Which practice should be minimized to protect biological soil crusts?

• A. Seed sowing
• B. Mulching
• C. Controlled grazing
• D. Off-road traffic

Answer: (D)

Biological soil crusts are a thin, living layer of cyanobacteria, lichens, mosses, and fungi that stabilizes soil surface, enhances water retention, and supports nutrient cycling. They are extremely sensitive to physical disturbance because the organisms sit right at the soil surface; even light compression or scraping can break the crust and leave bare patches that accelerate erosion and slow recovery.

Minimizing off-road traffic directly protects these crusts by preventing the crushing, tearing, and smothering of the surface layer. Vehicles and people moving across crust disrupt its structure, compact the soil, and create bare areas where wind and water erosion can remove the crust or invite invasive species. Once damaged, recovery is slow—often years to decades—so reducing this disturbance helps maintain crust integrity and the ecosystem services they provide.

Seed sowing and mulching can threaten crusts if applied over crustal surfaces—they can bury or physically disturb the layer—but when used carefully and away from crusts, their impact is less direct. Controlled grazing, likewise, can be managed to minimize damage and even help protect crusts by preventing overgrazing, though poor grazing management can harm them. The most direct and consistently damaging practice is off-road traffic, which is why it should be minimized to protect biological soil crusts.