If you travel south, past the tip of South America, you reach Isla Hornos, at the edge of Drake Passage. That small island was Brian’s target. The only thing beyond it is the icy continent of Antarctica.
His Chilean and American team spent days searching the island on foot, using GPS and grid mapping. Then, there it was, the southernmost tree on Earth. It hardly looked heroic — just two feet tall, growing sideways more than upward. Brian said it seemed to be “hugging the ground, as if holding on for dear life.”
It’s a specimen of Magellan’s beech, Nothofagus betuloides.
Brian’s question wasn’t only where the last tree grows, but why it stops there. Ecologists had assumed that temperature determines the limits of trees. But Isla Hornos is surrounded by ocean, which moderates its climate.
What seems to stop trees from spreading farther south isn’t cold — it’s wind. Storms there reach hurricane force, so trees, like Brian’s, survive only in sheltered pockets.
But the real limiting factor is that trees run out of land! If there were other islands just a bit further south of Isla Hornos, Brian and his team would have found them there, in spots protected from those powerful winds.
Sometimes the story of a single small tree reveals the powerful forces that shape our living world.
