Kala Vijayraghavan

There's a forest in Utah where every single tree is actually the same tree. 47,000 trunks growing out of one giant root system, all clones of the same parent. The whole thing weighs about 13 million pounds, around 40 blue whales worth. It's called Pando, and it's been alive for around 80,000 years. Humans hadn't even started painting in caves yet when this thing took root. It's the heaviest living thing on Earth. Trees do some properly weird stuff. When a giraffe starts eating an acacia tree in Africa, the tree releases a warning smell into the air within minutes. Other acacia trees nearby pick up that smell and immediately start pumping bitter chemicals into their own leaves, before the giraffe even gets there. Giraffes have actually figured this out and learned to walk upwind, so they can get a few bites in before the trees notice them. In 1997, a Canadian scientist named Suzanne Simard found that trees in a forest are connected to each other underground, through a giant web of tiny fungus threads that link them all together. Her experiments showed that one tree can send food and chemical messages to another tree through this fungus network. The press nicknamed it "the wood wide web." Some of the bigger claims about trees being one happy family are still being argued over by scientists, but the basic idea, that trees pass signals to each other underground, is now solid science. And some live for thousands of years. There's a tree in California called Methuselah, a kind of pine, that is almost 4,860 years old. It was already 200 years old when the first Egyptian pyramid was built. There's another one growing nearby that scientists think is over 5,000 years old. Both were already ancient when Stonehenge went up. Trees also do something to your body when you're around them. A Japanese researcher named Qing Li ran an experiment. He had people spend a few days walking in forests, then took their blood. The cells in their immune system that fight off viruses and tumors had jumped sharply, and the boost lasted for over a week after they got home. He had another group take the same kind of trip but to a city instead. They got nothing. The trees were releasing some kind of compound into the air that the city didn't have. The tallest tree in the world is in California too, a coast redwood named Hyperion. 381 feet tall (taller than the Statue of Liberty), around 700 years old. A single trunk holds 550 million leaves. You're sharing the planet with all of this.