Image from a 2010 article by Thurstan, Brockington, and Roberts. It describes the cycle of the UK fishing industry, which collapsed because of overfishing in the late 1970s.
The two graphs above (from a 2010 article by Thurstan et al.) speak by themselves. We have here a real life example of the overexploitation of natural resources; that is, of the tendency of people of destroying their own sources of wealth. Other classic examples can be found with the 19th century whaling industry and with the Canadian cod fishery.
Overexploitation typically generates the "Hubbert curve," the name given to a bell-shaped production cycle best known for the case of crude oil, but affecting all the resources which can be exploited faster than they can reform by natural processes. This behavior can be explained by means of mathematical models, but, qualitatively, it is the result of the falling profits generated by the diminishing resource stock. In the long run, lower profits discourage investments and the result is a general production decline. A particular case of this mechanism is when the industry initially reacts to diminishing returns by aggressively increasing the amount of capital invested. In this case, the stocks of the resource are depleted very fast and the result is a crash of the production rate; we still have a bell shaped curve, but skewed forward. The rapid decline that occurs after the peak is what I called the "Seneca Cliff."
There are several historical examples of the Seneca cliff; in the case of fisheries, it is especially evident in the case of the Canadian cod fishery and for the Caspian Sturgeon; but it is evident also in the case of the UK fishing industry. Note, in the figure above, the steep decline of the landings of the late 1970s, it is significantly steeper than the growth of the left side of the curve. This is the essence of the Seneca mechanism. And we can see very well what causes it: the start of the decline in production corresponds to a rapid growth of investments. The result is the increase of what the authors of the paper call "fishing power" - an estimate of the efficiency and size of the fishing fleet.
The results were disastrous; a textbook example of how to "push the levers in the wrong directions", that is, of a case when the attempt to solve a problem worsens it considerably. In this case, the more efficient the fishing fleet was, the more rapidly the fish stock was destroyed. This is a classic mechanism for falling down the Seneca cliff: the more efficient you are at exploiting a non renewable (or slowly renewable) resource, the faster you deplete it. And the faster you get into trouble.
This case, as others, is such a staggering disaster that one wonders how it was possible at all. How could it be that nobody in the fishing industry or in the government realized what was happening? In their article on this subject, Thurstan and his colleagues don't comment on this point, but we can cite an article by Hamilton et al. on the Canadian Atlantic Cod fishery, where they say "Some say they saw trouble coming, but felt powerless to halt it." That seems to be not describing not just the fishing industry, but our entire civilization.
