One way to view our lonely little world is as a remote, isolated island with a finite sustainable carrying capacity. Like any large island, some items – such as food and water – are endlessly regenerable when utilized within limits, and some items – such as metals located in the ground and fuel supplies – are either gone forever when expended, or extremely difficult to replenish. Within the confines of the island, the sustainable standard of living will obviously be determined by the number of people living on it. And the future of the island’s population will obviously depend on how wisely it allocates its resources.
In keeping with this analogy, most estimates reasonably project that the sustainable carrying capacity of our island planet is approximately 1-2 billion people at the U. S. standard of living. However, in the absence of the dreaded Malthusian catastrophe, and with advances in food production somewhat maintaining parity with demand, the Earth currently supports over 7 billion – although at vastly varying standards of living – and with a projected increase to 10 billion by mid-century. Yet, it is easy to see that this cannot continue forever. In competition with all the other life on this planet, the human population currently utilizes 40% of all the worlds biomass, has cleared 40% of all available landmass into city-space and farmland, utilizes over 50% of the world’s fresh water, produces more nitrogen that the rest of the world’s biomass combined, and introduces over 100 million tons of synthetic material into the environment every year. In the U. S. alone, 98% of all the rivers have had their flow diverted
to other use. Competition with other life forms has placed 25% of all mammal species, 29% of all reptile species, and 14% of all bird species at risk. Raising the world’s population to 10 billion is expected to further increase food demands by 70%. To believe that we can continue unabated is indeed living a Pollyannaish dream.
The point is that we have been doing quite a good job of destroying our biosphere in the absence of global climate change. Indeed, the unrelenting rise in CO2 is merely the byproduct of unrestrained population growth. Thus, while the geographical changes that a warming planet will bring about are quite dire, it is merely fuel on the fire. The real problem is that we are literally a species out of control. Until we can find a way to check our unquenchable need to eat, drink, and occupy everything on this planet, rising seawater level will be the least of our worries.