Sources: Vegetation and a Stream

The observations below compare the same hillside before and after its plant cover declined.

Science Text: When Plant Cover Changes

Plants are part of the biosphere, and their roots help hold soil in the geosphere. Leaves also soften the impact of raindrops. When many plants are removed, water can flow more quickly over the ground instead of soaking in. This runoff may carry soil into a stream, linking changes in the geosphere to the hydrosphere. With fewer plants shading the stream, its water may warm. Warmer water can hold less dissolved oxygen, which may affect fish and other living things. Plants also exchange gases with the atmosphere: during photosynthesis they use carbon dioxide and release oxygen, using energy from sunlight. These connections can form feedback. If erosion removes soil that plants need, fewer plants may grow, allowing even more runoff and erosion. Matter, including water, soil, and gases, moves among Earth’s spheres, while energy from the Sun drives many changes.

Part A: Read the Evidence

Part B: Create a Four-Sphere Model

Use the hillside evidence or choose another change, such as heavier rainfall or warmer air. Identify the starting change and trace its effects through Earth’s systems.

Part C: Evidence and Explanation

Use the sources above to support a prediction about how Earth’s spheres interact.