The Impact of Leaf Removal on Soil and Wildlife

Leaf fall is coming to an end, especially in colder regions, where trees are now almost entirely bare. There are often only a few leaves left on our property, which we can choose to pick up or leave where they are.

More and more people are adopting leafcycling, an ecological practice that involves recycling fallen leaves by leaving them in place or saving them for other uses. This process mimics the natural processes of forests, where fallen leaves slowly decompose, enriching the soil and promoting plant health.

For example, leaves can be shredded directly on the lawn with a lawnmower to speed up their decomposition. Alternatively, they can simply be left in the flower beds, where they act as a natural mulch. Another option is to store them for use in compost or as mulch for future plantings. Either way, it’s a lot less work than bagging them up and hauling them off to the street.

Leaves and Bugs

Published in September 2024, the study entitled Removing autumn leaves in suburban yards as a landscaping practice reduces the spring emergence of overwintering insects was carried out by a team of researchers including Max Ferlauto and Karin Burghardt from the Department of Entomology at the University of Maryland. Based on a rigorous methodology, the study examines how autumn leaf collection affects insect emergence in the spring.

The researchers conducted their work in several suburban yards in Maryland, where they compared areas where leaves were systematically removed with those where they were left in place. Each area was delimited into experimental plots, with treatments consisting of either removing or retaining the dead leaves. They then measured the emergence of insects in the spring by installing insect nets and traps that captured species emerging from the soil after their overwintering period. Data was collected over several seasons to ensure reliable results.

Key Results

The study revealed that, in areas where leaves were removed, total insect emergence in spring was reduced by 17%. Butterflies and moths fell by 45%, beetles by 24%, and spiders by up to 67%. Insects dependent on leaves for hibernation, such as caterpillars and larvae, were particularly affected. These results show that leaf removal compromises the winter habitat of insects, disrupting local food chains by depriving birds and other predators of their resources.

Decomposition and Carbon in the Soil

The same team, Max Ferlauto and Karin Burghardt, this time accompanied by Lauren Schmitt, published in January 2024, Legacy effects of long-term autumn leaf litter removal slow decomposition rates and reduce soil carbon in suburban yards. This research examines the impact of prolonged leaf removal on soil health and decomposition processes in peri-urban yards. The aim of the study is to determine whether leaf management practices have lasting effects on soil decomposition and carbon storage.

The researchers studied yards where leaves were either left in place or removed over a period of 3 to 30 years. They compared these practices with recent changes (leaving or removing the leaves for 1 or 2 years). Decomposition was measured using the Tea Bag Index, while soil organic carbon (SOC) was assessed from samples taken at a depth of 18 cm (7 inches).

Key Results

Soils where leaves had been removed over the long term showed a 17% reduction in decomposition rates, indicating weakened microbial activity. These soils also contained 24% less organic carbon than those where leaves were retained. These effects, known as “legacy effects”, persist despite recent changes in leaf management, showing that it takes several years for the soil to recover its ecological functions.

Recommendations for Gardeners

Both studies highlight the importance of managing fallen leaves in an environmentally-friendly way, and offer a number of practical recommendations for gardeners.

First of all, leaving leaves in place is strongly encouraged, as it supports biodiversity by providing an essential habitat for hibernating insects.

For areas where aesthetics are a priority, it is recommended to group leaves in less visible areas or around trees. This preserves the ecological benefits while making leaf management more practical and harmonious with the garden’s appearance. Another option is to use leaves as mulch. This technique protects plants from winter cold, reduces weeds and conserves soil moisture, while enriching the soil as the leaves decompose.

Finally, leaf shredding, while practical for accelerating decomposition and reducing volume, should be used sparingly. This practice can disturb the insects that use leaves as shelter. It is therefore advisable to limit this method to areas where it is necessary, while taking care to preserve certain areas of the garden intact to encourage biodiversity.

Leaving Leaves on the Ground Isn’t Laidback

So, if you don’t pick up your leaves, it’s not because you’re Laidback – quite the contrary! You’re showing genuine concern for soil health, environmental protection and biodiversity. By letting your leaves decompose naturally, you’re helping to enrich the soil, preserve habitats for beneficial insects and maintain a precious ecological balance in your garden. Plus, it gives you more time to go fishing – if that’s your thing!