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Ferns display color in late August near West Lake Creek in Edwards. The smaller shrubs and plants turn first, with the more mature aspens changing last.
Chris Dillmann |

It hits without warning: one late summer day while walking outside, you inhale a crisp, familiar scent, and it becomes apparent that fall is in the air. I’ve always loved the smells of fall, particularly the smell of leaves decomposing on the forest floor.

The love of this smell got me thinking: Why do dead, decomposing leaves have such a sweet smell, and why do I enjoy it so much? This spark of curiosity prompted me to research why people have such a fondness for fall smells, and it seems that the answer is rooted in both scientific processes and emotional associations.

The musky, sweet smell that we associate with the turn of the season is the result of a chemical change taking place within the leaves of deciduous trees, which are trees that lose their leaves annually. Lack of sunlight and cooler temperatures cause the leaves of deciduous trees to stop converting sunlight into sugar, resulting in a loss of chlorophyll (the phytochemical responsible for the green color of leaves), and is the reason behind the color changes the leaves undergo. After the leaves stop producing energy for the trees, they fall to the bed of the forest floor and begin to break down in the soil, releasing sugars and other organic compounds, which is what yields those captivating fall smells.

Another contributing factor is that when the air temperatures drop in the fall, the prominence of smells becomes more discernible to humans. This is due to the scent molecules in the air being less concentrated and moving more slowly than in the hot summer months where they are more condensed, overwhelming our senses.

The most interesting discovery I found within the science behind why many people enjoy the smells of fall, is the way that scents themselves are perceived by humans. When we see or hear something, the sight or sound gets processed first through thoughts, and then gets interpreted into emotions. On the contrary, when we breathe in scents, we actually have an emotional response first and then we associate the emotional response with a thought.

This could be the reason that many people feel deep emotional connections to fall. Some common emotions people associate with fall are nostalgia, comfort, warmth, anxiousness, melancholy, and joy. The variation of these emotions has to do with memory association, and whether or not these scents are associated with positive or negative experiences, or a combination of the two.

The strong associations between fall smells and memories may also explain why our feelings and energy often seem to shift with the onset of fall before our consciousness fully catches up. We have an emotional response that our surroundings are changing, which even subconsciously can trigger emotional responses before we are made aware of them.

Personally, I always feel a sense of urgency and melancholy, tinged with gratitude during the fall. I tend to associate fall with the temporality of life. Because the season itself is so short, I begin to feel like I need to soak in the fleeting window of sweet smells, vivid colors, and longer amounts of daylight as much as I can before it’s all covered in a snowy blanket and the days become short and dark. Whatever your association with fall scents, we can all learn a thing or two from the natural cycles around us.

What memories and emotions do you associate with the smells of fall?

Cassy Brown is the youth programs coordinator at Walking Mountains Science Center. She loves the sound of leaves crunching under her tires while mountain biking through aspen groves. 

Source: Curious Nature: Have you smelled it? Fall is in the air |