Which of the following statements about positive feedback interactions in Earth's systems is correct?

• A. Positive feedback interactions can occur naturally without human involvement.
• B. Positive feedback interactions always lead to system stability.
• C. Positive feedback interactions only occur in biological systems, not in Earth's systems.
• D. Positive feedback interactions are always a result of human action.

Answer: (A)

Verified step by step guidance

1. Understand the concept of positive feedback: Positive feedback is a process in which an initial change in a system leads to further changes that amplify the original effect. For example, in Earth's systems, melting ice reduces the reflective surface (albedo), causing more heat absorption and further ice melting.
2. Analyze the first statement: 'Positive feedback interactions can occur naturally without human involvement.' This is true because many natural processes, such as the ice-albedo effect, occur without human intervention.
3. Evaluate the second statement: 'Positive feedback interactions always lead to system stability.' This is incorrect because positive feedback typically destabilizes a system by amplifying changes rather than counteracting them.
4. Assess the third statement: 'Positive feedback interactions only occur in biological systems, not in Earth's systems.' This is incorrect because positive feedback occurs in various systems, including Earth's climate, geology, and ecosystems, not just biological systems.
5. Review the fourth statement: 'Positive feedback interactions are always a result of human action.' This is incorrect because positive feedback can occur naturally, as seen in processes like volcanic eruptions or natural climate cycles, without human involvement.