These Pine Trees Always Lean Towards the Equator

Cook pine trees in Hawaii, all slightly tilted south. Deb Nystrom/Flickr

There's only one latitude in the world where these unusual pine trees stand straight up. Everywhere else, they have a characteristic lean.

Cook pine trees, conifers endemic to the remote archipelago of New Caledonia in the Pacific Ocean, can be recognized due to their slender, spire-like crowns and the fact that they all tend to tilt in the same direction. In their native habitat, which is located in the Southern Hemisphere, they always tilt north.

But when Matt Ritter, a researcher at California Polytechnic State University in San Luis Obispo, California, was recently writing up a description of the Cook pine for a new book, he noticed that all of the trees that he observed were tilted south. He wondered if there might be a pattern, so he rang up colleagues from around the world and asked about the Cook pines growing near them.

Incredibly, he found that Cook pines located in the northern latitudes all tilted south. Those located in the Southern Hemisphere leaned north. In other words, here was a tree that seemed to always lean towards the equator.

“We got holy-smoked that there’s possibly a tree that’s leaning toward the equator wherever it grows,” said Ritter of his eureka moment, to New Scientist.

In all, Ritter's team studied 256 Cook pines scattered across five continents, from 18 locations between latitudes of 7 and 35 degrees north, and 12 and 42 degrees south. They calculated that the trees tilt by 8.55 degrees on an average, but they also found that the trees slant more the further they are from the equator in both hemispheres. In fact, one tree in South Australia was found slanting at an extreme 40 degrees.

At this juncture it's unclear why the trees lean like this, but researchers suspect it has to do with getting more sun. You might say that the trees always conveniently point toward warmer weather.

“We could be just dealing with an artifact of its genetics that we are seeing now when we have spread it all over the world,” said Ritter.

The study was published in the journal Ecology.