Question 6 (2 points) The single greatest threat to irrigated agriculture is increased human consumption of coal. groundwater depletion global warming flooding Question 7 (2 points) Which of the following lumber harvesting strategies does the most damage to a forest ecosystem? sustainable forest management selter wood-cutting cutting clear-cutting Question 8 (2 points) Erosion can result in a vicious cycle of worsening erosion because rainwater increasingly soaks into the ground plants are less likely to grow in an eroded region the accurnulation of humus inakes erosion more tikely the pH of the soil increases as erosion continues

**Question 6** 1. Irrigated agriculture relies heavily on consistent water supplies. 2. One major issue is that excessive reliance on groundwater extraction can deplete the water available for irrigation. 3. Thus, the single greatest threat is \( \textbf{groundwater depletion} \). **Question 7** 1. Lumber harvesting strategies vary in the level of disturbance they cause. 2. Sustainable forest management and selective wood-cutting aim to minimize damage to the ecosystem. 3. In contrast, clear-cutting removes all trees in an area, leading to drastic habitat and soil changes. 4. Therefore, the approach causing the most damage is \( \textbf{clear-cutting} \). **Question 8** 1. Erosion removes the nutrient-rich top layer of soil. 2. The reduction of this fertile topsoil diminishes the establishment and growth of vegetation. 3. With fewer plants to stabilize the soil, erosion accelerates, creating a vicious cycle. 4. Hence, the process worsens because \( \textbf{plants are less likely to grow in an eroded region} \).