I disagree with the idea that the idea of �carrying capacity� is a constant. It is a measurement (usually by weight called �bio-mass�) of different living things to use their environment. As such, it is variable. Here are some examples.
Imagine two identical ponds in the South. Let�s stock LMB in one pond and gizzard shad in the other. Let�s wait five years and come back and seine both ponds. If carrying capacity were a constant, we would expect the same weight of fish in both ponds. Obviously, we would find a much more weight of gizzard shad than LMB because gizzard shad can use their environment much more intensively than LMB can.
Here is another example. You stock a pond with LMB and a carrying capacity is reached. Then you add another species, bluegills. The bluegills can use resources in the ponds that the LMB could not and a new carrying capacity is reached. However, the bluegills are also competing for resources with the LMB. Let�s add a third species, channel catfish. Again, the catfish is able to use resources in the pond that the LMB and bluegill could. The carrying capacity of this pond increases again. However, the catfish are also competing for resources with the LMB and bluegills. Let�s add a fourth species, redear sunfish. Again, they are able to use resources in the ponds (snails for instance) and so the carrying capacity of the pond increases again. Again, they also compete with the other three species for resources. The point of this is that we have developed four different carrying capacities for exactly the same pond.
So why don�t we just keep adding species to all of our ponds? Because most of us really don�t care about carrying capacity. What we do care about is maximizing production of something like big LMB or large panfish. Remember, as we increase diversity, we increase competition for resources. That means individual fish don�t grow as fast or as big as they would with less competition.
In my case, I don�t care about trophy bass or lots of panfish to eat. What we do get is lots of good size fish of many different species that are always hungry.
