The open question is whether humans are still functioning as K-strategists, and so tend to follow the logistic curve illustrated. While it’s true you are long-lived and have few children compared to jellyfish, the current situation has no previous analog: humans are now, in effect, hybrid organisms in a symbiosis with fire. While your living biomass is based on the same structure you have had for hundreds of thousands of years, your effective metabolic biomass is an order of magnitude (10x) higher, because your fossil-energy- powered “extended phenotypes” breathe and use environmental resources at an exponentially increasing rate. This means that ecologically your species is acting like rapidly reproducing r-strategists. Your high use of fossil energy makes you now effectively detritivores - converting fossil energy to food via industrialized agriculture. Ninety percent of your ecological footprint is due to your r-selection-like proxy carbon slaves, a.k.a. the fossilized remains of Cambrian organisms. 89 The rate of metabolic oxidation, ecosystem degradation, and energy generation of these slaves over the past two centuries dwarfs even the huge rise in human population during that same time. While this may seem to be a rather abstract excursion into the interaction between lifestyle and carrying capacity, I urge you to think about which sort of curve you would wish to have your species follow, and to also reflect on humans’ recent main effect on the planet: rapid environmental change. The side-effects of your brain problems might well select against the future existence of large brains on Earth. The Bottom Line: Evolution has come up with very different strategies for r vs. K-selected species. Rapid environmental change enables the r’s to replace the Ks.
Carrying Capacity (and Overshoot)
Summary: The carrying capacity of an environment, relative to a species, is the population size which that specific environment could, in principle, indefinitely sustain. This concept thus folds together many different requirements such as food, water, nutrients, recycling of wastes, sufficient space to exist, and other factors. If these parameters change, then so does the carrying capacity. This concept may be used on many scales: to describe small populations in isolated environments or the limits to biomass at
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