These Pine Trees Almost Always Lean Toward the Equator

Cook pine trees stand tall on the Kuto Peninsula in New Caledonia. Ross Barnett/Lonely Planet Images/Getty Images

The Cook pine tree (Araucaria columnaris) is a curious specimen. For one, it's an unlikely globetrotter: It was originally found in (and confined to) New Caledonia, a group of islands in the Southwest Pacific Ocean, and was transported to and flourished in all sorts of places around the world. But the quirk that's sure to make you tilt your head with curiosity is that the pine grows, quite dramatically in some cases, with a characteristic tilting trunk.

Now, scientists have realized something startling about the leaning trees: No matter where they are in the world, the Cook pine tilt toward the equator.

Matt Ritter, a botanist working on a book about common urban trees in California, made the discovery pretty simply — by calling up a colleague in Australia and asking if, perchance, its Cook pine trees leaned north instead of south. When the colleague answered in the affirmative, researchers (including Ritter and his colleague) began a study that measured 256 trees in 18 regions and five continents. Indeed, they found that the trees almost always orient themselves toward the equator, and even slant more dramatically the farther from it they're located. Less than 9 percent of the trees don't conform to the pattern of leaning toward the equator, the researchers report.

One thing they didn't figure out? Why the heck the trees grow like this. Most trees know that their roots should grow down and their trunk should grow up. But the researchers posit that Cook pine has an evolutionary hitch that causes the tilt, or a predilection for aiming toward more sunlight. Although there are plants that lean toward the sun, trees typically don't have this tendency, and more research is needed to figure out exactly why the Cook pine prefers to tilt toward the equator.