In the context of a lawn, fallen leaves are often seen as a mess to be cleaned up and sent away as waste. In a natural system, however, leaves are a valuable resource.
In nature, fallen leaves stay near the plant they fell from. Lying on the ground over the winter, they cover and insulate the plant’s roots, protecting them from temperature fluctuations, freeze-thaw cycles, and frost heaves.
Leaf litter serves as an important habitat element for many insects, which overwinter in, or lay their eggs in, the fallen leaves. The insects or their offspring emerge the following year to continue their life cycles. Raking away leaves interrupts these cycles, leaving a crucial gap in ecosystem functioning.
With the return of warmer weather, fungi and microorganisms get to work decomposing the leaves, returning them to the soil. Plants are then able to reabsorb those nutrients, and turn them into a future year’s leaves.
When leaves are raked to the street, they must be taken away by fossil-fuel-consuming vehicles. While they are waiting to be picked up, rain can wash their nutrients into stormdrains and then into the lakes, where they contribute to harmful algae blooms. For these reasons, Madison encourages homeowners to “leave the leaf“.