pine beetle, but the real cause was the fact that Montana rarely gets the bitterly cold weather that once kept insects in check. They've run rampant through the forests of the Rocky Mountains and are now munching their way across Canada.

Since my first story on Milarch he has continued his project, now called the Archangel Ancient Tree Archive. It's a quest to make copies of old growth trees, especially redwoods and sequoias, and plant the offspring of those proven survivors, all to create living libraries of their DNA and new old growth forests, he says. He's also cloned the living parts of stumps of some of the largest redwoods that ever lived. Last week he planted 10 of those redwoods at a place called the Lost Gardens of Heligan in the United Kingdom, owned by Sir Tim Smit, a renowned record producer.

And I have also written a book called "The Man Who Planted Trees" about Milarch's project, but more importantly about the science, known and unknown, of trees and forests. And here's the upshot: We know precious little about trees and the essential role they play anchoring human life on this planet, and, as the climate grows warmer and the weather gets weirder, they are in big trouble, dying from drought, disease, pests and at the hands of illegal loggers.

The things we don't know about trees are legion and vital. Who's ever heard that trees emit aerosols into the air? These medicinal mists are antiviral, antifungal, antibiotic and some of them prevent cancer — and help maintain the health of the natural world. Bees, for instance, gather this healing resin from willow and aspen leaves and use it to line their hives to protect against disease.

Japanese scientists study something called "forest bathing." A walk in the woods, they say, reduces the level of stress chemicals in the body and increases beneficial cells in the immune system. Landscaped environments in inner cities are shown to lower anxiety, depression and even crime.

Trees are powerful water filters, capable of cleaning up even the most toxic wastes, including explosives, solvents and organic wastes, through a dense community of microbes around the tree roots, a process known as phytoremediation. Tree leaves filter air pollution, and one study found that more trees in urban neighborhoods correlate with a fewer cases of asthma.

Trees are great for fish and other sea creatures. When their leaves decompose, they leach acids into rivers and oceans that fertilize microscopic plankton — fish food. In a tree planting project called Forests are the Lovers of the Sea, fisherman have re-planted forests along coasts and rivers and brought fish and oyster back in large numbers.

Then there is the role forests play in weather. It's poorly understood but vital. Experts blame the drought now devastating Brazil, for example, on deforestation.

I always felt that planting trees was a kind of feel good thing, but not a solution for the serious problems we face. But as I've drilled down on the story of the world's trees and forests, I've found they might be one of our best bets.

They are our heat shield. Simply planting trees in a city can cool the hot asphalt by 10 degrees. They soak up carbon dioxide, the heat-trapping gas causing our predicament.

There is some evidence we can geo-engineer the climate with trees. A cleric in Tanzania, Bishop Shoo, has had parishioners plant thousands of trees to cool the hot breezes that blow across the plains, in hopes of keeping the snows of Kilimanjaro from melting, and prevent a crippling loss of water.

Besides addressing the problem of climate change I've found that trees, if used strategically as a kind of eco-technology, may be the best hope we have to mend the broken pieces of our planet — to restore rivers and wildlife habitat, to enhance agriculture, and to make the planet's ecosystems more resilient in the face of a warmer world.

There's hope for the mess we are in, it's called trees. We need a crash course in understanding the things they can do. And we need start protecting and planting them.

Jim Robbins has written about science and the environment for the New York Times from Helena, Montana for 35 years, and is the author of five books, including "The Man Who Planted Trees: A Story of Lost Groves, the Science of Trees and a Plan to Save the Planet" just out in paperback. He is a co-producer of a documentary based on the book, which is just getting underway.

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