Final answer:
Topsoil loss most importantly leads to erosion, resulting in nutrient-poor soils and subsequent issues like desertification and salinization, all of which are detrimental to plant growth.
Step-by-step explanation:
When topsoil is lost, affecting plant growth, the most harmful outcome is erosion. Erosion is the process by which soil is removed from an area, typically due to water, wind, or other natural forces. This topsoil is essential for plant growth because it contains nutrients and organic matter critical for plant health.
The loss of topsoil can lead to a variety of ecological problems. Among them, nutrient-poor soils become a common issue, making it difficult for plants to grow. Over time, this can lead to desertification, which is the transformation of arable land into desert as a result of inappropriate agricultural practices, deforestation, or drought.
Additionally, the loss of topsoil through erosion contributes to salinization, particularly in arid areas. When shallow-rooted crop plants replace native deep-rooted plants, the water table can rise, bringing soil salts to the surface and harming plant growth. Prolonged irrigation without proper drainage can exacerbate this issue, further reducing the land's productivity.