Forests on Forests

In this episode of Radiolab, hosts Latif Nasser and Robert Kralwich explore the hidden world of forest canopies—revealing a previously overlooked ecosystem that exists high above the forest floor. Building on the groundbreaking 'From Tree to Shining Tree' episode about underground fungal networks, they dive into the discovery of 'canopy soils': rich, deep layers of organic matter that form on tree branches, supporting entire miniature ecosystems. Ecologist Nalini Nadkarni recounts her pioneering work in the 1980s, climbing old-growth trees in Washington’s Olympic rainforest and uncovering soil, moss, lichens, earthworms, and even aquatic copepods hundreds of feet in the air. Scientists like Karina Mifune reveal that these canopy soils are not just habitats but vital nutrient reservoirs—especially during spring when forest floor resources are scarce. Trees actively grow roots into these elevated soils, effectively creating 'sky gardens' that act like secret pantries, giving them a competitive edge. The episode paints a picture of forests as layered, fractal worlds—trees within trees, life within life—challenging our assumptions about where ecosystems begin and end. The narrative closes with wonder at nature’s hidden complexity and the idea that forests are not just below us, but all around and above us.