Biologists find the world’s southernmost tree on a wind-battered island in Chile
Wind, and not temperature, is the biggest determinant of where it lives (and where it does not)
At the beginning of 2019, a group of 14 researchers led by biologist Brian Buma from the University of Colorado-Denver, made the days-long journey to Isla Hornos in the Cape Horn archipelago, near the tip of southern Chile. Their goal? To lay eyes on the southernmost tree in the world.
Their trip was not simply another expedition documenting life at the world’s extremes: the data they collected is important in understanding what environmental factors limit plant life on earth. Their findings have recently been published in the journal Ecography.
The expedition team surveyed trees across Isla Hornos, a craggy island just nine square miles in size. Their approach to surveying its plant life was similar to methods used by forest ecologists around the world: they identified and measured trees, and took wood cores from them to determine their ages. But in contrast to tropical forests, which can have well over 500 species of tree per hectare, just three types of tree can be found on Isla Hornos. And, because the wind that whips across the island is so strong, the trees there grow horizontally instead of vertically.
Most of the island was treeless, so the researchers found picking out the southernmost tree to be fairly easy. This record-holder is a 42-year-old Magellan’s beech tree (Nothofagus betuloides). It is just 57 centimeters tall – a little above knee-height – but stretches two meters horizontally. The wood core data told them that this tree was much younger than the trees in the more forested areas, which were over 100 years old.
From the wealth of data they collected during their expedition, the researchers concluded that at these southernmost reaches of the planet, trees are limited more by wind exposure than by temperature. This is unlike other treelines around the world. But similar to other trees, those on Isla Hornos will change as Earth’s climate does. The island is already one of the windiest places in the world, with wind speeds topping 72 kilometers per hour (~45 mph).
Isla Hornos is projected to get even windier with climate change. If that happens, someday the world’s southernmost tree might not quite be so far south — the record-holding Magellan beech will die and the treeline's edge could contract to the north, where there is protection from other trees. And, given that the National Geographic staff writer that accompanied the research team, Craig Welch, noted that they “hiked and camped through gales that knocked us down,” I wonder if biologists will even be able to get there to see it.