In one of the most easy to interpret essays I’ve ever read, Paine states in quotes the hypothesis to be “local species diversity is directly related to the efficiency with which predators prevent the monopolization of the major environmental requisites by one species.” He goes on to say that the study he performed was on rocky, intertidal marine organisms, though the results may have wider applications.

To test his theory, Paine observed undisturbed portions of intertidal seashore rock to establish a baseline of the eating habits and caloric intake of the represented carnivorous life. In doing this, he identified what he considered to be the “terminal carnivore” or as other people might know it, the top of the food chain. The idea of the terminal carnivore is that, in each local environment, there is one animal that kills and eats without being killed and eaten. After determining the average eating habits within this environment and illustrating the food web, the environment was kept free of the terminal carnivore for a period of time, while all other factors remained natural. In the case of this study, the terminal carnivore was a species of starfish. Also represented in the food web were mollusks, carnivorous aquatic snails, herbivorous aquatic snails, and barnacles. The information on specific ratios and species may be found within the publication itself and henceforth I will be writing about the ideas and conclusions of the paper more so than data.

The results of the removal of the terminal carnivore was that within four months 60-80% of the surface area of the rock face was covered in a particular species of barnacle, six months after that that species was being crowded out by another. The system itself had decreased in diversity from a 15 species environment to an eight species environment.

The interpretation of this data was that the removal of the most efficient predator had a negative effect on the number of species living in an environment. The presence of the second most efficient carnivore, even taking into account an increase in density of up to 2,000%, did not seem to be sufficient to prevent the monopolization of space by one of the represented species, at the expense of the presence of others. In the absence of a complicating factor, in this study predation, the competition for space can be “won” by a particular species. The removal of the top predator has an outsized effect on the simplification of an environment.

The author later suggests two follow up studies. The first is to determine if resource monopolies are less frequent in areas with diversity than in similar environments with fewer represented species (an attempt to observe the results of this experiment without the human interference of artificially removing the top predator, if I understand) and to study more thoroughly the food subwebs.

When I was in AmeriCorps, one of the projects my team worked on brought us to Raccoon Creek State Park near Pittsburg, PA. While we were there, one of the park rangers gave the team a class on the local wildlife. After the class, because she was going to be working closely with us, the ranger began asking us questions about what we enjoyed doing outdoors, including asking about whom among us was a hunter. After one of the team members expressed objection to the hunting of deer, the ranger explained population control to us. Human beings had disrupted the food chain in the region three hundred years previously by hunting local wolf populations to near extinction. The wolves were competition for hunting game as well as being predacious of livestock. The result of the vast reduction in wolf population was a boom in the population of the wolves main prey, deer. As the deer population boomed, wildflower populations plummeted because they were being consumed by deer. The decline in wildflower population effected bees, which effected pollination among all sorts of vegetation, etc. As a result of all of this, the State of Pennsylvania, to this day, must release hunting licenses to keep in check the deer population.

I don’t know whether or not that park ranger ever read Robert Paine’s “Food Web Complexity and Species Diversity”, but once I realized the parallels between the two stories, I immediately understood much better what Paine was hypothesizing. I largely agree with Paine’s hypothesis and conclusions, though I’m still somewhat hesitant to agree that “in the absence of a complicating factor (predation), there is a “winner” in the competition for space, and the local system tends toward simplicity.” In this essay he admits that the area under study never reached equilibrium in the time it was under observation. My instinct leads me to believe that if the observation were extended until such a time that equilibrium were again reached the diversity may have climbed again to levels near where they were at the start of the experiment.