Dear Science,

I'm trying to figure out the worth of climax community. It's very important for me to see if it has any validity. I had hoped to establish a moral system on the basis of opposing pioneer communities and climax communities.

Charles Mudede

The climax community hypothesis is indeed an appealing idea: For any given place, there is a collection of plants and animals ideally suited to it, interconnected in a balance that can sustain itself indefinitely. Over time, if the climax community hypothesis is true, one would expect a given region's organisms to slowly reach this idealized mix—with the less ideally adapted organisms succeeded by those better suited to the environment. It's like thinking of the development of a place as we think of the development of an organism—an orderly progression from a starting nucleus to a complete, complex, and carefully balanced living thing. In essence, entire places are thought of as gigantic superorganisms—the forest is a living thing, with individual living things and species in the forest analogous to organs. Described by the ecologist Frederic Clements early in the 20th century, the hypothesis has been built upon by subsequent ecologists.

One could apply similar thinking to human environments. Instead of a forest, one could think of a city, a neighborhood, or a block as a sort of superorganism, with people as the organs that make the community flow. In a similar way, one would imagine a community slowly gravitating toward an ever more ideal mix of people—each balanced in what they need from and can provide to the whole.

If we are to approach this as scientists, an appealing idea is not enough. We must go looking for evidence that the idea does, or does not, describe well what happens in the real world. On this measure, the climax community idea falls short. In the same location—over brief periods of time—we can observe entirely different ecosystems arising. Unlike organisms, communities don't really demonstrate clear boundaries from one to the next. Rather, there are often gentle gradients—a blurring of boundaries, resulting in a more interesting set of overlapping combinations of living things that don't seem to follow sharp edges.

Finally, the climax community idea—at least in the minds of some ecologists—doesn't account well enough for random events: disasters, the slow change in the nature of a given place due to the drift of tectonic plates, changes in the atmosphere, solar activity, and a multitude of other factors that change the underlying nature of a place. Things happen to change a place well before the living things in it can reach their idealized place.

The short of it: Don't fall too deeply in love with a lovely idea. Empirically, things are usually more complex and more interesting.

Communally yours,


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