22 Oct 2026 4 min read

Breakdown Dead Ahead

In the aftermath of fading glory

Newly fallen cottonwood leaves. Photo by David Lukas

The blazing colors of autumn get all the glory, but what happens after everyone heads home and stops paying attention?

For one brief, glorious moment each fall, forests enchant us with their brilliant displays of changing leaves. People arrive in hordes to catch the leaves in their prime, articles are written, and stories are broadcast on the evening news. But then the colors fade, leaves drop, and everyone stops noticing what could be one of the most remarkable processes on Earth.

western larches — When the colors fade, most of us stop paying attention. Photo by David Lukas

First of all, it helps to realize how insanely abundant leaves are and what happens when they fall. As I mentioned in a previous newsletter, it is estimated that leaves have twice as much surface area as all the landmasses on Earth combined, and that 60% of all living tissues are leaves!

aerial view of forest — The Earth is wrapped in leaves. Photo by Wirestock Creators/Shutterstock

While small numbers of leaves fall all the time, the mass of leaves that drop in the autumn is almost impossible to comprehend. Although leaves typically weigh less than a gram, a single branch can have hundreds of pounds of leaves, and individual trees can produce several tons of leaves.

tree canopy — Trees are built to hold huge numbers of leaves. Photo by Wirestock Creators/Shutterstock

When these numbers are multiplied across an entire forest, and leaves fall, they constitute the largest source of stored energy and nutrients delivered to the Earth's land surfaces each year. And this stored energy then supports an incredibly complex web of life from microscopic bacteria to the Earth's largest trees.

leaves on ground — Leaves accumulating on forest floor. Photo by David Lukas

Within hours or days, rains begin to leach water-soluble sugars, amino acids, and minerals from fallen leaves into the soil, where they are readily consumed by microorganisms. Then, as leaves begin to soften, larger decomposing organisms like earthworms, millipedes, and mites begin to nibble on fallen leaves, consuming many of the most easily accessed nutrients and breaking leaves into smaller fragments that are then attacked by countless fungi and bacteria.

fungi on leaf — Fungi generally consume leaves when they're buried, but you can sometimes find fungi eating leaves above ground. Photo by David Lukas

Throughout this multi-stage decomposition process, elements stored in leaves are converted from organically bound forms to inorganic forms that accumulate in the soil and ultimately provide 70-90% of the nutrients needed for plants to grow.

fall colors — Leaves decompose at different rates in different mixes of forest trees. Photo by David Lukas

If you've ever had to rake leaves in your yard or if you've kicked your way through leaves on a late autumn hike, you're familiar with how many leaves accumulate on the ground. But decomposition proceeds so quickly that up to 20% of the weight of these leaves can be lost in the first 20 days, and 50-80% of their mass may be lost within the first year. After a while, all that's left are the more indigestible components of leaves, and then decomposition proceeds at a much slower pace over several more years.

leaf in soil — In healthy ecosystems, leaves are quickly converted into soil. Photo by Rohane Hamilton/Shutterstock

What I love about this story is that you can imagine the forest floor breathing in and out each year. In the autumn, the forest takes a quick deep breath, and the forest floor rises; then over the following year, it slowly lets its breath out, and the forest floor sinks again. Up and down, in and out, year after year, the beating heart of a healthy ecosystem.

leaves on forest floor — If you were to take a time-lapse video of the forest floor, you would see it rising and falling with the seasons. Photo by Wirestock Creators/Shutterstock

It's a simple image of the forest as a breathing organism, but behind this image lies a complex web of life worth noticing.

🍂

This is my favorite time of year, and I hope you've been seeing autumn colors and leaves where you live. It's a pleasure to share this week's topic with you, and I hope you will consider helping support my work by upgrading to a paid subscription. In addition, you can also make a separate one-time donation to help me continue to produce amazing stories like this!

Further Reading:

Leaf decomposition is a topic of great interest to scientists, with over 4000 papers published on this subject. Unfortunately, I still haven't found any "easily digested" books or papers I would recommend for a general audience, but here's a short and simple YouTube video that illustrates the material I covered above.