When colorful autumn leaves gather in your garden this season, it might be wise to leave them there. This leaf litter, often seen as an eyesore, is actually a rich microcosm of biodiversity. It acts as a cover for the habitat richest in species: the soil, which houses more than half of life on Earth. Beneath the piles of leaves, twigs, and bark, numerous small creatures thrive, including small reptiles like salamanders and frogs, as well as invertebrates like snails, earthworms, and spiders. When invertebrates consume leaf matter, they break it down into smaller pieces. Then, working together, bacteria and fungi further break these pieces down, converting them into valuable nutrients that trees and other plants can use, such as nitrogen, calcium, and sulfur. These natural processes help rebuild the soil and support the cycle of life, as dead plant matter transforms into food for living plants. Although leaf litter may look still, a microscopic world is active beneath the surface. **ENVIRONMENTAL BENEFITS** As a micro-habitat, leaf litter is diverse. Structurally, it consists of plant debris, such as leaves, flowers, bark, seeds, and twigs. Chemically, it contains substances like cellulose and lignin. According to a 2023 study, this litter can strengthen the biodiversity of ecosystems by making soil more fertile and reducing the risk of pathogens left behind by animals. Vegetable litter goes through three stages of decomposition to become soil. The top layer is the visible litter. The second layer, composed of decomposing leaves, is the fermentation layer. The last layer, fully decomposed, is made of thick, dark organic matter called humus, which provides the ideal environment for plants to grow. According to Sue Barton, a plant and soil specialist at the University of Delaware, it is important to see soil as a complete ecosystem. "The soil system contains the mineral component, such as sand, silt, and clay. It also contains spaces filled with air or water, and organic matter. Then a living component, such as earthworms and fungi and bacteria. It is good to consider the soil as a complex system rather than a single entity." The decomposition of plant litter not only releases nutrients into the soil but can also help trap carbon dioxide. Forests capture this greenhouse gas from the atmosphere through photosynthesis. Carbon is transformed into biomass, which eventually dies and becomes plant litter or dead wood. Leaf litter also serves as an important habitat for animals. During winter, dead leaves provide shelter for wildlife. Under the debris, moth and butterfly cocoons nest, and bumblebees dig to avoid the cold and hibernate. "Most butterflies and moths overwinter in this landscape either in the form of eggs, caterpillars, chrysalises, or in their adult form," explains Sue Barton. "The moon butterflies, Baltimore butterflies, and Isabella tiger moths curl up in a pile of leaves to protect themselves from the cold and predators. Calycopis cecrops lays its eggs on fallen oak leaves. The swallowtail butterflies disguise their cocoons and chrysalises as dead leaves and thus blend in with the real leaves." **WHAT TO DO WITH LEAF LITTER** There are several options for preserving your leaf litter. Sue Barton suggests removing the leaves from your lawn with a rake and placing them on your flower beds, because covering the grass, the litter prevents light from passing through and therefore prevents the photosynthesis of the lawn. To avoid leaves completely covering your lawn, you can use a lawnmower equipped with a "mulching" function to shred the leaves into small pieces. According to Sue Barton, this "improves the quality of the soil, and therefore the plants growing in this area have more nutrients to absorb. They will benefit from a softer and more open soil that has a better structure. This promotes better root growth, and therefore obviously better plant health." She, however, warns against sending your leaf litter to the landfill. "What you should not do is put them in a plastic bag and send them to the landfill somewhere, because you would be getting rid of a resource. If you send it to the landfill, this resource cannot be reused in someone's garden." A second option is to compost the leaves. You can compost your pile of leaves and put it back on your lawn or around your plants. The goal is to recycle the litter; putting it on flower beds or making compost will achieve this goal. If you are interested in creating a more environmentally friendly garden, consider the benefits of native plants and the replacement of your lawn with clover.