Fig. 2. (A) An illustration of the power of feedback control. Curves indicate three output signals: red: no control (farmers do not respond to rainfall variation and cultivate the same area each year), green: gain = 5 (farmers are moderately responsive), blue: gain = 10 (farmers are very responsive), black: desired output. Under no feedback control (red), the curve follows the rainfall disturbance regime exactly. The higher the gain, the better the feedback controller can do in keeping the output near the desired state, i.e., the blue curve is closer to the desired output than the green curve. (B) Disturbance regime with a temporary period in which the disturbance regime temporarily changes to a higher frequency. (C) System response to the disturbance signal shown in (B) when gain = 5. (D) System response to the disturbance signal shown in (B) when gain = 10. See text for further discussion.