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Feedback Loops

A feedback loop is a process in which a system’s output serves as an input to that same system
Negative Feedback Loop

Stabilizes a system: output that results when the system moves in one direction acts as an input that moves the system in the other direction

Drives a system further toward an extreme instead of stabilizing it (example- exponential growth)

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Isn’t positive feedback “good” and

Negative feedback “bad”?

Example #1��(positive feedback loop)

An example of a positive feedback loop in nature is drought. Droughts become more intense due to a positive feedback loop. When there isn't enough rain, plants die off, which limits how much water vapor is added to the air from the planet's surface.

Example #2��(Positive Feedback Loop)

If we look at an apple tree, with many apples, seemingly overnight they all go from unripe to ripe to overripe. This will begin with the first apple to ripen. Once ripe, it gives off a gas known as ethylene (C₂H₄) through its skin. When exposed to this gas, the apples near to it also ripen. Once ripe, they too produce ethylene, which continues to ripen the rest of the tree in an effect much like a wave. This feedback loop is often used in fruit production, with apples being exposed to manufactured ethylene gas to make them ripen faster.

Example #3 (positive feedback loop)

A positive feedback loop occurs when sea ice melts during the polar spring. As ocean and air temperatures increase, the sea ice begins to melt, with the result that the bright white, highly reflective surface of the ice is progressively replaced by open water, which is darker in colour and has a lower reflectivity (albedo). That lower reflectivity has the knock-on effect of increasing the amount of solar radiation that is absorbed at the surface, which in turn raises ocean and air temperatures further, leading to more rapid melting of the remaining sea ice.

Example #4 (Negative Feedback Loop)

A negative feedback loop in the environment occurs as a result of the interaction between predators and their prey. In ideal conditions, one might expect the numbers of predators and prey animals to be approximately balanced, since the numbers of the former are usually dependent upon the numbers of the latter. If the number of prey animals temporarily increases (perhaps due to an unusually successful breeding season), then a short-term surplus of food becomes available for the predators whose numbers may subsequently increase in response. But the greater number of predators will begin to have an impact upon the size of the prey population, which may reduce substantially, leaving the predators short of food.