Why does removing vegetation (like plowing up prairie grassland) dramatically increase soil erosion?
AVegetation blocks sunlight from reaching the soil
BPlant roots hold soil in place, leaves break the impact of raindrops, and stems slow wind at the surface — without vegetation, soil is directly exposed to erosive forces
CVegetation makes the soil heavier so it cannot blow away
DPlants absorb all the rainfall, leaving none to cause erosion
Vegetation protects soil in multiple ways. Roots bind soil particles together like a net. Leaf canopy intercepts raindrops, reducing their impact energy when they hit the soil. Stems and low-growing plants slow wind speed at the surface. Dead leaves and organic matter (mulch) cover the soil surface. Remove the vegetation and the soil is fully exposed to rain impact, water flow, and wind — all of which can rapidly strip away topsoil.
Question 2 Short Answer
What caused the Dust Bowl of the 1930s?
Think about your answer, then reveal below.
Model answer: Farmers in the Great Plains plowed up millions of acres of deep-rooted native prairie grasses to plant wheat. When a severe drought hit in the early 1930s, the crops failed and the exposed, dry topsoil — no longer held in place by grass roots — was picked up by wind and carried away in massive dust storms. The combination of poor land management and natural drought created one of the worst environmental disasters in US history.
The Dust Bowl led directly to modern soil conservation practices and the creation of the Soil Conservation Service (now the Natural Resources Conservation Service). It demonstrated that soil is a finite resource that can be destroyed by mismanagement, even in a country with seemingly unlimited farmland.
Question 3 True / False
It takes mainly a few years to replace topsoil lost to erosion.
TTrue
FFalse
Answer: False
Topsoil formation is extremely slow — it typically takes 100 to 500 years to form one centimeter of topsoil through the slow processes of weathering, organic matter accumulation, and biological activity. A single heavy rainstorm or windstorm can erode centimeters of topsoil in hours. This means that topsoil lost to erosion is effectively nonrenewable on any practical human timescale.