Question

Though earthworms are often celebrated as beneficial helpers in home gardens, their introduction to the glaciated forests of North America has had a dramatically different impact. Historically, these northern forests developed without native earthworms since the last ice age. In their absence, a thick layer of decomposing leaves and organic matter, known as duff, accumulated on the forest floor. This duff layer served as a vital habitat for native wildflowers, ferns, and tree seedlings, while also acting as a sponge that retained moisture in the soil. When non-native earthworms are introduced—often discarded by anglers or transported in the soil of potted plants—they rapidly consume this duff layer. The earthworms break down the organic matter much faster than native fungi and bacteria can, converting the thick duff into a thin, compacted soil. As a direct result of this rapid consumption, the forest floor loses its ability to retain moisture and support the growth of understory plants, leading to a decline in native wildflower populations.

According to the passage, what is a direct effect of introduced earthworms rapidly consuming the forest's duff layer?