It doesn’t really matter if you believe in climate change, but carrying capacity is real and we need to think about what we are doing to the earth.

Imagine for minute a field with grass, clover and lots of other plants rabbits like to eat. Then a few rabbits come into the field, and since they have plenty of food, the rabbits will happily move in, set up a community and breed. Now imagine that once the rabbits enter the field they cannot leave. And since rabbits, like all species, reproduce faster than they die of natural causes, the population of rabbits will grow. At some point the rabbit population will grow so large that they will begin to destroy their field. Their waste will begin to poison the streams, they will eat too many of the plants, and they will begin to suffer greatly. Some of the rabbits will be killed in fights over food or water, or some will die of starvation or exposure. Eventually the rabbit population will be reduced enough for the plants to come back, and at some point the rabbits and plants will reach a balance where there are not too many of either to survive. But in the meantime the individual rabbits will suffer a great deal.
Biologists call this steady-state (or equilibrium) the carrying capacity of an environment. Adding predators, competing species, or other food sources can change the size of the carrying capacity, but there is a finite carrying capacity for every environment. In the example above, the field is the Earth, and we are the rabbits. We have not reached the Earth’s carrying capacity yet, but we are approaching it. You can tell that we are getting closer by the way we are contaminating our environment. Pollution is one symptom, there are floating piles of garbage in both the Atlantic and Pacific oceans. Climate change is another symptom, the waste from our energy usage is beginning to build up and change the long term energy dynamics of the planet. We haven’t reached our ability to extract food and energy from the Earth, nor have we reached the Earth’s ability to cope with our waste, but we are starting to stress it. Despite our great ability to build tools to enlarge the Earth’s carrying capacity, and even mitigate the damage our waste products do, this trend cannot go on forever.
There are two ways to avoid reaching the Earth’s carrying capacity; either reduce our rate of reproduction, or reduce our rate of consumption and production of waste. I find it hard to believe that either solution will work by itself, but that some combination of reducing our consumption of energy and production of waste combined with a slower population growth may push the crisis of reaching the earth’s carrying capacity far into the future. The sad truth is that people only have one major predator – other people. So we either need to find a way to avoid reaching the earth’s carrying capacity, or we will be fighting over more and more scarce resources and we will reduce our population in the worst way imaginable, by killing each other.

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