A new time-lapse video of over 6,000 leaf photos reveals the biology behind fall foliage.
Every year, as autumn sets in, the leaves of deciduous trees undergo dramatic color changes before forfeiting their newfound hues, fading to brown and dying. The process can take weeks, but Owen Reiser, a mathematics and biology student at Southern Illinois University Edwardsville, wanted to see the leaves change in a matter of seconds. “I’ve been getting into wildlife photography and time-lapse for a while, and I couldn’t find a time-lapse of leaves changing color, so I just went for it.” Over the course of six weeks, Reiser took more than 6,000 close-up photographs of leaves in his homemade time-lapse studio, which includes a macro lens and a camera he purchased on eBay, a $10 LED light and a battery that allows the camera to run continuously. “It’s basically a cardboard box and a bunch of duct tape, but it gets the job done,” he says.
Reiser gathered leaves from eight different deciduous trees and took a photograph of each one every 30 to 60 seconds for up to three days. By stitching together thousands of images into a single video, he has truly captured nature's process, revealing the dynamic inner workings of the plants as they transform.
Despite the popularity of fall foliage, the science behind the changing leaves isn’t widely known. “Every fall, people write about color change, and typically the articles are full of all kinds of mistakes,” Lee says. One of the biggest misconceptions is that red and yellow leaves change in the same way, when they actually undergo completely different processes.
The yellow leaves of plants like witch hazel follow a traditional textbook explanation for color change: The breakdown of green photosynthetic pigments called chlorophylls exposes the yellow pigments, or carotenoids, hiding underneath. (Carotenoids are the same type of pigment that gives pumpkins and carrots their distinct hues.) As the leaves continue to waste away, they produce tannins and turn brown.
On the other hand, most red tones, like those in red oaks, come from a pigment called anthocyanin that’s produced as the leaf dies. “People argue that the red color is [also] an unmasking from the breakdown of chlorophyll, and that’s simply wrong,” Lee says. “The red color is actually made when the chlorophyll is beginning to break down - there’s a synthesis of those pigments, so it’s quite a different thing.”
While the science of color change is still shrouded in mystery, Lee thinks it will continue to fascinate both researchers and curious observers for many autumns to come. With work like Reiser’s video, we can now examine the changing leaves with a fresh perspective, bringing new questions into focus and magnifying the puzzle of nature’s ever-evolving palette.