Elyse C. McCormick | February 2, 2026

Part 1 and Part 2 of this post series

Late autumn brings a decided change in atmosphere; the skies are grayer, the air is chillier. After the radiant reds and outstanding oranges of color change, the gorgeous golden cascades fall to become… a jumbled heap of leaves coating the ground. You’ll see it on forest floors if you go for a late-autumn hike, but you’ll also see leaves coating yards and sidewalks of residential areas, leaving bare branches reaching for the clouds. Fallen leaves are the bane of most lawn-owners. As a society, we’ve decided to rake and collect these leaves to “clean” our lawns, putting in hours of sweat and sometimes carbon emissions to beautify lawns. But what if I told you that your leaf piles were hiding a whole world beneath their crunchy depths? Or that maintaining your leaves (or at least setting them aside) could be a simple way to be an ecological hero? Let’s talk about why leaf litter is ecologically important!

In temperate climates, the onset of winter presents a challenge for many organisms. As we discussed last time, deciduous trees are able to deal with this by losing their leaves to protect themselves from water loss and ice. Many animals, particularly small ones, have come up with a fantastic strategy to avoid the cold – they hide in the fallen leaves! You’re probably familiar with hibernation, with a classic example being bears that take a long winter snooze. Small animals do this too, even insects, and they’ve co-opted fallen leaves to use as blankets.

Many butterflies and moths adopt this strategy (Figure 1). One example is the luna moth, which makes chrysalises by wrapping themselves in green leaves that are still attached to the tree. When that leaf falls off, the chrysalis falls into a pile of leaves, where it will stay and overwinter until spring [1]. Other butterflies, such as the morning cloak, question mark, and eastern comma, overwinter as adults within leaf litter and wood piles [2,3]. Some caterpillars even depend on decomposing leaves to eat overwinter before they metamorphose in the spring!

Figure 1. A Question mark butterfly (Polygonia interrogationis) suns itself in leaf litter in the late November sun. (Photo: Elyse McCormick)

Speaking of pollinators: while you may be more familiar with helping them by planting flowers, bees are another insect that take advantage of leaf litter. Queen bumble bees overwinter underground, but are protected by leaves before they start a new spring colony (Figure 2) [4,5]. Other native bees, solitary bees overwinter in old stems, logs, rock crevices, and in holes in the ground. These places are frequently protected and insulated by leaf litter [6]. 

Figure 2. A young queen bumble bee searching for an overwintering spot in leaf litter.  (Photo: Elyse McCormick)

But it’s not just insects that take advantage of the protection, a wide variety of species depend on protected and insulated leaves to live. Leaf litter contains a full ecosystem of fungi and bacteria that aid the decomposition of the leaves and other materials, insects and other small invertebrates like spiders and snails. Bigger animals, like frogs, salamanders, and even hibernating turtles, also benefit from the protection of leaving leaf litter to act as a barrier from the cold and hide their hibernation spot. In wild and natural areas, when leaves hit the forest floor they remain relatively undisturbed, creating a perfect habitat for all of these creatures.

But in urban and suburban communities, humans frequently rake, blow, or shred their leaves, creating catastrophe for all the overwintering creatures sleeping in these leaf piles. So, how can we make a difference? Well, The Xerces Society, a national non-profit committed to preserving and conserving invertebrates, advises that we “Leave the Leaves” [7]. But that doesn’t mean that you have to completely sacrifice your lawn! Leaves don’t need to be left exactly where they fall, they can be moved into gardens, landscaping beds, or back corners of your yard. If you rake gently, you can move your piles into areas that aren’t in your way, and still let the insects and other animals benefit. However, if you have the ability, you can also just leave the leaves as they are! The insects and bacteria will shred your leaves and fertilize your lawn for you (though they may be slightly slower at it). Every time you make the choice to let leaf litter be, you help a whole community of creatures overwinter safely until spring comes again! 

For more information and fantastic tips about how you can winterize your yard to maximize the ecological benefits, head to www.xerces.org/leave-the-leaves. And spread the word! Telling your friends about the simple things we can do to leave the world a better place helps make real, incremental change. Taking simple steps like these can put you well on your way to being an ecological hero for the little guys sleeping winter away in your backyard.  

Figure 3. Leave the leaves alone this year and support a wide range of beautiful creatures! (Created in Canva by Elyse McCormick)

References:

1. Bouseman, John K., and James G. Sternburg. “Field guide to silkmoths of Illinois.” Illinois Natural History Survey Manual no. 10 (2002).
2. Cambridge Day. “Eastern comma butterfly has antifreeze blood and is tough enough to even chase after birds”. Jeanine Farley. [October 31, 2025]. https://www.cambridgeday.com/2023/05/06/eastern-comma-butterfly-has-antifreeze-blood-and-is-tough-enough-to-even-chase-after-birds/
3. National Wildlife Foundation Blog. “How Fallen Leaves Support Moths and Butterflies”. Braelei Hardt and Robert Watkins. [October 31, 2025]. https://blog.nwf.org/2024/09/how-fallen-leaves-support-moths-and-butterflies/ 
4. Williams, Paul, Robbin Thorp, Leif Richardson, and Sheila Colla. Bumble bees of North America: an identification guide. Princeton University Press, 2024.
5. Hines, Heather M. “Comparative Evolution of Social and Ecological Traits in Bumble Bees.” Annual Review of Entomology 71 (2025).
6. Danforth, Brian N., Robert L. Minckley, and John L. Neff. The solitary bees: biology, evolution, conservation. Princeton University Press, 2019.
7. Xerces Society. “Leave the Leaves: Winter Habitat Protection”. Xerces Society. [October 31, 2025]. https://www.xerces.org/leave-the-leaves