Help
feedback loop — English
A lesser, repetitive cycle within a larger open system of energy and matter flow. Most open systems contain numerous feedback loops. Such systems function on a response-control principle. At a certain point in a system, enough energy or matter (that is, potential energy) flow forward in the system to exceed a threshold-limit and trigger a reactive process in the system. A simple example is the feedback loop of refugees or illegal immigration from one country to another. A number of Zimbabweans moved to South Africa when conditions in Zimbabwe became too difficult to endure. They were not turned back, but granted asylum or temporary resident rights and started to make a new living. This encouraged other Zimbabweans to do the same, which reinforced the whole feedback loop. A constant inflow of Zimbabweans into South Africa has ensued. This is a typical positive feedback loop. Had the first arrivals been turned back, a sustainable loop would not have developed and a negative feedback loop would have developed with less and less Zimbabweans daring to move to South Africa, and those already in South Africa would have tried to get out of the country. In natural systems, feedback is even more common. The destruction of vegetation in an area causes accelerated run-off, which leads to the increased washing away of the topsoil and ends in an accelerated removal of the surface layer. When an eroding slope is revegetated, a negative feedback loop immediately kicks in, and soil erosion is then halted and might be under control. Correlation diagrams (correlation structures) are usually used to graphically represent the feedback loops in a system.
