Carrying capacity noun For any given species, carrying capacity is the maximum population size of that species that a given environment can sustain indefinitely, given suitable habitat, food, water and other life necessities available in that environment. The carrying capacity for any given environmental area is not fixed. It may vary for different species, and may change over time for all species due to a variety of changeable factors such as food availability, water supply, living space and, especially, environmental conditions.
Earth carrying capacity for the human species
Estimates of how many people the earth’s natural resources can keep alive are so variable that most can have little to no credibility. Guesstimates gleaned from 94 scientists range from a low 500 million to a high one sextillion (that’s 21 zeroes). So much for those guys. Among other estimates somehow deemed “better,” quite a few scientists place Earth’s carrying capacity at around 9-10 billion people. Other scientists, equally credentialed, think our present 7.8 billion is already far beyond “way too many” and may be enough to sink the ship. Mind you, these are all seasoned scientists who know a lot—about other things. I personally think all but those last ones wrong. What do you think?
Reasonably credible figures say we’re already consuming food and raw materials at one and a half times the planet’s sustainable rate. I think these are probably right because increasing worldwide shortages of clean drinking water alone seem to make the case. It is obvious that clean fresh water is in such short supply only because so much of it is too polluted to drink or use due to the gross industrial and bodily wastes we discharge into it.
Another group says, not unreasonably, that the planet’s sustainable rate for human population cannot be determined, because that limit depends on the unknowable variable of how people live their lives and how much they choose to consume. These are clearly right too, and their reasoning seems to imply a quite high sustainability for H. sapiens–IF we all switch to that thin, watery porridge known as gruel. For perspective, let your imagination compare the consumption extremes of 1) a Park Avenue corporate baron and 2) an Amazon forest native; or, say, 3) a migrant farm worker and 4) a Congressman.
In elementary logic, if carrying capacity for a species is exceeded, the population of that species “declines” (a euphemistic term meaning suffer for a prolonged period, and then die) because its environment can no longer support its excess numbers. Glossing over details on the grisly nature of the declining, this is called overshoot. The consequence of overshoot is variously termed a “collapse,” “crash” or “die-off”, all of which mean a rapid decline (that word again) of a given species’ population density.
Over the past few decades, overshoots have resulted in drastic declines in the populations of a majority of bird, fish, insect and land animal species virtually everywhere on earth. In undeniable fact, almost every species on earth is in serious decline—except, so far, Homo sapiens, dogs, cats, and cows that convert to steaks or produce milk and then convert to steaks. Recent science magazines are full of fresh realizations that insects have declined drastically all over the world in just the past thirty years. German scientists have found that three-fourths of all insects disappeared in their part of Europe between1989 and 2016. A comparable drop in New Jersey was eighty percent, accompanied by a forty percent drop in diversity of insect species. Eighty percent of all animals are insects, and their vanishing would mean immediate chaos because most flowering plants, especially fruit crops, rely on insect pollination. One hardly needs to add that all humanity depends on bugs to pollinate virtually all the food crops we depend on to eat and stay alive.
Note however, these species have declined not because their populations grew too large, but because the earth’s carrying capacity was itself reduced by the exponential spread of humans and their human activities into the habitats the birds, fishes, insects and animals formerly depended on. Such human encroachment has driven some five hundred species extinct over the past mere ten decades, and the rate of extinctions is rapidly accelerating.
Animal populations today average less than half their size as recently as 1970—a year I remember well—and scientists are in full recognition of the onset of the sixth mass extinction since life began on Earth. Soon to follow, as the facts sink in, will be widespread public recognition that the loss of these little fellow species negatively affects the natural ecosystems we humans depend on to stay alive—depend on utterly, whether we know it or not. Such recognition is now a constant sad background in the Audubon Society’s annual volunteer bird counts, which are way, way down.
The same recognition is dawning in the boardrooms of industries that send out giant factory ships to harvest the world oceans’ stocks of profitable food fish, which are also way, way down and declining, and the boardroom suits are fretting about what can be done to keep profits up. As all the “better-eating” fish get used up one by one, processing further and further down the chain of “by-catch” can go on for only so long…
People in systemic context
In pursuit of better understanding what’s changing all around us, let us conduct a logical chain of reasoning on this matter, and see where it leads. First assumption: there are too many people now on the earth. If true, the reasoning should make it logically evident.
We humans, like most other living things, can be thought of as little individual systems that move about. Like systems we 1) require inputs, such as food and water; 2) conduct processes, such as consuming food for energy and expending the energy on various activities; and 3) we generate outputs, such as poop and garbage, sometimes a baby.
The input side, otherwise known as consumption, involves how much we need—or want—of those subsistence basics necessary to sustain life, known as food, clothing and shelter, i.e., the bottom tier of Maslow’s hierarchy. Provision of each person’s subsistence basics, multiplied by the number of humans on earth, yields a number that tells us the minimum quantitative human demand to consume earth’s natural resources. This can be and is scientifically computed in many places today, notably at the United Nations. A relative few humans actually do manage to get by on a minimal quantity of the basics. Among these few, those who live independently in geographically remote areas are by and large vigorously healthy, while those living in large cities tend to be less healthy and not live long. Altogether the minimalist people place slight demand on the earth’s resources. But they are few indeed.
Totaling far greater consumption are 1) the relatively few people of great wealth, 2) the great many middle-class lesser beings who aspire to more wealth than they’ve got, and 3) everybody else on down to the disgruntled stiff working three jobs just to keep afloat and who’d love to afford a bare few of the gleaming objects, goodies and stuff seen on TV and in the junk mail. All of these consume far more than the aforementioned subsistence minimum of natural resources, or would if they could, and many consume quite a lot indeed—certainly, sad to say, as Leader said—far more than their basic needs require.
