In various places around the world, you can find rows of tall pine trees that all lean curiously in the same direction. These trees are known as Cook pines, and scientists now believe they always lean towards the equator.
Originally from New Caledonia, a tropical archipelago in the southwest Pacific Ocean, Cook pines were first classified during Captain James Cook’s second mission to circumnavigate the globe. The trees grow up to 197 feet tall and have a characteristic narrow appearance due to their short branches. The other identifying characteristic of Cook pines is the way they lean to one direction, rather than growing straight up in the air.
Scientists now have a hypothesis for why Cook pines lean as they do. After noticing the pines leaned south in California and Hawaii, but north when in the southern hemisphere, Matt Ritter of California Polytechnic State University and his colleagues decided to unravel the mystery behind the leaning trees.
Ritter and his team measured 256 trees from across 18 regions on five continents, including New Caledonia. The researchers excluded any trees whose growth could be impacted by another object, like a building or electricity pole. The team recorded the height of each tree, trunk diameter, and compass direction and extent of the lean.
Cook pines turned out to be more predictable in their leanings than expected. On average, the pines tilt by 8.05 degrees, leaning south in the northern hemisphere and the opposite direction in the southern hemisphere. The further away the trees grew from the equator, the greater the slant.
Though some plants lean towards a light source, they typically correct this tilt as they grow. The Cook pines, however, are an exception. It is possible the trees have a genetic feature that lets them lean to seek out more sunlight in latitudes other than their native range. Thus far, the scientists have not been able to draw a firm conclusion as to the exact reason for the lean.
