Legacy effects of long-term autumn leaf litter removal slow decomposition rates and reduce soil carbon in suburban yards,” published February 22, 2024, in the journal Plants, People, Planet. “By now, most people probably know that driving less and using energy efficient appliances reduces carbon dioxide emissions, and that carbon dioxide is one of the major greenhouse gases causing global warming. But very few people realize they can personally help pull carbon out of the environment and lock it in place so it can’t turn into carbon dioxide They can’t do it themselves, but their yards can, supported by landscaping decisions that directly influence how much carbon their yard can store. A recent study by University of Maryland researcher Max Ferlauto found that in places where people historically have left their fallen leaves to decompose, without removing them, the soil holds up to 32% more carbon on average. That may seem like a drop in the bucket, but if every lawn adds a drop, the bucket fills quickly. The EPA estimates that 35 million tons of grass clippings and fallen leaves are removed annually from urban and suburban landscapes. Scientists have estimated that in Minneapolis, MN, 11% of residential carbon output is due to yard waste removal, and in Boston, MA, about half the carbon that falls to the ground as leaves is removed from the city. Ferlauto is a PhD candidate in the Department of Entomology, and he was studying how removing fallen leaves affects insects during the winter months, when he began to wonder about soil carbon. “Soil is one of the main ways the earth stores carbon,” Ferlauto said, “But there hadn’t been any studies looking at the effect of removing fallen leaves on soil carbon function in suburban yards and urban areas. What we show in this study is that removing leaves reduces both the carbon and the nutrients in the soil, and that changes the ability of the soil to perform fundamental ecosystem functions. Carbon is essential for healthy soil. It provides structure, makes the soil more fertile and enables it to hold more water during storms, decreasing runoff. Soils depleted of carbon need more chemical fertilizers and more frequent watering to support a green lawn. And when it rains, more of the rainwater runs off into nearby waterways, carrying those chemicals with it. One of the study’s key findings was that changing lawn management practices to leave fallen leaves on previously raked lawns for two years was insufficient to restore depleted soils. “In these suburban areas, removing leaves over years and years, we’ve really done some damage to the soils, and it’s going to take time to restore them,” Ferlauto said.

Ferlauto suggests that people who want to improve soil carbon and the health of their yard’s ecosystem should consider the purpose of having a lawn. If you have children and pets who use the back yard, maybe cleaning up fallen leaves makes sense. But people who don’t use their yards much may consider clearing only the front yard, or even rewilding their lawns, turning green space into meadow or a more natural forest floor environment with native understory plants such as ferns and other species adapted to grow in areas with a leaf layer.”