And as economic wellbeing comes to increasing majorities of earth’s formerly minimalist citizens, even in countries where everyone used to live in mud huts, strong majorities now have, or aspire to, modern houses with plumbing and a TV even if their governments can’t keep the electricity on. Their collective consumption of the earth’s natural resources is increasing at exponential rates, trying to catch up with towering consumption in the U.S. and other developed countries. Such modernized consumption by those formerly abjectly poor gets quite a lot of press, while grotesquely, obscenely extravagant consumption by the extreme wealthy few in all countries gets hardly any press at all.
The natural resources being thusly consumed include, among other things, the millions of acres over-used to grow crops for food or weaving into clothes; the gas and oil wells used to fuel our millions of machines and provide plastic for millions of purposes; and gigantic mines above and below ground where ores are dug out for iron and all the other minerals demanded by modern mechanized, militarized and mobile civilization. Adding in all the rest of our worldwide industrial colossus, the magnitude of humanity’s consuming demands on the earth’s fixed amount of resources is beyond comprehension.
It is not hard to see—though many willfully refuse to see—how continuing increases in world population are causing overshoot. The more the number of us increases, the greater grows our demand for the remaining natural resources. This is quite a serious problem and a threat to every kind of future stability. It is growing, and promises to grow worse in the decades immediately ahead for our children and grandchildren to deal with.
Did you know that the batteries for each and every new electric car require about 187 pounds of copper, 123 pounds of nickel, fifteen pounds of manganese and fifteen more of cobalt? Did you know that if we successfully replace all billion of the conventional oil-fueled cars on the planet with electric cars, the conversion will require several times more metal than all existing land-based supplies of these ores? That’s counting none of the rising billions of new middle class earth residents who would also like to own a car. In response to this profitable market potential, and since remaining land-based ores are increasingly fewer and harder to get to, the barons of mining have launched digging of ores from the deep ocean floors—where their disturbances must release megatons of more carbon. How deadly, this Catch-22 corner we have painted ourselves into.
That our planet’s land-based natural resources are being fast used up has gone largely unnoticed except by those few with a financial stake in raw materials markets. Iron ore will peak around 2025 and be gone by 2075. Tin will peak even sooner, but declining supplies might last until 2100. China’s exclusive supply of rare earths—predicted to be mined out by 2040—includes ores such as dysprosium, neodymium and lanthanum, all in vital demand for products such as cell phones and studio lighting. Those who favor fossil fuels should worry that natural gas supplies may last only sixty more years and known oil supplies a mere forty. On the bright side, they say there’s enough phosphorus left to keep manufacturing artificial fertilizer for a whole hundred years, so until then we’ll have it to put on our nutrient-depleted fields. I’ve seen no statistics on leaf mulch or compost.
Notice that tiny phrase “land-based.” The ores remaining are harder to get to, and much costlier, because most of the easily accessible stuff was mined out years ago. The more world population increases, and demand for consumption increases along with it, the faster these resources are being used up. They don’t say much about this in the news. Neither do the media volunteer news about corporate extension of mining operations into the ocean depths—now already beginning—with devastation of ocean habitats a certainty. The Clarion-Clipperton Fracture Zone defines a zone of the North Pacific, lying between Hawaii and Mexico and larger than the United States, where corporations already hold exploration permits granted by the obscure International Seabed Authority. They are expected to dredge thousands of square miles each year from now on.
In terms of input, it is axiomatic that supply (e.g., broker corporations) always expands, or tries to, in order to profit from demand (e.g., consumers in need or want). With human populations increasing almost everywhere, increased cropland is required to grow food. But ability to grow food is declining in countries rich and poor because of 1) fields lost to increasing droughts and 2) overworked soil so depleted of natural nutrients that growers around the world have become dependent on manufactured fertilizer. Buy it or starve. More croplands are being lost as earth’s over-warming atmosphere causes deserts to expand (e.g., African Sahel, American southwest, most of Australia). Compared to the looming worldwide loss of soil fertility, our 1930s dust bowl was as a blip in the wind.
Brazilian peasant farmers and profiteers are creating new temporary land for crops and cattle by burning the Amazon rainforest that has been storing much of the planet’s excess carbon. These new fields—the formerly damp but well leached forest floor—are viable for about three years, then the farmers and profiteers must move on and burn again. Over one-fifth of that unique, precious and irreplaceable Amazon world resource is now lost and the tempo of loss is skyrocketing under Brazil’s reactionary new president.
A majority of ocean food fish species have indeed been overfished to depletion—alas, the long-gone mighty banks of cod, alas the haddock, groupers and sturgeons, even the lowly Slimehead Fish now deviously renamed “Orange Roughy” to bypass your disgust reflex enroute to your taste buds and wallet.
In the United States the high cost of land and equipment so inhibits young would-be farmers that producing farmers now average 58 years of age, many laboring on into their eighties. New extremes of temperature and rainfall, too high as well as too low, are disrupting growing seasons around the globe. Some American grain farmers were simply unable to put out a crop in 2019, others were unable to harvest crops that then ruined where they stood. Traditional patterns of food crop production and distribution to food consumers are everywhere changing, and almost everywhere in negative, declining ways.
Where will all the hungry mouths turn for their essential inputs when the remaining edible fish are too small and too few in number to be worth the cost of sending out the factory ships, when most of the farm fields under produce, and famine stalks the land?