Editing Twelve leverage points (section)

=== 7. Gain around driving positive feedback loops===

A [[positive feedback]] loop speeds up a process. Meadows indicates that in most cases, it is preferable to slow down a positive loop, rather than speeding up a negative one.
{{quote|The [[eutrophication]] of a lake is a typical feedback loop that goes wild. In a eutrophic lake (which means well-nourished), much life, including fish, can be supported. An increase of [[nutrient]]s will lead to an increase of productivity, growth of [[phytoplankton]] first, using up as much nutrients as possible, followed by growth of [[zooplankton]], feeding up on the first ones, and increase of fish populations. The more available nutrients there are, the more productivity is increased. As plankton organisms die, they fall to the bottom of the lake, where their matter is degraded by decomposers. However, this degradation uses up available [[oxygen]], and in the presence of huge amounts of organic matter to degrade, the medium progressively becomes [[hypoxia (environmental)|anoxic]] (there is no more oxygen available). In time, all oxygen-dependent life dies, and the lake becomes a smelly anoxic place where no life can be supported (in particular no fish).}}