When summer fades and autumn arrives, landscapes transform into a vibrant mix of red, yellow, and orange hues as leaves begin to fall. While the sight may be beautiful, it also presents a dilemma—what should be done with the fallen leaves?
Fallen Leaves Are Beneficial
Leaf litter refers to organic material, including leaves, twigs, and other plant debris, that fall to the ground. Three layers comprise leaf litter: the litter layer (with dead leaves), fermenting layer (with rotting leaves), and humus layer (materials that are completely rotted). Over time, leaf litter breaks down through natural processes and becomes a rich humus essential for plant growth.
Leaf litter is vital to forest ecosystems because they provide habitat and food for various organisms. Once leaf litter is colonized by fungi and microorganisms, invertebrates like beetles and earthworms consume and break it down into smaller pieces. This process is crucial as this organic matter is then mixed with and enriches the soil.
Leaves left on the ground in yards or wooded areas can also create microhabitats for insects and small animals like frogs, salamanders, and hedgehogs. The cover provided by leaf litter offers shelter for amphibians and helps retain moisture in the soil, which is particularly important during dry periods.
The Pitfalls of Burning or Landfilling
Burning leaves releases harmful pollutants into the air, including particulate matter that can exacerbate asthma-related symptoms when inhaled. Carbon monoxide and benzo(a)pyrene (found in cigarette smoke) are also emitted, the latter which can be a potential factor in lung cancer.
When leaves and other organic materials decompose in a landfill under anaerobic (no oxygen) conditions, they produce methane, a greenhouse gas (GHG).
According to data from the US Environmental Protection Agency, yard trimmings (including grass, leaves, and tree and bush trimmings) accounted for 35.4 million tons in municipal solid waste in 2018. Although 22.3 million tons (about 63%) were composted or mulched and 2.6 million tons (about 7.4%) were combusted, the remaining 10.5 million tons (about 29.7%) were landfilled.
When leaves and other organic materials decompose in a landfill under anaerobic (no oxygen) conditions, they produce methane, a greenhouse gas (GHG). Moreover, some leaves (such as from soybeans) are also found to emit nitrous oxide, another GHG.
Leaving leaves on streets or sidewalks is also unfavorable, as they can become slippery hazards when wet or frozen. A study found that the timely removal of leaf litter from streets can significantly reduce phosphorus and nitrogen levels in stormwater runoff. When washed into local waterways, these nutrients can contribute to water pollution and algae blooms, harming aquatic ecosystems.
Composting for Soil Health
One of the best ways to handle autumn leaves is by composting them.
To compost leaves effectively, it's helpful to shred them down into smaller pieces, allowing for quicker decomposition. This can be done with a leaf shredder or by running over them with a lawnmower. Shredded leaves themselves can also be used for “mulching perennial flower beds, shrub borders, and over tree roots,” with a 2 to 3 inch layer being ideal.
Having the right ratio of “brown” (carbon) to “green” (nitrogen) is essential for composting, with an ideal (C:N) ratio of 30:1. Leaves are rich in carbon, with a C:N ratio of 40:1 to 80:1. However, to create a more balanced compost pile, leaves should be mixed with nitrogen-rich "green" materials like grass clippings, vegetable scraps, or coffee grounds.
Having the right ratio of “brown” (carbon) to “green” (nitrogen) is essential for composting, with an ideal (C:N) ratio of 30:1.
Nitrogen can also be added through dried blood, cottonseed meal, or bone meal. However, having too much “green” materials can make the pile smelly and attract nuisance animals.
In Toronto, Canada, the city’s leaf composting program diverts 90,000 tons of yard waste from landfills annually and has gained popularity for its impact on local gardens and green spaces. The program collects leaves from residential areas, processes them into compost, and gives it to the public for free during “Community Environment Days.” This initiative showcases how communities can turn what might be considered waste into a valuable resource while encouraging sustainable practices.
Many municipalities provide programs that collect leaves for composting or mulching, ensuring they are reused rather than wasted.
Mulching For Weed Control
In addition to composting, fallen leaves can be used as mulch, providing multiple ecological benefits. Mulching with leaves helps retain moisture in the soil, prevent erosion, and suppress weeds.
In one to two years, [leaves] will naturally break down into a substance known as leaf mold, which can be used as a soil amendment or 2-inch mulch layer.
For gardeners, leaving a thin layer of leaves on garden beds can act as a natural mulch to suppress weeds. If a yard generates more leaves than can be used for compost, excess leaves can be saved for later use by piling them up in a corner of the yard. In one to two years, they will naturally break down into a substance known as leaf mold, which can be used as a soil amendment or 2-inch mulch layer.
By adopting sustainable practices such as composting and mulching, individuals and communities can turn autumn leaves into a beneficial component of the natural world. Rather than seeing leaves as a seasonal nuisance, they should be appreciated for their vital role in supporting soil health and biodiversity.
*Ellie Gabel is a freelance writer from North Carolina who specializes in covering the latest innovations in science and technology and how they can be used to better the world we live in. In addition to writing for publications like Power Magazine, Global Trade Magazine, and Electronics360, Ellie is also the associate editor at Revolutionized.com.
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