Four pests campaign
Marx, Engels, Lenin, MAO
". . . results of this extermination drive were felt soon enough. The whole campaign had been initiated in the first place by some bigwig of the Party who had decided that the sparrows were devouring too large a part of the harvests… Soon enough, however, it was realized that although the sparrows did consume grain, they also destroyed many harmful insects which, left alive, inflicted far worse damage on the crops than did the birds. So the sparrows were rehabilitated. Rehabilitation, however, did not return them to life any more than it had the victims of Stalin’s bloody purges, and the insects continued to feast on China’s crops.
(Mikhail Antonovich Klochko, 1961. Translation by Andrew MacAndrew)
This man-made plague of locusts reduced harvests by 20%, leading to the deaths of two million people.
It is an extreme example, but characteristic of the disasters that happen when linear optimizers plow headlong into complex situations. Complex systems do not react to linear force in linear ways. This is because feedback loops make the relationship between cause and effect circular. The harder we try to optimize toward the goal, the more energy we pump into feedback loops. Eventually, some loop spins out of control, and the system kicks back
