Final answer:
Desertification in Africa decreases soil fertility, vegetation cover, and water availability, which are all interrelated factors contributing to environmental degradation.
Step-by-step explanation:
Human activities and changes in rainfall patterns have indeed contributed to the desertification of many countries in Africa. The impact of desertification on the environment includes a rapid decrease in several areas. These areas are: A) Soil fertility, B) Vegetation cover, and C) Water availability.
Therefore, the correct answer to the student's question is D) All of the above. Desertification leads to nutrient-poor soils, which can be further degraded by erosion or salinisation. Vegetation cover is reduced as the area becomes more desert-like, which can lead to changes in species distribution and loss of biodiversity. Additionally, water availability is often compromised due to reduced rainfall and the loss of plants that would have contributed to the hydrological cycle, exacerbating drought conditions.