Leave Some Leaves to Help Yard Ecosystems Thrive, Entomologist Advises Homeowners
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Autumn means hot chocolate on crisp nights, comfy sweaters and colorful leaves crunching underfoot as we rake and scoop them into paper yard-waste bags.
But hold up—one of these things isn’t as cozy as the others. Clearing away those beautiful fallen leaves can disrupt a delicate and beneficial ecosystem, according to research by University of Maryland entomology Ph.D. candidate Max Ferlauto.
“Raking fallen leaves could impact the complex ecosystems around your home,” explained Ferlauto, who studies urban ecology in the lab of entomology Assistant Professor Karin Burghardt. “Removing leaf litter means killing or disturbing the insects that hibernate on the forest floor, especially the ‘good’ ones that provide beneficial ecological benefits like natural pest control or pollination.”
Ferlauto has been working with 20 homeowners in suburban Maryland for over the last few years, studying the general biodiversity of local lawns and the presence of beneficial critters—namely moths, which are important pollinators, and parasitoid wasps, which feed on many garden pests.
In his research, Ferlauto removed or retained autumn leaf litter in residential yards and collected insects emerging from the ground in the spring. He learned that typical leaf litter removal practices resulted in vast reductions of moth abundance and biodiversity.
Based on those studies, Ferlauto devised ways homeowners can limit disturbances to the winter hibernation patterns of insects.
Don’t relentlessly remove and discard all leaf litter in autumn or spring. Such disposal reduces moth emergence from winter hibernation by almost half. In areas where leaf litter was removed, Ferlauto also found fewer moth species overall.
Do keep some leaves on the ground in spots you’re willing to sacrifice a little neatness—or regard from more uptight neighbors. While many insects make their winter homes in leaf litter, which can be both their food source and blanket, others burrow themselves deeper into the soil under leaves. Ferlauto found that areas where leaf litter was removed had reduced temperature buffering. Keeping litter intact will allow these insects to stay protected from the harshness of winter and variability of spring.
Don’t shred or mulch your leaves. Ferlauto found that doing so causes as much damage as gathering leaves up and disposing of them in leaf bags. Placing leaves in compost bags kills the insects on the leaves. Putting leaves and compost through a mulcher or woodchipper also destroys the insects clinging to the leaves.
Do make some leaf piles, and then leave them. Creating small, shallow pockets of leaves in safe spaces is a great alternative if you can’t bear to just leave them where they fall. Homeowners can select places for piles based on their own preferences or, even better, their knowledge of areas where beneficial insects like to flock.
Ultimately, Ferlauto hopes homeowners can find a balance between their landscaping needs and ecologically friendly land management practices. With just a few changes in their routines, homeowners can keep their yard presentable while also supporting the health and longevity of natural ecosystems all year round.
“Many of us are already helping our local ecosystems to flourish by planting native wildflowers and other plants in our gardens, attracting ‘good’ insects to our homes,” Ferlauto said. “We still don’t know as much about when they’re in an inactive life stage—hibernation—but we do know that keeping their hibernation homes intact is key to keeping them around longer.”
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