- [first lines]
- David Attenborough - Narrator: Trees, surely among the most magnificent of all living things. Some are the largest organisms on Earth, dwarfing all others. And these are the tallest of them all.
- [ascending 100s of feet into a redwood]
- David Attenborough - Narrator: At the Tiaga's northern extent, the growing season can last for just one month a year. It can take 50 years for a tree to get bigger than a seedling.
- David Attenborough - Narrator: These forests were growing here long before humans walked the Earth. They were in their prime 20million years ago, and existed before the Swiss Alps or the Rocky Mountains were even raised.
- David Attenborough - Narrator: [baby owl's first flight] If you're going to fall here, it's quite a good idea to do it in stages.
- David Attenborough - Narrator: Having fed the predators, the cicadas leave one final gift for the forest itself. The nutrients in a generation of cicadas are returned to the soil all at once, and the trees enjoy a marked spurt in growth. This may be the single largest dose of fertilizer in the natural world.
- David Attenborough - Narrator: Whether trees have needles or broad leaves, it is their ability to survive annual change that has enabled them to cover such vast areas of the Earth, and made the seasonal forests the greatest forests of all.
- Warwick Sloss - Cameraman: [regrouping after a minor hot air balloon accident] We're just deciding which tree to try and crash land into. Preferably the hardest, spikiest one that's nearby. That one looks good. There's some nice, sort of sticking out thorns on it.
- David Attenborough - Narrator: This giant sequoia, a relative of the redwood, is the largest living thing on Earth. Known as General Sherman, it's the weight of ten blue whales.
- David Attenborough - Narrator: Higher up in the nearby mountains, bristlecone pines. The oldest organisms on the planet. Some have been here for 5,000 years. They were alive before the pyramids were built, and were already 3,000 years old when Christ was born.