I have known about the concept of carrying capacity for a long time, but have been thinking about it more lately, as world news brings more and more evidence of humans bumping up against our planet's physical limits. It also is in the back of my mind as I consider what this 40 acres ( 16 hectares) might ( or should) look like in 20 years.
Carrying capacity is another of those fractal things, where it can be viewed from the planetary level, right on down to plant spacing in a garden row.
Carrying capacity is also complex in that it's not just the human centric view of how many humans can be supported ( though that's usually what is implied) , but should really focus on long term overall health of the entire biota. And local ecosystems are not static either, evolving and going through cycles on different and sometimes random durations.
In looking at our farm, and food production in general, it can be tricky to draw an appropriate system boundary and fully account all the inputs and outputs crossing that boundary. Thought needs to be given on what a reasonable area is for calculating carrying capacity.
A watershed? A region? A homestead? I happen to live in the Kickapoo River drainage basin, or watershed. No question at all that I still import large amounts of fossil fuel enabled external inputs in our little farm, but I hope year by year to reduce that.
The reality is, humans have been transporting resources and materials across distances for millennia, though of course for the last century give or take, we are a couple orders of magnitude beyond what can be done with muscle power or water or wind.
It is pretty obvious that carrying capacity of a specific area is lower if no material movements or cross subsidies are done, and some balance will be struck at a much lower rate of production as we end the fossil fuel era.
And human activity can affect the "base" carrying capacity absent external inputs as well. Trees can be cut down, soil eroded, square miles paved over in urban areas, with regrowth or healing taking from decades to centuries. In the other direction, trees can be planted, water retention structures built, or complex and resilient plant communities can be nurtured.
Overall the planetary carrying capacity has been degraded by human actions quite a bit. A couple years ago, I posted about humans as a keystone species that lost our way. The rogue keystone species
I guess I'm still dwelling on it, and still hoping we can renew our role as a positive contributor and an intelligent collaborator with our fellow organisms.
Humans are ( hopefully, maybe?) a special case, in that we are able to anticipate, or imagine possible futures, and then steering our actions in the present to make them so. Human scale agriculture, permaculture, animal husbandry, and similar technologies give us the chance to increase our species' individual carrying capacity, but with wisdom, we could be improving the carrying capacity of a region for all its inhabitants.