Biodiversity Capital

Tropical rainforests cover only about 6% of Earth's land, yet they hold more than half of all known plant and animal species.

The numbers get stranger up close. A single patch of Amazon forest can contain more tree species than all of the United States and Canada put together. Step a few miles in any direction and the cast of species changes again.

Why so much life packed into so little land? Time and stability.

The tropics have stayed warm and wet for millions of years. While ice ages repeatedly froze and reset the rest of the planet, this band kept running uninterrupted. Evolution had a long, undisturbed stretch to keep splitting one species into many.