Cold, Damp ‘Sky Islands’ Are Hotspots for Unusual Plants and Animals

Author: Jessica Leigh Hester / Source: Atlas Obscura

On a clear day, when Mount Mantalingahan isn’t cloaked by rain or fog, it provides a commanding view of the Philippine lowlands and ocean far below. Rising 6,841 feet above Palawan Island, the mountain is steep and isolated.

Anyone who makes the climb up will notice that the summit, almost always cold, foggy, and wet, bears little resemblance to the tropical setting below. And that’s exactly why scientists are attracted to it.

Mount Mantalingahan is what is called a “sky island.” Unlike Palawan Island itself, the peak is not physically surrounded by water, but it falls under a broader definition of “island”—any place that is somehow sequestered from its neighbors, and develops an ecosystem all its own.

For researchers, the multi-day hike to the summit is worth it because of the unique environment that has evolved there. Sky islands are known for being hotspots of biodiversity. Larry Heaney, a curator of mammals at the Field Museum in Chicago, learned that years ago, after many seasons of field work in the Philippines. Conventional wisdom holds that tropical lowland rain forests are the best engines of terrestrial biodiversity. That’s true for ants and termites, and for birds and bats, Heaney says. But “it’s not true for earthworms, not true for small mammals, not true for oak trees, not true for orchids, all sorts of things.” For many different groups of plants and animals, he says, peak biological diversity occurs “well up into the mountains.

”

The top layers of the Philippine mountains—above hot, muggy rain forest—dip down to around 40 degrees, too warm for for snow or frost, but sufficiently uncomfortable with the constant damp. “We’re talking 12 to 15 feet of rain per year,” Heaney says. “You smell the kind of aroma you have when you’re working in the garden and soil is wet.”

High atop sky islands, he says, the “character in the forest changes completely.” Unlike the volcanic, nutrient-rich earth across much of the country, that mountain soil can be thick with nickel and other metals that discourage plant growth. It’s not uncommon for mountain trees in the Philippines to be just waist-high, even when fully grown.